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Previous experimental and computational results have confirmed that the thermal conductivity of a two-dimensional (2D) material can be considerably affected by strain. Numerous attention has been paid to explore the relevant mechanisms. However, the strain effects on the interfacial thermal conductance (ITC) of 2D heterostructure have attracted little attention. Herein, the non-equilibrium molecular dynamics (NEMD) simulations were conducted to the graphene/hexagonal boron nitride (GR/h-BN) heterostructure to investigate the strain effects on the ITC. Three types of strains were considered, i.e., tensile strain, compressive strain, and shear strain. The results indicate that the strain can adjust the ITC for the GR/h-BN heterostructure effectively, and the strain loading direction also influences the ITC. Generally, the tensile strain reduces the ITC of the heterostructure, in addition to the BN-C system at small tensile strain; both the compressive strain and shear strain increase the ITC, especially at a small strain. For the NB-C system, it is more sensitive to the strain loading direction and the yx shear strain of 0.06 is the most effective way to strengthen the ITC. Our results also show that the out-of-plane deformation weakens the in-plane vibration of atoms, leading to a reduction of the interfacial thermal energy transport.

Tungsten as a material exhibits broad and increasingly important applications; however, the characterization of its ductile-to-brittle transition (BDT) is currently limited to large-scale scenarios and destructive testing. In this study, we overcome this challenge by implementing small-scale techniques to provide a comprehensive understanding of the BDT behavior of pure tungsten. In order to predict the failure mode at various temperature ranges, the practical fracture analysis diagram has been proposed to describe the resistance to shear flow and cracking behavior with temperature. High temperature nano-indentation tests have provided the inherent mechanical responses corresponding to the maximum shear stress at various temperatures, which is required for dislocation activities in an atomic scaled activation volume. On one hand, atomistic simulations have provided the temperature dependence of brittle fracture stress, where the atomic bonds break due to intergranular or intragranular fracture. We considered four tungsten specimens having various microstructures prepared using different processing conditions of cold-rolling and post-annealing, and their BDT ranges were inferred using the obtained fracture analysis diagram with the statistical data processing. The fracture analysis diagram of each specimen obtained were compared with the direct observation of fracture responses in macroscopic mechanical tests, which conclusively indicated that the small-scale inherent mechanical properties are greatly relevant to the macroscopic BDT behavior in pure tungsten. Based on the BDT estimations by small-scale characterization, we provided further insights into the factors affecting the BDT behavior of tungsten, focusing on the contributions of different types of dislocations.

Deformation behavior of a FeCrNi medium entropy alloy (MEA) prepared by powder metallurgy (P/M) method was investigated over a wide range of strain rates. The FeCrNi MEA exhibits high strain-hardening ability, which can be attributed to the multiple deformation mechanisms, including dislocation slip, deformation induced stacking fault and mechanical twinning. The shear localization behavior of the FeCrNi MEA was also analyzed by dynamically loading hat-shaped specimens, and the distinct adiabatic shear band cannot be observed until the shear strain reaches ~14.5. The microstructures within and outside the shear band exhibit different characteristics: the grains near the shear band are severely elongated and significantly refined by dislocation slip and twinning; inside the shear band, the initial coarse grains completely disappear, and transform into recrystallized ultrafine equiaxed grains by the classical rotational dynamic recrystallization mechanism. Moreover, microvoids preferentially nucleate in the central areas of the shear band where the temperature is very high and the shear stress is highly concentrated. These microvoids will coalesce into microcracks with the increase of strain, which eventually leads to the fracture of the shear band.

Multiple ballistic impacts are carried out on a 2024-T4 aluminum alloy by spherical steel projectiles (5-mm diameter) at ∼ 400 m s − 1 , to investigate its dynamic deformation and damage. The ballistic impact process is captured with high-speed photography. Postmortem samples are characterized with optical imaging, three-dimensional laser scanning, microhardness testing and electron backscatter diffraction. With increasing number of impacts, crater diameter increases slightly, but crater depth and crater volume increase significantly, and strain accumulation leads to microhardness increase overall. Crater parameters all follow power-law relations with the number of impacts. Twin-like deformation bands and macroscopic deformation twins are produced by impact as a result of spontaneous dislocation self-pinning under high strain rate, large shear deformation. Under multiple impacts, shear strain accumulation in the arc-shaped region of the crater induces deformation twinning when it exceeds a critical value ( ∼ 1.1 − 1.6 ). It is highly possible that the deformation twins are related to deformation bands, since they both share one set of the { 111 } pole with the initial matrix grain. A finite element method model is optimized to reproduce experimental observations and interpret deformation mechanisms.

Toward accurately simulating both hardening and softening effects for metals up to failure, a new finite strain elastoplastic J2-flow model is proposed with the yield strength therein as a function of the plastic work in the explicit form. With no need to identify any adjustable parameters, the uniaxial stress-strain response predicted from this new model is shown to automatically and accurately match any given data from monotonic uniaxial extension tests of bars. As such, the objectives in three respects are achieved for the first time, i.e., (i) both the hardening and softening effects up to failure can be simulated in the sense of matching test data with no errors, (ii) the usual tedious implicit procedures toward identifying numerous unknown parameters need not be involved and can be totally bypassed, and (iii) the model applicability can be ensured in a broad sense for various metallic materials with markedly different transition effects from hardening to softening. With the new model, the complete response features of stretched bars and twisted tubes up to failure are studied, including the failure effects of bars under monotonic extension and tubes under monotonic torsion and, furthermore, the fatigue failure effects of bars under cyclic loading. The results show accurate agreement with the uniaxial data, and the results for both the shear stress and the normal stress at the finite torsion display realistic hardening-to-softening transition effects for the first time.

The mechanochemical effect on the microcutting of AA6061 alloy is studied through characterization on the chip. A pronounced reduction of machining forces and chip thickness was observed with mechanochemical effect during microcutting. Furthermore, electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) observations were performed on the chips and shear bands. The result reveals much coarser grains (24.6 μm in size) in the surfactant-affected chip than that in the surfactant-free chip (13.5 μm). Different grain orientations are induced by microcutting. {100} and {110} grain orientations are majority for surfactant-free chip, and {110} and {100} dominate most for all grain orientations for surfactant-affected chip. Additionally, since less localized shear strain and lower temperature are generated inside the shear band with mechanochemical effect, almost no recrystallization phenomena can be observed in this region. TEM analysis shows that fewer subgrains and dislocations could be observed inside the shear band of the surfactant-affected chip in comparison with the surfactant-free chip. Based on the high-resolution transmission electron microscopic (HRTEM) observations, dislocations were observed at the atomic scale. The results show that the main dislocation motion mode in shear bands of surfactant-free and surfactant-affected chips are dislocation climb and dislocation glide, respectively.

