Dissolution of precipitates by excess heat from friction stir welding (FSW) diminishes the joint quality of precipitation strengthened AA2014 alloy. Minimum quantity lubrication (MQL) technique is employed in this study to dissipate the unwanted heat. Graphene nanofluid prepared using two-step method with graphene nanoplatelets in water is used as the coolant. The development of grain structure and precipitation is studied using optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. The results show that the distinct thermal cycles occurring at each combination of rotational speed and welding speed transform the precipitates differently, thereby regulating the weld properties. The formation of precipitate free zones has been successfully eliminated. n-MQL has been observed to develop stable θ precipitates that produce higher weld properties. The process window for superior properties is established at the rotational speed of 1200 r/min and welding speed of 72 mm/min.

In this work, Nd: YAG laser beam welding was applied to join the grade 2 titanium tubes. Metallurgical characterization and mechanical tests were carried out to study the effect of laser power. The findings showed that when power increased, the bead geometry shape changed from wedge to parallel. The weld zone displayed a rough, uneven, and serrated coarse granular texture. The laser power had a significant impact on the misorientation angle patterns. High laser power revealed large pores. In the weld zone, dislocation pattern with high density and more sub grain boundaries were seen. The weld zone was strengthened during laser welding and less strengthening was observed at higher laser power in microhardness analysis. Higher tensile strength was achieved at lower laser power. The ductile failure was observed due to fine voids in the fracture surface analysis.

The work is devoted to the study of structural features and mechanical properties of thick-walled samples of Al-Mg alloy got by direct arc growth. This method has attracted particular attention in recent decades, mainly because of its high productivity and low cost. The high productivity of the process makes the wire arc additive manufacturing technology suitable for the production of large wall thicknesses. It is possible to achieve the correct formation of thick-walled elements and to get the specified dimensions by changing the overlap coefficient. It is important to consider that changes in the overlapping coefficient led to changes in size, morphology, as well as the intermetallic distribution, which will affect the mechanical behavior of the samples. The paper considers the features of grain structure formation, phase intermetallic components and their influence on the mechanical properties of thick-walled samples got at different overlapping coefficients. Two types of intermetallic compounds Mg₂Si and Al₆(Fe, Mn) were identified in the sample. Their size and morphology differ in relation to the overlap coefficient. As a result, the samples demonstrate anisotropy of mechanical properties. The highest values of tensile strength, yield strength and elongation obtained at 0.4 overlapping coefficient and were 319 MPa, 150 MPa and 16.1 %, respectively.

Water pollution problem is a significant trouble in our life. The photodegradation of organic pollutants in water, which is an environmentally friendly and economically feasible approach, has attracted considerable attention. Titanium oxide (TiO₂) is one of the most popular photocatalysts with high oxidation ability and excellent stability. In order to break the limitation of light absorption caused by the wide band gap, we synthesized metal ions doped TiO₂ via sol-gel method. The doped TiO₂ exhibited remarkable activity and stability in photocatalytic degradation of methylene blue (MB). Among the obtained materials, V/TiO₂ and Mo/TiO₂ had the superior performance of of > 98% within 30 min for photodegradation of MB. Further investigation of the mechanism revealed the promoted utilization of solar energy as well as the enhanced electron hole pairs of V/TiO₂ and Mo/TiO₂, which allowed the boost of catalytic activity.

The hard damping coating via atmospheric plasma spraying (APS) method was proposed to inhibit crack propagation of blade specimens in this paper. The fatigue test of uncoated and coated thin-walled blade specimens was carried out under resonance, and experimental results show that hard damping coating has the ability of crack retardation. Then, the finite element (FE) model of standard blade specimens with breathing crack was established and verified by natural frequency change of blade specimens with crack propagation. Furthermore, the crack propagation model was introduced. The crack tip stress intensity factors (SIFs) of uncoated and coated blade specimens under different crack lengths were calculated, and the crack retardation mechanism of coating was explained. Finally, the crack propagation curves of the blade specimens were calculated, and the effects of the thickness, elastic modulus and density of the coating on the crack growth were discussed. The influence of coating treatment in different stages on crack propagation was analyzed. The effects of crack depth and crack angle on crack propagation were discussed, which can help optimize coating layout. Experimental and numerical analysis show that hard damping coating can effectively delay the crack propagation, which is a practical technology in engineering application of crack propagation retardation.

