Maximum Shear Stress Decrease Research Articles

Axial pulling of a neo-Hookean fiber embedded in a generalized neo-Hookean matrix

In this paper, we study the mechanical behavior of a slightly compressible neo-Hookean fiber, which is subjected to an axial pullout displacement, embedded in a slightly compressible generalized neo-Hookean matrix. We study three different boundary value problems containing both fully and partially embedded fibers. We study the effect of material and geometric parameters on the force required to axially displace the fiber, the shear stress at the interface and in the interior of the fiber–matrix system, and the norm of the Green–St. Venant strain. We found an interesting result in that the maximum shear stress occurs in the interior of the matrix when the shear modulus of the fiber is comparable to that of the matrix. Furthermore, as the fiber and matrix becomes more compressible, the maximum shear stress decreases.

Finite element analysis of the flange with different fillet radius in tubular wind tower

Today’s modern world has more demand for electricity to perform most of the activities. In this regard, wind turbines are used to convert the wind energy into electrical power, where turbines are mounted at the top of the tower called wind tower. To meet the high power generation demand, the wind energy towers will have to become taller because winds are stronger at higher altitudes. In the present, work Modal analysis of the wind tower is done using ANSYS, and Campbell diagram is plotted to check the frequency of resonance between the tower natural frequency and the natural frequency of the rotating blades. Considering the different fillet radius in the flanges, the critical conditions are simulated under the same loading condition. Finite Element Analysis (FEA) results show that by increasing the fillet radius the Equivalent stress, Maximum principle stress and, Maximum shear stress decreases. The safety of the tower is ensured through the Campbell diagram where the excitation frequency of any blade is not crossing the exciter box.

Numerical Simulation of the Geothechnical Effects on Local Scour in Inclined Pier Group with FLow-3D Softaware

When the bridge piers are located in front of the water flow, vortices are formed against it and due to their activity, the materials of the river bed are eroded around the bridge piers and the scouring hole is created. If the foundation depth and bridge pier piles are insufficient, the bridge will fail.The study of total shear stress in the flow bed at different leveling of the pile caps shows that the highest shear stress is created when the pile cap position is at the same level as the river bed; by installing the pile cap at a lower level than the river bed, the maximum shear stress decreases. This may be due to the fact that in this case, the distance between the pier group increases and the presence of the second pier decreases the flow rate in the pier group and different pier in the one pier group acts as the two independent piers in the formation of the flow pattern. By comparing the final longitudinal sections of the scouring at different leveling of the pile cap, it is concluded that the largest reduction in scouring depth occurs in aerofoil-shaped pile caps and pile caps with the sharper nose and better aerodynamic shapes are good options to control the horseshoe vortices and will reduce the scouring depth around the inclined pier group.

A numerical study of fracture initiation under different loads during hydraulic fracturing

The fracture initiation behavior for hydraulic fracturing treatments highlighted the necessity of proposing fracture criteria that precisely predict the fracture initiation type and location during the hydraulic fracturing process. In the present study, a Mohr-Coulomb criterion with a tensile cut-off is incorporated into the finite element code to determine the fracture initiation type and location during the hydraulic fracturing process. This fracture criterion considers the effect of fracture inclination angle, the internal friction angle and the loading conditions on the distribution of stress field around the fracture tip. The results indicate that the internal friction angle resists the shear fracture initiation. Moreover, as the internal friction angle increases, greater external loads are required to maintain the hydraulic fracture extension. Due to the increased pressure of the injected water, the tensile fracture ultimately determines the fracture initiation type. However, the shear fracture preferentially occurs as the stress anisotropy coefficient increases. Both the maximum tensile stress and equivalent maximum shear stress decrease as the stress anisotropy coefficient increases, which indicates that the greater the stress anisotropy coefficient, the higher the external loading required to propagate a new fracture. The numerical results obtained in this paper provide theoretical supports for establishing basis on investigating of the hydraulic fracturing characteristics under different conditions.

