In this presentation, I summarize recent experimental and theoretical studies from my group on the breakup and coalescence of polymer drops in a second immiscible polymeric fluid. A particular focus is the role of “compatibilizers” in these processes. Compatibilizers are typically di-block copolymers of the two bulk polymers, and thus they act as large surfactants insofar as the breakup and coalescence processes are concerned. Compatibilizers inhibit coalescence, and lead to major changes in the distribution of drop sizes when a drop is stretched by a flow and then breaks by capillary instability when the flow is stopped.

The effects of fluid elasticity in the flow of non-Newtonian fluids in microfluidic converging/diverging geometries are investigated. We investigate the structure and dynamics of inertio-elastic flow instabilities and elastic corner vortices which develop upstream of the contraction plane, and explore their dependence on the relative magnitudes of inertia and elastic stress generated by the high deformation rates in the contraction geometry. The results show that the shape, size and evolution of these flow structures varies with the elasticity number, which is independent of the flow kinematics and is only dependent on fluid properties (viscosity, density and polymer relaxation time) and the characteristic size of the channel.

We consider developments in small amplitude oscillatory-shear testing, from the advent of the first post second world war commercial rheometers to the present day. To facilitate such a survey, we concentrate on the case where the test fluid is contained between two plates, which are initially parallel and horizontal. In the earliest experiments, the bottom plate performed small amplitude torsional oscillations about a vertical axis, with the motion of the upper plate constrained by a torsion wire. Somewhat later, a new kind of rheometer appeared, in which both plates rotated with the same angular velocity about two axes, which were both normal to the plates, but not coincident, (the so-called ‘Orthogonal Rheometer’). This led to an impressive (but relatively short-lived) period of research activity, before the device fell out of favour. At about the same time, a ‘tilted-plate rheometer’ was proposed and the basic theory developed. However, there is no evidence that such a technique was ever investigated experimentally. In recent years, there has been a growing interest in the so called ‘Compressional’ technique, in which the bottom plate is stationary, while the top plate performs small amplitude oscillations in the vertical direction. Such a device is shown to have some advantages over the earlier techniques, especially at high frequencies. Of particular interest in the present study is the way that the effect of ‘fluid inertia’ has been accommodated in the various experimental techniques and some recent theoretical and experimental work carried out at the author’s laboratory on the Compressional instrument is discussed in detail.

A continuum theory of constitutive equation of co-rotational type is developed for the anisotropic viscoelastic fluid-liquid crystalline (LC) polymer. According to the new concept of anisotropic viscoelastic simple fluid, the stress tensor is considered as a functional on whole history of deformation gradient and hole history of spin tensor measured with respect to co-rotational coordinates. Using the concept and generalizing the co-rotational Oldroyd fluid B model, a continuum theory of constitutive equation of co-rotational type is developed for the fluid. The theory is specialized to constitutive equations of LCP-H model and LCP-Qs model. The orientational motion and the anisotropic material functions are introduced in the equation to describe behaviour of the anisotropic effects of LC polymer fluid. Using the equation analytical expressions of apparent viscosity, first and second normal stress differences and extensional viscosity are given which are in a good agreement with the experimental results. The bifurcation of extrusion-extensional flow is observed for the fluid flow.

The functional for minimization following from the upper bound theorem depends on the constitutive law chosen. The effect of simultaneous deformation of viscoplastic and rigid perfectly plastic materials on the mathematical formulation of upper bound solutions is studied. The results show that, in contrast to the conventional formulation in the theory of rigid perfectly plastic solids, it is in general impossible to get an upper bound of the load applied. Instead, an approximate value of this load can be found. The theory is illustrated by a solution for plane-strain compression of a three-layer strip between two parallel, rough plates.

To identify rheological constitutive model of geo-materials, one generalized constitutive law is applied. So, the problem of model identification is transformed to the problem of traditional parameters identification. According to the relationship of objective function and optimization methods, the global optimization method, such as evolutionary algorithm, is very suitable to solve parameter identification problems. A new fast-convergent genetic algorithm is applied in this study. In this new algorithm, there are only two individuals in one population. So, the whole computation efficiency of optimization back analysis will be very high. Using this new back analysis method, a real engineering example of one underground coal mine roadway is used to verify the computing ability of the algorithm to real problems. The results show that the efficiency of optimization back analysis can be improved greatly with this new algorithm.

Nearly 30 years ago the PTT constitutive equation for molten polymers and solutions was published, and since then it has been widely used. In the intervening time much progress has been made in polymer science and mechanics, especially via network and tube theories. It is natural to unite these points of view in a revisitation of PTT-type models. We show that a new improved form of the PTT model, called the PTT-X model, can closely describe, in particular, the rheological behaviour of low-density polyethylene in (steady and transient) shear and elongational flow and in recoil from an elongational stretch. The results of an attempt to reduce the number of parameters are also described and we place the new model within the context of general network theory and tube theory.

A general nonlinear slip of fluid flow at a solid surface is proposed in the present paper. The theoretical prediction shows that the slip length keeps as a constant (an initial slip length) at a small shear rate, then increases with the shear rate, and finally is approximately proportional to the slip velocity at a high shear rate. The nonlinear slips occurring at both of the simple flow in a parallel sliding system and a complex flow between two approaching spheres are investigated. It is found that the initial slip length controls the slip behavior at a small shear rate, but a critical shear rate controls the boundary slip at the high shear rate. Our theoretical predictions are in well agreement with the experimental measurements of boundary slips for both a simple fluid and a complex fluid.

The objective of this study is to well understand the migration and orientation of thin micro-particles, such as talc and mica, in a suspension flow by means of both experiments and numerical simulations as well as to obtain the knowledge of the processing operations of thin micro-particle reinforced composites. A slit channel was mounted on the sidewall of a large reservoir in the experimental setup. For this reason, the thin disk-like particles were subjected by a planar extensional flow in a reservoir, then by a simple shear flow through a slit channel. The evolution of the orientation of thin disk-like particles was studied in both a planar extensional and simple shear flows by numerical calculation of the Jeffery equation: thin disk-like particles aligned in the parallel orientation to the upper- and lower-walls of the slit channel in a planar extensional flow through the reservoir, then entered into the inlet of the slit channel. On the other hand, in a simple shear flow through the slit channel, the disk-like particles kept this parallel orientation except the occurrence of flip-over. The period of the flip-over became longer with a decrease in aspect ratio (thickness/diameter) of the disk-like particles. Furthermore, the measurements of the orientation of the talc particles in a suspension flow through the slit channel clearly showed that almost the same period of the flip-over was found in spite of different particle size. The experimental result arises from complex geometries and no accurate data of the thickness of talc particles.

Some distinctive computer technologies, which lead to multiscale computational experiments and investigations of peculiarities of micromechanical behavior of heterogeneous composite media, taking into consideration of atomic-molecular formations, were discussed. The results calculated by Monte-Carlo approach were considered as a perspective method for description of the important features of atomic and molecular texture and energetics of heterogeneous polymer media. The quantum-mechanical approach was discussed as the method for solutions of top problems of micromechanics of polymer composites, namely, an investigation of the interaction of soot model particle with non-terminated and H-terminated surface with segments of polymer chain with different chemical structures. The parallel technologies of calculations and supercomputer were used. Optimization of viscoelastic behavior of composite media such as rubbers leads to the procedure of identification. Validity of reinforcement effect on the basis of the relaxation properties analysis of materials seems very perspective.

The thixotropy-loop tests of a LDPE (PE-FSB-23D022/Q200) melt were described in the present paper by using the simplified Acierno-type constitutive equation, which was formed by a modified upper convected Maxwell model and a kinetic equation. The simplified Acierno model is a single-mode equation and only contains three parameters. The descriptions of the simplified Acierno model show partial agreements with the triangular-form thixotropy loop tests of the LDPE melt, in which the calculations of the model show agreement with the tests experiencing short- and medium-time shearing, but show some deviation with the experiment experiencing long-time shearing. The simplified Acierno model can reflect some typical viscoelastic properties of the melt.

The blood and tissue liquid flow are studied by microcirculation method or porous flow model. The blood flow in capillaries is studied by used the porous media flow model in this paper. The advantage of the model is to research the whole flow characteristics, and it can be used to study the blood flow in animal viscera. By used the Casson constitutive model, the differential equation of blood flow in capillaries is derived, and the characteristics of steady flow and transient flow are solved by numerical method. The result shows that the more threshold stress is, the bigger flow resistance is, and the flow is different from the newtonian fluid flow. This method is a new useful approach to study the biological fluid mechanics.

