Von Mises Stress Distribution Research Articles

Limit Elastic Analysis of Functionally Graded Rotating Disks Under Thermo-Mechanical Loading

In this work, the thermo-mechanical limit elastic speed analysis of functionally graded rotating disk has been reported. Three different material models, i.e., power law (P-FGM), sigmoid law (S-FGM), and exponential law (E-FGM), along with varying disk profiles, namely uniform, tapered, and exponential disk profiles, are considered. The methodology adopted is variational principle wherein the solution has been obtained by Galerkin’s error minimization principle. Halpin–Tsai method was used to estimate the modulus, modified rule of mixture for yield strength, and the rule of mixture for density and coefficient of thermal expansion. This study aims to analyze the effects of material models, grading indices, aspect ratio, and disk geometry on disk performance when subjected to combined thermal and mechanical loadings. Finite element analysis has been performed to validate this study and good agreement between both the methods is seen. The study shows a substantial difference in the limit speed for different disk profiles changing from uniform thickness to exponentially varying thickness. The von Mises stress distribution and location of yielding at limit speed are shown for different indices, material models, and disk profiles. In P-FGM, limit speed decreases with the increase in grading indices whereas in E-FGM, limit speed decreases with the decrease in grading indices. For increase in aspect ratio, limit elastic speed decreases in all the cases.

Positive or negative anteromedial cortical support of unstable pertrochanteric femoral fractures: A finite element analysis study

ObjectiveTo explore the mechanical stability of unstable pertrochanteric fractures with proximal femoral nail anti-rotation (PFNA-Ⅱ) fixation under different anteromedial cortical support reduction patterns. MethodsA 65-year-old healthy male volunteer with no history of hip or systemic disease was recruited. High-resolution computed tomography images with a slice thickness of 0.67 mm of his right femur were obtained. These images were used to establish three-dimensional (3D) models. The lesser trochanter and lateral femoral wall were cut off to create an AO Foundation/Orthopaedic Trauma Association type 31-A2 unstable pertrochanteric fracture model. PFNA-Ⅱ was used to simulate fixation. Nine different fracture reduction patterns, which included positive-positive, positive-neutral, positive-negative, neutral-positive, neutral-neutral, neutral-negative, negative-positive, negative-neutral, and negative-negative cortical support reductions, were simulated. A load of 700 N was applied to simulate a 70 kg elderly patient standing on one leg. The models were subjected to finite element analysis. The displacement and von Mises stress distributions were analyzed. ResultsThe positive-positive cortical support reduction pattern showed minimal stress and the negative-negative reduction pattern showed maximal stress on the intramedullary nail. The stress was mainly concentrated at the junction of the helical blade and the main nail and at the site of the lateral aspect of the insertion point of the nail in the great trochanter. The positive cortical support reduction patterns seemed to have smaller maximum displacements of the entire fragment-implant assembly and relative displacements between the head-neck and shaft fragments. Meanwhile, the negative reduction patterns seemed to have larger displacements. ConclusionThe positive-positive support reduction pattern showed better mechanical stability for unstable pertrochanteric fractures. The negative-negative support reduction pattern was prone to fixation failure and should be avoided during an operation.

Influence of Progressive Versus Minimal Canal Preparations on the Fracture Resistance of Mandibular Molars: A 3-Dimensional Finite Element Analysis

IntroductionThis study compared the residual tooth strength and stress distribution of a mandibular molar prepared with different variable tapered file systems using finite element analysis (FEA). MethodsTwo preaccessed mandibular molar TruTeeth (Endo 3DP; Acadental, Lenexa, KS) were subjected to simulated endodontic treatment in this study. One tooth was instrumented with ProTaper Gold (Dentsply Tulsa Dental Specialties, Tulsa, OK), and the other was instrumented with V-Taper 2H (SS White Dental, Lakewood, NJ). The 2 teeth were scanned using micro–computed tomographic imaging, and stereolithographic surface meshes were developed for FEA. Each model was subjected to a 200-N multipoint load-simulating mastication. The results of the FEA provided quantitative and qualitative measurements for von Mises stress distribution and total deformation. ResultsThe maximum von Mises stress was greater in the ProTaper Gold–prepared model than the V-Taper 2H prepared model. In both models, total deformation values were highest in the clinical crown on the buccal aspect of the tooth. The highest stress values were found in the pericervical dentin, and stress decreased apically through the root. ConclusionsWithin the limitations of this study, it can be concluded that the maximum stress values within the tooth prepared by ProTaper Gold were higher than those in the tooth prepared by V-Taper 2H. Canal preparation with the V-Taper 2H system preserves more pericervical dentin, which may increase the resistance to fracture.

