Von Mises Stress Research Articles

Nanomechanical-ferroelastics behavior, and the low-temperature ferroelectric manifestation of BiMnO3 thin films

Ferroelastic-nanomechanical behavior of BiMnO3 thin films on (100) Nb-doped SrTiO3 substrate is studied at the nanoscale, for the first time using the theories of depth sensing indentation and finite element analysis. This was to understand the redirection of polarization in ferroelastic behavior using piezoelectric direct effect and applying a controlled local force by nanoindentation. The values of the nanomechanical properties Young’s modulus (E), hardness (H), and Stiffness (S) were measured to be E = 142 ± 3 GPa, H = 8 ± 0.2 GPa, and S = 44072 ± 45 N m−1 respectively. Using the experimental mechanical properties, a finite element analysis was carried out to understand the relationship between the irreversible work versus depth curve and plastic-deformation evolution of the thin film-interface-substrate system, associated with the pop-in observed. Von Mises stress maps are presented to clearly illustrate the deformations, mechanical failures, and influences between the BiMnO3 film and the SrTiO3 Substrate. The ferroelastic range for BiMnO3 material was observed between 0 to 12 nm, and the yield strength was Y = 2.6 ± 0.7 GPa. The ferroelectric properties through hysteresis curves were evaluated at two different temperatures of 200 K and 300 K in order to observe the effect of polarization with temperature. Providing better polarization performance at lower temperatures; P s = 9.14 ± 0.01 ( μ C cm–2), P r = 2.23 ± 0.02 ( μ C cm–2) and H c = 0.77 kV cm−1.

Finite element model of ocular adduction with unconstrained globe translation

Details of the anatomy and behavior of the structures responsible for human eye movements have been extensively elaborated since the first modern biomechanical models were introduced. Based on these findings, a finite element model of human ocular adduction is developed based on connective anatomy and measured optic nerve (ON) properties, as well as active contractility of bilaminar extraocular muscles (EOMs), but incorporating the novel feature that globe translation is not otherwise constrained so that realistic kinematics can be simulated. Anatomy of the hemisymmetric model is defined by magnetic resonance imaging. The globe is modeled as suspended by anatomically realistic connective tissues, orbital fat, and contiguous ON. The model incorporates a material subroutine that implements active EOM contraction based on fiber twitch characteristics. Starting from the initial condition of 26° adduction, the medial rectus (MR) muscle was commanded to contract as the lateral rectus (LR) relaxed. We alternatively modeled absence or presence of orbital fat. During pursuit-like adduction from 26 to 32°, the globe translated 0.52 mm posteriorly and 0.1 mm medially with orbital fat present, but 1.2 mm posteriorly and 0.1 mm medially without fat. Maximum principal strains in the optic disk and peripapillary reached 0.05–0.06, and von-Mises stress 96 kPa. Tension in the MR orbital layer was ~ 24 g-force after 6° adduction, but only ~ 3 gm-f in the whole LR. This physiologically plausible simulation of EOM activation in an anatomically realistic globe suspensory system demonstrates that orbital connective tissues and fat are integral to the biomechanics of adduction, including loading by the ON.

Effect of notch angle on creep deformation and rupture behavior of 304HCu SS

Abstract Multiaxial creep deformation behaviour of U-notched 304HCu austenitic stainless steel (304HCu SS) has been studied by altering the angle of the U-notch, by 30°, 60°, 90°, and 120°, for a fixed root radius of 1.25 mm. The associated stress concentration factor for the U-notch geometry is about 1.8–1.86 with decrease in notch angle. Creep rupture lives of all notched specimens are above the un-notched specimen. However, decrease in rupture life and increase in creep rupture ductility has been observed with an increase in notch angle. At all notch angles, nearly intergranular creep cavitation failure with isolated cavities was observed at the notch center. In contrast, at the notch root, with decrease in notch angle the fracture mode changed from mixed mode to intergranular fracture. Finite element analysis (FEA) of stationary state of stress distribution indicated that von-Mises stress throughout the notch throat plane and maximum principal stress near the notch root region were found to increase with increase in notch angle. However, away from the notch root the maximum principal stress was found to decrease with increase in notch angle. Hydrostatic stress distribution remained same near the notch root at all the notch angles, but tends to increase towards the specimen center with decrease in notch angle. Similarly, at the notch throat plane, triaxiality factor (TF) was found to increase with decrease in notch angle. The creep damage evaluated through FEA coupled with continuum damage mechanics (CDM) proposed by Kachanov-Rabotov (K-R) model was found to increase with an increase in notch angle, resulting in decrease in creep rupture life. Creep damage evaluated as a function of notch depth, during initial creep exposure, revealed significant damage for 1.675 mm notch depth in comparison to 2 and 2.5 mm notch depths which resulted in lower rupture life for 1.675 mm notch depth.

