Variation Of Stress Distribution Research Articles

Stress modeling for the upper and lower crust along the Anninghe, Xianshuihe, and Longmenshan Faults in southeastern Tibetan plateau

Earthquake occurrence depth in the crust is related to stress, temperature, and brittle–ductile transition, which is also near the transition depth of the upper to lower crust. The composition variation between the upper and lower crust causes remarkable changes of rheological properties and variation in stress distribution. Clarifying the detailed stress distribution in the upper and lower crust is crucial for understanding the brittle–ductile transition and the stress environment of the seismogenic zone. The Southeastern Tibetan Plateau (SETP), with wide spread of active strike−slip faults and clustered earthquakes, provides a natural field for investigating the relationships between crustal stresses, deformation behaviors, and earthquake mechanics. By considering the rheological properties of granite and anorthite, this paper established stress models with different boundary depths (15, 20 and 25 km) between the upper and lower crust along the Anninghe, Xianshuihe, and Longmenshan Faults in the SETP with a horizontal strain of 6 × 10−4 extracted from in situ stress data. The stress model with different geothermal gradients and a boundary depth of 20 km between the upper and lower crust suggests two distinct types of the brittle–ductile transition below these three faults. Simultaneously, the stress model can account for the continuity of earthquake depth distribution below the Longmenshan Fault and the seismic gap below the Anninghe and Xianshuihe Faults. The continuity of earthquake depth distribution or seismic gap below these three faults can be explained by their different geothermal gradients. These findings provide new insights for understanding the stress environment of the seismogenic zone in the SETP. Our model reveals the relationships between differential stress, seismicity, brittle–ductile transition, and boundary depth of the upper and lower crust in the continental crust, and connects the multiple observations from geophysics and geology. Furthermore, our model provides insights for studying multiple processes in the continental crust, such as crustal deformation, fault slip, and earthquake occurring.

Numerical simulation of pressure vessel explosions using metallic and composite materials: A comparative study

In light of the growing interest in hydrogen as an eco-friendly fuel source, ensuring the safe transportation of hydrogen is becoming increasingly vital for future mobility solutions. This research delves into the structural responses of various pressure vessel designs when exposed to explosive events, simulating hydrogen releases through finite element analysis. The study employs a TNT equivalent model to represent the energy liberated during a pressurized gas explosion. The objective is to compare the performance of metallic pressure vessels with two composite variants: one based on Quasi-Isotropic composites and the other utilizing the Double-Double fabrication technique. The analysis centers on stress and deformation within each model. The findings reveal that steel and Quasi-Isotropic models exhibited maximum stresses close to 5000 MPa, showcasing variations in stress distribution. In contrast, the Double-Double composite experienced higher stress levels, nearing 8000 MPa. In terms of deformation, steel exhibited the smallest displacement, followed by Quasi-Isotropic and Double-Double, with respective values of approximately 8 mm, 6 mm, and 4 mm.

“The TA loop” better force delivery through better design

Introduction: This study evaluates and compares stress distribution and deformation generated on the periodontal ligament, cortical and cancellous bone by a novel loop design, the TA (Tarun Anu) loop used for anterior teeth retraction and compare it with the conventional Mushroom loop using finite element analysis (FEM). Aims and Objective: Evaluation of the efficacy of a novel loop design named as TA loop with the conventional Mushroom loop (M loop) using FEM. Materials and method: Finite element models of both the loops and maxilla and mandible was created using ANSYS Software and for geometric modelling, SolidWorks Software was used. The loading condition was designed to mimic retraction forces determined from two different activations and the results were obtained. Results: FEM affirmed that the stresses generated by the TA loop were within the permissible range which could be taken up by the roots and the surrounding tissues without causing any deleterious effect. The TA loop includes two helices on either side of the horizontal section, resulting in increased wire length and enhanced force delivery. Conclusion: Significant variations in stress distribution and deformation were observed between the two loops, highlighting the TA loop’s superior efficiency in achieving a consistent force delivery due to increased range of actions.