Amorphous carbon/graphite coupled polyhedral microframe with fast electronic channel and enhanced ion storage for potassium ion batteries

Carbonaceous materials are well suitable for potassium-ion batteries (KIBs) anode due to the advantages of low cost and excellent K+ intercalation/deintercalation reversibility. Nevertheless, it is attractive but challenging to achieve satisfactory electrochemical performance in terms of rate, capacity and stability. Herein, N-doped amorphous carbon/graphite coupled polyhedral microframe (NCM) is successfully synthesized as an advanced anode for KIBs. The graphite acts as fast electronic channel while the amorphous carbon can host more K+ and accommodate the volume change, thus boosting its rate, capacity and stability. The von Mises stress distribution after K+ intercalation is also studied to demonstrate the optimization process of strain caused by the volume change through the finite element method. Along with the large interlayer spacing (0.368 nm), rich active sites and highly accessible surface, the NCM electrode exhibits high reversible capacity of 358.4 mAh g−1 at 500 mA g−1, outstanding rate property (272.2 mAh g−1 at 1000 mA g−1) and superb cycling performance (189.5 mAh g−1 after 1800 cycles at 2000 mA g−1). Moreover, a K-ion full cell is successfully assembled on the basis of potassium Prussian blue (KPB)/NCM, exhibiting large energy density (177.6 Wh kg−1) and good cycling stability.

Evaluation of Initial Stress Distribution and Displacement Pattern of Craniofacial Structures with 3 Different Rapid Maxillary Expansion Appliance Models: A 3-dimensional Finite Element Analysis.

This study aimed to describe the displacement of anatomical structures and the stress distributions caused by the Hyrax, fan-type, and double-hinged expansion screws via the 3-dimensional (3D) finite element method (FEM). The 3D FEM was based on the computed tomography data of a 12-year-old patient with a constricted maxilla. The Hyrax model included 1,800,981 tetrahedral elements with 2,758,217 nodes. The fan-type model included 1,787,558 tetrahedral elements with 2,737,358 nodes. The double-hinged model included 1,777,080 tetrahedral elements with 2,722,771 nodes. The von Mises stress distributions after 0.2 mm of expansion and displacement patterns after 5 mm of expansion were evaluated. The highest stress accumulation was observed in the sutura zygomatico maxillaris area with all 3 appliances. An increase in stress was noted at the pterygomaxillary fissure, the medial and lateral pterygoid process of the sphenoid bone, and the nasal areas. The wedge-shaped skeletal opening was observed with all 3 appliances. In the transverse plane, maximum posterior expansion was achieved with the Hyrax appliance, whereas the maximum anterior expansion was observed with the double-hinged appliance. The maxilla moved inferiorly and anteriorly with all the 3 appliances. The greatest inferior displacement of the maxilla was recorded with the Hyrax appliance, whereas anterior maxillary displacement was the greatest with the double-hinged appliance. All the appliances showed similar stress distributions. The use of double-hinged screw caused a slight anterior displacement of point A. The fan-type and double-hinged appliances were shown to be more effective on anterior maxillary constriction, whereas the Hyrax appliance might be chosen for resolving maxillary posterior constriction.

Predicting phonon scattering and tunable thermal conductivity of 3D pillared graphene and boron nitride heterostructure