Progressive damage analysis of double-layer variable thickness 3D woven composite scaled engine casing

Due to the excellent mechanical properties and strong design flexibility, the 3D woven composite engine casing shows great potential in high performance fields. This article adopted the method of double-layer weaving and adding yarn to achieve the variable thickness of the 3D woven composite engine casing. The purpose of this article is to study the compression performance and failure mechanism of this variable thickness casing in different thickness zones through experiments and numerical simulations to lay a foundation for future optimization and inclusiveness research on this casing with complex thickness changes. Three types of representative volume cells are established for progressive damage analysis. 3D-Hashin criteria and von-Mises stress criterion are used as damage criteria for yarns and matrix. The progressive damage process and the proportion of damage in the inner and outer layers of three types of 3D woven tubes under axial compression load are analyzed. Results show that the main failure modes of the three types of tubes are yarn-matrix compressive cracking along direction 3 and matrix failure. The damages are mostly concentrated in the warp bending area. The proportions of warp yarn damage in the inner and outer layers of three tubes are different.

Studies on Mechanical and Dielectric Properties of the Ni(OH)2 Filler Reinforced Polymer Composite Materials for Structural Application

Polymer composite materials play a vital role in many automotive and wind turbine industries because of their high mechanical properties. The present work emphasises the improvement of polymer composites used for different environmental conditions. The glass and basalt fibers with epoxy and vinyl ester matrix have been prepared individually with 3 % Ni(OH)2 filler. The mechanical and dielectric properties were investigated separately for each material. The mechanical properties of the glass fiber with vinyl ester and Ni(OH)2 filler showed better results. The dielectric strength of the glass fiber with vinyl ester and Ni(OH)2 filler material in a saline environment showed only a 38.16 % reduced dielectric value before saline treatment. The FE validation was also validated using Digimat- FE software for evaluating the void stress in the filler matrix. From the validation the glass fiber with epoxy resin and Ni(OH)2 filler showed the lowest von-Mises stress and shear stress values compared to the other materials. The overall results highlight the improvement of mechanical and electrical properties after the addition of Ni(OH)2 filler materials in offshore environment to meet the demands of the wind turbine industry.

Stress distribution pattern in all-on-four maxillary restorations supported by porous tantalum and solid titanium implants using three-dimensional finite element analysis.

Success/failure of dental implants depends on stress transfer and distribution at the bone-implant interface. This study aimed to assess the stress distribution pattern in all-on-four maxillary restorations supported by porous tantalum and solid titanium implants using three-dimensional (3D) finite element analysis (FEA). In this FEA, a geometric model of an edentulous maxilla, Zimmer screw-vent tantalum and solid titanium implants were modelled. Four models with the all-on-four concept were designed. The fifth model had 6 vertical implants (all-on-six). Two different implant types (porous tantalum and solid titanium) were modelled to yield a total of 10 models, and subjected to 200 N bilateral vertical load. Pattern of stress distribution and maximum von Mises stress values in cancellous and cortical bones around implants were analysed. In tantalum models, the effect of increasing the distal tilting of posterior implants was comparable to the effect of increasing the number of implants to 6 on von Mises stress values in cortical bone. However, in cancellous bone, the effect of increasing the tilting of posterior implants on stress was slightly greater than the effect of increasing the number of implants to 6. In solid titanium models, the effect of both of the abovementioned parameters was comparable on stress in cancellous bone; but in cortical bone, the effect of increasing the implant number was slightly greater on stress reduction. Despite similar pattern of stress distribution in bone around implants, higher maximum von Mises stress values around tantalum implants indicate higher stress transfer capacity of this type of implant to the adjacent bone, compared with solid titanium implants.

