The present work reviews different decision making tools (material comparing and choosing tools) used for selecting the best material considering different parameters. In this review work, the authors have tried to address the following important enquiries: 1) the engineering applications addressed by the different material choosing and ranking methods; 2) the predominantly used decision making tools addressing the optimal material selection for the engineering applications; 3) merits and demerits of decision making tools used; 4) the dominantly used criteria or objectives considered while selecting a suitable alternative material; 5) overview of DEA on material selection field. The authors have surveyed literatures from different regions of the globe and considered literatures since 1988. The present review not only stresses the importance of material selection in the early design stage of the product development but also aids the design and material engineers to apply different decision making tools systematically.
Cast Al alloys are widely employed for engine components, structural parts, gear box, chassis, etc. and subjected to mechanical cyclic load during operation. The accurate fatigue life prediction of these alloys is essential for normal operation as fatigue cracks initiated during operation induce the lubrication oil leak and serious safety hazard. Microstructural heterogeneity, including shrinkage/gaspores and secondary phase particles, is the most detrimental factor that affects fatigue life of cast Al alloys. The approximate fatigue life cycles could be estimated based on the size distribution and locations of shrinkage pores/defects. The relationship between crack population and stress was reported by statistical distributions and the cumulative probability for cast Al alloys fail at a certain stress could be predicted by combination of Paris law and pore size distribution. Pore depth was found to dominate the stress field around the pore on the surface and the maximum stress increases sharply when the pore intercepted with the surface at its top. The microstructure of cast Al alloys usually is composed of primary Al dendrites, eutectic silicon, Fe-rich particles and other intermetallic particles are dependent upon alloy composition and heat treatment. The coalescence of microcracks initiated from the fractured secondary phases was clearly found and can accelerate the initiation and propagation of the fatigue cracks. A link between defect features and the fatigue strength needs to be established through a good understanding of the fatigue damage mechanisms associated with the microstructural features under specific loading conditions. This paper reviews the influences of shrinkage/gaspores and secondary phase particles, formed during casting process, on the fatigue life of Al-Si-Mg cast Al alloys.
Plasmon induced transparency (PIT) in the transparent window provides new insights into the design of optical filters, switches and storage, and integrated optics. The slow light effect makes PPIT applicable to both sensors and slow light devices. Besides, PPIT can overcome the diffraction limit of light, which makes it possible to manipulate light on a half-wavelength scale and brings good news to the miniaturization of optical devices. In this paper, we first summarize the researches of Pit phenomenon based on metal-dielectric-metal (MDM) waveguide systems and analyze the physical mechanisms of Pit including bright-dark mode interactions and phase-coupling-induced transparency. Then, we review the applications of Pit in optical sensing, optical filtering, optical switching, slow light devices and optical logic devices. At last, we outline important challenges that need to be addressed, provide corresponding solutions and predict important directions for future research in this area.
The Pb-free solders have attracted a great deal of attention recently due to the environmental concerns. The present work focuses on the effect of cobalt content (0, 0.5 and 3.0) on the microstructural characteristics, melting point and corrosion performance of extruded Sn-9Zn solder alloys. The results reveal that the Zn-rich precipitates with spherical or needle-like shape in the Sn-9Zn-xCo alloys are refined remarkably by forming the γ-Co5Zn21 and Co2Sn2Zn Co-contained intermetallic compounds, though the melting point and eutectic reaction temperature decrease slightly. It is suggested that the corrosion property of the extruded Sn-9Zn-xCo alloys is improved significantly by adding the cobalt element, while the content should be controlled reasonably. Combining the corrosion morphology, the influence of cobalt content on the corrosion behavior of the Sn-9Zn-xCo alloys is analyzed in terms of the refined microstructure and the enhanced passive film stability.
In the present work, TiAlN coatings were deposited on Ti(C, N)-based cermet substrates by physical vapor deposition method. Emphasis was focused on the influence of grain size of cermet substrates on the microstructure, growth behavior, mechanical properties, adhesion strength and wear behavior of the coatings. The results show that finer Ti(C, N) grain size leads to higher nucleation density and lower growth rate of coatings, indicating the crystallite size of the TiAlN coatings decreases with decreasing Ti(C, N) grain size. Nanoindentation tests show that the coatings deposited on cermets of the finest grain size exhibit the highest hardness (H), elastic modulus (E), H/E and H3/E2 of 34.5 GPa, 433.2 GPa, 0.080 and 0.22, respectively. The adhesion strength between coating and substrate is also enhanced with decreasing Ti(C, N) grain size by scratch test, which corresponds to the grain size and H/E and H3/E2 of the coating. Besides, the lower surface roughness and better mechanical properties of the coating deposited on finer grained cermet contribute to the better wear resistance of the coating.