In this work, we have studied the transfer of phonon energy in hybrid structure of pillared graphene and boron nitride film. The obtained results showed that, due to the occurrence of ballistic transfer with the elongation of heterostructure, thermal conductivity was increased. We also found that the amount of interfacial thermal conductivity was changed by changing the direction of thermal flux and the application of thermal flux along the direction of pillared graphene nanostructure was more favorable. We observed that increase of temperature from 100 to 700 K increased the amounts of interfacial thermal conductance (ITC) in C-N and C-B models by 19 and 10%, respectively. Since defects are inevitable during the fabrication and growth of these structures, in this work, we investigated the concentration and arrangement of these defects at joint interface and found that increase of defect concentration decreased thermal flux and ITC and also type of defects had a significant effect on thermal rectification. Also, the detection of these defects in a controlled manner can help making thermal conductivity tunable. We evaluated the effect of tensile from 0 to 10% in heterostructure with and without vacancy defects and found that ITC was decreased by 45% and 30% and temperature jump was increased by 80% and 45% at interface, respectively. In addition, to further analyze the obtained results, phonon vibration power spectra were also examined. Finally, by using Von Mises stress criterion, stress distribution and concentration through sheets and interface in the presence of mechanical strains and various defects were investigated.

The biomechanical study of cervical spine: A Finite Element Analysis.

The biomechanical study helps us to understand the mechanics of the human cervical spine. A three dimensional Finite Element (FE) model for C3 to C6 level was developed using computed tomography (CT) scan data to study the mechanical behaviour of the cervical spine. A moment of 1 Nm was applied at the top of C3 vertebral end plate and all degrees of freedom of bottom end plate of C6 were constrained. The physiological motion of the cervical spine was validated using published experimental and FE analysis results. The von Mises stress distribution across the intervertebral disc was calculated along with range of motion. It was observed that the predicted results of functional spine units using FE analysis replicate the real behaviour of the cervical spine.

Lothenbach’s Model of Von Mises Stress Distribution in Portland Cement in Curing and Temperature Gradient Conditions

The paper presents the two-dimensional Lothenbach’s model of Portland cement curing based on the finite element method. The cement curing lasts for 7 days in the temperature gradient conditions ranging from 65 to −20 °C. A cement rod 7×70 cm in size is used for modelling the temperature and von Mises stress distributions. It is shown that in the temperature gradient and curing conditions, the stress maximum in Portland cement shifts toward the hot edge of the cement rod and exceeds the minimum stress level more than two times. The stress growth is significant at the interfaces between the concrete timber and the cement rod, especially at its cold edge. Such a distribution of von Mises stress is connected with the heat flow generation and their superposition with reverse heat flows. At the interfaces, superposition of the negative heat flows generates higher stresses, than superposition of the positive heat flows. The concrete timber and the interface stability are the additional factors that increase the stress level and contribute to the fracture of the pore walls.

Bendable 3D-structured x-ray photodetectors based on pure PbI2 single crystal

PbI2 crystal is a typical layered material with a I–Pb–I monolayer as a repeating unit. Benefiting from the coexistence of ionic and van der Waals bonding, the crystal exhibits low hardness and a low Young’s modulus, slips easily along the a–b plane, and is endowed with inherently high flexibility. In this work, bendable three-dimensional (3D)-structured x-ray photodetectors based on PbI2 crystal were prepared, and finite element simulation was employed to reveal the von Mises stress distribution from the surface to the bulk of the crystal, indicating the bending stress associated with the crystal’s thickness. The uniformly distributed electric bias field inside the crystal constrains the carrier transport process, provides a consistent geometric variation and electrical contact between the crystal and the electrodes, and further ensures a high effective collection area and enhanced collection capacity for photocarriers, even when the device is subjected to bending. The degradation percentage of the sensitivity after 100 bending cycles is 12.7% and 6.6% for thick (100 μm) and thin (10 μm) samples, respectively. All the simulated and experimental results indicate that PbI2 crystal, when used to construct a 3D-structured device of appropriate thickness, is a promising candidate for the development of flexible x-ray photodetectors.

StressGAN: A Generative Deep Learning Model for Two-Dimensional Stress Distribution Prediction

AbstractUsing deep learning to analyze mechanical stress distributions is gaining interest with the demand for fast stress analysis. Deep learning approaches have achieved excellent outcomes when utilized to speed up stress computation and learn the physical nature without prior knowledge of underlying equations. However, most studies restrict the variation of geometry or boundary conditions, making it difficult to generalize the methods to unseen configurations. We propose a conditional generative adversarial network (cGAN) model called StressGAN for predicting 2D von Mises stress distributions in solid structures. The StressGAN model learns to generate stress distributions conditioned by geometries, loads, and boundary conditions through a two-player minimax game between two neural networks with no prior knowledge. By evaluating the generative network on two stress distribution datasets under multiple metrics, we demonstrate that our model can predict more accurate stress distributions than a baseline convolutional neural-network model, given various and complex cases of geometries, loads, and boundary conditions.