Characteristic rheological behaviors of polymer nanocomposites were studied in shear flow and uniaxial elongational flow. Solid-like plateau storage modulus, strong shear thinning at low frequency regions, and strain hardening at elongational flow were observed. Especially, strain hardening was clearly observed for polymers without long chain branches if nanoparticles were homogeneously dispersed in the polymer matrix and interactions between nanoparticles and surrounding polymer molecules were sufficiently strong. Reptation models were used to model the nanoscale dynamics of nanoparticles and macromolecular chains, and the characteristic rheological behavior of nanocomposites could be explained. Brownian dynamics simulation of Doi-Edwards reptation model was applied and two particle constraint coefficients were introduced to express the influence of nanoparticles on molecular orientation and reptational diffusion of polymer chains. In the simulation, stress tensor including link tension coefficient which characterizes anisotropic friction coefficient of the molecular chain was used to obtain material functions by assuming that the anisotropy of friction was altered by the presence of nanoparticles. Additional frictional force between polymer chains and nanoparticles was considered and the suitable relaxation process and chain stretch were incorporated by considering the full chain geometry of polymer molecular chains. All the reptation models considering the effect of nanoparticles were verified by comparing the theoretical results with experimental data for polymer nanocomposites in shear and elongational flows.

A mathematical model of the polymer solution flow in porous media is established with the different concentration distribution. The polymer solution is treated as the power law non-Newtonian fluid with its power law index depended on the concentration of the solution. The finite element method is used to solve the problem by considering the effects of the concentration distributions and the different boundary conditions on the process of pressure conduction. The wellbore pressure and pressure distribution have been determined. For the different case, the type curve of pressure and its derivate have been analyzed. Some in situ test data are analyzed to verify the new model by using the type curve matching method. The results show that the concentration distribution of the polymer solution in the porous media is clearly reflected by the power law indexes changed along the distance. The characteristic parameters of the porous media and the polymer solution distribution can be determined by analyzing the in situ test data. The new model has been extended to more complicated boundary cases.

Three-dimensional flows of liquid crystalline polymers in rectangular abrupt contraction and expansion channels were numerically analyzed using a modified Doi model as a constitutive equation. The orientational behavior of molecules was mainly investigated using the director and the orientational order parameter, and the relation between the orientational field and the velocity field was analyzed at several Deborah numbers De. In the contraction flow, flow aligning of molecules occurred in the main flow near the contraction owing to elongational flow. In the expansion flow, molecules near the mid-plane were aligned perpendicular to the flow direction just downstream of the expansion and this alignment related to a concave velocity profile appeared in this region. The order parameter increases just downstream of the expansion and the orientation more slowly relaxes along the flow for larger De. In addition, negative elongational flow downstream of the expansion causes a highly three-dimensional structure of directors called a twist structure.

A continuum theory of constitutive equation of co-rotational derivative type was developed for anisotropic viscoelastic fluid—liquid crystalline(LC) polymer. The theory was specialized to a constitutive equation of co-rotational type LCP-H model and LCP-Qs model. Using the constitutive equation of LCP-Qs model, the shear-extensional flow was studied for the extrusion process near the die exit of the fiber spinning of liquid crystalline polymer melt. Bifurcation of extensional viscosity was observed in the case without orientation and the two cases when the directors were parallel to flow and vertical to flow for the LC polymer melts. The extensional viscosity increases when the director rotates from the flow direction to that vertical to flow. Based on the LCP-Qs model a computational analytical theory was developed for extrusion process of LC polymer melt, contraction of the extrudate was predicted by the theory. The computational symbolic manipulation such as computer software Maple was used for the problem solution. An important conclusion can be drawn that the director tumbling has remarkable influence on extensional viscosity but no principal one on LC polymer melt extrusion.

A long-standing question is readdressed as to whether the viscoelasticity can have a measurable effect on lubrication characteristics in thin-film flows. Specifically, a perturbation method based on the upper convected Maxwell constitutive equation is employed to analyze thin-film flows of a non-Newtonian fluid between two surfaces. The results show that there is a significant enhancement on the pressure field in the presence of viscoelasticity when the minimum thin-film thickness is sufficiently small. This mechanism suggests that viscoelasticity does indeed produce a beneficial effect on lubrication characteristics, which is consistent with experimental observations.

A new variational principle is used to establish more reasonable finite element method, which set no limits to physical equations, that is, appropriate to general situations including elasticity, plasticity and rheology. According to theory of finite element method, tanking the Lagrange multiplier as unknown variables with unit joint stress, the corresponding calculating formula of the finite element method is derived. Through solving the equations about basic unknown variables, all unknown variables such as the strains and stresses in the whole solving area, can be work out. A problem about elastic body and a problem about Maxwell body are given and work out, and the results are both identical with the results in the corresponding literature. So the finite element calculating formula can be used to solve the problem of structure analysis with different stress-strain relations and may offer a new alternative way for some more complex problems, for example, the study on the elasticity-plasticity interface. And the other difference with the finite element calculation of common generalized variational principles is: the Lagrange multipliers are not determined beforehand, but to join in the calculating of finite element to get their physical meaning, the train of thought is more natural and the range for solving is expanded.

A new statistical approach to assessing the friction factor correlations was presented. Fourteen correlations, published from 1959 to 2003, were collected to calculate friction factors for power law fluids in turbulent pipe flow. A series of Fanning friction factors, f, were computed from these equations. Then the relations between the calculated values of f and Re_MR (Metzner-Reed Reynolds number) were analyzed, when the rheological behavior index, n, was given. To verify the foregoing analysis result, in addition, the relations between the calculated values of f and n were analyzed, when Re_MR was given. The f value calculated from each equation was compared with each mean value of all the f values from the 14 equations, when each combination (n, Re_MR) (n ranging from 0.4 to 1.4 and Re_MR from 4 000 to 100 000) was set. The comparison results were surveyed in the relative deviation table of the calculated f values. It shows that the overall mean relative deviation (OMRD) of the Dodge-Metzner correlation is the minimum, 1.5%. Therefore, the Dodge-Metzner correlation is recommended for predicting the friction factors for the turbulent pipe flow of power law fluids.

Translational motion of a single tiny spherical gas bubble subject to a weak acoustic standing wave field is studied both analytically and numerically assuming that the liquid surrounding the bubble is a viscoelastic fluid obeying the second-grade rheological model. Equations of motion are derived in radial and translational directions for this particular fluid model and shown to be coupled through the virtual mass effect. A perturbation analysis is carried out first to show that the natural frequency of a gas bubble is increased the higher the fluid’s elasticity. Fourth-order Runge-Kutta method is used to investigate the effects of a fluid’s elasticity on the bubble dynamics in the translational direction. It is shown that bubbles exhibiting erratic behavior in the translational direction for the case of Newtonian fluids can be stabilized provided that the liquid surrounding the bubble is sufficiently elastic.

The nonlinear iteration method of compelling displacement of boundary support was presented, combined with the nonlinear element method of space beam and Newton-Raphson nonlinear iteration, which can succeed flexibly in finding equilibrium configuration under complicated external loads. The relationship between space configuration of flexible pipe, constraint forces and active load by mining machine was studied. The result shows that the computing method is important to engineering.

The rheological properties of water-based magnetic fluids (MFs) were measured using rotating and capillary rheometers. It is found that the rheological behaviors of MFs with high solid content under an applied magnetic field can be described using the Herschel-Bulkley (H-B) model. Two-dimensional numerical simulation was performed to investigate ejection phenomena of the MF from a capillary with the H-B model. Experiments was conducted to observe drop formations. The measured numerical results are validated by the experimental findings.

Based on the widely used second-order essentially non-oscillatory(ENO) scheme, a modifying coefficient approach was defined on non-uniform mesh. By modifying its coefficient, without extending modifying coefficient ENO scheme’s stencil, a new scheme was obtained. The new scheme gives the accuracy of one higher order, and preserves most of the properties (Upwind, TVD and TVD etc) of the primitive ENO scheme. The numerical experiments show that modifying coefficient ENO scheme is more efficient and of higher accuracy in smooth regions when compared with ENO scheme.

Flow properties such as viscosity and gel point of waxy crude oils, particularly the beneficiated waxy crude oils, are sensitive to shear history that the crude oil experienced, called the shear history effect. To understand quantitatively this shear history effect is necessary to oil pipeline design and operation. For experimental simulation of the shear process during pipelining, shear rates of turbulent pipe flow, and flow through centrifugal pumps and throttle valves are necessary. Stirred vessels are usually used for shear simulation in laboratory, therefore, shear rate in the stirred vessels has to be known before shear simulation. Based on relationship between energy dissipation rate and the shear rate, approaches are developed and presented for calculation of shear rates in the above-mentioned specific flows. Combined with the entropy generation due to viscous flow in the shear process, which has been proved to be a proper parameter for simulation of the shear history effect, the shear history effect on viscosity and gel point of the beneficiated waxy crude oils has been experimentally simulated accurately.

An experimental study was performed on two-phase pressure drop of gas/non-Newtonian liquid systems in co-current horizontal flow. The effects of superficial velocities and polymer concentrations on two-phase pressure drop were investigated. A total of 180 experimental tests were conducted for the following conditions: superficial liquid velocity from 0.18 m/s to 1.42 m/s, and superficial gas velocity from 0.13 m/s to 2.59 m/s. The results show that the drag reduction will occur when the value of flow behavior index, n, is smaller than 0.6, and the lower the value of n is, the greater the effect of drag reduction will be.