The overall safety of anchorage engineering is jeopardized by the corrosion failure of low-carbon steel anchor bolts in a complicated geotechnical environment. To research the corrosion behaviour of low-carbon steel anchor bolts in carbonaceous mudstone slopes and to reveal the corrosion characteristics and mechanism of low-carbon steel anchor bolts under different corrosion time, solution corrosion, electrochemical corrosion and microscopic tests of low-carbon steel anchor bolts were carried out using a carbonaceous mudstone soaking solution and low-carbon steel anchor bolts as corrosion specimens. The results show that the low-carbon steel anchor bolts undergo obvious electrochemical corrosion in the carbonaceous mudstone environment. The corrosion product colour gradually deepened and the corrosion area gradually increased with increasing corrosion time. In the early stage of corrosion (0–10 d), the corrosion rate per unit area rapidly increased, and a thin oxide layer formed on the surface of the low-carbon steel anchor bolts. However, with the oxidation of Fe ions on the surface of the low-carbon steel anchor bolt body, the oxide film was gradually destroyed, resulting in the accumulation of corrosion products on the entire low-carbon steel anchor bolt surface. At this time, the entire reaction process was dominated by charge transfer and substance transfer.

To solve the problem of low recovery and heavy losses of indium in water-quenched slag and copper-containing pig iron in the process of reduction smelting, a new idea of adding lead into the zinc-indium system to recover indium from zinc is proposed in this paper. First, the feasibility of the mixed smelting of zinc-indium-lead is studied theoretically by means of ab initio molecular dynamics simulation and the optimal mixing ratio is obtained. Then, the theoretical calculation results are verified experimentally. The calculated results show that the interaction between Pb-In is stronger than that between Zn-In and surrounding atoms. After kinetic simulation, In and Pb aggregate together, and the effect is the most obvious when the molar ratio between lead and indium is 3:1. The miscibility experiment of the lead-indium-zinc alloy proves the correctness of the simulation results. The results of industrial experiments further verify that the recovery rate of indium is the best when molar ratio of Pb to In is 3:1. This study provides a feasible method for the recovery of indium and a new idea for the recovery and utilization of nonferrous metals.

The caustic soda autoclaving process for digesting scheelite (CaWO₄) is a unique and widely used tungsten (W) metallurgy technology in China. However, some experimental phenomena still need a proper theoretical explanation. In this work, some operational details and the theoretical basis of the technology are reported. During the digestion, some impurities, such as P, As, and Si are also digested. The P impurity was taken as an example. Based on the analysis of thermodynamic equilibrium phase diagram analysis, low levels of P impurities in the leaching solution were obtained. However, during the next dilution of the residue, P was supplemented as an inhibitor to reduce W loss. The inhibition of the reverse reaction mechanism is explained. The washed Na₂WO₄ solution containing excess NaOH can be reused in the evaporation–crystallization process; meanwhile, the supplemented P should be removed by adding Ca(OH)₂. A theoretical analysis of the thermodynamic equilibrium phase diagram shows that there is an area where Ca₅(PO₄)₃OH is stable, but CaWO₄ is not. The experimental results show that over 90% of P can be removed by adding the theoretical Ca(OH)₂ amount at the beginning of the evaporation-crystallization step. The W loss ratio can be controlled below 0.2%.

Gypsum sludge refers to a hazardous solid waste produced by the non-ferrous smelting industry, and its disposal and utilization are environmentally challenging. To investigate the feasibility of replacing limestone with gypsum sludge for smelting slagging, the effect of gypsum sludge and smelting conditions on high lead slag reduction smelting was studied through thermodynamic calculation and experiments. It was found that calcium sulfate in the gypsum sludge consumed the reducing agent and vulcanized the metal oxide, thus, controlling its dosage was necessary. The optimal conditions for comprehensive recovery of valuable metals were as follows: calcium silicon mass ratio, dosage of carbon powder, mole ratio of calcium sulfate to calcium oxide, smelting temperature, and holding time were 0.8, 3.5 wt%, 1: 5, 1200 °C, and 1.5 h, respectively. The direct recovery of lead and zinc under these conditions was 94.43% and 58.43% respectively. Meanwhile, toxicity leaching experiment of sulfuric acid and nitric acid method indicated that the collaborative melting process stabilized the reduced slag.