Pearlitic ductile irons (PDIs) are used in transportation and nuclear energy industries. In heavy loading situation, the service life of PDI is affected by numerous tribo aspects. In this study, surface of the PDI is alloyed with WC-12%Co powder using a high power fibre laser. The wear properties of the base material and laser alloying samples were investigated by tribometer with various parameters, i.e., temperature, load and sliding speed. Based on experimental test, the load has maximum percentage of contribution and followed by sliding speed and working temperature. The optimized tribological parameters by Grey relational analysis (GRA) were established and those values are closely matched with predicted values. Besides, base material and laser alloying surfaces were examined through Vickers hardness machine, scanning electron microscopy (SEM) and roughness tester. The laser altered specimen shows no defects and improves the wear properties than substrates. The identified optimal tribological parameters are load of 30 N, speed of 0.5 m/s and working temperature of 300 °C, and load of 30 N, speed of 0.5 m/s and working temperature of 200 °C for base metal and laser alloying samples, respectively.
In the present work, paraffin phase change material is used as quenchant for the heat treatment of 42CrMo4 alloy and compared with water, air, and CuO doped paraffin. The samples were prepared based on ASTM E 8M-98 standard for tensile test and then heated up to 830 °C, kept for 4 h in an electric resistance furnace and then quenched in the mentioned media. Elastic modulus, yield strength, ultimate tensile strength, elongation, and modulus of toughness were determined according to the obtained stress-strain curves. Moreover, the hardness and microstructural evolution were investigated after the heat treatment at different media. The samples quenched in paraffin and CuO-doped paraffin are higher in ultimate tensile strength (1439 and 1306 MPa, respectively) than those quenched in water (1190 MPa) and air (1010 MPa). The highest hardness, with a value of HV 552, belonged to the sample quenched in CuO-doped paraffin. The microstructural studies revealed that the non-tempered steel had a ferrite/pearlite microstructure, while by quenching in water, paraffin and CuO-doped paraffin, ferrite/martensite microstructures were achieved. It is also observed that using the air as quenchant resulted in a three-phase bainite/martensite/ferrite microstructure.
Mg-Zn binary alloys fabricated by the gas-phase alloying technique under vacuum condition were investigated in the state of initial state and after heat treatment for the microstructure and electrochemical behaviors. Different from the traditional Mg-Zn alloys preparation methods, alloys prepared by gas-phase alloying have a large number of intermetallic compounds, such as MgZn, Mg7Zn3 and MgZn2. After solution treatment, the boundary of the eutectic disappeared and the size of α-Mg increased from 100 μm to 150 μm. At the same time, the value of the resistance of charge transfer increased, which indicates that the resistance of the charge transfer and the corrosion resistance of the alloys increased. After artificial aging treatment, the distribution of α-Mg was more uniform and its size was reduced to about 50 μm, and there was new eutectic structure formed. The newly formed eutectic structure forms galvanic cells with the alloy matrix, which makes the corrosion resistance of the alloy weaken.
The precipitation performance and kinetics of gibbsite from sodium aluminate solution with different sodium oxalate concentrations as well as the corresponding influence mechanism of oxalate during the seed precipitation process were systematically investigated by physicochemical properties test, using SEM and Raman spectra. As the concentration of sodium oxalate increases, both the precipitation rate and particle size of gibbsite decrease. The presence of sodium oxalate not only increases the viscosity of sodium aluminate solution, but also promotes the transformation of Al(OH)4- to Al2O(OH)62. The overall reaction rate constant decreases and the apparent activation energy of gibbsite increases with the increasing sodium oxalate concentration, the rate controlling step of which is chemical reaction. The needle-like sodium oxalate precipitates on the gibbsite crystals and covers the active Al(OH)3 seed sites, which leads to the lower precipitation rate and the finer particle size of gibbsite during the seed precipitation process.