A set of experimental equipment was established for falling film evaporation. The aqueous CMC (carboxymethylcellulo) solution was used to simulate the non-Newtonian fluid that obeys the power law model. Effects of rheology of the non-Newtonian fluid on heat transfer were investigated experimentally. A theoretical model was developed and coupling characteristics between rheology and heat transfer were described in non-Newtonian environmental fluid falling film in evaporation process. The different theoretical models were established for the developing region and the fully developed region in this evaporation process, respectively. Using finite difference method and shooting method, the simulated calculations were obtained. Furthermore, by introducing the generalized Reynolds number and the Prandtl number, which includes the necessary physical properties of the non-Newtonian fluid, a correlation about the Nusselt number was proposed for non-Newtonian fluid falling film in evaporation process.

The rheological properties of solution of polyethersulfone(PES) in dimethyl sulfoxid(DMSO) were investigated on a HAAK RS150 cone-and-plate rheological instrument, including the dependence of non-Newtonian Index, apparent viscosity, zero shear viscosity on concentration and temperature of the solutions. Apparent viscosity η_a at same shear rate increases with increasing PES concentration. Non-Newtonian Index n decreases with increasing concentration and increases with increasing temperature. Zero shear viscosity decreases in an index manner with increasing temperature. When PES content is 24%(mass fraction), amount of macromolecule tangling points of solution is near saturation value. Tangling points do not increase or increase little with increasing PES concentration so that the flow activation energy E_η changes little.

A capillary rheometer operating at prescribed temperature and pressure was set up. The measurement principles of the capillary rheometer were introduced. The equipment constant was obtained using standard liquids (e.g. water with known viscosity), and the rheometer was thus calibrated. The different carrier liquids viscosities of Fe₃O₄ magnetic fluid (MF) were measured at different flow rates. The experimental data were compared with the results of a theoretical equation derived in this study. Finally, the effect of temperature was investigated. Due to the effect of different carrier liquids, xylene-based and silicon oil-based MF show Newton behavior, but the hydroxyethyl-cellulose (HXC)-based MF shows non-Newton behavior of shear thinning. The difference between the experimentally measured viscosity and the theoretical prediction is lower for dilute MF, whereas, the difference is large for highly concentrated MF. The viscosity decreases quickly with the increase of temperature.

Polycrystalline PbZr_0.52Ti_0.48O₃ (PZT) thin films with different thicknesses were prepared by metal-organic decomposition (MOD) at different thermal decomposition temperatures, and their effective elastic constants were evaluated with X-ray diffraction (XRD) techniques. The relative intensities of textures in the thin films were analyzed from XRD patterns, and the effective elastic constants were calculated by averaging over orientations according to the relative intensities. On the other hand, Gaussian distribution functions were used to fit the normalized intensities of (001) pole figures, and the effective elastic constants of PZT thin films were calculated according to the grains’ orientation distribution described by Gaussian distribution functions. The results show that the effective elastic constants of PZT polycrystalline thin films evaluated by XRD patterns are in good agreement with those evaluated by pole figures, and the differences are within 10%. The effective elastic constants of PZT thin films are greatly affected by the thermal decomposition temperature, while the effects of thickness of thin films are relatively small.

The focus of rheology is generally on shearing because shear is the dominant mode of deformation in most transport processes. At the same time, there are processes in which extension is the dominant motion, and then the rheological challenge is to characterize fluid resistance to extensional deformation. While extensional motion is important in polymer processes such as film blowing and extrusion, this work focuses on extensional motion of solutions and suspensions primarily because extensional motion of these fluids is all printing and coating processes, including roll coating and inkjet printing. In this paper, the state of extensional rheometry is briefly reviewed and then a new technique to measure extensional flow resistance is introduced.

New methods must be developed in order to access rheology’s full potential. The tools that allow a researcher (or student) to move freely and rapidly between the most advanced rheological theories, or between experimental data and theory are envisioned. This combination would enable him/her to reach a deeper understanding of rheology. The Amherst rheology platform(ARP) intends to facilitate this valuable process. ARP connects dedicated software modules, which perform calculations and return the corresponding results to the graphics screen of ARP. The experimental part of ARP has been completed, and the ARP implements the most powerful tools of data analysis. In addition, rheology experts have begun to write theory modules that seamlessly connect into ARP; several modules are complete and more are in progress.

For describing anisotropic behaviour of the material, thermotropic and lyotropic liquid crystalline polymers were investigated by polariscope to take microstructural photos. Experimental investigation on the rheological and rheo-optical behaviour of the HPC was reported. The HPC was used in a extrusion test, a small contraction, nearly planar extrudate and resonance instability due to shear disturbance were observed when the lyotropic LC polymer HPC solution was extruded. A simple stability theory of orientational motion of director vector was developed for the LC polymer fluid that extended flow of thermotropic LC polymer melts is very effective in producing a high degree of macroscopic orientation.

Melt of a segmented block copolymer constituting of poly (lauryl lactam) as the hard segment and poly (tetramethylene oxide) as the soft segment was investigated by rheological techniques. Storage modulus of the polymer melt exhibits the non-terminal behavior resembling those of diblock and triblock copolymer melts, indicating the existence of a microphase separated structure. Contrarily to most block copolymers, the melt of the segmented block copolymer transforms from a weak structure to a stiff one upon raising temperature. Atomic force microscopic data in tapping mode reveal that at low temperatures the structure of the melt is constituted of small spherical soft domains dispersed in a hard matrix and the hardness of the matrix differs slightly from that of the domains; at high temperatures the spherical domain structure preserves but the domain becomes larger and so does the hardness difference between the domain and the matrix. Infrared spectrum analysis shows that the temperature induced structural change is related to the dissociation of hydrogen bonding between the hard and the soft segments.

The stress relaxation behavior of polypropylene (PP) was investigated at room temperature. Displacement controlled experiment was simulated using engineering computational software ANSYS and performed on PP. Both results were compared with each other. The utility of numerical simulation was also discussed. The experiment results are well in agreement with the numerical ones.

The current models for the entanglement dynamics of flexible polymers are mostly based on the molecular picture of dynamic tube dilation (DTD). The full-DTD picture, assuming the equivalence of the relaxed portions of the chains and a simple solvent at any time t, fails for binary blends of long and short linear polyisoprene (PI) chains at intermediate t, as revealed from comparison of viscoelastic and dielectric data. In contrast, the partial-DTD picture considering the extent of DTD determined by the constraint release (CR) process gives much better description of the data. The failure of the full-DTD picture and success of partial-DTD picture are noted also for star-branched PI chains. The partial-DTD picture, achieving consistent coarse-graining of the length and time scales, would serve as a good starting point for constructing refined models.

Melt compounding with a twin-screw extruder was used to prepare exfoliated polypropylene (PP) nanocomposites of organophilic montmorillonite clay compatibilized with maletaed polypropylene (PPgMA). Several grades of PPgMAs of different melt flow indices (MI) and molecular masses were analyzed for the effectiveness of melt exfoliation of organoclay. The extent of clay exfoliation in the nanocomposites was confirmed by X-ray diffraction spectroscopy. It was found that the nanoscale dimensions of the dispersed clay platelets led to significantly increased oscillatory shear flow properties. At a clay loading of 5%(mass fraction), which is much smaller than that of conventional macrocomposites, the hybrid materials exhibited unbound increase of shear viscosity at low frequencies; and nonterminal low-frequency plateau in the linear storage modulus. The relative dynamic properties revealed a systematic trend with the state of exfoliation and dispersion in the nanocomposites.

The linear Mohr-Coulomb and nonlinear Hoek-Brown failure criteria, which neglect the effects of intermediate principal stress, are widely used in soil and rock engineering. However, much experimental data shows that the failure envelope relates to the intermediate principal stress. Employing the failure criterion and the generalized plastic potential function, the stability of rock cavity driven in an isotropic and homogeneous medium was investigated under the condition of plane strain considering the effects of intermediate principal stress. The closed-form solutions for stresses and displacement around a rock cavity were given in the elastic and plastic zones. Based on the closed-form solutions, the intermediate principal stress has an important effect on cavity stability.

The rheological behavior and wall slip phenomena in the shear flow of a commercial polymethylvinylsiloxane (PMVS) and a high density polyethylene (HDPE) were studied by using a rotary rheometer with parallel plates fixtures. The damping function obtained from the stress relaxation experiment was compared with the prediction results of Doi-Edwards theory with the independent alignment approximation (IAA) and that of Marrucci et al model. Wall slip phenomena in the steady shear flow for PMVS and HDPE were studied by checking the gap dependence of the shear-stress and shear-rate relation. The results show that when strain grows, the discrepancy between the experiment and theory increases probably in that single reptation considered is not enough for polydisperse systems. As the strain applied in stress relaxation increases, more than one peak stress values are obtained, suggesting that strain localization or stratified strain may occur inside the samples. In the shear stress range from 100 to 5 000 Pa, anomalous slip behavior can be observed for PMVS, while no obvious slip for HDPE.