Coal gangue is a solid waste discharged in coal mining and dressing process. Large-scale decarbonization and activation treatment are key steps toward massive and efficient utilization of coal gangue. In this paper, a new process for the preparation of a cement admixture from coal gangue by effectively utilizing its calorific value was developed. The mineral composition, crystal structure, and microstructure of the sintered products obtained under different sintering conditions were investigated using XRD, FTIR, SEM and mechanical property analysis to reveal the activation mechanism of coal gangue. The blended cement containing 30% activated coal gangue prepared by adding 3% coal and no return fine exhibited the best mechanical properties. Furthermore, the mechanical properties of the cement containing 30% activated coal gangue prepared without coal and return fine were adequate, reaching a productivity of 0.96 t/(m²·h). The results show that the thermal activation of exhaust sintering can greatly improve the cementitious activity of coal gangue. Finally, the applied technology is promising for industrial application.

Al-starch has been successfully used in the inhibition for fine chlorite and calcite, while its fundamental feature and structure have not been explored. This study has found that the size and zeta potential of Al-starch are much larger than those of single starch. When starch chelates with aluminum ions, the initial characteristic peaks of Fourier transform infrared spectroscopy shift significantly, and new O—Al functional group appears. Meanwhile, the X-ray photoelectron spectroscopy detects the increase of O and Al atom concentration, and the O—Al peaks and metal group peaks are generated after the reaction of starch with Al ions. Moreover, the single molecule of starch is optimized through the cluster calculation, involving the trans-glucose and cis-glucose. The trans-glucose is easier chelated with aluminum ions to obtain optimal structure. Under this structure, the O₁ and O₆ of starch molecules covalently bind Al³⁺ to form the O₁—Al—O₆ chelation structure with shortest bond length and lowest interaction energy. Meanwhile, the frontier molecular orbital analysis confirms that the Al³⁺ provides empty orbitals to accept the electrons of glucose during the chelation. Furthermore, an efficient flotation separation of scheelite from ultrafine calcite and chlorite is achieved using Al-starch, which demonstrates the feasibility of this depressant.

In this study, the microscopic properties of spent magnesia-chromium refractories before and after leaching were detected by SEM-EDS and BSE. In addition, the influence of conditions on magnesium leaching was studied by leaching kinetics test, and the kinetics of the leaching process was analyzed by statistical and graphical methods. The results indicate that the relationship between different phases in raw material is complicated that the leaching residue is chromite spinel, and the particles have various holes and cracks. Increasing temperature, hydrochloric acid concentration and liquid-solid ratio can accelerate leaching velocity of magnesium, thereby promoting the whole leaching process, and the promotion effect of temperature is the most significant. The process of leaching magnesium from spent magnesia-chromium refractories conforms to the progressive-conversion model with chemical reaction being the rate-controlling step, in which the corresponding apparent activation energy was 69.11 kJ/mol, and its kinetic equation can be expressed as follows: X/(1−X)=4.898×10⁸×C_HCL^0.7982×(L/S)^0.7407×e^−8312/T×t^0.9276.

Backfilling the pillar to form a pillar-backfill collaborative bearing structure is the key to cut and fill method. The pillar-backfill bearing system is also an important support structure to maintain the stability of the underground stope. This paper analyzed the load-bearing capacities and failure modes of the backfilled pillars through biaxial compression tests, and the combined effects of lateral stress, fill ratio, and backfill mechanical properties were investigated. The results showed that the mobilized interface friction force between the pillar and backfill (fill ratio <100%) and effective backfill strength (fill ratio=100%) increased faster than pillar strength with lateral stress gain, which were the main reason for the increase in the load capacity of the backfilled pillar under biaxial loading. In addition, due to the significant stiffness difference between the pillar and backfill, the effective strength of the backfill in the biaxial loading test was lower than uniaxial compressive strength. The increase of lateral stress could not only improve the interface friction and the effective strength of backfill, but also affect the failure modes of the pillar and backfill. The experimental results will have reference value for studying the interaction of pillar-backfill structure.

