Highest Von Mises Stress Research Articles

Biomechanical effects of different miniplate use on bone and miniplate systems in multiple mandible fracture: A finite element study

The aim of this study is to evaluate the biomechanical efficiency of different miniplates in the treatment of multiple mandibula fractures. Mandible, miniplates, and screws were modeled using the Solid Works v2015 (Dassault Systèmes, France) program, Subsequently two fracture lines were created on the right parasymphysis and angulus mandible. Models were divided into two main groups according to the plates used in the anterior fracture line: group A, 2 piece 4-hole-bar-I plate, and group B, ellipse plate. Each group was divided into five subgroups according to the plates used in the posterior fracture line (I, X, G, 3D, E) and 10 study models were created in total. Under three different biting forces (anterior, right, left), maximum von-Mises stresses seen on miniplates/screws, and Pmax/Pmin stresses seen in the cortically/cancellous bone were analyzed using the Ansys 16.2 software (ANSYS, Inc., USA). Data was visualized using a color distribution scale and interpreted. The highest von-Mises stress, seen in plates, was found in the I plate (353.82 MPa) at the angulus region of model A1. The highest Pmax and Pmin stresses, revealed in cortical bone, were found respectively in model A1 (181.63 MPa) and model B2 (115.01 MPa). The ideal results on plates were seen in models B3 and B5, in which E plates were used in the parasymphysis and G/E plates were used in the angulus region. Grid and ellipse plates provide successful results and plate geometry is more critical than number in terms of stress distribution.

Patient-specific finite element analysis of four different fixation methods for transversely unstable radial head fractures

Plate fixation is a common treatment option for radial head fractures (RHFs). Due to the benefits of less invasiveness and fewer complications of internal fixation, the application of small-diameter headless compression screws (HCSs) to treat RHFs has become a new trend. This study aimed to compare the mechanical stability of four distinct internal fixation protocols for transversely unstable RHFs via finite element analysis. Using computed tomography data from 10 patients, we developed 40 patient-specific FE models of transversely unstable RHFs fixed by parallel, crossed, and tripod HCSs and mini-T plate (MTP). Under simulated physiological loading of the elbow joint, the construct stiffness, displacement, and von Mises stresses were evaluated and verified by a biomechanical experiment. Under shear loading, the MTP group exhibited lower construct stiffness, larger displacement, and higher Von Mises stress than the HCSs group. The stiffness of tripod HCSs was greater than parallel and crossed screw fixation techniques. There was a strong relationship between apparent bone density and construct stiffness (R = 0.98 to 0.99). In the treatment of transversely unstable RHFs, HCSs have superior biomechanical stability than MTP. The tripod technique was also more stable than parallel and crossed fixation.

Study on the performance characteristics and failure analysis of exhaust valves

Abstract Exhaust valves are a type of valve that can commonly be found in the top section of the cylinder block in an engine. When failures occur on the exhaust valve, the engine has a high possibility to result engine failure or breakdown. This will affect the user where the user requires to spend a huge amount on repairing costs or engine replacement. Thus, this research aims to investigate the effect of the exhaust valve’s material on its performance and identify the appropriate material which could increase its fatigue life in a four-stroke internal combustion diesel engine. A three-dimension (3D) Computer-aided design model of the exhaust valve was generated by using SOLIDWORKS and undergo static structural analysis as well as thermal analysis. The measure variables are von-mises stress, total deformation, temperature, total heat flux and directional heat flux by using ANSYS Finite Element Analysis. Stainless steel 304 alloy and Aluminium-Silicon Carbide (Al-Sic) materials are the manipulated variable that was applied to the 3D CAD model exhaust valve to undergo all the analyses. Before performing all the analyses, the appropriate mesh method and mesh sizing was identified by referring to the mesh metrics spectrum and performing a mesh independence test. The results from the analysis were collected and tabulated for comparison and discussion purposes. From the analysis, the maximal thermal stress was determined in the valve stem region. By appointing Stainless Steel 304 alloy on the exhaust valve, the durability and the fatigue life are improved as the material can achieve a smaller value of temperature distribution, total heat flux, total deformation, and higher von-mises stress. This research provided a better understanding of the effect of an exhaust valve material on its performance characteristic.

Computer-aided Design of Distal Femoral Osteotomy for the Valgus Knee and Effect of Correction Angle on Joint Loading by Finite Element Analysis.