FE Analysis on Size Effect in Torsional Behavior of Rectangular RC Beams with and Without FRP Strengthening

Although torsion is usually considered a secondary consideration in structural design, it can lead to failures, especially in structures with irregular geometry exposed to seismic forces or in unique situations. While some studies have explored the size effect on the torsional behavior of RC beams, none have addressed the impact of reinforcement. This paper investigates the size effect on the torsional behavior of RC beams with varying reinforcement ratios, including both FRP sheets and steel rebars. In this study, the torsional behavior of reinforced concrete (RC) beams with and without FRP strengthening was investigated numerically. Modeling was carried out by Finite element (FE) software ABAQUS and validated using experimental data from literature. The torsional behavior of 24 models with differences in cross-section size and reinforcement ratio were investigated. Concrete damage plasticity, Hashin damage criteria, and von Mises stress were used to investigate the damage in concrete, FRP, and steel, respectively. The cracking torsional moment, ultimate torsional moment, and torque-twist curve of the beams were evaluated and presented. The results indicated the presence of a significant size effect in the torsional strength of beams. After reinforcing the beams with FRP fabrics, the average cracking moment increased by a range of 1.72% to 36% across different groups of beams. An 8.2% increase in ultimate strength is observed with just a 0.4% rise in the FRP strengthening ratio. Post-cracking behavior was seen in 8 models with adequate steel and FRP reinforcement ratio.

Application of a combined cancellous lag screw enhances the stability of locking plate fixation of osteoporotic lateral tibial plateau fracture by providing interfragmentary compression force

BackgroundInsufficient interfragmentary compression force (IFCF) frequently leads to unstable fixation of osteoporotic lateral tibial plateau fractures (OLTPFs). A combined cancellous lag screw (CCLS) enhances IFCF; however, its effect on OLTPF fixation stability remains unclear. Therefore, we investigated the effect of CCLS on OLTPF stability using locking plate fixation (LPF).Materials and methodsTwelve synthetic osteoporotic tibial bones were used to simulate OLTPFs, which were fixed using LPF, LPF-AO cancellous lag screws (LPF-AOCLS), and LPF-CCLS. Subsequently, 10,000 cyclic loadings from 30 to 400 N were performed. The initial axial stiffness (IAS), maximal axial micromotion of the lateral fragment (MAM-LF) measured every 1000 cycles, and failure load after 10,000 cycles were tested. The same three fixations for OLTPF were simulated using finite element analysis (FEA). IFCFs of 0, 225, and 300 N were applied to the LPF, LPF-AOCLS, and LPF-CCLS, respectively, with a 1000-N axial compressive force. The MAM-LF, peak von Mises stress (VMS), peak equivalent elastic strain of the lateral fragment (EES-LF), and nodes of EES-LF > 2% (considered bone destruction) were calculated.ResultsBiomechanical tests revealed the LPF-AOCLS and LPF-CCLS groups to be superior to the LPF group in terms of the IAS, MAM-LF, and failure load (all p < 0.05). FEA revealed that the MAM-LF, peak VMS, peak EES-LF, and nodes with EES-LF > 2% in the LPF were higher than those in the LPF-AOCLS and LPF-CCLS.ConclusionIFCF was shown to enhance the stability of OLTPFs using LPF. Considering overscrewing, CCLS is preferably recommended, although there were no significant differences between CCLS and AOCLS.

Evaluation of the Effect of Ununion Percentage of Scaphoid on Stress and Displacement of Fragment Part of Scaphoid in Various Degrees of Wrist Extension with and without External Force