Numerical modeling of the effect of pile geometry and pile cap leveling on the local scour under inclined pier group

When the bridge piers are located in front of the water flow, vortices are formed against it and due to their activity, the materials of the river bed are eroded around the bridge piers and the scouring hole is created. If the foundation depth and bridge pier piles are insufficient, the bridge will fail. Now, due to the importance of identifying the mechanisms affecting the scouring on this types of bridge piers, the effect of the geometric shape of the piles that installed under the inclined piers and also the effect of the pile cap leveling in the sedimentary bed have been investigated and the properties of the scouring around the inclined pier group was studied numerically and using the Flow-3D software. The study of total shear stress in the flow bed at different leveling of the pile caps shows that of the highest shear stress was created when the pile cap position is at the same level with the river bed and by installing the pile cap at a lower level than the river bed, the maximum shear stress decreases. This may be due to the fact that in this case the distance between the pier group increases and the presence of the second pier decreases the flow rate in the pier group and different pier in the one pier group act as the two Independent piers in the formation of flow pattern. By comparing the final longitudinal sections of the scouring at different leveling of the pile cap, it is concluded that the largest reduction in scouring depth occurs in aerofoil-shaped pile caps and pile caps with the sharper nose and better aerodynamic shapes are good options to control the horseshoe vortices and will reduce the scouring depth around the inclined pier group.

Effect of pre-stress on the onset of yielding in bulk metallic glasses

To investigate the intrinsic effect of the pre-stress (σpre) on the onset of yielding, nanoindentation experiments are performed on two metallic glasses (MGs) which are elastically-bent and constrained within a home-made apparatus. Statistical calculations for the first pop-ins are made and noticeable decrease in maximum shear stress (τmax) is observed under tensile pre-stress, but only slight increase under compressive one, without considering the pre-stress effect on the ratio (0.29) of τmax to the maximum contact pressure (p0). This asymmetry phenomenon is related to the anharmonic and asymmetric nature of the interatomic interaction potential caused by the applied pre-stress. Moreover, finite-element analysis is conducted to obtain the elastic stress field of the pre-stressed region upon indentation, which becomes anisotropy and quarter-symmetric. τmax for the specimen is defined as 0.29p0 + 0.50σpre for the tensile-stressed region and 0.29p0 for the compressive-stressed region within elastic strain limit of MGs, which requires the correction for the intrinsic τmax with tensile σpre, but not for compressive σpre. The corrected τmax and activation energy barrier of shear transformation zone are found to be independent on σpre, suggesting that the intrinsic shear stress is a constant and the yielding of MGs obeys the maximum shear stress criterion.

Development of dynamic behavior of the novel compositeT-joints: Numerical and experimental

In this paper dynamic behavior (modal analysis and dynamic transient response) of a novel sandwich T-joint is numerically and experimentally investigated. An epoxy adhesive is selected for bonding purpose and making the step wise graded behavior of adhesive region. The effect of the step graded behavior of the adhesive zone on dynamic behavior of a sandwich T-joint is numerically studied. Finite element analysis (FEA) of the T-joints with carbon fiber reinforced polymer (CFRP) face-sheets is performed by ABAQUS 6.12-1 FEM code software. Modal analysis and dynamic half-sine transient response of the sandwich T-joint are presented in this paper. Two verification processes employed to verify the dynamic modeling of the manufactured sandwich panels and T-joint modeling. It has been shown that the step wise graded adhesive zone cases have changed the second natural frequency by about 5%. Also, it has been shown that the different arranges in the step wise graded adhesive zone significantly affect the maximum stresses due to transient dynamic loading by 1112% decrease in maximum peel stress and 691.9% decrease in maximum shear stress on the adhesive region.