Faulted gas reservoirs are very common in reality, where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties. This kind of gas reservoirs is also known as linear composite (LC) gas reservoirs. Although some analytical/semi-analytical models have been proposed to investigate pressure behaviors of producing wells in LC reservoirs based on the linear composite ideas, almost all of them focus on vertical wells and studies on multiple fractured horizontal wells are rare. After the pressure wave arrives at the leaky fault, pressure behaviors of multiple fractured horizontal wells will be affected by the leaky faults. Understanding the effect of leaky faults on pressure behaviors of multiple fractured horizontal wells is critical to the development design. Therefore, a semi-analytical model of finite-conductivity multiple fractured horizontal (FCMFH) wells in LC gas reservoirs is established based on Laplace-space superposition principle and fracture discrete method. The proposed model is validated against commercial numerical simulator. Type curves are obtained to study pressure characteristics and identify flow regimes. The effects of some parameters on type curves are discussed. The proposed model will have a profound effect on developing analytical/semi-analytical models for other complex well types in LC gas reservoirs.
In this work, hydrothermal method was used to prepare the CaZnAl-CO3 ternary layered double hydroxides (CaZnAl-CO3-LDHs) with various Ca/Zn/Al molar ratios, which were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FT-IR) and scanning electron microscopy (SEM) techniques. The obtained results demonstrate that the samples were well-crystallized and flake-structured. The CaZnAl-CO3-LDHs used alone for thermal stability of poly (vinyl chloride) (PVC) resin, with different Ca/Zn/Al molar ratios and varying additive amounts, were investigated through the tests such as static thermal aging, mass loss and congo red, respectively. The optimum Ca/Zn/Al molar ratio and additive amount were 3.6:0.4:2 and 5 phr (parts per hundred PVC resin), respectively. In addition, the synergistic effects of Ca3.6Zn0.4Al2-CO3-LDHs and CaSt2 were discussed in detail, showing better thermal stability compared with Ca3.6Zn0.4Al2-CO3-LDHs used alone, and the optimum additive amounts of Ca3.6Zn0.4Al2-LDHs and CaSt2 were 6 and 1.0 phr, respectively.
The measurement of the surface quality and the profile preciseness is major issues in many industrial branches such that the surface quality of semi products directly affects the subsequent production steps. Although, there are many ways to obtain required data, the hardware necessary for the measurements such as 2D or 3D scanners, depending on the problem’s complexity, is too expensive. Therefore, in this paper, what we put forward as a novelty is an algorithm which is verified on the model of simple 3D scanner on the image processing basis with the resolution of 0.1 mm. There are many ways to scan surface profile; however, the image processing currently is the most trending topic in industry automation. Most importantly, in order to obtain surface images, standard high resolution reflex camera is used and thus the post processing could be realized with MatLab as the software environment. Therefore, this solution is an alternative to the expensive scanners, and single-purpose devices could be extended by many additional functions.
In this study, we considered the three-dimensional flow of a rotating viscous, incompressible electrically conducting nanofluid with oxytactic microorganisms and an insulated plate floating in the fluid. Three scenarios were considered in this study. The first case is when the fluid drags the plate, the second is when the plate drags the fluid and the third is when the plate floats on the fluid at the same velocity. The denser microorganisms create the bioconvection as they swim to the top following an oxygen gradient within the fluid. The velocity ratio parameter plays a key role in the dynamics for this flow. Varying the parameter below and above a critical value alters the dynamics of the flow. The Hartmann number, buoyancy ratio and radiation parameter have a reverse effect on the secondary velocity for values of the velocity ratio above and below the critical value. The Hall parameter on the other hand has a reverse effect on the primary velocity for values of velocity ratio above and below the critical value. The bioconvection Rayleigh number decreases the primary velocity. The secondary velocity increases with increasing values of the bioconvection Rayleigh number and is positive for velocity ratio values below 0.5. For values of the velocity ratio parameter above 0.5, the secondary velocity is negative for small values of bioconvection Rayleigh number and as the values increase, the flow is reversed and becomes positive.
Due to the limited scenes that synthetic aperture radar (SAR) satellites can detect, the full-track utilization rate is not high. Because of the computing and storage limitation of one satellite, it is difficult to process large amounts of data of spacebome synthetic aperture radars. It is proposed to use a new method of networked satellite data processing for improving the efficiency of data processing. A multi-satellite distributed SAR real-time processing method based on Chirp Scaling (CS) imaging algorithm is studied in this paper, and a distributed data processing system is built with field programmable gate array (FPGA) chips as the kernel. Different from the traditional CS algorithm processing, the system divides data processing into three stages. The computing tasks are reasonably allocated to different data processing units (i.e., satellites) in each stage. The method effectively saves computing and storage resources of satellites, improves the utilization rate of a single satellite, and shortens the data processing time. Gaofen-3 (GF-3) satellite SAR raw data is processed by the system, with the performance of the method verified.