Coal burst is a catastrophic event that induced by a large variety of certainty and uncertainty factors, and many methods have been proposed to evaluate the risk of this hazard. Conventional evaluation models or empirical criteria are influenced by the complex modelling process or undesirable accuracy. In this study, a total of 147 groups of coal burst records were used to establish the empirical classification model based on elastic energy index (W_et) and impact energy index (K_c). The classification boundaries of coal burst liabilities (CBLs), which was fitted to quantitatively analyze the risk level, and its distribution characteristics are displayed on 2D chart using Kriging method. Additionally, 43 groups of test samples were collected to further validate the reliability of the constructed spatial interpolation model. The results revealed that the classification performance of Kriging model outperforms other uncertainty-based method with accuracy 91%. It can be a valuable and helpful tool for designers to conduct the geological hazard prevention and initial design.

In this analysis, we explore a nanofluid model that represents the role of ciliary carpets in the transport of magnetohydrodynamic fluid in an electroosmotic channel. Hybrid nanofluid features are also taken into interpretation. The equations leading the flow analysis are converted into non-dimensional form by supposing long wavelength and low Reynolds number approximations. Analytical solutions for velocity distribution, pressure gradient and stream function are acquired and solved by a mathematic solver. The effects of the relevant physical parameters are graphically noted. The consequence of the present model has remarkable applications, which can be used in various areas of biological transport processes, artificial cilia design and in the operation of other mechanical devices.

This communication numerically studies the micro-rotation effects of tangent hyperbolic hybrid nanofluid past a porous sheet. The fluid motion is developed by virtue of linear stretching sheet. This study further incorporates multiple flow and thermal phenomena such as porous media, inclined magnetohydrodynamic (MHD) fluid, Joule heating along with velocity and thermal slip factors. Mathematical formulation prompts a set of non-linear coupled partial differential equations. To achieve a similar solution, similarity variables are introduced. Numerical solution of leading differential equations is attained via Runge-Kutta-Fehlberg 45 (RKF-45) along with shooting technique. Graphical outcomes are obtained to present the physical significance of the relevant parameters. In order to validate the numerical results, comparison is made with the data already published. It is assumed that the fluid velocity reduces with increasing Weissenberg number and permeability parameter. In addition, the angular velocity of the fluid accelerates significantly with an increase in surface condition parameter. It has been established that higher volume percentage of silver and copper nanoparticles has potential to improve the thermal conductivity of the flowing fluid. Hybrid nanofluid plays a significant role in various engineering applications, including nuclear cooling, desalination, machining, refrigeration, heat exchangers, solar collectors, and engine cooling. Furthermore, mixing hybrid nanofluid in the micro-rotating tangent hyperbolic fluid enhances the thermal abilities of the system, that is applied in many mechanical systems that rely on heat transfer. Skin friction coefficient effectively decreases with increasing Weissenberg number while increases for huge velocity slip parameter.

This paper investigates the influence of polymers on the flow and heat transfer of nanoparticles and microorganisms past a horizontal stretching sheet. The fundamental motivation for this paper is the potential effects of polymers on drag coefficient, Nusselt, Sherwood, and motile density numbers control. Dispersion was chosen to investigate the behavior of polymer additives using FENE-P model. The nonlinear system of partial differential equations governing non-Newtonian polymeric fluid flow is reduced to a correct similar form using an appropriate similarity transformation. The modified nonlinear system of ordinary differential equations is numerically solved using MATLAB code bvp4c based on finite difference scheme, together with modified boundary conditions. Tabular results are presented to investigate how various flow parameters affect physical quantities of industrial importance. The impact of the physical parameters involved on velocity, temperature, concentration, and microorganism profiles was analyzed in detail. Polymeric additives are responsible for reducing the drag coefficient and Nusselt number. In addition, it is noted that Sherwood and motile density numbers are significantly influenced by polymer additives.

In the present article, authors communicated the impact of the Cattaneo-Christov model (C-C model) and quadratic thermal radiation with convective boundary conditions on ternary hybrid nanofluid (TiO₂−SiO₂−MoS₂/kerosene oil) flow over a rotating disk. The Darcy-Forchheimer porous medium and suction/injection influence were also considered. A comparative analysis of ternary hybrid nanofluid (TiO₂−SiO₂−MoS₂/kerosene oil) and hybrid nanofluid (TiO₂−SiO₂/kerosene oil) was also presented. The set of partial differential equations was converted into the ordinary differential equations by von Karman’s transformation and solved by the bvp4c function in MATLAB. The graphs were also sketched to show variations in radial and tangential velocity and heat transfer. The ascendancy of the various parameters: magnetic field, Forchheimer number, porosity parameter, slip parameter, radiation parameter, thermal relaxation, mixed convection, suction/injection, Biot number, heat source/sink, and volume fraction was discussed in detail. Higher values of radiation and thermal relaxation parameter increase the heat transmission rate. The results of this study will be helpful to many transportation processes, rotating machinery systems, co-rotating turbine systems, enhanced oil recovery systems, medical fields that utilize nanofluids, and so on.