Mechanical Properties of Unsaturated Polyester Filled With Silica Fume, Glass Powder and Carbon Black

In this study a polymer matrix composites (PMCs) have been prepared with the aid of ultrasonic wave dispersion method for mixing , using of unsaturated polyester resin with Silica Fume(SF), Glass Powder (GP)and Carbon Black (CB). Moulds were prepared by hand-made from silicon rubber according to the ASTM standard table (4). The fillers added separately with different ratios as (0%,0.5%, 1%, 1.5 %, 2%,2.5% and 3%).The results show increase the hardness and impact strength when added GP, SF, and CB to polymer matrix. Flexural strength and maximum shear stress decrease when added silica fume , but when added glass powder and carbon black led to increase flexural strength and maximum shear stress to certain percent at ( 2%, 1.5% for GP and CB respectively) then dropped when increase weight fraction of GP, CB . Compressive strength decrease when added glass powder and carbon black, while it is increase when added silica fume to polymer matrix. Wear rate decrease when increase weight fraction of carbon black but it increases when added GP and SF.

Cyclic direct shear behaviors of an artificial frozen soil-structure interface under constant normal stress and sub-zero temperature

The soil-structure interface between structures and frozen soil ground is an important element to the structure safety in permafrost regions. This interface is usually subjected to a constant normal stress and cyclic shear loadings such as seismic, wind, and wave loadings. Hence, the cyclic direct shear behaviors of this interface have critical impacts on the safety and durability of the structure. This paper investigated the cyclic direct shear behaviors of an artificial frozen soil-structure interface under four constant normal stresses and four sub-zero temperatures by using a large-scale multi-functional direct shear apparatus. Cyclic shear stress and normal displacement were measured under normal stresses of 100, 300, 500, and 700kPa and at sub-zero temperatures of −2, −6, −10, and −14°C, respectively. These measurements revealed the following mechanical properties of this artificial interface: (1) The maximum shear stress is always observed in the initial stage of the first cycle. This maximum shear stress is linearly related to the normal stress. (2) Both the internal friction angle and the cohesion of this interface at the maximum shear stress decrease with the increase of sub-zero temperature. (3) The internal friction angle decreases with further cycles. This angle becomes significantly smaller in the stabilized cycles than that in the first cycle. (4) The maximum dilation measured by normal displacement is always observed in the first cycle. This dilation is decreasing with higher normal stress and at lower sub-zero temperature. However, the final normal displacement always contracts and its magnitude increases with the increase of normal stress or the decrease of sub-zero temperature. Finally, a simple damage model is proposed to describe these behaviors of this artificial interface and its performance is checked through its prediction for experimental data.

Atomistic simulations of the nanoindentation-induced incipient plasticity in Ni3Al crystal

In this work, the indentation-induced incipient plasticity of Ni3Al crystal is investigated by performing molecular dynamics (MD) simulations. Simulation results reveal that the incipient plasticity of Ni3Al is originated from the homogeneous nucleation of the 1/6〈112〉-type Shockley partial dislocation. The critical load, critical contact pressure, dislocation nucleation site and active slip system are significantly affected by crystallographic orientation, model size, indenter radius and temperature. The choice of interatomic potential has significant implications for the indentation behavior of Ni3Al. Some benchmarks for evaluating the credibility of interatomic potentials are presented. The pop-in phenomena are correlated with dislocation generation, multiplication and reactions. The formation mechanisms of complex stacking faults (CSFs), antiphase boundaries (APBs) and superlattice intrinsic stacking faults (SISFs) are clarified. The highest indentation modulus is obtained in (111) indentation followed by the (110) and (100) cases. The indentation modulus and the depth of nucleation sites increase with increasing indenter radius but the maximum shear stress decreases. The maximum shear stress and indentation modulus decrease linearly with increasing temperature, reflecting the stress-assisted and thermally activated nature of dislocation nucleation.

Effect of Holding Time on Rheological Characteristics of the Semisolid Magnesium Alloy

The semisolid shear rheological properties of AZ91D alloy were tested. The effect of holding time on the rheological characteristics was investigated. The results show that: during the shear rheological test at 570 °C, a critical shear stress and a maximum shear stress are happened. And with the holding time increasing, solid fraction decreasing and solid particles distributing more uniformly, the rheological rate increases, but the critical shear stress and the maximum shear stress decrease.