Abstract Background Scaphoid fractures are almost two-thirds of different kinds of carpal fractures. Surgeons usually have challenges in deciding if the wrist should be mobilized or immobilized for the patients with different percentiles of partial union of scaphoid. This study's aim was to investigate different percentiles of union (25–50–75) in waist and proximal pole of scaphoid fracture to find the union percentile which can tolerate normal daily activities to help surgeons in taking appropriate decisions in this regard. Method A model of wrist joint was developed in this study based on computed tomography scan images of wrist joint. Various percentage of union in waist and proximal poles of scaphoid with and without internal fixation were tested in this study. The stress applied on scaphoid and displacement of fragment parts were evaluated in Abaqus software during motion of wrist from neutral to 40 degrees of extension. Results Although Von Mises stress of scaphoid bone increased following use of external force, the difference was significant for conditions 3 and 6 (75% of union in middle and distal parts). The stress applied on scaphoid increased depends on conditions (ununion percentage of bone). Moreover, its stress depends on the angle of wrist extension. Use of internal fixation screw decreased stress of scaphoid in most of conditions. Conclusion The stress developed in scaphoid depends on the nonunion percentage of scaphoid and the amount of motion of wrist joint. It is better to use external fixation screw especially for conditions 3 and 6 (75% of union in middle and distal parts) to decrease the displacement of fragment parts and to decrease the stress applied on scaphoid in wrist extension. Type of Study and Level of Evidence Case study, level of evidence: III.

Failure analysis of the rotating shaft in the rail grinding car

Rail grinders belonging to special vehicles have fewer accidents than general railroad vehicles and parts, and the causes are diverse. Therefore, there is a lack of basic data for inspection methods and preventative measures necessary for accident prevention, and the collection and analysis of accident cases are also necessary. In this paper, a failure analysis of the recently derailed rail grinding car's rotating shaft was conducted. Various analyses, including fractography, chemical analysis, metallography and hardness measurement, were performed on the failed shaft. In the fracture surface of the shaft, ratchet marks and fatigue striations indicative of fatigue failure were observed. Consequently, it was confirmed that the failure of the shaft was attributed to fatigue, with the primary cause being identified as the cracks found on the fillet area surface. Chemical analysis of the observed inclusions in the sample revealed manganese (Mn) at 6.16 wt% and sulfur (S) at 1.35 wt%. These are attributed to non-metallic MnS inclusions, which are presumed to have adversely affected the fatigue strength of the material. Additionally, hardness deficiency due to heat treatment defects on the shaft surface was identified. The surface hardness measured approximately HV400, suggesting that it is desirable to achieve a surface hardness of HV600 or HRC55 or higher during high-frequency heat treatment. Lastly, the finish state of the fillet area surface was not smooth. Given that the fillet area is a region where stress concentration occurs, the presence of such machining traces raises the possibility of progressing into fatigue cracks. Finite element analysis revealed that the von-Mises stress was less than the yield strength of the material, and a safety factor based on the yield strength was calculated to be 3.5. The results confirmed that fatigue cracks in the fillet area were caused by the hardness deficiency due to the poor heat treatment, the rough surface finish, and the presence of non-metallic inclusions.

Mechanical and Computational Fluid Dynamic Models for Magnesium-Based Implants.

Today, mechanical properties and fluid flow dynamic analysis are considered to be two of the most important steps in implant design for bone tissue engineering. The mechanical behavior is characterized by Young's modulus, which must have a value close to that of the human bone, while from the fluid dynamics point of view, the implant permeability and wall shear stress are two parameters directly linked to cell growth, adhesion, and proliferation. In this study, we proposed two simple geometries with a three-dimensional pore network dedicated to a manufacturing route based on a titanium wire waving procedure used as an intermediary step for Mg-based implant fabrication. Implant deformation under different static loads, von Mises stresses, and safety factors were investigated using finite element analysis. The implant permeability was computed based on Darcy's law following computational fluid dynamic simulations and, based on the pressure drop, was numerically estimated. It was concluded that both models exhibited a permeability close to the human trabecular bone and reduced wall shear stresses within the biological range. As a general finding, the proposed geometries could be useful in orthopedics for bone defect treatment based on numerical analyses because they mimic the trabecular bone properties.

Study of nanoindentation behavior of NiCrCoAl medium entropy alloys under indentation process using molecular dynamics