Kinetics of grain boundary migration in nanosized Al polycrystals

Classical theories of grain growth assume that grain boundary curvature and velocity are linearly correlated. However, recent experimental observations seem to imply that the relationship is more complex in polycrystalline materials. Here, we determined the velocity and curvature of approximately 12000 grain boundaries from molecular dynamics simulations of the annealing of randomly textured nanosized polycrystalline Al. The grain boundary kinetics was studied at different scales and compared with theoretical predictions. At the grain level, that is, attributes averaged over all grain boundaries of a grain, the kinetics behavior showed a linear correlation of curvature and velocity. When studying grain-boundary-level behavior (i.e., attributes of individual grain boundaries are considered), we found a clear correlation between the sign of the grain boundary curvature and the direction of migration. Nevertheless, considering all the grain boundaries, the correlation coefficient between the magnitude of velocity and curvature was found to be low (0.34) although a strong linear correlation was observed for a subset of high angle, long-lived, initially large grain boundaries with uniform curvature distribution and similar 5 crystallographic degrees of freedom. Furthermore, some grain boundaries that are close in crystallographic space showed different kinetics. This elucidates the complexity of grain boundary migration in the nanocrystalline ensemble as a result of complex dependence of grain boundary mobility and energy on grain boundary character, and the existence of other driving forces that affect the behavior of grain boundary migration. Among others, defect distributions and variation in stress distribution between neighboring grains are found to influence grain boundary migration.

Variation in stress distribution modified by mandibular material property: a 3D finite element analysis

BackgroundTemporomandibular joint disorder (TMD) is a common oral and maxillary facial disease. Finite element method (FEM) has been widely used in TMD studies. Material assignment significantly affects FEM results. The differences in the methods of material assignment used in previous studies have not been comprehensively assessed for further calculations. MethodsThe mandible material modelling approaches were of four types, namely: uniform modelling with (A) cortical bone; and (B) cancellous bone; (C) semi-uniform modelling with division of cortical and cancellous bone; and (D) non-uniform modelling with Computed tomography (CT) gray value related modulus. Meanwhile, the Young's modulus of values ranging from 20 to 300 GPa were considered for the teeth. Ten modellings were used to analyze and discuss the differences in contact pressure and contact force. Results(1) The increase in teeth elastic modulus increased the maximum contact pressure on the alveolar bone and contact force on teeth, but induced insignificant stress variation on the temporomandibular joint; (2) The location of the maximum contact pressure was steady for all four modelling approaches of the mandibular material. However, the maximum contact pressure and contact force exhibited an insignificant difference. ConclusionsTeeth with a higher elastic modulus significantly enhanced the stress concentration in the alveolar bone; in contrast, it induced minor variations in the temporomandibular joint stress states. The extreme stress regions predicted by the four mandibular models were consistent with the actual damaged regions. However, non-uniform modellings based on CT values could better describe the mechanical properties of the human bone, which should be primarily considered.

Simultaneous optimization of process parameters in hot forging of axisymmetric part of AA7075 by minimizing forming force and considering variation of stress distribution

Simultaneous optimization of process parameters in hot forging of axisymmetric part of AA7075 by minimizing forming force and considering variation of stress distribution

Mechanism analysis and improved model for stick-slip friction behavior considering stress distribution variation of interface

Studying the evolution of interface contact state, revealing the “black box” behavior in interface friction and establishing a more accurate friction model are of great significance to improve the prediction accuracy of mechanical system performance. Based on the principle of total reflection, a visual analysis technology of interface contact behavior is proposed. Considering the dynamic variation of stress distribution in interface contact, we analyze the nonlinear characteristics of contact parameters in different stages of stick-slip process using the above-mentioned experimental technology. Then, we find that the tangential stiffness of the interface is not a fixed value during the stick-slip process and the stress distribution variation is one of the important factors affecting the tangential stiffness of interface. Based on the previous experimental results, we present an improved stick-slip friction model, considering the change of tangential stiffness and friction coefficient caused by the stress distribution variation. This improved model can characterize the variation characteristics of contact parameters in different stages of stick-slip process, whose simulation results are in good agreement with the experimental data. This research may be valuable for improving the prediction accuracy of mechanical system performance.