Performance of high conformability vs. high radial force devices in the virtual treatment of TAVI patients with bicuspid aortic valve

ObjectiveTranscatheter Aortic Valve Implantation (TAVI) is a consolidated procedure showing a low operative risk and excellent long-term outcomes in patients with aortic stenosis. Patients presenting a bicuspid aortic valve (BAV) often require valve replacement due to the highly calcific nature of the aortic leaflets. However, BAV patients have usually been contraindicated for TAVI due to their complex valve anatomy. The aim of this work was to compare the performance of devices featuring high conformability (HC) against those with high radial force (HRF). MethodsFour BAV patients undergoing TAVI were retrospectively selected. The aortic roots including the native leaflets and calcifications were reconstructed from pre-operative Computed Tomography scans. In each patient, both HC and HRF devices were virtually implanted using Finite Element Analysis simulations. After implantation, paravalvular orifice area, von Mises stress distribution, root contact area, and device eccentricity were calculated. ResultsSimulations showed good agreement with intraoperative imaging. In 3 out of 4 patients, the HRF device resulted in a lower paravalvular area than the HC. Stress distribution was also more homogeneously distributed in the HRF group as compared with the HC group. Despite their lower adaptability, HRF devices showed consistently higher stent-root contact area. ConclusionHRF devices showed improved results with respect to HC valves after being deployed in BAV anatomies. We hypothesize that the ability to reshape the annulus is the major determinant of success in this subgroup of patients featuring highly calcified leaflets.

Modeling of Stress Distribution During Portland Cement Curing in Temperature Gradient Conditions

The paper presents the two-dimensional model of Portland cement curing based on the finite element method. The cement curing lasts for 2 days in the temperature gradient conditions ranging from 65 to −20 °C. A cement rod 7×70 cm in size was used for modeling the von Mises stress distribution. It is shown that in the temperature gradient conditions, the stress maximum in curing Portland cement shifts toward the hot edge of the cement rod and exceeds the minimum stress level more than two times. The stress growth at the interfaces between the concrete timber and the cement rod exceeds the stress maximum inside the latter. This stress distribution is connected with the heat flow generation and superposition of direct and reverse heat flows. Superposition of the negative heat flows generates the stresses at the interfaces, which are higher than those generated by the positive heat flows. The concrete timber and the interface fixation are the additional factors that increase the stress level at the interfaces and promote the cement fracture.

Mechanical performance comparison of two surgical constructs for wrist four-corner arthrodesis via dorsal and radial approaches

BackgroundFour-corner arthrodesis, which involves fusing four carpal bones while removing the scaphoid bone, is a standard surgery for the treatment of advanced stages of wrist arthritis. Nowadays, it can be performed using a dorsal approach by fixing a plate to the bones and a new radial approach is in development. To date, there is no consensus on the biomechanically optimal and most reliable surgical construct for four-corner arthrodesis. MethodsTo evaluate them biomechanically and thus assist the surgeon in choosing the best implant orientation, radial or dorsal, the two different four-corner arthrodesis surgical constructs were virtually simulated on a 3D finite element model representing all major structures of the wrist. Two different realistic load sets were applied to the model, representing common tasks for the elderly. FindingsResults consistency was assessed by comparing with the literature the force magnitude computed on the carpal bones. The Von Mises stress distribution in the radial and dorsal plates were calculated. Stress concentration was located at the plate-screw interface for both surgical constructs, with a maximum stress value of 413 MPa for the dorsal plate compared to 326 MPa for the radial plate, meaning that the stress levels are more unfavourable in the dorsal approach. InterpretationAlthough some bending stress was found in one load case, the radial plate was mechanically more robust in the other load case. Despite some limitations, this study provides, for the first time, quantified evidence that the newly developed radial surgical construct is mechanically as efficient as the dorsal surgical construct.