Abstract The mechanical properties and deformation behavior of CoCrNiAl medium entropy alloy (MEA) subjected to indentation by an indenter tooltip on the substrate are explored using molecular dynamics (MD) simulation. The study investigates the effects of alloy compositions, temperature variations, and ultra vibration (UV) on parameters, such as total force, shear strain, shear stress, hardness, reduced modulus, substrate temperature, phase transformation, dislocation length, and elastic recovery. The findings indicate that higher alloy compositions result in increased total force, hardness, and reduced modulus, with Ni-rich compositions demonstrating superior mechanical strength. Conversely, increasing alloy compositions lead to reduced von Mises stress (VMS), phase transformation, dislocation distribution, and dislocation length due to the larger atomic size of Ni compared to other primary elements. At elevated substrate temperatures, atoms exhibit larger vibration amplitudes and interatomic separations, leading to weaker atomic bonding and decreased contact force, rendering the substrate softer at higher temperatures. Additionally, higher initial substrate temperatures enhance atom kinetic energy and thermal vibrations, leading to reduced material hardness and increased VMS levels. Increasing vibration frequency enlarges the indentation area on the substrate’s surface, concentrating shear strain and VMS with vibration frequency. Higher vibration amplitude and frequency amplify force, shear strain, VMS, substrate temperature, and dislocation distribution. Conversely, lower vibration amplitude and frequency result in a smaller average elastic recovery ratio. Moreover, increased amplitude and frequency values yield an amorphous-dominated indentation region and increased proportions of hexagonal close-packed and body-centered cubic structures. Furthermore, this study also takes into account the evaluation of a material’s ability to recover elastically during the indentation process, which is a fundamental material property.

Microplate Versus Combined Microplate-Miniplate in Fixation of Zygomaticomaxillary Complex Fractures: An In-Silico Analysis of Biomechanical Parameters.

To compare the biomechanical parameters of microplates and the combined miniplate-microplate for fixing zygomaticomaxillary complex (ZMC) fractures using nonlinear finite element analysis (FEA). Two samples of ZMC fracture models were prepared. In sample 1 (S1), the fractures were stabilized with microplates, and in sample 2 (S2), with miniplates plus microplates. FEA software was used to measure the displacement, Von Mises stress distribution (VMSD), and maximum principal stress distribution (MPSD). The displacement was 6.7 μm in the L-shaped plate of both samples, 4.4 μm in the S1 lateral-edge plate, 4.8 μm in the S2 lateral-edge plate, 5.8 μm in the S1 bottom-edge plate, and 5.6 μm in the S2 bottom-edge plate. The VMSD was 41.1 MPa in the S1 lateral-edge plate, 24.3 MPa in the S2 lateral-edge plate, 7.6 MPa in the S1 Lshaped plate, 9.6 MPa in S2 L-shaped plate, 28.5 MPa in the S1 bottom-edge plate, and 11.8 MPa in the S2 bottom-edge plate. The MPSD was 46.2 MPa in the S1 lateral-edge plate, 26.4 MPa in the S2 lateral-edge plate, 3.6 MPa in S1 L-shaped plate, 4.2 MPa in S2 L-shaped plate, 30.9 MPa in S1 bottom-edge plate, and 14.1 MPa in the S2 bottom-edge plate. The L-shaped and lateral-edge plates in both samples had the highest and lowest amount of displacement, respectively. The lateral-edge plates in both samples had the highest VMSD and MPSD, which was higher in S1 than S2. The L-shaped plate had the lowest VMSD and MPSD in both samples.

Thermal and Structural Modelling of Laboratory-Scale Pyrolysis Reactor

This paper presents the steady-state thermal and static structural modelling of a laboratory-scale pyrolysis reactor for the thermal degradation of biomass wastes. A laboratory-scale pyrolysis reactor of volume 9.203 x 10-3m3 was developed to pyrolyse Palm Kernel Shell (PKS) and Palm Fruit Bunch (PFB) at varying temperatures of 350oC, 400oC, 450oC, 500oC, and 550oC. The reactor chamber was simulated for static-steady thermal and static structural analysis to determine the temperature distribution and thermal stresses induced in it. The model was developed using SolidWorks software, and a Computational Fluid Dynamics (CFD) simulation was carried out using ANSYS Workbench 19. A total number of 2,459 elements was generated composed of 8630 nodes using Hexahedra dominant meshing method. It was observed from the simulation result that the temperature distribution inside and outside the reactor chamber were 454.29oC and 550oC respectively. The maximum heat flux of 8.3466e+005 W/m² occurred at the inner chamber of the reactor due to the high concentration of the biomass waste and devolatization reaction, and the maximum equivalent (von-Mises) stresses the material can withstand at higher temperature is 1.6674e+009 Pa without rupture. It was found out from the simulation result that at a maximum temperature of 550oC, the equivalent (von Mises) stresses induced at the outer and inner chamber is 1.8585e+008 Pa, which is far lower than the maximum stress the material can withstand without rupture. Thus, the reactor is safe to operate at a temperature higher than 550oC without failure.