Relaxation behavior and shear-induced isothermal crystallization of two commercial high-density polyethylenes (HDPE) were investigated by using a rotational rheometer with cone-plate configuration. The excessive free energy was estimated by the measured shear stress and the first normal stress difference, based on a model proposed by Marrucci, in which the molecular orientation brought about by shearing was responsible for the increase of free energy. The results show that a small change of free energy can significantly increase the crystallization rate, thus the induction time of crystallization decreases rapidly as the shear rate increases. The excessive free energy and the induction time of isothermal crystallization can be correlated by an exponential function.

This paper presents experimental observations and numerical simulations of six polyethylene melts with different molecular structures in the planar flow with a confined slit. The polyethylene melts investigated include three low-density polyethylene grades (LDPE), two high density polyethylene grades (HDPE), and one linear low density polyethylene (LLDPE). The objectives are to reveal the differences in the rheological and processing flow properties of these polyethylene melts, and correlate those properties with their molecular structures. Through this study, the author would also like to present a successful approach using simple shear data, in terms of a Wagner integral constitutive equation, to predict processing flow behaviors of polymer melts at a reasonable accuracy.

The influence of relative molecular mass (MM) of LLDPE on the rheological, thermal and mechanical properties of two sets of m-LLDPE/HDPE blends of low and high branch content (BC) was studied. Blends of m-LLDPE with linear HDPE reveal no influence of MM (60–100 kg/mol) on melt miscibility at low BC (about 20 branches/1 000 C). However, at high BC levels (about 40 branches/1 000 C), MM affects the melt miscibility of m-LLDPE/HDPE blends. The DSC results suggest that compatibility in the solid state is independent of MM and BC. For all blends studied, the HDPE-rich blends are found to contain single crystal populations, suggesting high degree of cocrystallization, whereas, m-LLDPE rich phase shows separate crystallization. Mechanical properties of these blends are found to be a strong function of blend compatibility and the specific properties of the blend components. In general, the high BC pairs show poor mechanical properties.

A tree gum which is mainly composed of natural heteropolysaccharides, namely PG gum, was presented. The rheological characteristics of PG gum based drilling fluids at different concentrations and aging temperatures were studied by means of a rotating rheometer. The effects produced by the addition of inorganic salts (NaCl and CaCl₂) on the rheological properties of PG gum based drilling fluids were also studied. The results show that PG gum based drilling fluids investigated behaves as non-Newtonian shear-thinning fluids. With the increase of PG gum concentrations from 0.5% to 2.5%, the consistency coefficient increases while the viscosity behavior index decreases. The aging experimental data indicate that temperature has a slight effect on the rheological properties of PG gum based clay suspensions when the aging temperature is below 120 °C. Whereas, when temperature is above 120 °C, the rheological parameters of the suspensions, containing apparent viscosity, plastic viscosity and yield point, decrease significantly. The PG gum shows a better resistance to an increase in salinity or divalent cations concentration.

A thermotropic liquid crystalline polymer (TLCP) based on hydroxybenzoic acid, hydroquinone and sebacic acid was used as a processing aid in the extrusion of high molecular mass polyethylene (HMMPE)/clay nanocomposites. Clay/TLCP with optimal mass ratio loading in HMMPE matrix has better thermal stability than that of clay or TLCP blends. Capillary rheometry experiments were carried out at processing temperature 190 °C with TLCP in the full nematic phase. TLCP is an effective processing aid agent with viscosity reduction in excess of 95%. The mechanism is proposed and analyzed by morphological study and surface analysis. TLCP has been shown to act as both a compatiblizer between nanoclay and the HMMPE matrix and a processing aid for the nanocomposite.

Organoclay was dispersed in polystyrene of five different relative molecular mass by melt blending. Melt rheology was used to screen the resulting nanocomposite samples for a plateau in the elastic modulus G′. Presence of this plateau behavior indicates a solid-like network in the blend, brought about by dispersion of the organoclay. Using the values of the G′ plateaus for the PS blends, a percolation theory was tested for the nanocomposites and two solvent/organoclay blends. Lowering the blending temperature to take advantage of high mixing viscosity and subsequent high mixing stress allowed for stronger networks to be formed than when processing conditions favored increased diffusion. A constant viscosity mixing study shows that the relative molecular mass is the most prominent variable affecting dispersion in PS nanocomposites and has reaffirmed the importance of stress over diffusion. By applying high stress to 18 kg/mol PS with 1% organoclay, we were able to disperse the clay to an aspect ratio of 60. Several master batching methods and PS-NH₂ compatibilizer were also considered.

An experimental study was carried out to investigate phase and flow behavior of hydrophobically modified hydroxyethyl cellulose (HMHEC) solution with or without nonionic surfactant C₁₂E₅. Shear thickening behavior is observed at moderate shear rates for pure HMHEC solutions at modest concentrations. Shear thickening becomes less significant with increasing temperature and disappears at temperature reaching 25 °C for 0.2%(mass fraction) HMHEC. Also, the shear rate at which the maximum viscosity occurs increases with temperature. Addition of a very small amount of C₁₂E₅, even below its critical micellar concentration, can promote the thickening and the strongest thickening occurs at around 6×10⁻⁵(mass fraction) C₁₂E₅. A further addition, however, can suppress the thickening phenomenon that eventually disappears at high enough C₁₂E₅ concentrations. It therefore implies that when the surfactant reaches a certain amount and starts to weaken the gel strength, the imposed flow can no longer enhance the networking. While the pure HMHEC solutions always remain a single phase, phase separation takes place for polymer-surfactant mixtures when the C₁₂E₅ concentration exceeds about 1.5×10⁻⁴.

The rheological characteristic of polymer solution directly influences the oil displacement efficiency in the process of polymer flooding, and it is necessary that rheological characteristics of polymer solution used in polymer flooding are researched. Loss modulus and storage modulus of polymer solution with different mass concentration and relative molecular mass are studied and the relationship between them is analyzed through steady and dynamic shear experiments. The first normal stress difference at low angular rate is calculated based on loss modulus and storage modulus, and combined with the first normal stress difference obtained by steady shear flow experiments at high shear rate. The first normal stress differences at a wider range of shear rate can be obtained and the relationship between the first normal stress difference and shear rate is set up. The results show that the relationship established between the first normal stress difference and shear rate at wide range shear rate is feasible. The higher the mass concentration or the relative molecular mass of polymer solution is, the higher the first normal stress difference coefficient is.

The small-deformation shear behavior at 25 °C of 1%–4%(mass fraction) cross-linked waxy corn starch (CWCS) and 0.5%(mass fraction) κC mixtures with and without KCl were studied. Dispersions were heated (1.5 °C/min) to 90 °C, held for 10 min, then cooled (1.5 °C/min) to 90 °C. When the volume fraction of CWCS is about 0.5 to 0.7, the rheological behavior is governed by the continuous phase, while above these values the disperse phase dominates the rheological behavior. When carrageenan is in a disordered state without KCl, the swollen granules are dispersed in a macromolecular solution. With KCl, the rigidity of the gels increases by effect of CWCS, carrageenan and salt concentrations. However, salt concentrations above 100 mmol/L lead to a marginal increase in rigidity. Results can be interpreted in terms of two types of systems: particles suspended in a macromolecular solution and composite gels of particles embedded in a network matrix when both κC and KCl were added.

An equimolar mixture of a cationic surfactant, cetylperidinium chloride (CPyCl) and the salt sodium salicylate (NaSal) forms wormlike micelles in aqueous solutions. Under shear, the solution shows a pronounced shear-thickening behavior, which is coupled with oscillations in shear rate and the apparent viscosity. In this shear-thickening regime the formation of shear-bands is observed, which also oscillate in position and intensity. Fast Fourier Transformations (FFT) of the oscillating shear rate and intensity signals show a single dominating frequency in the power spectrum analysis. This characteristic frequency as well as the amplitude of shear rate oscillation is found to increase with stress. Experiments performed in transparent parallel-plate geometry show dampening of the shear rate oscillations and increase in the characteristic frequency with decrease in the gap. Rheo-small angle light scattering and rheo-optical techniques confirm the formation of different kinds of structures at smaller gaps.

A theoretical analysis of the phenomenon of boundary layer separation flow in power law pseudoplastic non-Newtonian fluids was made. Bifurcation solutions for skin friction were numerically represented for parameters of velocity ratio and power law exponent. The results indicate that both superior and inferior solutions are noticeable and the solutions not only depend on the velocity ratio of the plate to the velocity of the free stream, but also on the power law parameter.