We analyze transient dynamics during shear start-up in viscoelastic flows between two parallel plates, with a specific focus on the signatures for the onset of transient shear banding using the Johnson-Segalman, non-stretching Rolie-Poly and Giesekus models. We explore the dynamics of shear start-up in monotonic regions of the constitutive curves using two different methodologies: (i) the oft-used `frozen-time' linear stability (eigenvalue) analysis, wherein we examine whether infinitesimal perturbations imposed on instantaneous stress components (treated as quasi steady states) exhibit exponential growth, and (ii) the more mathematically rigorous fundamental-matrix approach that characterizes the transient growth via a numerical solution of the time-dependent linearized governing equations, wherein the linearized perturbations co-evolve with the start-up shear flow. Our results reinforce the hitherto understated point that there is no universal connection between the overshoot and subsequent decay of shear stress in the base state and the unstable eigenvalues obtained from the frozen-time stability analysis. It may therefore be difficult to subsume the occurrence of transient shear banding during shear start-up within the ambit of a single model-independent criterion. Our work also suggests that the strong transients during shear start-up seen in earlier work could well be a consequence of consideration of the limit of small solvent viscosity in the absence of otherwise negligible terms such as fluid inertia., 46 pages, 13 figures

Understanding the grain boundary deformation dynamics is very crucial to designing materials with stable microstructures. With this quest, the deformation behavior of coherent twin boundary under cyclic shear loading has been studied in {\alpha}-Fe using molecular dynamics simulations to understand the influence of strain amplitude and temperature. Twin boundary exhibited shear coupled migration along with cyclic irreversibility character at lower temperatures and gained almost perfect reversibility at higher temperatures of around 1500 K. TB exhibited more sliding than migration with an increase in temperature. The stress associated with the migration of twins was observed to fluctuate around its average value. This was caused by layer by layer propagation of twin boundary through the activity of 1/6 = 1/12 + 1/12 type edge partial dislocations on "\{"112"\}" twin plane. Complete twin reversibility and complex TB migration were noticed in the presence of multiple parallel twin nanowires. Twin migration was observed at the larger size nanowires with a proper combination of boundary conditions and strain rates; otherwise, it was absent. The influence of shear strain amplitude in offsetting the twin boundary was found to be minimal., Comment: 29 pages, 16 figures, 3tables, Journal paper

In sugar industry, the sugar processing done in different sections, but to increase total crushing per day (TCD) capacity, the milling section takes a vital role in the sugar industry. The sugar industry aims to extract the maximum amount of juice from sugarcane. In the milling section, the processed sugarcane is fed in between the three-roller shaft from the different arrangements, there are different loads applied on each part roller shafts. When load between all rollers varies then there is a chance of bending it is analyzed to check the roller shaft condition. The modeling is done on roller shaft with the help of CATIA V5. After modeling, we analyze the condition of the rollers, when different stress or forces are applied to different sections of the roller shaft it analyzed with the help of Finite element method using ANSYS WORKBENCH software. We were selecting titanium alloy materials for the roller shaft to analyze the variation in results. When comparing the calculated and software-based results using Maximum Shear stress and Total deformation for top, feed, and discharge rollers said the roller shafts are safe to use in the sugar industry and titanium alloy is the best material for these roller shafts.

Self-organizing nanostructure evolution through spinodal decomposition is a critical phenomenon determining the properties of many materials. Here, we study the influence of stress on the morphology of the nanostructure in binary alloys using atomistic modeling and atom probe tomography. The atomistic modeling is based on the quasi-particle approach, and it is compared to quantitative three-dimensional (3-D) atom mapping results. It is found that the magnitude of the stress and the crystallographic direction of the applied stress directly affect the development of spinodal decomposition and the nanostructure morphology. The modulated nanostructure of the binary bcc alloy system is quantified by a characteristic wavelength, $$ \lambda $$ λ . From modeling the tensile stress effect on the A-35 at. pct B system, we find that $$ \lambda _{001}< \, \lambda _{111}< \, \lambda _{101}< \, \lambda _{112}$$ λ 001 < λ 111 < λ 101 < λ 112 and the same trend are observed in the experimental measurements on an Fe-35 at. pct Cr alloy. Furthermore, the effect of applied compressive and shear stress states differs from the effect of the applied tensile stress regarding morphological anisotropy.

The split Hopkinson pressure bar and universal testing machine are used to study the dynamic response and failure behavior of U71Mn using a hat-shaped specimen under the compression-shear stress state. The shear stress–strain curves are presented at the shear strain rates ranging from 0.001 to 19,200 s−1 and temperatures ranging from 25 to 600 °C. It is observed that the effects of strain rate hardening, strain hardening, and thermal softening are closely related to the changes of the shear stress–strain curves. The coupling effects are very significant in the process of deformation failure. The fracture morphology and longitudinal section microstructures of U71Mn are investigated by scanning electron microscope. According to the results, the shear strain rates and temperatures greatly influence the failure mechanisms of the material. Furthermore, the increase in temperature promotes the occurrence of dynamic recrystallization and reduces the tendency of the pearlite flowing toward the center of the shear zone. Based on the quasi-static tensile tests and finite element analysis, the Johnson–Cook damage model parameters are fitted and applied to the finite element analysis of the hat-shaped specimen.