In fractured carbonate rocks, reservoir quality is controlled by the fracture properties. Fracture system characteristics in naturally fractured carbonate reservoirs are vitally important to any development plan. This paper analyzes the effect of effective structures on reservoir quality of the Asmari Formation located in one of the Iranian oilfields in NW of the Persian Gulf. These were accomplished using analysis and interpretation of FMI borehole image logs (full bore formation micro imager). The studied field is a NE-SW trending anticline; Asmari Formation contains three parts (upper and lower Asmari) and the Ghar Sandstone section between them. The image log of the studied well has been processed and corrected using Geolog software. Then the different types of natural structures have been recognized and interpreted, and their attitudes were measured as well. The orientation data of the structures have been analyzed by drawing statistical graphs and also from a structural point of view. The results indicated that bedding is almost horizontal in this well. Moreover, different types of fractures and stylolites could be structurally related to folding. The main observed structures could be categorized as longitudinal and transversal open fractures, longitudinal filled fractures, and parallel and normal bedding stylolites. A comparison of the frequency distribution of various structures with porosity logs (i. e., neutron, density, and sonic logs) shows that the open fractures cause an increase in porosity. However, in some part of the well the filled fractures and stylolites strongly decreased the porosity. Therefore, according to structural impacts on Asmari reservoir quality, it is suggested that any future drillings in the reservoir can be planned concerning the density and orientation of the structures (incredibly open fractures).

Based on the deep cores of Well Songke-2 (SK-2), uniaxial compression tests of deep rock from 8 different depths in the 4900–6830 m range were carried out, and deformation and failure characteristics were analyzed in detail. It was found that in the range of 4900–6830 m, the mechanical parameters of uniaxial compression tests of rocks changed nonlinearly with depth, and the strength was positively correlated with the hard mineral content. Comparing the rock failure of these samples with the 4500–7000 m core disc segment in SK-2, it was found that the failure of magmatic rock samples in both cases was smoother than that of sedimentary rock, indicating that deep magmatic rocks more easily released energy during the failure process. From depths of 4900–6000 m, prepeak characteristic stresses increased with increasing depth, while from depths of 6000–6830 m, they decreased with increasing depth. Fracture closure stress was used to characterize rock sampling damage at depths of 1000–6830 m, and it was found that sampling damage varied linearly with burial depth in sedimentary strata, while in igneous strata, sampling damage remained stable with increasing burial depth.

In the process of deep roadway excavation, the zonal disintegration phenomenon of surrounding rocks has attracted a lot of attention from rock mechanics. There are relatively few studies on zonal disintegration of rock specimens in laboratory experiments. In this paper, a split Hopkinson pressure bar device was used to perform compression tests on hollow cylindrical sandstone specimens under different confining pressures. The failure specimen shows zonal disintegration. According to the theoretical analysis of elastic-plastic mechanics, it is found that there is a maximum tensile strain at the elastic-plastic boundary, which leads to annular cracks in the radial direction and the formation of zonal fractures. In the plastic zone of the specimen, there is a large tensile strain near the hole. As a result, it is prone to spalling near the hole. In the elastic zone of the specimen, as the radius increases, the hoop strain is converted from compressive strain to tensile strain, resulting in tensile cracks on the outside of the specimen. The phenomenon was also simulated using ABAQUS. The simulation results are basically consistent with the experiments and can intuitively explain the spalling around the hole and the damage to the specimen.