Displacement and stress distribution pattern during complete mandibular arch distalization using buccal shelf bone screws - A three-dimensional finite element study.

To evaluate and compare the distribution of stress and displacement of teeth during mandibular arch distalization using buccal shelf screws. Three three-dimensional finite element models of mandibular arch were constructed with third molars extracted. Models 1, 2, and 3 were constructed on the basis of the lever arm heights of 0 mm, 3 mm, and 6 mm, respectively, between the lateral incisor and canine. A buccal shelf screw was placed at the area in the second molar region with the initial point of insertion being inter-dental between the first and second molars and 2 mm below the mucogingival junction. MBT pre-adjusted brackets (slot size 0.022 × 0.028") were placed over the clinical crown's center with a 0.019 × 0.025" stainless-steel archwire on three models. A retraction force of 300 g was applied with buccal shelf screws and a lever arm bilaterally using nickel-titanium closed coil springs. The displacement of each tooth was calculated on X, Y, and Z axes, and the von Mises stress distribution was visualized using color-coded scales using ANSYS 12.1 software. The maximum von Mises stress in the cortical and cancellous bones was observed in model 1. The maximum von Mises stress in the buccal shelf screw and the cortical bone decreased as the height of the lever arm increased. Applying orthodontic forces at the level of 6 mm lever arm height resulted in greater biomechanical bodily movement in distalization of the mandibular molars compared to when the orthodontic forces were applied at the level of 0 mm lever arm height. Displacement of the entire arch may be dictated by a direct relationship between the center of resistance of the whole arch and the line of action generated between the buccal shelf screw and force application points at the archwire, which makes the total arch movement highly predictable.

Finite Element Analysis of Stress Distribution and Range of Motion in Discogenic Back Pain.

Precise knowledge regarding the mechanical stress applied to the intervertebral disc following each individual spine motion enables physicians and patients to understand how people with discogenic back pain should be guided in their exercises and which spine motions to specifically avoid. We created an intervertebral disc degeneration model and conducted a finite element (FE) analysis of loaded stresses following each spinal posture or motion. A 3-dimensional FE model of intervertebral disc degeneration at L4-5 was constructed. The intervertebral disc degeneration model was created according to the modified Dallas discogram scale. The von Mises stress and range of motion (ROM) regarding the intervertebral discs and the endplates were analyzed. We observed that mechanical stresses loaded onto the intervertebral discs were similar during flexion, extension, and lateral bending, which were greater than those occurring during torsion. Based on the comparison among the grades divided by the modified Dallas discogram scale, the mechanical stress during extension was greater in grades 3-5 than it was during the others. During extension, the mechanical stress loaded onto the intervertebral disc and endplate was greatest in the posterior portion. Mechanical stresses loaded onto the intervertebral disc were greater in grades 3-5 compared to those in grades 0-2. Our findings suggest that it might be beneficial for patients experiencing discogenic back pain to maintain a neutral posture in their lumbar spine when engaging in daily activities and exercises, especially those suffering from significant intravertebral disc degeneration.

Asymmetric two-dimensional poroelastic analysis of heterogeneous smart discs considering hygrothermal loading

The objective of this study is to examine through the finite element method the impacts of employing two-dimensional (2D) properties grading on the behaviors of piezoelectric sensors/actuators due to their significance. These structures are modeled as variable thickness discs and are assumed to be exposed to simultaneous asymmetric loading conditions (thermal, hygral, electrical, and mechanical loads). Results demonstrate that the 2D grading is superior compared to the conventional one-dimensional grading for reducing the von Mises stress. The reduction reached, for instance, 8.3% allowing further increase of loading and/or safety. Also, the change of the displacement is varied between −4.5% and 31% depending on the considered grading pattern, and thus can be controlled to a desired value which helps to improve the sensing and actuating functionality for certain requirements. The study also examines the effects of porosity, and the results are compared to nonporous discs. Reductions of the maximum compressive tangential stress and von Mises stress reached 79.75% and 33.6%, respectively at specific porosity distribution patterns and volume fractions. These findings have significant implications for the manufacturing of smart structures, enabling them to operate in severe working conditions with better sensing and actuating capabilities than previously possible.