In this study, a mathematical model is formulated to examine the blood flow through a cylindrical stenosed blood vessel. The stenosis disease is caused because of the abnormal narrowing of flow in the body. This narrowing causes serious health issues like heart attack and may decrease blood flow in the blood vessel. Mathematical modeling helps us analyze such issues. A mathematical model is considered in this study to explore the blood flow in a stenosis artery and is solved numerically with the finite difference method. The artery is an elastic cylindrical tube containing blood defined as a viscoelastic fluid. A complete parametric analysis has been done for the flow velocity to clarify the applicability of the defined problem. Moreover, the flow characteristics such as the impedance, the wall shear stress in the stenotic region, the shear stresses in the throat of the stenosis and at the critical stenosis height are discussed. The obtained results show that the intensity of the stenosis occurs mostly at the highest narrowing areas compared with all other areas of the vessel, which has a direct impact on the wall shear stress. It is also observed that the resistive impedance and wall shear pressure get the maximum values at the critical height of the stenosis.

In roadways with high ground stress or burial depths, the joints distributed within rock formations are subject to complex stresses and interlayer misalignments frequently. Rock bolts and cable bolts anchored in the rock formations are subject to tensile and shear forces. Most of the bolts used in roadway engineering are local anchored, resulting in insufficient shear strength at the bolt free end close to roadway surface and increasing bolts breaking. The anchor cable and C-shaped tube (ACC) is a highly prestressed cable bolt that can withstand high shear force in its free end. This paper examines the effect of the relationship between C-shaped tube length and joint location on the shear resistance of ACC by double shear tests. To fully exploit the ACC’s shear resistance, the C-shaped tube ends should be at least 30 cm beyond the joint. The effect of preload and concrete spray thicknesses on roadway deformation and plastic zone is investigated by numerical simulation. Results show that ACC and concrete spraying layer can form a stable extruded arch structure, so that the broken and soft rock within the loosen zone is in three-dimensional-stress state, effectively improving surrounding rock properties and controlling its deformation size. Based on these results, the ACC support design method is proposed.

Modelling the high-pressure grinding rolls mass flow rate from the continuity principle represents a difficult task, partly because the ore may slip against the rolls. In effort to increase the understanding of this phenomenon, this paper introduces a state observer to estimate the slip profile in the HPGR working gap from the force balance equations and Coulomb friction criterion. The observer is used off-line and a posteriori, i.e. it requires a series of HPGR tests conducted at different levels of specific force and roll speed. It allows observing the slip profile on a gold ore at the pilot scale. As the material enters the compression zone, it descends at a slower rate than the vertical component of the roll peripheral speed. As it progresses downward, its velocity increases. It exceeds the roll peripheral speed at the working gap level and peaks below. The pressure peaking above the working gap makes slipping possible. It leads to the material above the working gap to push onto the one below and thus accelerating it.

Shock compression subjects materials to a unique regime of high quasi-hydrostatic pressure and coupled shear stresses for durations on the order of 1–10 nanoseconds for laser-driven loading of samples. There is, additionally, an attendant temperature increase due to the shock and the mechanisms of plastic deformation in metals whereby dislocations, twins, and phase transitions nucleate and propagate at velocities near the sound speed. Covalently bonded materials have, by virtue of the directionality of their bonds, great difficulty in responding by conventional plastic deformation to this extreme regime of shock compression. We propose that the shear from shock compression induces amorphization, as observed in Si, Ge, B4C, SiC, and olivine ((Mg, Fe)2SO4) and that this is a general deformation mechanism in a broad class of covalently bonded materials. The crystalline structure transforms to amorphous along regions of maximum shear stress, forming nanoscale bands, and thereby relaxing the shear component of the imposed shock stress. This process is usually preceded by the emission and propagation of a critical concentration of dislocations.

Optimization of mathematical model of flow field in slab continuous casting mold was performed by means of industrial measurement and mathematical modeling. The rod deflection method was used to quantitatively measure the velocities near the mold surface at high temperature. The measurement results were compared with the simulation results of three mathematical models at different argon gas flow rates of 6, 10 and 14 L min−1. The model 1 neglects the mold powder layer, thermal effect and solidified shell. The model 2 only considers the influence of mold powder layer. The model 3 considers the influence of mold powder layer, thermal effect and solidified shell on the flow field. In all three models, the diameter of argon bubbles obeys Rosin–Rammler distribution fitted according to the experimental data of others’ previous work. With increasing the argon gas flow rate, the velocity of liquid steel near the mold surface decreases. The model 1 seriously underestimates the shear stress of liquid steel near the mold surface, and its calculation results show higher velocity near the mold surface, lower turbulent kinetic energy and wider distribution of argon gas bubbles in the mold. The simulation results of model 2 only considering the viscous resistance of the mold powder layer to liquid steel makes the velocity near the surface lower than the measurement results obviously. The calculated velocities near the mold surface with model 3 are in best agreement with the measured results, showing the reasonable spatial distribution range of argon bubbles in the mold and the moderate turbulent kinetic energy. In the present conditions, the best argon gas flow rate is 10 L min−1 due to the moderate velocity near the mold surface, the appropriate distribution of argon gas bubbles in the mold and the smallest fluctuation amplitude on the mold surface.

A phenomenological ductile fracture model is proposed by a careful consideration of void nucleation, growth and coalescence during plastic deformation. Within the model framework, void nucleation is controlled by an equivalent plastic strain function. Void growth takes place through two ways, namely void dilation and void elongation, which are characterized by the normalized hydrostatic stress and normalized maximum shear stress, respectively. Void coalescence is characterized by the maximum shear stress. Aluminum alloy (AA) 6016-T6 sheets are selected to conduct ductile fracture (DF) experiments on specimens with different geometries, which can cover a wide range of stress states from simple shear to balanced biaxial tension. Subsequently, the new DF model is calibrated by using a robust hybrid numerical-experimental approach with a three-dimensional (3D) fracture surface constructed for AA 6016-T6. Ductile fracture data of other two aluminum alloys (AA 2024-T351 and AA 5083-O) are also used to evaluate DF model performance by establishing their 3D fracture surfaces. Finally, a cup drawing test is conducted and simulated as a case study showing how an applicable way of using the new model. Furthermore, the predictive accuracy of the proposed DF model for fracture initiation is compared with other three uncoupled models (modified Mohr–Coulomb criterion (MMC), Lou-Yoon-Huh model and Mu-Zang model) by ABAQUS/Explicit with a user subroutine (VUMAT), which shows a good performance of the proposed DF model.