Stress Distribution and Optimum Spacing Determination of Double-Withdrawal-Channel Surrounding Rocks: A Case Study of Chinese Coal Mine

In this study, the 31113 fully mechanised working face in the Lijiahao Coal Mine was selected as the project background. The failure characteristics and optimum spacing of a double-withdrawal-channel surrounding rock were extensively investigated through field measurements, theoretical analysis, and numerical simulations. The following results were obtained. The loading influence range of the working face was fixed. Under the influence of mining, the stress distribution variation in the double-withdrawal channels with spacing and the influence of stress distribution on the surrounding rock stability of the withdrawal channels were determined. The optimum distance between the double-withdrawal channels to achieve the stability of the surrounding rock was at least 25 m, and engineering measures are required to limit the mining height in the final mining stage. The rationality of the main and auxiliary withdrawal channel spacing of 25 m and measures to limit the mining height in the final stage were demonstrated. The findings of this study provide a valuable reference for constructing the layout of withdrawal channels in the adjacent working faces of the same mining area.

Comparison of Functionally Graded Hip Stem Implants with Various Second-Generation Titanium Alloys

Total hip Arthroplasty (THA) is performed every year at a very high frequency to improve the quality of life of thousands of patients all over the globe. Nevertheless, the expected service life of such surgery remains unsuitable for patients under 50 years old. This is mainly related to stress shielding and the potential adverse tissue reaction to some of the elements of the market-dominant implant materials. In this research, functionally graded (FG) implant designs of several titanium alloys layered with hydroxyapatite (HA) are proposed to provide lower implant stiffness compared to a solid stem to approach the requirements of human bone. Moreover, TNZT (Ti35Nb7Zr5Ta), and TMZF (Ti12Mo6Zr2Fe) second-generation titanium alloys are studied as a replacement for the famous Ti6Al4V alloy to avoid the adverse tissue reactions related to aluminum and vanadium elements. The different FG models are numerically tested using a 3D finite element simulation after virtual implantation in a femur bone under the dynamic load of a patient descending stairs. In the numerical study, the variation in stress distribution and strain energy in a femur bone is assessed for different FG hip stems as well as the axial stiffness of the hip stems. Results indicated an increase in strain energy and von Mises stress in the cortical and cancellous bones using FG hip stems. Additionally, the axial stiffness is reduced for all FG hip stems relative to the commercial Ti6Al4V hip stem.

Bond of Flax Textile-Reinforced Mortars to Masonry

This paper investigates the structural performance of Flax Textile-Reinforced Mortars (FTRM) systems bonded to a masonry substrate. Single-lap shear bond tests were carried out to assess the influence of bond length, the number of TRM layers and bonded width on the behaviour of two flax textiles of different architecture embedded in lime-‍based mortar. Conventional and non-contact measuring methods (Digital Image Correlation - DIC) were employed to gain additional insights into the development of stress transfer mechanisms and load-slip behaviour at the global and local scale. It was found that textile architecture significantly affects overall bond performance, with a smaller diameter and twisted yarns arranged in a denser mesh utilising the fibre strength to a higher degree. The effective bond length for the tested single-layer systems is between 150 and 210 mm, and failure is dominated by fibre rupture. A high variation in stress distribution was seen in multi-layer specimens with a wider bonded width, and this can lead to premature delamination. Finally, recommendations for testing in line with the existing RILEM experimental methodology are given to account for the high variability and unique failure modes observed in natural fibre TRM. This work aims to provide design guidelines for sustainable and effective structural strengthening solutions, which are particularly suitable for less developed countries.