The steady-state rheological properties of poly (m-phenyleneisophthalamide)(PMIA) in 1-n-butyl-3-methylimidazolium chloride [Bmim]Cl and DMAc/LiCl solutions are presented. The polymer in the concentration range investigated exhibits very different behavior between [Bmim]Cl and DMAc/LiCl solutions. Unlike in DMAc/LiCl solvent, PMIA/[Bmim]Cl solution exhibits maxima in apparent viscosity-concentration plots in the range studied. PMIA shows wormlike chain model when dissolved in DMAc/LiCl while the rodlike chain model in [Bmim]Cl. The different rheological behavior shows polymer-ionic liquids interaction which leads to the supermolecular aggregates in PMIA/[Bmim]Cl solution.

A series of experiments was carried out using a rolling-type tribometer to investigate the effects on friction behavior of the entraining velocity of the lubricant (ν) at the inlet to the contact zone and sliding velocity during deformation (Δν). Experiments with stainless steel sheets of two different surface roughness show that the variations in the friction coefficient with entraining velocity and sliding velocity are largely dependent on the initial surface texture of the workpiece. For a smooth workpiece, the friction coefficient decreases with increasing sliding velocity but keeps almost constant with increasing entraining velocity. However, for a rough workpiece, the friction coefficient initially decreases slowly and increases largely with increasing sliding velocity or decreasing entraining velocity. Observation of the rolled surface for a smooth workpiece shows that, with increasing entraining velocity, the slip band becomes more marked, and with increasing sliding velocity, the rubbed portions become more conspicuous. For a rough workpiece, galling occurs at high sliding velocity. The critical condition for galling outbreak is shown on the ν-Δν graph. The galling outbreak process is observed by interrupting the rolling process.

Polymer flooding for enhanced oil recovery (EOR), especially using polyacrylamide (PAM) based systems, gradually became the largest non-Newtonian fluid process of economic significance. Yet, the mechanistic understanding lags behind. In this paper, the relations of structures — rheological properties — EOR applications were reviewed and some recent laboratory studies on associated PAM and PAM soft gels were introduced. The multi scale understanding of polymer rheology was found to be an essential factor for future developments.

The change of interfacial viscoelasticity along with measuring time, the effect of polymer concentration and the type of polymer on interfacial viscoelasticity at the interface between polymer and dodecane were investigated by means of dilatational method. Moreover different viscoelasticity at different interfaces for polymer solution was also found. The result shows that the response of interfacial adsorption process can be made by interfacial viscoelasticity. Elasticity plays an important role in polymer/dodecane system even though contribution of viscosity in viscoelasticity goes up along with the increase of polymer concentration. Among those three interfaces, numerical value of viscoelasticity at polymer/air interface is the largest one, numerical value of viscoelasticity at polymer/dodecane interface the second, numerical value of viscoelasticity at polymer/crude oil interface the smallest. In addition, measurement of interfacial rheology is a useful method to evaluate polymer solution.

Several rheological phenomena involve discontinuities of some sort. Three of such non-linear effects were discussed in this contribution. The yield stress in suspensions, the bubble volume-velocity jump in multiphase systems and the stress jump in viscoelastic liquids were all considered.

The small-deformation behavior of single Newtonian oil drops covered by an adsorbed viscoelastic protein layer and suspended in a Newtonian protein-free matrix phase was investigated in simple shear flow. A simple but effective technique is presented to coat the drops with a layer of surface-active protein (lysozyme), which was adsorbed irreversibly to the oil/water interface. The adsorption and network formation at the interface are tracked by interfacial shear and dilatational rheometry using a biconical disk interfacial rheometer and pendant drop tensiometry. While the clean drop is deforming to the expected ellipsoidal shape in shear flow according to the Taylor theory, the protein-covered drop is able to resist the bulk shear stress to a much higher degree. We propose that this effect is due to the adsorbed protein, which is known to form strong, gel-like viscoelastic networks when adsorbed at oil/water interfaces.

The rheological properties of cellulose fiber suspensions were examined using a parallel-plate type rheometer. The suspensions consisted of various concentrations and types of cellulose such as: bacterial cellulose, microcrystalline cellulose made from cotton, fibrillated cellulose fiber and softwood pulp fiber. The dynamic moduli of the suspensions were almost independent of angular frequency. The concentration dependence of the moduli was discussed from the viewpoint of scalar transport of momentum. It can be said that these suspensions are in solid like under the measured condition. The dynamic storage moduli(G′) of the fiber suspensions show a strong dependence upon fiber concentration(c). The exponent is 9/4 for all the suspensions with three-dimensional isotropic networks. The value is consistent with that theoretically required for polymer gels. In contrast, the exponent is 3 for wet pulp fiber webs, which have laminated network structures, and 5 for a bacterial cellulose membrane with another laminated structure. This indicates that the exponent itself reflects the intrinsic properties of the fiber network structures. On the other hand, the front factor(k) of the power relation varies with the fiber axial ratio and fiber flexibility. Therefore, the factor reflects individual fiber characteristics. A simple two-dimensional lattice model is proposed to explain the power law.

Heat transfer in thin layers of magnetoelectrorheological fluids based on the γ-Fe₂O₃ and CrO₂ non-colloidal particles was studied in the presence of electric and magnetic fields. DC electric field causes significant rise of the heat transfer coefficient due to appearance of electroconvective vortexes in the volume of suspension. It is found that these vortexes can be effectively suppressed by applying magnetic field. AC electric field creates needle like structures lined up along the field in the volume of suspension. In the latter case the applying of magnetic field causes agglomeration of solid phase of suspensions in the vicinity of electrodes.

The mechanical properties of certain magnetorheological(MR) fluids were investigated and design method of the circular plate MR fluids brake was presented theoretically. The equation of torque transmitted by the MR fluids in brake was derived to provide the theoretical foundation in the design of brake. The design formulation of circular plate MR fluids brake was obtained. Based on this equation, the important impact parameters were discussed. After mathematically manipulated, these parameters such as the calculations of the volume, thickness and width of MR fluids within the circular plate MR fluids brake were yielded.

Magnetorheological(MR) fluids are intelligent materials whose mechanical properties will change with the magnetic field strength. Based on this behavior, the MR fluids can be used in wide practice fields. The constitutive equation is the most important problem of research of MR fluids. The mechanical experiments of a sort of MR fluids were conducted. By the Maxwell model, the visco-plastic behavior of magnetorheological fluids was discussed by a simple mechanical model. Then a new constitutive model was developed. The parameters of this model were investigated. The relation of the stress of MR fluids and the magnetic field strength was analyzed by this equation. The agreement of calculated curves with the experimented ones are very satisfactory. The results show that this constitutive model can be used to explain the mechanical properties of the MR fluids.

Magnetorheological fluids(MRF) are smart materials consisting of silicon oil and very small soft-magnetic particles. In a magnetic field, the viscosity and the flow behaviour of the fluid are considerably changed. MRF damper is a device to give damping by the shear stress of MR fluids. A MRF damper has the property whose damping changes quickly in response to an external magnetic field strength. The design method of a new MR fluid damper is investigated theoretically and the structure is presented. The equation of the damping by MR fluids within damper is derived to provide the theoretical foundations in the design of the damper. Based on this equation, after mathematical manipulation, the calculations of the volume, thickness and width of the annular MR fluids within the MR fluids damper are yielded and discussed.

Owing to the limits of formulation design and price of electrorheological fluid(ERF), as well as construction and performance of existing fluid unit, the test on fluid power transmission of ERF was carried out rarely. Based on Bingham rheological model, the basic equation of motion of ERF was put forward, then the control equation of ERF control unit was deduced. Through theoretic analysis, design principles of ERF control-unit was proposed. According to an experimental approach and a computer simulation, the correctness of the design principle is proved, it is the controllability of ER control-unit used in fluid power transmission.

The magneto-rheological (MR) response, like the better studied electro-rheological (ER) response, refers to the rapid and reversible viscosity increase seen in certain types of suspensions. The development of a 3D numerical simulation that is able to model the microstructural evolution of MR suspensions including hydrodynamic inter-particle interactions was reported. The current method is essentially a reduced version of the Stokesian Dynamics (SD) method^[1] with modifications to model the MR response. MR particles were modeled as rigid magnetizable spheres suspended in a Newtonian fluid. The Rotne-Prager Yamakawa tensor was used in the construction of the resistance matrix. Wall hydrodynamics were included with a formulation for sphere-wall interactions. MR forces were incorporated using superimposed sphere-pair dipole interaction forces. In simulations, particle cluster formations were observed, and the rheological responses due to these formations were examined. Some basic flow scenarios were studied, including periodic infinite shear flow under a constant magnetic field. MR suspensions are prone to suffer from sedimentation when unused. Their response may therefore be sluggish after an extended period of rest. We apply the simulation to the case of the re-suspension of sedimented suspensions (both normal and MR).

A disc-shape electro-rheological actuator was developed. The torque generated by a pair of rotary discs consists of two components: the torque from the viscosity of electro-rheological fluid(ERF) and the torque owing to the field-dependent yield shear stress. The former contributes to the viscous power loss. Changing the application of electric field between the two discs, the output torque of ER actuator can be controlled to amplify the torque of input signal to overcome the load and friction. Relationships between the main structure parameters, the dynamic characteristics of the device, the physical properties of ERF and the torque transmission, range of speed regulation, power loss, stiffness of system were discussed. A multi-object programming model was set up for the optimization design. Experimental simulations with step and pulse signals were presented.