This paper presented an implementation of entropy generation analysis in the main flow field of a water jet pump via the CFD method. This study aimed to identify the inefficient location of energy conversion and to analyse entropy generation sources in each region of the water jet pump. The 2D-axisymmetric model and realisable k-ε (RKE) turbulence model at steady-state conditions were performed to validate jet pump performance and to assess the entropy generation. Likewise, the effects of the projection ratio and throat-aspect ratio as independent parameters were investigated. As a result, the throat is the most inefficient part due to the high total entropy generation rate, following by diffuser part. Also, the entropy generation rate was assessed dominant than viscous dissipation due to the turbulent dissipation, which was caused by a turbulent shear stress layer of mixing the streams. In conclusion, the projection ratio influenced the growth of the shear stress layer as well as the entropy generation. Further, the throat-aspect ratio affected the distribution of entropy generation in the throat section. An appropriate combination of both parameters has an impact on the jet pump performance improvements reducing the entropy generation rate in the future.

The two-dimensional (2D) discrete element model (DEM) of semi-flexible pavement (SFP) is utilized to understand displacemental and mesomechanical responses of SFP under different wheel loads. Simulation results indicate that when the wheel load is increased, the changing tendency of vertical displacement is basically proportional to the wheel load change. The bulging on both sides of wheel load range becomes more obvious and the bulging range is also increased. The vertical displacement is decreased, but its decreasing rate becomes larger with the increase in wheel load when the pavement depth is increased. Additionally, most compressive stress of SFP is borne by the skeleton structure composed of aggregate and hardened cement mortar, and shows an important role during the transfer of compressive stress. The interfacial compressive stress between hardened cement mortar and aggregate is largely distributed along the vertical direction. Further, the tensile stress mainly distributes at the material interface which is in contact with asphalt mortar. The tensile stress mainly appears around aggregate and cement mortar in the horizontal direction. The existence of tensile stress ensures the structural stability of pavement. Finally, the shear stress is easy to appear in asphalt mortar. The interfacial shear stress between hardened cement mortar and aggregate shows the vertical distribution. The skeleton structural stability of SFP is directly determined by the shear strength of pavement material. This study lays the foundation to reveal the formation mechanism of rutting and crack of SFP.

The wall-shear stress (WSS) fluctuations in the interaction of an oblique shock wave with a flat-plate turbulent boundary layer are investigated by means of direct numerical simulation (DNS) at Mac...

We present a combined simulation and experimental study of the structure and dynamics of dilute, semidilute, and concentrated graphene oxide aqueous alkaline dispersions. These materials behave as lyotropic systems, with phase ordering as the concentration increases. The sheet spacing in the ordered phases is much broader than that expected by the classical Derjaguin–Landau–Verwey–Overbeek theory. Rheological responses in the isotropic phase are similar to rod-like liquid crystals (LCs), which follow the simplified Leslie–Ericksen (LE) model. The dispersions in the biphase and the discotic phase behave similarly to polydomain LC polymers, following the mesoscopic LE model [Larson–Doi (LD) model]. The LD model fits the time evolution of shear stress at startup flow, re-startup flow after the cessation of flow, and reversal flow in the discotic phase. Further, the Folgar–Tucker–Lipscomb model fits the stress overshoot in a startup flow, but not the reversal flow.

Although the rheology of strong colloidal gels is predominantly concerned with either pure shear or pure compressive deformation, the vast majority of practical applications involves an arbitrary combination of shear and compressive stresses and strains. This situation demands a tensorial rheology of colloidal suspensions, where the multidimensional response of these complex materials to arbitrary superposed stress states needs to be characterized and constitutive models developed. In this study, we use 2D discrete element modelling simulations in the absence of hydrodynamic interactions to probe the behavior of a model strong colloidal gel under combined shear and compressive deformation. We consider the deformation and failure of these gels under strain-controlled conditions that range from pure compression to shear-dominated consolidation. Particle-scale observations uncover how shear stresses act to stimulate nonaffine buckling and rupture of force chains during consolidation, leading to augmented failure and collapse of the particle network. At the macroscopic level, we find that the energy required to consolidate a colloidal suspension from the gel point to close packing passes through a minimum that corresponds to weak shear strain, indicating that small amounts of shear play a critical role in destabilizing the colloidal network. These results represent an important step toward a complete understanding of the tensorial rheology of strong colloidal gels.

The flow behavior of nanocrystalline cellulose (CNC) hydrogels in the presence of a monovalent electrolyte (NaCl) as a function of CNC and salt concentration is explored using a variety of linear and nonlinear rheological tests. We have first observed an apparent “slip yield stress” at small wall shear stress values that is mainly due to the onset of solidlike slippage of the hydrogels before their true yielding and deformation. This flow regime and the “slip yield stress” can be eliminated using a sandpaper of an optimum grit size. At higher wall shear stress values, two yielding points for the CNC/salt network are seen in strain sweep tests due to network disruption and cluster deformation that depend on the concentration of both CNC (1–5 wt. %) and electrolyte (0–100 mM). The first yield stress is due to yielding and flow of clusters, while the second one is due to breakage of clusters to small flocs and individual fibers. These yielding stresses were obtained by a variety of tests including strain amplitude sweep, creep, and steady shear, and their values are compared confirming their existence. Rheo-SALS (small angle light scattering) measurements confirmed structural changes as the scattering patterns change from isotropic to highly anisotropic with an increase of deformation and rate of deformation. Moreover, confocal laser scanning microscopy and polarized microscopy images confirm the gradual breakup of clusters to smaller ones and eventually to nearly individual fibers with an increase in the applied shear strain and rate.

A mathematical model was developed to simulate gas–matte–slag three-phase flow in ISASMELT furnace with a top-submerged lance. An experimentally verified simulation model was established by adopting a VOF multiphase model coupled with a realizable k−e turbulence model. The flow field in ISASMELT furnace during the top-blowing process can be divided into 5 parts including injection, splashing, strong-loop, weak-loop, and sedimentation zones. The optimal lance diameter of 0.4 m and lance immersion depth of 0.4 m which have been applied in industry were obtained by investigating the mean velocity, phase volume fraction, splashing quantity, and wall shear stress distributions. Compared to the original operating conditions, a higher concentrate feeding rate of 140 t/h, a longer lance life of > 15 days, and a longer furnace life of 56 months were achieved for an industrial ISASMELT furnace operation under the improved lance diameter and immersion depth.