Assessment of open hole flexural strength and progressive damage mechanism of CFRP composite as a function of stacking sequence

An experimental study was carried out to evaluate the flexural behaviour of CFRP composite laminate with introduction of open hole as well as by varying stacking sequence. Open hole is required in laminated composites to assemble the components through mechanical fasteners. Degradation in strength was observed due to the presence of a hole. Six stacking sequences have been analysed: [0]8, [90]8, [0/90]2s, [90/0]2s, [02/902]s, [902/02]s in which [0]8 is noticed to have highest flexural and open hole flexural strength. Strength retention is also evaluated in this study to compare retention strength of open hole laminate with laminates having no hole. Existence of both tensile and compressive failure modes during flexural loading makes overall damage mode complex. Furthermore, introduction of open hole in the laminate during flexural loading makes it more complex as variation in stress distribution activates different features of deformation and failures. Fractographic analysis has been done using scanning electron microscope to perceive damage progression mechanism during flexural loading. SEM micrographs confirmed the delamination between 90° and 0° plies as it is seen in stress strain graph as a stress drop.

Assessment of open hole flexural strength and progressive damage mechanism of CFRP composite as a function of stacking sequence

An experimental study was carried out to evaluate the flexural behaviour of CFRP composite laminate with introduction of open hole as well as by varying stacking sequence. Open hole is required in laminated composites to assemble the components through mechanical fasteners. Degradation in strength was observed due to the presence of a hole. Six stacking sequences have been analysed: [0]8, [90]8, [0/90]2s, [90/0]2s, [02/902]s, [902/02]s in which [0]8 is noticed to have highest flexural and open hole flexural strength. Strength retention is also evaluated in this study to compare retention strength of open hole laminate with laminates having no hole. Existence of both tensile and compressive failure modes during flexural loading makes overall damage mode complex. Furthermore, introduction of open hole in the laminate during flexural loading makes it more complex as variation in stress distribution activates different features of deformation and failures. Fractographic analysis has been done using scanning electron microscope to perceive damage progression mechanism during flexural loading. SEM micrographs confirmed the delamination between 90° and 0° plies as it is seen in stress strain graph as a stress drop.

Modeling and simulation of the non-equilibrium process for a continuous solid solution system in lithium-ion batteries

The capacity loss and cycling aging of lithium-ion batteries at high (dis)charging rate (C-rate) hinders the development of emerging technologies. To improve the performance of Li-ion batteries, it is important to understand the coupling effect of the mechanical behaviors and the electrochemical response of electrodes, as the capacity loss and cycling aging are related to the mechanics of electrodes during (dis)charging. Many studies have formulated the distribution of stress, strain and lithium-ion fraction of electrodes during lithiation/delithiation. However, few of them reported a self-consistent formulation that contains mechanical-diffusional-electrochemical coupling effects, solid viscosity, and diffusion-induced creep for an electrode with large deformation under non-equilibrium process. This paper considers the electrode of a Li-ion battery as a solid solution system. Based on continuum mechanics, non-equilibrium thermodynamics and variational theory, we develop a generalized theory to describe the variations of stress distribution, electrode material deformation and lithium-ion fractions of the solid solution system over a non-equilibrium process. The finite deformation, mass transfer, phase transformation, chemical reaction and electrical potential of the system are coupled with each other in a fully self-consistent formulation. We apply the developed theory to numerically simulate a Sn anode particle using the finite difference method. Our results compare the influences of different C-rates on the non-equilibrium process of the anode particle. Higher C-rate corresponds to stronger dissipation effects including faster plastic deformation, larger viscous stress, more polarization in the electrical potential, longer relaxation time and less electrical energy. With the formulation and simulation of the non-equilibrium process, this study refines our understanding of the mechanical-diffusional-electrochemical coupling effect in Li-ion batteries with high C-rate.