Mode Ⅰ fracture analysis of aluminum-copper bimetal composite using finite element method

The properties of Al–Cu bimetallic composite are investigated employing the finite element method to understand the nature of the composite materials under different loading conditions. In this regard, Al and Cu metallic sheets were implemented to analyze cold-roll bonding (CRB) and to monitor the bonding conditions. After rolling the materials were investigated for their stress distribution and bonding as well as fracture behavior. Finite element investigation was used by the ANSYS software to analyze the stress-strain distribution in the metal layers. The results indicate that the appropriate joining of Al–Al and Al–Cu can be achieved using the CRB process. The stress distribution based on the Von-Mises criterion was calculated and validated by simulation studies. For crack simulations, on the other hand, the results showed that during crack propagation, the materials showed different behaviors owing to the varying properties of Al and Cu. Also, for both the tests, stress distribution in 2D and 3D were simulated, and different stress criteria were obtained and compared. Moreover, optical and scanning electron microscopies were used to study the characteristics of the materials and to support FEM outputs.

3D crack propagation study of a railway component using XFEM method

This work develops a methodology to study the crack propagation through ABAQUS simulation. This simulation study uses the service condition of the mechanical component and the complex geometry of a manufacturing defect obtained by microtomography. It was concluded that the XFEM method is an essential tool in predicting crack propagation of a railway component. Furthermore, the type of criteria used in the XFEM method allowed the analysis of the propensity of the manufacturing defect to initiate crack propagation. The C3D4 elements were essential in realising the crack propagation simulation, considering a manufacturing defect. Having the pore’s complex geometry was crucial to developing the methodology presented in this study. The static analysis results indicated that the maximum stress concentration value in the pore is in a zone that can be identified as a hot spot. In addition, the pore showed a higher concentration of Von-Mises stresses than in the static simulation performed without a pore and of the material’s ultimate strength. In conclusion, the methodology presented in this work shows that developing a more realistic simulation study is possible. For a complete structural integrity study, the mechanical design simulation studies must include some complex geometries of intrinsic manufacturing defects.

Biomechanical effects of Evans versus Hintermann osteotomy for treating adult acquired flatfoot deformity: a patient-specific finite element investigation.

Evans and Hintermann lateral column lengthening (LCL) procedures are both widely used to correct adult acquired flatfoot deformity (AAFD), and have both shown good clinical results. The aim of this study was to compare these two procedures in terms of corrective ability and biomechanics influence on the Chopart and subtalar joints through finite element (FE) analysis. Twelve patient-specific FE models were established and validated. The Hintermann osteotomy was performed between the medial and posterior facets of the subtalar joint; while, the Evans osteotomy was performed on the anterior neck of the calcaneus around 10mm from the calcaneocuboid joint surface. In each procedure, a triangular wedge of varying size was inserted at the lateral edge. The two procedures were then compared based on the measured strains of superomedial calcaneonavicular ligaments and planter facia, the talus-first metatarsal angle, and the contact characteristics of talonavicular, calcaneocuboid and subtalar joints. The Hintermann procedure achieved a greater correction of the talus-first metatarsal angle than Evans when using grafts of the same size, indicating that Hintermann had stronger corrective ability. However, its distributions of von-Mises stress in the subtalar, talonavicular and calcaneocuboid joints were lesshomogeneous than those of Evans. In addition, the strains of superomedial calcaneonavicular ligaments and planter facia of Hintermann were also greater than those of Evans, but both generally within the safe range (less than 6%). This FE analysis study indicates that both Evans and Hintermann procedures have good corrective ability for AAFD. Compared to Evans, Hintermann procedure can provide a stronger corrective effect while causing greater disturbance to the biomechanics of Chopart joints, which may be an important mechanismof arthritis. Nevertheless, it yields a better protection to the subtalar joint than Evans osteotomy. Both Evans and Hintermann LCL surgeries have a considerable impact on adjacent joints and ligament tissues. Such effects alongside the overcorrection problem should be cautiously considered when choosing the specific surgical method. Level III, case-control study.