The experimental method of small punch tests (SPT) using miniature specimens has great advantages and broad application prospects for material research in space, nuclear plants and other extreme environments. However, at present, the application of this method lacks unified standards and norms, which affects its application effect. Based on these, the mechanical properties of φ3 mm disks miniature specimens of SIMP steel with different thicknesses are investigated through SPT experiments, finite element modeling (FEM) analyses and scanning electron microscopy observations. All the results demonstrate that the relationship of the mechanical properties of standard tensile test samples derived from the data of small punch test is established, and the method of establishing this mechanical relationship is also provided. Most importantly, based on the shear stress analyses of FEM calculations, most mechanical properties, such as yield strength, ultimate strength, fracture toughness and elastic modulus, can be obtained directly through SPT experiments. These findings may improve the possibility of establishing a widely accepted program for obtaining basic materials properties from SPT experimental data by using FEM simulations and provide a new comparison scheme (or norm) for obtaining accurate data from miniature specimens.

The purpose of this research is to improve the parameters of shear strength in granular volcanic soil, by adding a percentage of Portland type I cement. The first step for this research was to classify the soil through a Granulometry test, according to the Unified Soil Classification System (USCS), the result was considered as a poorly graded sand with gravel also considered by The American Association of State Highway and Transportation Officials (AASHTO) as “A-1-b”. In addition, the compaction curve of the volcanic soil has a Maximum Dry Density (MDD) of 1.21 kg/cm2 and an optimum moisture content of 17.8%. Also, the friction angle of 33.5° and a cohesion of 0 kg/cm2, and the results of the Direct Shear Test indicate the Residual Stresses of 0.63, 1.34 and 2.65 kg/cm2 according to the Normal Stresses 1, 2 and 4 kg/cm2, respectively. The second step was to apply a Modified Proctor Test as following: one sample for natural soil and four samples adding 3%, 5%, 7% and 9% of cement. Finally, applied the Direct Shear Test: one sample for natural soil and three samples adding 3%, 5%, and 7% of cement after 7 days of curing, then three more samples are taken adding 3, 5% and 7% of cement at 14 days of curing. The results of the Modified Proctor Test of the volcanic soil with the addition of 5% cement has a maximum peak of a Maximum Dry Density of 1.33 kg/cm2 and with an Optimal Moisture Content of 22.7%, improved the MDD by 10% in regard to the natural soil. And the results of the Direct Shear Test shown in each sample an increase from 14.6% to 79.1% in the friction angle in comparison with the natural soil from 25.8% to 161.5% in shear strength. Likewise, the behavior of the volumetric deformation is shown, presenting a greater contraction when a normal stress of 1 kg/cm2 is applied and a greater expansion when a normal stress of 4 kg/cm2 is applied. Also, the volcanic soil at 7 days of curing with 7% cement addition increases its resistance by 67.34% and the volumetric variation decreases by 50% and the volcanic soil at 14 days of curing with 5% addition of cement increases its resistance by 103.40% and the volumetric variation decreases by 25%.

The tip leakage flow formed by the tip clearance of a semi-open centrifugal pump adversely affects the energy performance and the energy waste. A T-shaped blade is proposed to be used to improve the energy characteristics. The internal flow field is simulated via the shear stress transport turbulence model to analyze the influence of the T-shaped blade on the performance of a centrifugal pump. It is shown that with the T-shaped blade, the hydraulic loss can be reduced, the Euler head can be increased, and the external characteristics can be improved. The maximum head and efficiency improvements are 3% and 1.6%, respectively. The relative flow angle near the tip clearance of the T-shaped blade decreases, and the strength of the backflow region is remarkably weakened. The area of the high entropy production region decreases, and the trend of the upstream diffusion is restrained under the design condition. The T-shaped blade can help to inhibit the diffusion of the high entropy production region to the hub under the low flow rate condition, but the entropy production and the mixing losses at the tip clearance are slightly increased. This research provides a new method for improving the energy performance of the semi-open centrifugal pump.

Mechanical components are frequently subjected to severe cyclic pressure and/or temperature loadings. Therefore, numerical and analytical low cycle fatigue methods become widely used in the field of engineering to estimate the design fatigue lives. The primary aim of this work is to evaluate the accuracy of the most commonly used numerical and analytical low cycle fatigue life methods for specimens made of 316 LN austenitic stainless steel and subjected to fully reversed uniaxial tension–compression loading, in the room temperature condition. It was found that both maximum shear strain and Brown–Miller criterions result in a very conservative estimation for uniaxially loaded specimens. However, maximum shear strain criteria provide better results compared to the Brown–Miller criteria. The total strain energy density approach was also used, and both the Masing and non-Masing analysis were adopted in this study. It is found that the Masing model provides conservative fatigue lives, and non-Masing model results in a more realistic fatigue life prediction for 316 LN stainless steel for both low and high strain amplitudes. The fatigue design curves obtained from the commonly used analytical low cycle fatigue equations were reexamined for 316 LN SS. The obtained design curves from Langer model and its modified versions are nonconservative for this type of material. Consequently, the authors suggest new optimized parameters to fit the given test data. The obtained curve using the currently suggested parameters is in better agreement with the experimental data for 316 LN SS.

Fiber-reinforcement is a common feature of many soft biological tissues. The response of fibrous biotissues to applied shear is thus of considerable current interest. We consider here the fundamental deformation of simple shear within the framework of transversely isotropic incompressible hyperelastic materials for fiber-reinforced specimens with a single family of parallel fibers oriented at a general angle to the direction of shear. It is well known that the normal stress effect characteristic of nonlinear elasticity plays a crucial role in maintaining an homogeneous deformation state in the bulk of the specimen. Here we investigate the effects of fiber-matrix interaction on the shear and lateral normal stresses. The inclusion of fiber-matrix interaction stiffens the shear stress response. As regards the normal stress, it is shown that the confining normal traction that needs to be applied to the top and bottom faces of a block in order to maintain simple shear can be compressive or tensile depending on the degree of anisotropy, fiber-matrix interaction and on the angle of orientation of the fibers. In the absence of such an applied traction, an unconfined sample tends to bulge outwards or contract inwards perpendicular to the direction of shear so that one has the possibility of both a positive or negative Poynting effect. It is shown that the fiber-matrix interaction enhances both the positive and negative Poynting effects. The results are illustrated using experimental data obtained by other authors for porcine brain white matter. In particular, it is shown that, for sufficiently small angles of orientation, a transition amount of shear exists at which the normal stress changes character from tensile to compressive with increasing amount of shear. An increase in the degree of fiber-matrix interaction enlarges the range of orientation angles for which this transition can occur and decreases the transition amount of shear. These transition amounts of shear are well within the physiological strain regime. The results obtained here are relevant to the development of accurate shear test protocols for the determination of constitutive properties of fibrous biological soft tissues.