An electrorheological(ER) actuator with double driving discs rotating at the same speed in the opposite directions was designed for studying the electrorheological torque experiments. The dynamic model of the disc transmission system consists of the linear part between the output angle and the electric torque, and the nonlinear part between the electric torque and the applied field strength dependent on the ER fluids. Using only the output sampled torque signals, an autoregressive model, the auto-spectral density function, the autoregressive(AR) bispectrum and the slices of the bispectra, taken to analyse the torque dynamic response, are obtained when a zero mean and non-Gaussian white noise interferes with the rotary disc system. The method for AR model order selection based on bispectral cross correlation is proposed and employed to determinate the model order. The experimental and theoretical results show that the time series analysis method and the parametric bispectrum might be helpful to establish the dynamic model of an ER actuator and to quantitatively analyse the torque response.

Creeping performance is one of the typical rheological properties. Creep tests under the same temperature and different stress levels were done on carbon constructional quality steels, the integral creep constitutive equation and differential stress-strain constitutive relationship were established according to relevant rheological model, and the integral core of the creep was achieved through the experiments. Moreover, the coefficient related with viscosity of 35 steel was obtained through creep experiments’ data. The viscosity coefficients of TC11 titanium alloy and Lc4 aluminum alloy were also compared and analyzed.

In order to describe the mechanical behaviors of viscoelastic material more accurately, the effect of damage on the constitutive model of viscoelastic material is necessary to be considered. The basis of building viscoelastic constitutive model with growing damage is to develop all kinds of measuring methods for damage, and then to obtain the damage evolution equation. Based on LEMAITRE-CHABOCHE’s damage model and the elasticity recovery correspondence principle, a novel measuring approach for damage of viscoelastic material was developed. In this approach, the recovered elastic stresses or strains in loading and unloading were obtained using the elasticity recovery correspondence principle, then the instantaneous elastic responses were gained, and a set of damage values were achieved by applying LEMAITRE-CHABOCHE’s damage model, the damage evolution equation and the constitutive model with damage were deduced finally. The measuring approach for damage is suitable not only for the case of axial tension, but also for the case of fatigue.

The numerical solution procedures for viscoelastic material subjected to deformation and mechanical damage were concerned. The analyses were based upon the constitutive model of viscoelastic material with damage derived from the elasticity recovery correspondence principle and Lemaitre-Chaboche’s damage model. The uniaxial tensile tests for specimens made of polymeric materials were carried out under different strain rates at room temperature, and the stress vs. strain curves were simulated by the constitutive model of viscoelastic material without damage. The results show that the stresses predicted by the model fit with experimental stresses moderately even if damage is not considered when the strain is smaller than a certain strain threshold. But when the strain exceeds this threshold, the damage parameter should be introduced into the constitutive model. It is verified that the constitutive model with damage proposed can more accurately estimate the stress response of a class of viscoelastic particle-reinforced composite, such as solid propellent, than the constitutive model without damage.

Nickel foam is well suited for battery applications such as in portable computers and mobile phones, and the use of it leads to a considerable increase of the energy density, whereas a high tensile strength is necessary for smooth processing of the foam during the battery production steps like ‘pasting’, calendaring and coiling. In order to understand the mechanical properties of nickel foam, the quasi-static uniaxial tensile tests of open-cell nickel foams with relative density of 0.039 were performed at room temperature. The empirical constitutive equation of this material was established, the anisotropy property of foam was recorded and analyzed. The results show that nickel foams present a significant anisotropic character, and the empirical constitutive equation used can predict quasi-static tensile response of the nickel foams well.

The mechanical behavior of two aluminum foams including open cells and closed cells with a variety of densities at room temperature and under compression loading was studied. Their response to strain rate was tested over a wide range of strain rates, from 1.0×10⁻³ to 1.6×10³ s⁻¹. The dynamic compression tests were made by Split Hopkinson Pressure Bar (SHPB) and the quasi-static tests were conducted using a displacement controlled CMT5305. Within this range, the experimental results show that all the compressive stress-strain curves of aluminum foams have three deforming regions such as linear elastic region, collapse region, and densification region. Aluminum foams have strengths that increase with increasing relative density and fall well below predictions of the Gibson-Ashby theory. For the open cell foam the stress is sensitive to the strain rate. However, the stress of the closed cell foam exhibits little or no strain rate sensitivity. Two aluminum foams with different cell structures exhibit different deforming models in the compressive tests. During the deformation of closed cell foams the deformation is not spatially uniform. However, there is no apparent collapse band and plastic deformation is homogeneous for open-cell foams.

Seven different types of phenol formaldehyde (PF) resins samples with five different pH values were used in order to investigate the effects of resin pH on the creep behaviour of cured PF resins. The results suggest that the effect of resin pH value on the creep behaviour of PF resins is significant. Alkali presence increases the hygroscopicity and enhances time dependent creep of PF resins due to the plasticisation of adhesive. The PF resins with a high pH have great potential to develop delayed elastic creep. The acidified resins also develop greater creep rate. Resols reacted under acidic conditions may form linear linkages. These structural changes in cured resins will increase the flexibility of these resins, and thus, enhance the creep rate and therefore improve stress relaxation in glue lines.

Stress induced change in intrinsic time scale was investigated by nonlinear creep tests of polypropylene (PP) at room temperature of 27 °C. The time-dependent axial elongations of the specimen were measured at 5 different stress levels, from 10.2 to 20 MPa, and modeled according to the time-stress superposition principle. The test duration was only 1 h. The test results show that the creep compliance vs logarithm time curves at different stresses depart from each other, indicating nonlinear viscoelastic behavior, and can be horizontally shifted to overlap onto a smooth master curve up to 51.5 h at the reference stress of 10.2 MPa. It is demonstrated that the time-stress superposition principle provides an accelerated test technique to evaluate the materials’ long-term mechanical properties.

Conservation of natural resources and preservation of environment are the essence of any development. The use of recycled aggregate concrete(RAC) is an attempt and an answer to some of the problems in constructional engineering. So recycling the decasting concrete catches more attention in the world. It depends on the strength for construction bearing to utilize recycled concrete(RC), but the strength calculation formula of RC has not been put forward yet. There is a linear relation between the common concrete compression strength and cement strength with cement-water mass ratio, whether this relationship also exists in recycled concrete or not it should be verified by experiment. Based on some experiments, the relationship between recycled concrete compression strength and its cement-water mass ratio was established, and the method to determine A′ and B′ values in Bolomey Formula was discussed.

The dependence on the temperature and stress level of PMMA’s crazing damage was researched through the real-time and on-line experiment of PMMA’s crazing damage at different temperatures and stress levels under creep condition. Based on the theory of time-temperature superposition principle, the WLF equation on time-temperature-stress of PMMA’s crazing damage was obtained. By dealing with the experiment data, we got the parameters of WLF equation.

There are a large number of random distributing pores and cracks in rock mass, and the initial damages of different causes of formation may be grown with engineering action or changes of all kinds of natural conditions, and the physical and mechanical properties of rock are changed and the structure of rock mass is also changed. At the same time, not only the rock caverns located under groundwater table are subjected to the coupling action of stress field with seepage field, but also the deformation of surrounding rock varies with time. In order to consider these effects in the process of hydro-mechanical coupling, the rheological damage model of hydro-mechanical coupling was set up, based on the fundamental theories of rock mass hydraulics and rheological mechanics and damage mechanics. The according finite element analysis (FEA) formulas for rock mass were derived, and the concretely executive process was given for the FEA of coupled stress field with seepage field under the condition of considering rheological and damage for rock mass. The rheological damage model established may be applied to the long-term stability analysis for underground caverns and slope engineering under the condition of hydro-mechanical coupling.

The layer composite rock mass is composed of soft rock and hard rock. The difference of their mechanical characteristics is obvious. So it is difficult to describe comprehensively the complicated property with the existent constitutive model. Based on the creep properties of soft rock and hard rock in the composite rock mass and the creep experiment curves, the creep model was used by connecting Burgers model in series with a plastic component. The creep curves of the composite model under diverse stress levels were attained by multi-staged loading. The simulated result was proved to be good by comparing the theoretical curves and the experimental curves. The rheology principium of the complicated rock mass was illuminated well by the model so that it can be popularly used in engineering practice.

Based on different surrounding rock classifications, the numerical simulation of visco-elasto-plastic surrounding rock was studied for three roadway tunnels with small spacing, especially analyzing the visco-elasto-plastic effect in the process of rock mass excavation by the step. By the numerical imitation and comparing analysis, the damage characteristic and the deformation law of surrounding rock were given under the same construction method for different surrounding rock classifications of three driveway tunnels, and the deformation law of interval wall and the relationship between the surrounding rock classification and the interval were obtained under the particular construction method for tunnels with small spacing. The minimum interval was selected for engineering design reference under the same excavation way, and a set of reasonable value ranges was given. The reference data and the theoretical basis were provided for the development and construction design of roadway tunnels with small spacing.