To evaluate the geotechnical properties of coarse-grained soil affected by cyclic freeze-thaw, the electrical resistivity and mechanical tests are conducted. The soil specimens are prepared under different water contents, dry densities and exposed to 0-20 freeze-thaw cycles. As a result, the stress-strain behavior of the specimen (w =14.0% and ρd=1.90 g/cm3) changes from strain-hardening into strain-softening due to the freeze-thaw effect. The electrical resistivity of test specimen increases with the freeze-thaw cycles change, but the mechanical parameters (the unconfined compressive strength qu and the deformation modulus E) and brittleness index decrease considerably at the same conditions. All of them tend to be stable after 7−9 cycles. Moreover, both the dry density and the water content have reciprocal effects on the freeze-thaw actions. The failure and pore characteristics of specimens affected by freeze-thaw cycles are discussed by using the image analysis method. Then, an exponential function equation is developed to assess the electrical resistivity of specimens affected by the cyclic freeze-thaw. Linear relations between the mechanical parameters and the electrical resistivity of specimens are established to evaluate the geotechnical properties of the soil exposed to freeze-thaw actions through the corresponding electrical resistivity.
The buoyancy effect on micro hydrogen jet flames in still air was numerially studied. The results show that when the jet velocity is relatively large (V≥0.2 m/s), the flame height, width and temperature decrease, whereas the peak OH mass fraction increases significantly under normal gravity (g=9.8 m/s2). For a very low jet velocity (e.g., V= 0.1 m/s), both the peak OH mass fraction and flame temperature under g=9.8 m/s2 are lower than the counterparts under g=0 m/s2. Analysis reveals that when V≥0.2 m/s, fuel/air mixing will be promoted and combustion will be intensified due to radial flow caused by the buoyancy effect. However, the flame temperature will be slightly decreased owing to the large amount of entrainment of cold air into the reaction zone. For V=0.1 m/s, since the heat release rate is very low, the entrainment of cold air and fuel leakage from the rim of tube exit lead to a significant drop of flame temperature. Meanwhile, the heat loss rate from fuel to inner tube wall is larger under g=9.8 m/s2 compared to that under g=0 m/s2. Therefore, the buoyancy effect is overall negative at very low jet velocities.
Textile-reinforced concrete (TRC) is suitable to repair and reinforce concrete structures in harsh environments. The performance of the interface between TRC and existing concrete is an important factor in determining the strengthening effect of TRC. In this paper, a double-sided shear test was performed to investigate the effects of the chloride dry-wet cycles on the average shear strength and slip at the interface between the TRC and existing concrete, also considering the existing concrete strength, bond length, textile layer and short-cut fiber arrangements. In addition, X-ray diffraction (XRD) technology was used to analyze the microscopic matter at the interface in the corrosive environment. The experimental results indicate that the interface performance between TRC and existing concrete would decrease with continued chloride dry-wet cycles. Compared with the specimen with a single layer of textile reinforcement, the specimens with two layers of textile with added PVA or AR-glass short-cut fibers could further improve the properties of the interface between the TRC layer and existing concrete. For the TRC with a single layer of textile, the average shear strength tended to decrease with increasing bond length. In addition, the strength grade of the existing concrete had a minor effect on the interface properties.
A series of true-triaxial compression tests were performed on red sandstone cubic specimens with a circular hole to investigate the influence of depth on induced spalling in tunnels. The failure process of the hole sidewalls was monitored and recorded in real-time by a micro-video monitoring equipment. The general failure evolution processes of the hole sidewall at different initial depths (500 m, 1000 m and 1500 m) during the adjustment of vertical stress were obtained. The results show that the hole sidewall all formed spalling before resulting in strain rockburst, and ultimately forming a V-shaped notch. The far-field principal stress for the initial failure of the tunnel shows a good positive linear correlation with the depth. As the depth increases, the stress required for the initial failure of the tunnels clearly increased, the spalling became more intense; the size and mass of the rock fragments and depth and width of the V-shaped notches increased, and the range of the failure zone extends along the hole sidewall from the local area to the entire area. Therefore, as the depth increases, the support area around the tunnel should be increased accordingly to prevent spalling.