The detachment of attached shock waves and the attachment of detached shock waves frequently occur for various supersonic air vehicles. The transitional boundary plays a crucial role in clarifying the detachment and attachment processes of shock waves, which are always accompanied by remarkable aerodynamic characteristic differentials. In this work, a computational study is performed to investigate the detachment and attachment conditions of shock waves for profound understanding of the shock wave dynamics. The result of computational fluid dynamics is validated against existing experimental data in the open literature. An excellent match is obtained using the shear stress transport k-omega turbulence model. From the theoretical analysis, attached shock waves can transform into detached shock waves abruptly and vice versa. Realistic transitional regions with a certain range are numerically established. The differences in the detachment and attachment phenomena of shock waves are produced as a hysteresis process.

Cold welding technique at room temperature is the preferred option in nano-assembly and nano-jointing. In this study, the cold welding behavior and mechanical strength of Cu50Zr50 metallic glass nanowires (MGNWs) in head-to-head contact are investigated by molecular dynamics simulation based on the embedded atom method potential. Effects of welding velocity, operating temperature, and size of nanowires are discussed with the consideration of stress, shear strain, atomic deformation processes, and weld quality. Our simulation results demonstrate that a desirable weld quality can be obtained at room temperature. With an increase in welding velocity, the shear deformation zones of the welded MGNWs increase, leading to a decrease in mechanical strength. However, the effect of temperature on the weld quality is not pronounced. Besides, the elongation ability of the welded MGNWs increases with increasing diameters of nanowires. Smaller diameter results in better weld quality due to the size effect of metallic glass. For a pair of MGNWs with different diameters, the necking and fracture of the welded MGNWs occur in the regions of the nanowire with a relatively smaller diameter. This study carries major implications for the fabrication and structural assembly of metallic glass-based nanomaterials.

How do large shear stress and stress ratio peaks, which are avalanche precursors, occur in granular layers in an inclining box and why do the precursors have periodicities? The answers are our main objectives. The large and small shear stress peaks which are constituted by the large and small sticks and slips are found in our simulation results. Small sticks and slips, which occur after the large slip, change the granular structure until the stress ratio becomes equal to or larger than the frictional coefficient of granular materials. Here the next large slip with the large stick and slip, which shows the precursor, occurs. The precursors which are constituted by the series of the large stick–slip events have naturally periodicities because the stick–slip events are oscillation phenomena. Our 3-dimensional simulation results using the smoothed particle hydrodynamics (SPH) method based on our constitutive equations obtained by the 3-dimensional discrete element method (DEM) present the precursors in the bulk and on the surface and show the difference between them. The precursors are also found in the longitudinal and the depth directions of the granular layer. The simulated periodicities agree with the published experimental results.

In this study, the discrete-element model (DEM) of asphalt pavement is established to discuss the effects of temperature changes of interlaminar bonding layer on mechanical responses of asphalt pavement in different seasons. Calculated and test results indicate that the temperature within the depth range of 0–5 cm in asphalt pavement is obviously affected by ambient temperature. The heat is accumulated within the pavement depth range of 2–5 cm, greatly affecting the interlaminar bonding state. In addition, lower temperature in winter increases the continuity of asphalt pavement layers, reducing the compressive stress in upper layer. In addition, higher temperature in summer weakens the interlaminar bond, increasing the horizontal tensile stress in upper layer and at the interlaminar interface. Further, lower interlaminar bonding strength increases the maximum shear stress at the interlaminar interfaces between asphalt pavement layers, as well as at the interface between asphalt mortar and aggregate. As the pavement depth is increased, the horizontal shear stress is increased. Finally, the high temperature increases the tensile strain near the bottom of upper layer. The displacement directions of more aggregate particles move vertically downward at low temperature, but move to two lateral sides at high temperature.

The main objective of the research is examining the influence of solids concentration on the shear stress and viscosity in fine-dispersive lime slurry collected from a flow installation existing in a selected processing plant producing lime. The analysis presented in the paper deals with slurry of average-size particles the diameter of which equals to 46μm, solid density ranges from 1140 kg/m3to 1330 kg/m3and solids concentration by volume from 10.12% to 23.70%. It has been shown that for solids concentration up to 18.28% by volume, the shear stress increases moderately with increasing concentration. If solids concentration is higher than 18.28% by volume, the shear stress increases exponentially. The determination of the boundary concentration above which the increase in shear stress is exponential is a fundamental guideline in determining the transport parameters of fine-dispersive lime slurry. The expected results of the analysis should be recommended for the transport of slurry with several times higher mass concentration and thus reducing the amount of water while increasing the economic profitability of the applied solution.

Accurate evaluation of life-limiting failure behavior is a prerequisite to ensure the successful design and application of ceramic matrix composites (CMCs). To investigate life-limiting failure behavior of CMCs, it is necessary to evaluate the in-plane shear strength. In this paper, the in-plane shear strength (IPSS) of two-dimensional carbon fiber reinforced silicon carbide matrix (2D C/SiC) composites at elevated temperatures in air was studied by a modified Iosipescu method. A simplified Iosipescu loading configuration without mechanical connections or a fastening assembly was proposed. According to finite element analysis, an almost pure in-plane shear stress field and an in-plane shear failure mode were obtained. The modified Iosipescu method was adopted to evaluate the IPSS of 2D C/SiC at room temperature (RT), 800 °C, and 1000 °C. The in-plane shear failure mode was observed, and the IPSSs were obtained. Based on the microstructure analysis, the release of the tensile stress at elevated temperatures can account for the increase in the IPSS from RT to 800 °C. The decrease in the IPSS from 800 °C to 1000 °C may have resulted from the oxidation of carbon fibers. The modified Iosipescu method can be used to measure the in-plane properties of CMCs. This study may be beneficial to reveal the failure mechanisms and guide the design of CMCs.