Compression Shear Properties of Bonded–Bolted Hybrid Single-Lap Joints of C/C Composites at High Temperature

Based on previous research, in this paper, the compressive shear failure behavior and mechanical properties of bonded–bolted hybrid single-lap joints of C/C composites at high temperature were studied. The compression shear test was performed on the joints at 800 °C to obtain the load–displacement curve and failure morphology. The failure modes of joints were observed by digital microscopy and scanning electron microscopy. A numerical analysis model was implemented in finite element code Abaqus/Explicit embedded with the user material subroutine (VUMAT). The numerical results were compared with the test results to verify the correctness of the model. The interrelationship of the compression shear loading mechanism and the variations in stress distribution between bonded joints and bonded–bolted hybrid joints at high temperature were explored. The progressive damage of hybrid joints and the variations in the ratio of the bolt load to the total load with displacement were obtained.

DEM modelling of screw pile penetration in loose granular assemblies considering the effect of drilling velocity ratio

Screw piles have been widely used as foundations for various types of structures. Drilling velocity ratio, the ratio of rotational velocity to driven velocity, is a critical parameter that affects the driven behaviors of screw piles. Three dimensional discrete element method, with a particle refinement method to enhance computation efficiency, is used to study the driven behaviors of screw piles to compare with the laboratory mini screw pile test results achieved by Shi et al. (Rock Soil Mech 39(6):1981–1990, 2018). The driven behaviors of a mini screw pile (900 mm long and 40 mm shaft diameter) with a variable diameter auger into loose granular assemblies under 0.5, 1 and 1.5 critical drilling velocity ratios are studied. The variation of stress distribution in the assemblies, particle movement around the piles, and evolution of void ratio in the assemblies are investigated. The results indicate that particles around the piles behave differently under different drilling velocity ratios. The reduction of driven force with the increase of drilling velocity ratio can be explained using the direction of particle movement around the piles and the vertical force acting on the screw blades. It was found that under high drilling velocity ratio, higher downward vertical force can be provided by the blades.

A new method for pull out test of reinforcing bars in plain and fibre reinforced concrete

The bond of reinforcing bars in concrete is crucial in anchorage of reinforcing bars and crack control of reinforced concrete. It is generally measured by pull out test of a reinforcing bar embedded in a concrete block. However, the different test methods yield different test results. In this research, finite element analysis was carried out to reveal the variations in stress distribution inside the concrete block due to uneven contact pressure and friction at the concrete block-steel platen interface of the test setup. To minimize the test errors due to such uneven contact pressure and friction, the test setup was redesigned by inserting a rubber pad and a PTFE film at the interface. Using the redesigned setup, pull out tests of reinforcing bars in plain and fibre reinforced concrete were conducted and the results compared to those obtained without rubber pad or PTFE film installed. It was found that the new test would yield lower and less variable bond strength and stiffness results. This improved test method would provide more accurate bond properties for structural analysis and design.

Stress Distribution on Root Dentin Analogous to Natural Teeth with Various Retentive Channels Design on the Face of the Root with Minimal or No Coronal Tooth Structure: A Finite Element Analysis

Aim:The aim of this study was to evaluate post-core design on Stress distribution in maxillary central incisor with various designs retentive channels placed on the face of the root with no remaining coronal tooth structure.Materials and Methods:3 dimensional finite element model of a maxillary central incisor was developed and seven other study modes were developed. Tooth was scanned using CBCT unit, with reverse engineering software. 3D wire mesh, with ten node tetrahedral element, developed was transferred to ANASYS software. Composite was used for post-core-crown as post endodontic restoration. Mechanical properties were assigned to each component for FEA. All the materials were assumed to be isotropic, linearly elastic, homogenous and tightly bonded. A load of 100N were applied from vertical, horizontal and lateral oblique from incisal and palatal surface respectively.Results:Analysis revealed that stresses were concentrated at the point of load application on crown(vertical(V) 14.35MPa, horizontal(H) 27.04 MPa and lateral oblique(L)13.75MPa) and depending on the post core design the stresses were homogenous evenly distributed over the root dentin, core and least over the post. There was variation in stress distribution under vertical horizontal and lateral oblique load.Conclusion:Teeth with no remaining coronal structure and by placing retentive channels on the face of the root will enable homogenous stress distribution, promote mechanical retention and stability to the post core crown post endodontic restoration.