Investigation of the Semisolid Rheological Characteristics of AZ91D Alloy

The semisolid shear rheological characteristic of AZ91D alloy were investigated. The results show that: during the shear rheological test at 570 °C, a critical shear stress and a maximum shear stress are happened. And with holding time increasing, the solid fraction decreasing and the solid particles distributing more uniformly, the rheological rate increases but the critical and maximum shear stress decrease. At last, based on rheological theory, a five-component rheological model of the semisolid AZ91D alloy is established, which is H1 - (N1 / H2) - (N2 / S).

Evolution of fracture surface morphology in rocks

The authors have related the stress state and surface roughness of fractures in rocks: with growth of maximum normal stress in the area of a fracture, surface roughness on the site of the maximum shear stress decreases. Based on the found relationship, the authors propose a method of estimating stress state of a material by value of the material fracture surface roughness.

Dynamic response of top-down cracked asphalt concrete pavement under a half-sinusoidal impact load

A 3D finite element analysis model of cracked asphalt pavement is established by the FEM software ABAQUS. Based on dynamics mechanics, fracture mechanics and finite element theory, this paper studies the influence of various vehicle speeds, crack location, crack depth, damping ratio etc. on the dynamic response. The results show that the surface deflection, the maximum tensile strain at the bottom of the asphalt layer, and the maximum shear stress of the asphalt layer decreased with the increase in vehicle velocity when there is no crack in the pavement. No matter where the transverse position of the crack is the stress intensity factors increase with the increase in crack depth and decrease exponentially with the increase in longitudinal distance between the vehicle center and the crack. In the case of the crack locating in the center of wheel clearance, the surface deflection increases with the crack depth increasing. But if the crack is at the edge of the wheel track, there will be a critical vehicle velocity where the surface deflection is smaller than the asphalt pavement without crack if the vehicle velocity is above it. The maximum tensile strain at the bottom of the asphalt layer and the maximum shear stress of the asphalt layer are also smaller than the asphalt pavement without crack. The maximum tensile strain and the maximum shear stress decrease with the damping ratio increasing. So the increase in damping ratio can help to alleviate the propagation of cracks.

Direct shear tests on sand treated with xanthan gum

The present study aimed to discuss the applicability of biotechnologies in geotechnical engineering. For this purpose, a laboratory investigation was performed to investigate the effect of introducing a biomaterial, xanthan gum, on the behaviour of a sand using a direct shear testing apparatus. The factors addressed included the xanthan gum content and time of curing. The experimental data showed that the shear strength of the sand increased as the biological material content increased beyond 1% xanthan gum content. Increases in maximum shear stress of around 14–166% occurred in specimens with 3% xanthan gum content, and around 93–288% occurred in specimens with 5% xanthan gum content. A decrease in maximum shear stress of around of 7–60% occurred in specimens with 1% xanthan gum content. Within the range of parameters covered by the investigation, the principal factors governing the rate of this increase/decrease in maximum shear stress was the xanthan gum content. The impact of curing time was not significant. This report is intended to serve as an additional discussion and comments on the significance of collaboration between biologists and geotechnical engineers.

Effect of Poisson’s ratio on stress state in the Wenchuan MS8.0 earthquake fault

The Wenchuan MS8.0 earthquake occurred on the Longmenshan fault which inclines at a dip angle exceeding 60 degrees. Since most thrust earthquakes occur on faults with dip angles of about 30 degrees, it is enigmatic why the Wenchuan earthquake occurred on such a steep fault. In this study we use a simple finite element model to investigate how the stress state in the fault changes with the variation of Poisson’s ratio. The results show that, with the Poisson’s ratio in the fault increasing, the magnitudes of the principal stresses increase and the maximum shear stress decrease, and, especially, the angle between the maximum principal stress and the fault plane decreases, which will enhance the driving force to overcome the frictional resistance on the fault. The increase of Poisson’s ratio in the fault may be an important factor to affect the occurrence of the fault earthquakes with large angles between maximum principal stress and fault plane.