This paper theoretically investigates the effects of wall conduction and viscous dissipation on a steady natural convection Couette flow in a vertical channel with some thickness of the bounding slabs. The coupled governing equations have been solved analytically using homotopy perturbation method. The effects of the flow and thermophysical parameters are depicted on graphs and tables. It is noteworthy to mention that the velocity and temperature distributions of the working fluid dropped near the heated plate when the thickness of the plates (d) is increased while a reverse case was observed near the cold plate. It is discovered that the shear stress increases on the cold plate with increase in (d) while it decreases on the heated plate. It is further observed that the rate of heat transfer on both the plates decreases with increase in (d) while it increases on the cold plate with growing viscous dissipation (Br). A decrease in rate of heat transfer was observed at the cold plate with increase in (d). For a fixed value of heat source/sink, the volume flow rate increases with increase in (d).

This study investigates the effect of opening position on the indoor airflow of a natural ventilated isolated building model. Furthermore, the opening configuration which generate the highest ventilation is to be determined. Seven different opening configurations were considered by varying the opening position on the windward and leeward walls which include three cases of aligned openings and four non-aligned openings. Models with different opening position were simulated using Computational Fluid Dynamics (CFD) with 3D RANS turbulence model Shear Stress Transport (SST) k- ω. Simulation result indicates the indoor air velocity as well as pressure distribution highly depends on both inlet and outlet opening positioning. Different opening configuration influences the recirculation zone generated within the building model. Comparison shows openings located near the roof generate 6.52% higher ventilation rate compared to openings located near the ground. The study concludes that opening position holds a crucial role in affecting internal airflow pattern, air recirculation and ventilation rate for a natural cross ventilated building.

The descending aortic aneurysm is one of the most catastrophic cardiovascular emergencies resulting in high mortality worldwide. Clinical observations have pointed out that stent implantation in the sick aorta should probably allow stabilization of the hemodynamic state of the patient's aorta. To better understand the hemodynamic impact of a stent-treated aneurysm, numerical simulations are used to evaluate hemodynamic parameters. These latter including flow profile, velocity distribution, aortic wall pressure and shear stress, which are difficult to measure in vivo. It should be noted that the numerical modeling assists in medical planning by providing patterns of blood circulation, in particular, the distribution of pressures and shear stresses in the wall. In this context, the pulsatile blood flow in the aneurysmal aorta with stent is studied by CFD (Computational Fluid Dynamics) simulations. Realistic boundary conditions time dependent are prescribed at the level of the different arteries of the complete aorta models. The hemodynamic profile of the aneurysmal aorta with stent was analyzed by contour planes of velocity vectors, pressures and shear stresses at different times during the cardiac cycle. The obtained results made it possible to show the effect of the stent on the improvement of the blood flow by solving the problems of hemodynamic disturbances in the aorta. The methodology used in this work has revealed detailed and necessary information for the cases studied and shows the interest of the numerical tool for diagnosis and surgery.

Rutting resistance is an important consideration for paving asphalt mixes. The cause of rutting is a shear strain in the asphalt pavement structure. Here, the rutting behavior of asphalt pavements was evaluated through laboratory simulations using the Hamburg Wheel-Tracking Test (HWTT), UK Wheel-Tracking Test (UKWTT), and Scaled Accelerated Load Simulator (SALS) test. The correlation between the three simulation tests was analyzed to determine the conversion factor (CF). Two parameters of temperature and speed of simulation testing were evaluated in this study. Subsequently, the representative frequency and dynamic modulus were calculated with consideration of viscoelasticity and time–temperature superposition. Using logical analysis, CF between the three simulation tests was validated. The results showed that the full-scale test yielded the highest stiffness modulus of 4,015 MPa, and the UKWTT yielded the lowest stiffness modulus of 1,857 MPa at 60 °C. From the HWTT results, it was found that the impact of moisture damage at 40 °C is not substantial compared to that at 50 °C. The conversion factor of HWTT at 40 °C, HWTT at 50 °C and UKWTT at 60 °C to SALS were 0.92, 0.74, and 0.63, respectively. Furthermore, the similar rutting performance among SALS, HWTT at 40 °C in dry and wet conditions, and HWTT at 50 °C in dry condition can be observed when the CF is applied. Lastly, the effectiveness of the conversion factor is diminished with increasing rutting damage.

A numerical investigation utilizing the 3D displacement discontinuity method is performed to examine the stress perturbations and induced displacements near a weak fault with arbitrary orientations and dip, assuming zero shear stress and normal displacement. The in-situ stress field near the fault is taken as known and varied with depth. The modelling is constructed based on indirect boundary integral equations. In this work, the fault plane is first modelled as a rectangular plane with negligible thickness between the adjacent surfaces. The fault plane is then divided into numerous rectangular boundary elements with imposed shear singularities on the surface, which is normal to the fault plane to simulate a traction-free scenario. The numerical results of the total induced stresses and displacements are then compared to the existing solutions of a penny-shaped crack for validation purpose. With validated results, the paper moves on to the discussion of various factors that have impacts on the induced stress and displacements, including: aspect ratio which is defined by strike over dip; orientation of the strike on the horizontal ground surface; as well as dip. The boundary integration method with modification is also used to model an elliptical distribution of singularities with inner, corner, and edge elements to accommodate more complex shape of a discontinuity; small differences are observed. Cited as: Chai, Y., Yin, S. 3D displacement discontinuity analysis of in-situ stress perturbation near a weak fault. Advances in Geo-Energy Research, 2021, 5(3): 286-296, doi: 10.46690/ager.2021.03.05

Subsequent yield surfaces of ductile solids, pre-strained in shear and/or tension, exhibit various characteristic features that depend on the proof strain used to detect yield. These features include kinematic hardening when the proof strain denoting yield is low, isotropic hardening when it is high, formation of a ‘nose’ in the loading direction and flattening of the rear part of the yield surface. With the aid of a computational homogenisation scheme that allows application of arbitrary macro stress or macro deformation gradient to a unit cell, we show that essential features of the subsequent yield surfaces owe their origin to the extent of plasticity accumulated within the unit cell. For instance, a simple unit cell containing a spherical void, where the void serves to create a heterogenous distribution of plastic strain, suffices to computationally reproduce the experimentally observed features. Moreover, in contrast to experiments which generally allow plotting of the yield surface in a normal stress – shear stress plane, the computational scheme allows fuller exploration of the subsequent macro yield surface in the macro stress space. We find that what seems to be a translation and distortion of the yield surface in experiments, is actually most pronounced near some critical octahedral planes characterised by levels of triaxiality induced by the pre-straining process. The evolution of the yield surface in regions where the triaxiality is higher is considerably different. Moreover, as homogeneous yielding is approached with loading of the unit cell, the material seems to forget the nature of the pre-straining process and undergoes isotropic hardening.