Numerical Analysis of Shear Buckling of Steel Plate with Cut Outs

For more than three decades, global attention and interest have grown in the application of steel plate walls for building lateral load resisting system. Some apparent advantages of using steel plate walls in a building include adequate energy dissipation, stable hysteretic characteristics and enhanced stiffness, strength and ductile behaviour. One of the simplest and cost effective solutions is to cut openings in steel plate in order to achieve high ductility which inturn results in an intense variation in stress distribution. In this paper, the shear buckling behaviour of a steel plate having cut outs is assessed numerically using ANSYS finite element program. The developed methodology is validated with results available in the literature. A parametric study is also carried out to study the buckling behaviour of steel plate with different shape and size of the cut outs. The study can be further modified to develop detailed methodology to perform buckling analysis of diagonally stiffened steel plate shear wall with cut outs.

Nonlinear Static-Oriented Pushover Analysis of Reinforced Concrete Columns Using Variable Oblique Finite-Element Discretization

A fast converging and fairly accurate nonlinear simulation method to assess the behavior of reinforced concrete columns subjected to static-oriented pushover force and axial loading (sections under biaxial-bending moment and axial loading) is proposed. In the proposed method, the sections of column are discretized into “Variable Oblique Finite Elements” (VOFE). By applying the proposed oblique discretization method, the time of calculation is significantly decreased, and since VOFE are always parallel to neutral axis, a uniform stress distribution along each oblique element is established. Consequently, the variations of stress distribution across an element are quite small which increases the accuracy of the calculations. In the discretization of section, the number of VOFE is significantly smaller than the number of “Fixed Rectangular Finite Elements” (FRFE). The advantages of using VOFE compared to FRFE are faster convergence and more accurate results. The nonlinear local degradation of materials and the pseudo-plastic hinge produced in the critical sections of the column are also considered in the proposed simulation method. A computer program is developed to calculate the local and global behavior of reinforced concrete columns under static-oriented pushover and cyclic loading. The proposed simulation method is validated by the results of tests carried out on the full-scale reinforced concrete columns. The application of the “Components Effects Combination Method” is compared with the proposed “Simultaneous Direct Method” (SDM). The obtained results show the necessity of applying SDM for nonlinear calculations. Especially, during the post-elastic phase, which occurs frequently during earthquake loading.

Failure behavior of adhesive bonded interface between steel and bamboo plywood

Bamboo–steel composite structure is constructed with bamboo plywood and cold-formed thin-walled steel, which are bonded by structural adhesive. To investigate the failure behavior of the adhesive bonded interface between bamboo plywood and steel, both experimental and numerical analyses were performed. An adhesive bonded member was designed to observe the failure behavior through the variation of stress distribution on steel sheet under tension. Further analysis of failure behavior was carried out by the numerical model through the stress analysis at the adhesive bonded interfaces. The experimental and numerical analyses revealed the failure mainly occurred at the adhesive bonding interface, caused by the stress concentration at the end of the overlap. The influences of modulus of elasticity of bamboo plywood in the parallel to grain direction and the thickness of steel sheet on the stress distribution at the adhesive bonding interface were investigated, which indicated the stress distribution had a major effect on the load-carrying capacity of the composite structural member. It also suggests enlarging the geometry properly and choosing the bamboo plywood with large modulus of elasticity in the parallel to grain direction are effective to increase the load-carrying capacity.