The effects of cracks and materials on nonlinear dynamics behaviors of cracked viscoelastic plates were investigated. Based on the nonlinear plate theory and the isotropic viscoelastic constitutive relation, the nonlinear dynamic equations of the viscoelastic thin plates with an all-over part-through surface crack were derived, and the corresponding boundary conditions and the crack continuity conditions were also introduced. In order to satisfy the boundary conditions and the crack continuity conditions, the suitable expressions of stress functions and deflection shape functions were put forward. In the example calculations, the materials of the plate were assumed to be standard linear solid, and the movable simple supports on four edges of the plates were adopted as the boundary conditions, moreover, in the crack continuity conditions, the Rice crack model was applied. Under the action of transversely distributed simple harmonic loads, and with the use of the Galerkin procedure, the numerical results of the bifurcations and chaos of the cracked rectangular viscoelastic plates were obtained and then expressed by the Poincare maps. According to the numerical results and the Poincare maps, the effects of the crack-depth and the crack-location, as well as the viscoelastic parameters, on the bifurcations and chaos of the plates were discussed. And some significant conclusions were obtained: 1) when the crack-depth increases or when the crack-location approaches the center of the plates, the motions of the plates are changed from single period to periodic bifurcations and then to chaos; 2) when the viscoelastic material parameter increases, the motions of the plates are changed contrarily from chaos to periodic bifurcations and then to single period states.

Polymethyl methacrylate(PMMA) is a kind of typical viscoelastic polymer materials, whose deformation and rheologic fracture are related not only with time and temperature, but also with strain rate on loading. By the quasi-static uniaxial tension test at defferent loading rates, the strain-rate-dependent stress-time equation of PMMA material was gotten with H-K mode. In the range of given strain rates, tes, E₂(

) is almost not varied with strain rate, but E₁(

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) and η₁(

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) augment with strain rate reducing, which shows that viscosity of PMMA material responds more strongly; whereas, they reduce with strain rate increasing, which shows that the viscosity of PMMA material responds more feebly; when the strain rate is added up to infinite, E₁(

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) goes to constant and η₁(

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) to naught, which shows that PMMA material responds elasticity by constitutive mode. Based on the theory of continuum mechanics, median stress is defined as the ratio of fracture strain energy density to fracture strain, according to the energy conservation law and Cauchy median law. The median stress of PMMA is not related with strain rate in the range of the given strain rates, so it is represented as a parameter to scale the fracture of PMMA.

Segmental motion in polystyrene (PS) thin and ultrathin films supported on substrates was studied by dynamic viscoelastic measurement. A polymer film, which has the thickness comparable to or less than twice of radius of gyration of an unperturbed chain (2R_g), is defined as an ultrathin film. In the case of PS, α_a-relaxation process corresponding to the segmental motion was generally observed at approximately 380 K. Even for both the PS thin and ultrathin films, the α_a-absorption peak was clearly observed. A rheological analysis reveals that the α_a-relaxation behavior for the thin films with the thickness of about 200 nm is the same as that of the bulk sample. On the contrary, in the case of the PS ultrathin films, the α_a-absorption peak on temperature-loss modulus (E) curve is broadened toward both lower and higher temperature sides. This can be interpreted by taking into account that the segmental motion in the vicinity of surface and interface is detectable for such ultrathin films, which should be faster and slower than that in the bulk, respectively. And, it is found that the apparent activation energy (ΔH) for the α_a-relaxation in the ultrathin films becomes smaller than the bulk value probably due to the surface effect. Finally, an interfacial effect on the ΔH was studied by using different substrates. When the interaction between PS and substrate becomes stronger, the ΔH value for the α_a-relaxation in the ultrathin films increases. The results imply that the segmental motion in the polymer ultrathin films is strongly influenced by surface and interfacial effects.

Combined closely with the practical production of rectifier internal hood deep-drawing thermal forming, in order to provide parameters of material properties for the numerical simulation, the standard samples of TC1 Ti-alloy sheet of 0.8 mm in thickness were made, and the tensile tests under 8 kinds of different temperature and 4 sorts of strain rate were done so that the effects of material’s thermo-rheological mechanical properties are worked out.

The viscoelastic interaction between a screw dislocation in the matrix and a circular inhomogeneity with an interfacial crack under remote antiplane shear is dealt with. Utilizing the Laplace transform method, the viscoelastic problem is reduced to an associated elastic one. The viscoelastic solutions are presented in the transformed field by using complex variable method. The full stress field and the intensity factors of crack tips and the image force acting on the dislocation are derived analytically through Laplace inverse transform method. The numerical analysis and discussion results show that the image force depends much on the visco-effects of materials, which is different from the case of elastic materials. The influence of the location of dislocation and the length of crack upon the image force decreases obviously and evolves toward a stable terminal state as time elapses. The results presented in this study are in agreement with the previous solution as special cases.

The viscoelastic interaction between a screw dislocation and a circular interfacial rigid line under remote antiplane shear is investigated. By using the Laplace transform method, the viscoelastic problem is reduced to an associated elastic one. The viscoelastic solutions to this problem are presented in the transformed field by means of the complex potential technique. Then the full stress field and the image force acting on the dislocation are derived analytically through Laplace inverse transform. Especially, the closed form solutions for viscoelastic materials modeled by the standard linear solid are derived explicitly. Numerical analysis and discussion results show that the image force depends much on the visco-effect of materials and the image force will change direction as time elapses. The results presented are in agreement with the previously known solutions as special cases.

Hill’s quadratic yield criterion and flow theory is employed to describe anisotropic plasticity of sheet metal during forming procedure. Based on Continuum Damage Mechanics, an isotropic damage model is developed to give a damage-coupled localized necking criterion. Experiments of formality of sheet metal in three plane states are performed on IF steel. By measuring the density, the damage curves obtained are compared with calculation results based on the damage-coupled model, which shows a good coincidence. Furthermore, for the uniaxial and biaxial tension states, the relations between the damage of density and strain in thickness are analyzed, which helps to discuss the forming mechanism of IF steel sheet metal.

Polyblend behaviour in the single-screw extrusion process was studied. Melting mechanism for LDPE/PS polyblend was investigated, as well as a morphology development was observed. A computer model was developed to study polyblend behaviour. The model is based on the flow field description in the single screw extrusion process given by SSEM model.

By experimental investigation, the various viscous models are compared and evaluated. The proper viscose model is selected for the application in the metal powder injection molding processing analysis. The effects of the different processing parameters, such as the viscose parameters, temperature, pressure, die cavity size on the isothermal and non-isothermal cavity filling processing are simulated. The optimized injection pressure and die geometric size are determined.

The different tungsten powder injection molding feedstocks were prepared by changing the additive concentration and tungsten powder loadings. The rheological evaluation includes the viscosity measurements and its sensitivity to the shear rate, the temperature and the binder components were studied. The viscous activation energies of some feedstocks were calculated and the mechanism of the additives effect on the rheological behavior were investigated.

By introducing the lattice model, the relationships among interaction energy and particle size and solid loading in the metal powder injection molding(MIM) feedstock were established. With the help of interaction energy relationships, the interactions between the particles and the binder polymer in the Fe-Ni-PW-PE MIM feedstock system were analysed. According to the theoretical study and rheological experimental investigation, the relationship between the shear stress and the shear rate was determined. The microstructure of the Fe-Ni-PW-PE MIM feedstock was observed by scanning electron microscopy. The uniform microstructure is obtained.

The slot die coating of poly (vinyl alcohol, PVA) solutions with particles such as TiO₂ and SiO₂ added was examined. The physical properties such as viscosities and surface tensions of PVA solutions with particles were measured and analyzed. The coating experiment was carried out in a lab coater and a flow visualization technique was applied to observe the flow behavior in the coating bead region. The effect of different particles, particle sizes, concentrations and surface characteristics were analyzed on the operating window of PVA solutions. The results show that adding a certain amount of particles to PVA solutions can effectively expand the operating window of PVA solutions. The attraction of function groups of PVA to the particle surfaces is considered as the major factor to expand the operating window.

Sulfated konjac glucomannan gel beads(KGMSB) were prepared, its dynamic adsorption abilities for blood low-density lipoprotein and very low density lipoprotein cholesterol(LDL+VLDL-C) and the effect on hemorheology were studied. Konjac glucomannan(KGM) was used as raw material, after cross-linked by epichlorohybrin solution, and was then prepared into gel beads, hardened, and sulfated, final product KGMSB was obtained. The structure of KGMSB was observed by SEM. SEM analysis shows that KGMSB possesses cross-linked porous network structure. In vitro dynamic adsorption indicates that the adsorption rate for total cholesterol(TC), low-density and very low-density lipoprotein cholesterol(LDL+VLDL-C), high-density lipoprotein cholesterol(HDL-C) of KGMSB are (62.10±7.96)%, (63.42±8.27)%, (40.25±5.73)% (n=6), respectively. The ratio of HDL-C/LDL-C is increased by (30.12±7.07)%. The hemorheology studies show that whole blood viscosity and plasma viscosity are changed significantly (p<0.05). KGMSB can selectively adsorb LDL+VLDL-C from the whole blood, it can also reduce the blood viscosity and modulate hemorheology properties. KGMSB is a potential material to be developed into a novel blood LDL adsorbent.