Vortical structures of a submarine with appendages are fully turbulent and complex. Thus, flow control and vortex manipulation are of great importance for the hydrodynamic performance and acoustic characteristics. Take the generic submarine model DARPA Suboff as the test case, a vortex tuning method based on the Liutex force field is proposed to manipulate the vorticity field. Viscous flow past the submarine model in straight-line motion at a Reynolds number of 1.2×107 is achieved by solving the Reynolds averaged Navier-Stokes (RANS) equations. Multi-block structured mesh topology is used to discretize the computational domain, and the shear stress transport (SST) k - ω turbulence model is implemented to close the equations. The control of vortex is achieved by introducing additional source terms based on Liutex vortex definition and identification system to the RANS equations. The resistance acting on the submarine, flow field as well as the vortical structures are compared and analyzed. Results show that Liutex force model can effectively reduce the resistance by 9.31% and change the vortical structures apparently.

Concerning the demand for upscaling in severe plastic deformation (SPD) processes, in this research, a novel method is presented, during which a billet with a rectangular cross-section is enforced under a cross-sectional shear strain, and its cross-section is changed to the parallelogram. Then the parallelogram is again enforced under another cross-sectional shear strain, and its shape is changed back to the original rectangular shape. Due to the form of the deformation and the manner in which cross-section changes, the method is entitled “Simple Shear Forging” (SSF). A new apparatus was designed and manufactured to impose plastic strain on the billet in a plane strain condition, while a hydrostatic pressure is applied, and without any change in the cross-sectional area, which ensures the repeatability of the process. In order to study the process parameters, most notably friction and pressure, simulation of the process was carried out using the commercial finite element code ABAQUS/Explicit, and the resultant strain distributions were investigated. The presented method is applied to Al 1050 billets, and the Vickers microhardness test was carried out for different numbers of applied passes. The results indicate that the SSF method is capable of introducing high strain values and grain refinement. Unlike most of the previous methods, it is not necessary to remove and reinsert the billet after each pass, which consequently enhances the productivity of the process significantly.

In this study, the substructure formation in a multi-pass rolled aluminium single crystal {001} was investigated by the crystal plasticity finite element model, and the predations were validated by experimental observations at both macro- and micro-scale. A finite element model for multi-pass rolling was developed to follow the real experimental rolling scheme, by which the through-thickness macroscopic subdivision was successfully predicted up to a 90 % reduction. The macro-subdivision was featured by forming matrix bands through the thickness, and the deformation behaviours, in terms of slip activity, shear strain and crystal rotation, alternated between matrix bands. The development of matrix bands, stability of crystal orientations, and correlation between slip activity, shear strain and crystal rotation have been investigated. Another modelling method, Submodel, was used to exceedingly increase the mesh resolution in smaller regions of interest, and the experimentally observed microstructure, i.e., micro-subdivision was explicitly and spatially revealed. Similar predictions were obtained in Submodels with different element sizes, which proves the feasibility of this method in predicting microstructure formation. It was found that the substructure formation by varying slip activity and crystal rotation between domains is energy favourable. The procedure of substructure formation was explained based on the predictions, three types of substructure have been identified, and the substructure formation was discussed.

The flow behavior of silver paste during die bonding was analyzed by numerical simulation to clarify the formation mechanism of coarse-dense inhomogeneous distribution of silver particles in a die-attach layer. Depending on the loading speed of a die, silver particles in the paste flow and form a coarse-dense distribution under a die. The microstructure of the paste before sintering was observed by X-ray computer tomography (X-ray CT) and Scanning Electron Microscope (SEM). At a slow loading speed of 1.0 μm/s, the paste is densely packed with silver particles along the diagonal of the die. A coarse structure was observed in the other area of the paste. On the other hand, at a high loading speed of 60.0 μm/s, there was no clear segregation and the paste layer has an almost uniform structure. The SPH method was used to calculate the flow behavior of particles in the paste, and the flow velocity and shear stress of the paste were calculated. The paste velocity and shear stress in the region along the diagonal of the die is smaller than those in other area of the die. A comparison of the shear stress applied to the paste at different loading speeds showed that the smaller the loading speed, the larger the value of summation of shear stress. The difference between the maximum and minimum shear stress in a lateral direction through the center of the die increases with decreasing of loading speed. Thus, a large difference in local shear stress acting on the paste causes the formation of coarse-dense structure of the silver paste. It was found that it is necessary to eliminate local differences in the shear stress acting on the paste in order to achieve uniform joint the silver paste to the substrate without forming a coarse-dense structure.

The study on the structure and mechanical properties of Zr55Al10Ni5Cu29Y1 bulk metallic glasses (BMGs) indicates that deep cryogenic cycling treatment (DCT) is an effective method to improve room-temperature plasticity of BMGs containing trace rare earth elements. DCT not only increases the volume and size of STZs in BMGs, promotes the generation of multiple shear bands, but also reduces the maximum shear stress that occurs in pop-in events. Due to the internal stress generated during DCT, rejuvenation causes the larger volume and size of the shear deformation zone, which can promote the shear bands formation and generate multiple shear bands to accommodate plastic deformation. In different BMGs systems, the volume of STZs tends to decrease as v increases. STZ is more sensitive to the composition, and changes in trace elements can cause changes of the volume of STZs.

For simulation of hypersonic turbulent and transitional flows at high Reynolds numbers, a gas-kinetic scheme (GKS) strongly coupled with the turbulent kinetic energy equation in shear stress transp...