Maximum Shear Stress Analyses of the Cermet Cladding Part under Wear Condition

The interaction between a cermet cladding plate part and a homogeneous cylindrical part under wear condition is simplified as a plain strain contact problem. Based on Hertz contact theory, the theoretical model of the maximum shear stress in the cladding part is built; an example and its finite element analyses (FEA) are given. Theoretical results well coincide with those of the FEA. Both results show that, with the increase of the cladding thickness, the maximum shear stress decreases, its position shifts toward the clad surface. The effects of the wear load and the properties of the frictional materials on the maximum shear stress are also studied. The research results have great significances to the design of cladding parts under wear condition.

Coupling between different layers of the lithosphere under horizontal drag underneath

Based on a layered rheological model of the lithosphere, the velocity and stress distributions in the lithosphere under horizontal drag underneath were calculated using viscoelastic finite element method of plain strain with finite deformation. In the simulation, different conditions of drag and blocking were assumed to study their influences on the stress distribution and the coupling between different layers. Blocking depth has little influence on the stress level in the whole area and the coupling between different layers, but influences the stress state in the area around the blocking. The area covered by the high stress anomaly becomes larger when the blocking depth becomes deeper, but the magnitude of the value of the maximum shear stress decreases. The greater the viscosity differences between different layers of the lithosphere, the greater the possibility of decoupling between them. Under the drag of normal mantle convection (the convection velocity is about 20 cm·a −1 ), a lithosphere with a rheological structure similar to that of North China could not have decoupling between different layers, while could have stress distribution with magnitude of several MPa to tens of MPa and could have anomalous areas with stress accumulation if the geological structure is complicated.

Fault-valve behaviour in optimally oriented shear zones: an example at the Revenge gold mine, Kambalda, Western Australia

Quartz vein systems developed in and adjacent to shear zones host major gold deposits in the Kambalda region of the Norseman–Wiluna greenstone belt. At the Revenge Mine, two groups of mineralised reverse shear zones formed as conjugate, near-optimally oriented sets during ESE subhorizontal shortening adjacent to a major transpressional shear system. The shear zones developed at temperatures of about 400°C in a transitional brittle–ductile regime. Deformation was associated with high fluid fluxes and involved fault-valve behaviour at transiently near-lithostatic fluid pressures. During progressive evolution of the shear system, early brittle and ductile deformation was overprinted by predominantly brittle deformation. Brittle shear failure was associated with fault dilation and the formation of fault-fill veins, particularly at fault bends and jogs. A transition from predominantly brittle shear failure to combined shear along faults and extension failure adjacent to faults occurred late during shear zone evolution and is interpreted as a response to a progressive decrease in maximum shear stress and a decrease in effective stresses. The formation of subhorizontal stylolites, locally subvertical extension veins and minor normal faults in association with thrust faulting, indicates episodic or transient reorientation of the near-field maximum principal stress from a subhorizontal to a near-vertical attitude during some fault-valve cycles. Local stress re-orientation is interpreted as resulting from near-total shear stress release and overshoot during some rupture events. Previously described fault-valve systems have formed predominantly in severely misoriented faults. The shear systems at Revenge Mine indicate that fault-valve action, and associated fluctuations in shear stress and fluid pressure, can influence the mechanical behaviour of optimally-oriented faults.

構造用鋼 ローラーピッチング試験の接触応力に関する有限要素法解析

This paper deals with the effect of the tangential load on the contact stress distribution of the roller pitting test by two-dimensional finite element method. With increase in tangential load, the principal shear stress increases near the surface region and the depth of the maximum shear stress decreases. On the other hand, the effect of tangential load on the shear stress amplitude (the difference between the maximum τxy and minimum τxy at each depth) distribution is small. The tangential load in roller pitting tests was measured. Effect of maximum pressure and slip ratio on the tangential load is not so large and the ratio of tangential load to normal load is about 0.08. The change of the stress distribution by this