Gradation equation is one way to describe the gradation of coarse-grained soil conveniently, exactly and quantitatively. With the gradation equation, the influence of gradation on the mechanical behaviors of coarse-grained soil can be expressed quantitatively. A new gradation equation with a parameter is proposed. The basic properties and applicability of the new equation are studied. The results show that the proposed equation has the applicability to express coarse-grained soil gradation (CSG), and the range of the parameter β is found to be 0<β<1. The value of ß determines the gradation curve shape. If p>0.5, the gradation curve is sigmoidal, otherwise the gradation curve is hyperbolic. For well graded gradations, the parameter has the value of 0.13<β<1. Several CSGs used in domestic and foreign earth-rockfill dams are probed, and the value of the parameter p falls in the range of 0.18 to 0.97. The investigation of the range of β is of value to guide the design for CSG of earth-rockfill dam.
A series of dynamic model tests that were performed on a geogrid-reinforced square footing are presented. The dynamic (sinusoidal) loading was applied using a mechanical testing and simulation (MTS) electro-hydraulic servo loading system. In all the tests, the amplitude of loading was ±160 kPa; the frequency of loading was 2 Hz. To better ascertain the effect of reinforcement, an unreinforced square footing was first tested. This was followed by a series of tests, each with a single layer of reinforcement. The reinforcement was placed at depths of 0.3B, 0.6B and 0.9B, where B is the width of footing. The optimal depth of reinforcement was found to be 0.6B. The effect of adopting this value versus the other two depths was quantified. The single layer of geogrid had an effective reinforcement depth of 1.7B below the footing base. The increase of the depth between the topmost geogrid layer and the bottom of the footing (within the range of 0.9B) did not change the failure mode of the foundation.
Rock bolts are widely used in rock engineering projects to improve the shear capacity of the jointed rock mass. The bolt inclination angle with respect to the shear plane has a remarkable influence on the bolting performance. In this study, a new artificial molding method based on 3D scanning and printing technology was first proposed to prepare bolted joints with an inclined bolt. Then, the effects of the bolt inclination angle and boundary conditions on the shear behavior and failure characteristic of bolted joints were addressed by conducting direct shear tests under both CNL and CNS conditions. Results indicated that rock bolt could significantly improve the shear behavior of rock joints, especially in the post-yield deformation region. With the increase of bolt inclination angle, both the maximum shear stress and the maximum friction coefficient increased first and then decreased, while the maximum normal displacement decreased monotonously. Compared with CNL conditions, the maximum shear stress was larger, whereas the maximum normal displacement and friction coefficient were smaller under the CNS conditions. Furthermore, more asperity damage was observed under the CNS conditions due to the increased normal stress on the shear plane.
The present study deals with analytical investigation of temperature of a single burning iron particle. Three mathematical methods including AGM (Akbari-Ganji’s method), CM (Collocation method) and GM (Galerkin Method) are applied to solving non-linear differential governing equation and effectiveness of these methods is examined as well. For further investigation, forth order Runge-Kutta approach, a numerical method, is used to validate the obtained analytical results. In the present study, the developed mathematical model takes into account the effects of thermal radiation, convective heat transfer and particle density variations during combustion process. Due to particles’ small size and high thermal conductivity, the system is assumed to be lumped in which the particle temperature does not change within the body and all of its regions are at the same temperature. The temperature distributions obtained by analytical methods have satisfactory agreement with numerical outputs. Finally, the results indicate that AGM is a more appropriate method than GM and CM due to its lower mean relative error and less run time.
Once an opening is created in deep underground, the stresses surrounding the opening will be redistributed, inducing a gradient stress field. To understand how the ground rock in such a gradient stress field responses to dynamic stress loading, the gradient stress distribution at a circular opening was first analyzed and the propagation of 1D stress wave in rock mass under gradient stress field was theoretically derived. By using an implicit to explicit solution method in LS-DNA code, the dynamic mechanical behaviors of rock in gradient stress field were numerically investigated. The results indicate that the damage is mainly produced at or near the free face, partly due to the straight action of compressive stress wave and the tensile stress wave generated at the free face. The range of the induced damage zone is narrowed under the conditions of higher gradient stress rate and lower dynamic stress amplitude. However, under lower gradient stress field and higher dynamic stress, the damage becomes severer and wider with discontinuous failure regions.
The article title was wrong and it should be replaced as follows: Zircon U-Pb-Hf isotopes and mineral chemistry of Early Cretaceous granodiorite in the Lunggar iron deposit in central Lhasa, Tibet, China
The fifth author’s name was wrong and it should be replaced as ZHANG Jian-long(张建龙)2.