In the transient solutions of fiber spinning and film casting process dynamics accompanied by spinline flow-induced crystallization was investigated incorporating flow-induced crystallization kinetics into the mathematical model of the system and then devised proper numerical schemes to generate the temporal pictures of the system. It turns out that the difficulty obtaining the transient solutions of the processes accompanied by flow-induced crystallization lies in, among these, the extremely high sensitivity of the spinline velocity towards the fluid stress level. The transient solutions thus obtained will be used for developing optimal strategies to enhance the stability and productivity of the processes.

Based on equivalent Mohr-Coulomb criterion theory, it was successfully applied to FEM software-Ansys by artificial conversion among rock mass parameters, and the size relation between the transformed parameters and original parameters were verified. At the same time, in allusion to rheological characteristics of rock mass, by making use of the theory of rheological model with fractional order derivatives, a practical calculative method in which rheological characteristics were taken into account was presented, and rheological problem of rock slope were managed by changing material characteristics in the process of elasticity-plasticity analysis, an example shows that this method is feasible.

For continuum, the displacement gradient can be divided into symmetry part and asymmetry part. Based on Chen Zhi-da’s research, the asymmetry part is related with an orthogonal rotation. But the definition of rotation angle in Chen’s theory is not correct for large deformation or rotation. The definition of rotation angle was improved to be suitable for large deformation or rotation. The results show that the displacement gradient can be divided into symmetry part and orthogonal rotation part. This result improves Chen Zhi-da’s S-R decomposition theoretic research and Finger-Truesdell’s polar decomposition theorem. Based on the new formulation of displacement gradient decomposition, it shows that S-R decomposition can be extended to large deformation and large rotation cases. The symmetry part contains a coupling tensor directly related with rotation tensor, this coupling tensor causes that the strain defined significantly differ from actual value calculated based on measured stress field. The additional stress related with the coupling tensor is the function of square of elements of asymmetry part of displacement gradient. The strain defined on Finger-Truesdell’s polar decomposition theorem loses a factor related with expanding of rotation. As the rotation contains asymmetry stress, the traditional equilibrium equation only meets moment conservation, and the angular-moment conservation is derived to accept the asymmetry stress related with rotation. As the velocity gradient can be gotten by taking time differentiation of displacement, hence the results are also true for fluids.

Viscous effects on the drained stress-strain behaviour of kaolin (D₅₀=0.001 3 mm; plasticity index(PI) is 41.6, liquid limit (LL) is 79.6%) were evaluated by performing a series one-dimensional(1D) compression tests on saturated specimens. Cyclic loading with a large stress amplitude was applied during otherwise monotonic loading at a constant strain rate. In the tests, one observation consistent with the previous research is that, significant loading rate effects on the stress-strain behaviour of saturated clay due to the material viscosity, not due to the delayed dissipation of excess pore water pressure, were observed during not only primary monotonic loading but also unloading and reloading. The results in cyclic loading show that creep deformation characteristics change significantly by preloading history, which is simulated by incorporating the viscous property into a non-linear three-component rheology model having isotach type viscosity with hysteretic inviscid stress-strain property.

The frostbite situation of recycled concrete suffered one-time freezing was analyzed, and was then compared with that of the normal concrete. In order to improve the frost resistance of recycled concrete, antifreeze was used and good effect was obtained. The results show that the frost resistance of recycled concrete is inferior to that of recycled concrete. Differences exist in the microstructures of the recycled concrete and normal one, which makes the decrease of frost resistance. Antifreeze can improve the microstructure of recycled concrete, so the frost resistance of it is improved as well.

When the temperature of waxy crude oil is below the wax precipitation temperature, wax will precipitate out from oil solution. On further cooling, more and more wax crystals separate out and interlock to form a network that entraps liquid oil into its structure, resulting in gelation of the crude oil. The gelation extent and strength can be expressed with viscoelastic parameters. A controlled-stress rheometer RS150H was used to measure the viscoelastic parameters of Daqing crude under different history conditions by oscillatory shear experiment. The results indicate that the storage modulus and loss modulus increase in an exponential relation as the measuremental temperature is decreased. There exists a worst heating temperature for the rheological behavior. The strength of wax crystal structure and gelation temperature increase with decreasing cooling rate. Under the same shear temperature, the strength of wax crystal structure decreases rapidly and finally tends to a steady state as the energy dissipation due to viscous flow is decreased. Under the same energy dissipation due to viscous flow, the closer the shear temperature is to the measuring temperature, the lower the storage modulus, loss modulus and gelation temperature will emerge. When the shear temperature is close to or higher than abnormal point, the viscoelastic parameters vary little. The recovery of wax crystal structure after shear action exhibits an irreversible property.

Thermo-mechanical failures are the root cause of failures in integrated circuits. A major cause for these failures is the different coefficients of thermal expansion (CTE) of package materials. Compound material is necessary when assembling, which has different elastic modulus, poisson ratios and coefficients of temperature expansion under different temperatures. Therefore, the rheology of compound material used here is expected to have a pronounced influence on the local stress distribution in the passivation layer. The finite element simulations and the maximum principal stress theory are applied to investigate this influence, which paves the way for compound materials selection in IC packages.

The measurement on cellular concrete, mortar, hydraulic concrete and cold bituminous mixes are presented. A non-destructive device allows the setting to be monitored and to be clearly characterized. The device is based on the propagation of compressional waves. To prevent diffraction of waves from heterogeneities, a condition of long wavelength compared to the heterogeneity size is required, so low frequencies are used (about 800 Hz). Velocity and damping coefficients versus time are deduced, then related to rheological viscoelastic properties by an inverse analysis. The rheological evolutions of the different materials are presented and compared for different mix proportions.

The changes of the rheological parameters, such as apparent viscosity (µ_a), plastic viscosity (µ_p), dynamic yield stress (τ_yd) and static yield stress (τ_ys) with the proportion of KCl, silicate and bentonite were discussed. It is found that the acceptable values of µ_a, µ_p, τ_yd and τ_ys can be obtained when the mass ratio of bentonite, KCl and silicate is kept around 1:7:10. The effect of other factors, such as the particle size distribution of bentonite and zeta potential of clay, on the values of µ_a, µ_p, τ_yd and τ_ys is also discussed. This discussion result could pave the way for better understanding of the subtle interaction between KCl, silicate and bentonite particles.

In order to study the structural effect of soft rock rheology, the normal uniaxial compression test, and the triaxial compression test and the uniaxial compression creep test were performed using the similar material samples of soft rock with the single surfaces of different obliquities. On the basis of the test results a new multiple rheological model was put forward to describe the strong nonlinear creep and failure course of soft rock containing the structure face by combining two non-linear components of CYJ body and L body with the classic KELVIN body and HOKE body. Then the quantitative influence of the structure face and its varying obliquity on every strain component of soft rock creep was probed into so that the nonlinear experiential regressive equations between the obliquities of the structural surface and the mechanical parameters of the multiple model or the long-term strength can be gained. The results show that the creep deformation of soft rock contains components of the instantaneous elastic, instantaneous plastic, visco-elastic and the visco-plastic deformation and the existence of the structure face would enhance the capabilities of the instantaneous plastic, visco-elastic and the visco-plastic deformation when the soft rock creeps so that it shortens the time of the stable creep phase and hastens the appearance of the third phase of soft rock creep. In the meantime, the variation of the obliquity of the structure surface will make the creep failure of soft rock in one of three modes of “X” shear failure, the sliding failure along the structure surface and the mixture failure of shear and sliding.

Viscosity variation with temperature was measured by temperature scanning procedures in a coaxial cylinder viscometer. An eigen-temperature is found in viscosity-temperature chart generated from the temperature sweep experiment. It is the temperature corresponding to the maximum value of the curvature of a non-dimensional viscosity-temperature chart. The experimental results show that the eigen-temperature varies linearly with shear rate and cooling rate. Eigen-temperatures decrease either with decreasing the shear rate or with increasing the cooling rate. The eigen-temperatures of PPD-beneficiated crudes are more sensitive to the shear and cooling rate than those of virgin crudes. The eigen-temperature of virgin crude is almost equal to its pour point, while the eigen-temperature of PPD-beneficiated crude is much lower than its pour point. This indicates that the eigen-temperature may be applied to assess the flowability of waxy crudes with various shear and thermal histories, and may also provide a new means to evaluate the effect of PPD on the low-temperature flowability of waxy crude.