Investigation on the influence of Lead Zirconate Titanate piezo material on different diaphragm materials in the mechanical deformation process

This paper focuses on the effect of Lead Zirconate Titanate (PZT-5H) piezoelectric material on different diaphragm materials to investigate the mechanical deformation of piezo and diaphragm materials. This model is based on the application of piezoelectric devices for its actuator function by using the COMSOL Multiphysics simulation software. The fundamental theory of piezoelectricity is used to describe the deformation in which applied potential voltage is converted into mechanical deformation. For the electric potential of 10 V, 15 V and 20 V, the distribution of Von Mises stress, minimum & maximum deformation in piezo material and different diaphragm materials has been calculated. Thus the outcome of this technical paper may provide a better understanding of behaviour of different diaphragm materials for piezoelectric applications.

Numerical investigation of mechanical properties of aluminum-copper alloys at nanoscale

Nanoindentation is a powerful tool capable of providing fundamental insights of material elastic and plastic response at the nanoscale. Alloys at nanoscale are particularly interesting as the local heterogeneity and deformation mechanism revealed by atomistic study offers a better way to understand hardening mechanism to build a stronger material. In this work, nanoindentation in Al-Cu alloys are studied using atomistic simulations to investigate the effects of loading direction, alloying percentages of Cu via dislocation-driven mechanisms. Also, a low-fidelity finite element (FE) model has been developed for nanoindentation simulations where nanoscale materials properties are used from atomistic simulations. Material properties, such as hardness and reduced modulus, are computed from both the FE and MD simulations and then compared. Considering the fundamental difference between these two numerical approaches, the FE results obtained from the present study conform fairly with those from MD simulations. This paves a way into finding material properties of alloys with reduced simulation time and cost by using FE where high-fidelity results are not required. The results have been presented as load-displacement analysis, dislocation density, dislocation loops nucleation and propagation, von-Mises stress distribution and surface imprints. The techniques adopted in this paper to incorporate atomistic data into FE simulations can be further extended for finding other mechanical and fracture properties for complex alloy materials.

Study and evaluation of four bar polycentric knee used in the prosthetic limb for transfemoral amputee during the gait cycle

The prosthetic knee is one of the most important parts used in manufacturing of the above knee prostheses limb and it is considered the most important component. Accordingly, it became necessary to conduct a study and evaluate for different types a prosthetic knee. In present work, the mechanism of four bar 3R20 prosthetic knee were evaluated and studied. Virtual model of four bar 3R20 prosthetic knee joint was built using Solid Work 2018 program. The fifty parts of four bar polycentric knee were designed separately and then assembled together. The kinematic analysis of four bar polycentric knee was performed using geometric analysis and Grashof law for double rocket. The results of instant center of rotation (ICR) from analytical solution was estimated using MATLAB program. The kinetic model include data of two components of forces and joint moments which used for transfemoral amputee with (age, height, weight, and stump length) of (28 years, 178 cm, 78 kg, and 29 cm) respectively. The numerical analysis of four bar prosthetic knee involved select the element type in ANSYS Workbench 19.2 program. Quadrilateral and trihedral elements were used in the finite element analysis to generate the mesh. The static analysis was investigated during different segmentation of gait cycle. The results of equivalent (von Mises) stress distribution calculated during stance phase for different loading conditions showed that the maximum stress was printed at the loading response phase with 226.93 Mpa at the root region between prosthetic knee and socket when orientation angles θ 2 = 85.5° and θ 4 = 105.4° and ICR coordinates are −0.560 mm and 77.388 mm for X,Y respectively.

Stress Distribution in Maxillary Central Incisors without Ferrules: A Finite Element Analysis of Post and Core Systems

Purpose: The purpose of this study was to identify optimal post and core materials for central incisors without ferrules using three-dimensional finite element analysis and three-point bending tests. Methods: Stress analyses were performed with six models: cast metal post and core (MP), composite resin core alone, straight fiber-reinforced post-composite resin core (FSR), tapered fiber-reinforced post-composite resin core, straight titanium post-composite resin core (TSR), and tapered titanium post-composite resin core (TTR). A 100-N load was applied to the lingual surface at a 45° angle to the long axis of the tooth. Maximum von Mises stress distributions were calculated with finite element analysis software. Five samples each of composite resin, straight fiber-reinforced post, straight titanium post, straight fiber-reinforced post and composite resin, and straight titanium post and composite resin were subjected to three-point bending tests, followed by analysis of variance and Tukey’s multiple comparison test. Results: Stress distribution was optimal on TTR. Maximum von Mises stress on the cervical side of the post was greatest in TSR (693 MPa) and TTR (556 MPa). Maximum stress on the apical side of the post was greatest in MP (110 MPa). Maximum stress in surrounding dentin was lowest in MP (203 MPa) and TTR (250 MPa). Gap distance was smallest in MP (0.09 mm) and largest in FSR (0.26 mm). Mean maximum three-point bending force was lowest in composite resin (26.9 N/mm) and highest in titanium post and composite resin (97.1 N/mm). Titanium post bending strength was consistently greater than that of the fiber-reinforced post (p < 0.01). Conclusion: These results revealed optimal stress distribution and high bending strength with the tapered titanium post and resin combination, suggesting that this combination can most effectively prevent root or post fracture in an anterior tooth without a ferrule.