The triaxial mechanical behaviour of basalt fibre-reinforced coral aggregate concrete (BFCAC) was investigated in this study. The results show that an increase in the confining pressure and basalt fibre (BF) content causes an increase in the ductile deformation of BFCAC. The BF and confining pressure can increase the contraction volume deformation of BFCAC and reduce its expansion volume deformation. The confining pressure effect of the peak deviatoric stress and elastic modulus of BFCAC increases with BF content. The Poisson ratio of BFCAC increases as the BF content increases and decreases as the confining pressure increases. In addition, confining pressure causes BFCAC to transform from splitting failure to shear failure and extrusion plastic flow failure. When BFCAC is damaged, all the cracks penetrate through the coral aggregate. The relationship between the pore structure fractal dimension and the triaxial mechanical properties shows that the triaxial mechanical properties of BFCAC are affected by the BF as well as the BF’s effect on the pore structure. Finally, an improved nonlinear M-C strength criterion for BFCAC is established.

The tensile strength of rock salt is an important parameter in the salt cavern gas storage project. Due to the high requirements for experimental setup and rock specimens in the direct tensile test, it is necessary to find another alternative to obtain the tensile strength. Therefore, the tensile strength and acoustic emission (AE) characteristics obtained by the direct tensile test, Brazilian test with simplified ISRM standard, Brazilian test with China standard, and three-point-bending test were discussed in this paper. It is noticed that the tensile testing method has an effect on the tensile strength of rock salt and the AE counts, energy and spatial distribution. Based on the tensile strength determined by three-point-bending test and the AE evolution characteristics, the indirect tensile strength determined by three-point-bending test was much closer to the tensile strength determined by direct tensile test, meaning that the three-point-bending test could be considered as a good option to obtain the tensile strength of rock salt except direct tensile test.

In-situ stress and delay time in shaped charge jet blasting (SCJB) have significant effects on rock damage. In this study, the stress distribution pattern and damage mechanism of rock around the blast hole under coupled in-situ stress and blast loading are studied using theoretical analysis and numerical simulation. The effect of SCJB on rock crushed zone, jet erosion length and crack propagation characteristics under in-situ stress was explored. The results show that the SCJB method achieves directional crack extension and increases the crack extension length. Under equibiaxial in-situ stress condition, the crushed zone is circular, and the radius of the crushed zone, jet erosion length and crack length decrease with increasing in-situ stress level. Under an anisotropic pressure condition, on the other hand, the crushed zone is elliptical; the greater the difference between horizontal and vertical pressure, the more pronounced the anisotropy of the crushed zone. As the lateral pressure coefficient k decreases, the horizontal crack length tends to decrease whereas the vertical crack length increases. The vertical crack length of the delay blast hole increases with the increase of the delay time.

Accurately predicting the impact of shield tunnel construction under buildings on the ground surface can reduce the impact of construction on buildings. During the process of shield tunneling under multi-story buildings, the stiffness and load of the buildings affects the deformation of the formation. This study explored the degree and mechanism about influence of the above two factors. First, based on the Mindlin’s solution promoted in semi-infinite space, a method was developed for the calculation of ground deformation caused by shield tunneling under multi-story buildings, including the influence of additional stress and stiffness brought by the buildings. Second, based on the analysis of the composition of a surface settlement tank and a surface horizontal displacement curve, a modified Peck formula and the formula of O’Reilly and New were reviewed. Finally, according to the present empirical formula and a modified formula, the surface deformation caused by shield tunneling was compared and analyzed in four cases: without buildings, with load of buildings, with stiffness of buildings, and with load and stiffness of buildings. The results demonstrated that the maximum value of surface settlement was the smallest when only the stiffness was considered, and it was the largest when only the load was considered. In practical applications, the building stiffness and load should be considered simultaneously.

In a wind tunnel, the characteristics of wind barrier have a significant effect on the aerodynamic characteristics of a train. Using the improved delayed detached eddy simulation (IDDES) method and the shear stress transport (SST) k-ω turbulence model, the variations of the aerodynamic characteristics of the train with the length of the wind barrier were studied for different wind barrier thicknesses. The wind tunnel test results were used for comparison at a yaw angle of 30°. When the wind barrier exceeded a certain length, the aerodynamic load of the train did not change significantly, and it can be considered to have reached a critical length. The critical length of the wind barrier was determined by fitting the relationship between the aerodynamic coefficient of the train and the length of the wind barrier. The relationship between the thickness of the wind barrier and the critical length satisfied the quadratic function y= − 51.235x²+8.659x+29.014. When the thickness of the wind barrier was more than 0.5 m (full-size), the critical length could be obtained by substituting the thickness of the wind barrier into the above function during a wind tunnel test to study the aerodynamic characteristics of the train.