Polietereterketon ve İndirekt Kompozit Rezin Kalınlığının, Endokronla Restore Edilmiş Maksiller Premolar Dişteki Stres Dağılımına Etkisi: 3 Boyutlu Sonlu Elemanlar Analizi

Objective: The objective of this study was to evaluate the influence of polyetheretherketone substructure and indirect composite resin veneering material thicknesses on stress distribution in endodontically treated maxillary premolar teeth restored with endocrowns. &#x0D; Methods: A sound maxillary premolar teeth was used as control group. Polyetheretherketone substructure and indirect composite resin veneering materials were used as endocrown materials in all study groups. The occlusal thicknesses of the endocrowns were fixed at 3 mm in study groups. Thicknesses of polyetheretherketone and indirect composite resin veneering material were determined as; 1, 1.5 and 2 mm. Stress distributions of maxillary premolar teeth under 200 N vertical and oblique loads were analyzed. &#x0D; Results: Von Mises stress distributions were same in study groups. Von Mises stress values in enamel and dentin were same in all study groups and they were higher than sound teeth. The lowest Von Mises in restorative material were found in a study group with 2 mm PEEK substructure and 1 mm indirect composite resin veneering material thickness.&#x0D; Conclusion: Difference in polyetheretherketone and indirect composite resin veneering materials’ thickness didn’t affect von Mises stress values and distributions in enamel, dentin.

BIOMECHANICAL BEHAVIOUR OF THE TOTAL HIP PROSTHESIS SUBJECTED TO NORMAL GAIT CYCLE LOAD: IDENTIFICATION OF THE DAMAGE IN THE CEMENT MANTLE

Cement is the weakest link in the composition of total hip prosthesis in terms of mechanical properties. The knowledge of the intensity and distribution of stresses on the cement attaching the implant to the bone is of great importance for understanding the condition of the prosthesis and its failure. In this study, the finite element method is used to analyze the magnitude and the equivalent Von Mises stress distribution induced in different components of the total hip prosthesis (THP) as well as the identification of the damage induced in the cement and between two cavities located in the polymethyl methacrylate (PMMA). The crack propagation is determined and localized using the extended element method (XFEM). The results show that the fracture stress of the cement in its proximal part is very important. These stresses increase considerably with the interaction of the cavities in this binder, causing damage to the cement and the loosening of the prosthesis.

Yarış aracı aerodinamik kanatlarında atık granül kauçuk lastik ile oluşturulan kompozit malzemenin fizibilitesi

In recent years, reducing the cost of vehicles, fuel consumption, and producing environmental-friendly vehicles by minimizing exhaust emissions are the main topics that the automotive industry and researchers emphasize. In this way, more environmental-friendly vehicles will be produced and harmful gasses will be released less into nature. The main subject of this study is to obtain a lighter race wing by using waste rubber granule material. Reducing the fuel consumption and exhaust emission emissions of vehicles is possible by producing vehicles directly from lighter materials. The light weighting studies in recent years are provided by the production of composite materials that have better mechanical properties and enable the production of much lighter parts. In this study, a finite element analysis method was used to compare the application of foam core body and waste rubber granule application to formula vehicle racing wings. The results of the analysis are presented in the figures as distribution of total deformation and Von-Mises stresses. As a result, it has been found that the waste rubber granule material has good mechanical properties and reasonable cost, and it can be used in racing vehicles. In particular, it has been found that the cost of parts used per kilogram is reduced by a tenth.