Lateral open-wedge distal femoral osteotomy (DFO) has been used to treat valgus deformity of the knee, with good clinical outcomes. However, there is a lack of biomechanical studies regarding the angle of correction. The objective of this study was to apply computer-aided design (CAD) for osteotomy planning in a three-dimensional (3D) anatomical model and to assess the biomechanical differences among the varying correction angles on joint loading by finite element analysis (FEA). To model different angles of lateral open-wedge DFO correction, the CAD software package Mimics 21.0 was used to accurately simulate the operated knee. The femur was cut to 0°, 2°, 4°, 6°, 8°, and 10° of varus (equivalent to hip-knee-ankle angles of 180°, 178°, 176°, 174°, 172°, and 170°, respectively). The original knee model and the corrected models were processed by FE software. Then, the FE models were subjected to an axial force to obtain the von Mises stress (VMS) and shear stress distributions within the femoral cartilages and menisci. Under a compressive load of 740 N, the highest VMS in lateral and medial compartments of the intact knee model was 3.418 and 3.303 MPa. The maximum value of both the VMS and the shear stress in the lateral compartment decreased as the varus angle increased, but the corresponding values in the medial compartment increased. When the hip-knee-ankle (HKA) angle was 180°, the VMS in the lateral and medial compartments was balanced (3.418 and 3.303MPa, respectively). Meanwhile, when the HKA angle was 178° (3.488 and 3.625MPa, respectively), the shear stress in the lateral and medial compartments was balanced. In addition, the magnitude of change in the stress was significantly higher in the medial compartment (90.9%) than in the lateral compartment (19.3%). The optimal correction angle of the valgus knee is close to neutral alignment or slightly varus (0° - 2°). Overcorrection is not recommended, as it can result in a steep increase of the stress within the medial compartment and may accelerate the process of medial compartment OA.

Investigation of the biomechanical stability of Cfr-PEEK in the treatment of mandibular angulus fractures by finite element analysis

The purpose of this study is to explore the effectiveness of Cfr-PEEK, in the fixation of unfavorable fractures of mandibular angulus by comparing it with the titanium and resorbable biomaterials. 8 different fixation models were created. In the first 4 groups, a single mini plate was applied to the upper edge of the fracture line by the Champy method. In the other 4 groups, an additional plate was placed on the lower edge of the fracture line. In these models, titanium, resorbable and Cfr-PEEK plate/screw systems were investigated by the finite element analysis method. The highest Von Mises stress was observed on the upper plate in the group 5 while the lowest was seen in the lower plate in the group 7. The highest stress values on the screws were observed on the screws placed closer to the fracture line. Considering the stresses on the bone around the screws, the highest Pmax and Pmin values were seen in group 5, and the lowest values were seen in the group 7. The highest displacement was observed in the group 3, while the lowest was observed in the group 5. According to the results it can be said that Cfr-PEEK plate/screw systems may provide advantages by decreasing the stresses on the fixation systems over the titanium plates and providing more stable fixation over the resorbable systems. Cfr-PEEK plates of 2 mm thickness seems to be a potential alternative to 1 mm thick titanium plates.

Biomechanical investigation of maxillary implant-supported full-arch prostheses produced with different framework materials: a finite elements study.

Four and six implant-supported fixed full-arch prostheses with various framework materials were assessed under different loading conditions. In the edentulous maxilla, the implants were positioned in a configuration of four to six implant modalities. CoCr, Ti, ZrO2, and PEEK materials were used to produce the prosthetic structure. Using finite element stress analysis, the first molar was subjected to a 200 N axial and 45° oblique force. Stresses were measured on the bone, implants, abutment screw, abutment, and prosthetic screw. The Von Mises, maximum, and minimum principal stress values were calculated and compared. The maximum and minimum principal stresses in bone were determined as CoCr < ZrO2 < Ti < PEEK. The Von Mises stresses on the implant, implant screw, abutment, and prosthetic screws were determined as CoCr < ZrO2 < Ti < PEEK. The highest Von Mises stress was 9584.4 Mpa in PEEK material on the prosthetic screw under 4 implant-oblique loading. The highest maximum principal stress value in bone was found to be 120.89 Mpa, for PEEK in 4 implant-oblique loading. For four and six implant-supported structures, and depending on the loading condition, the system accumulated different stresses. The distribution of stress was reduced in materials with a high elastic modulus. When choosing materials for implant-supported fixed prostheses, it is essential to consider both the number of implants and the mechanical and physical attributes of the framework material.

Biomechanical effects of different bone cement diffusion patterns after vertebroplasty:finite element analysis

To investigate the biomechanical effects of different bone cement diffusion patterns in the treatment of osteoporotic vertebral compression fractures. One volunteer with L1 osteoporotic vertebral compression fracture was selected, male, aged 68 years old, heighed 172 cm, weighted 60 kg, and healthy before. CT scans were used from T10-L5, CT data was extracted with Mimics software, and Geomagic wrap and Solidworks were used to model, and the three-dimensional finite element model (T12-L2) of preoperative osteoporotic vertebral compression fractures in the thoracolumbar segment was established. Similarly, the situations of bone cement dispersion in vertebroplasty were simulated (the situations of bone cement dispersion had the three kinds, including the bone cement not contacts with upper and lower endplates, the bone cement only contacts with upper endplates, and the bone cement contacts with upper and lower endplates). According to different diffusion situations, five types of loads were applied to the model:upright, upright plus forward flexion, upright plus backward extension, upright plus left bending, upright plus right rotation. Meanwhile, the model was compared with the cementless lumbar spine model, and the deformation and stress distribution of each model under load were recorded and compared. After the establishing the finite element model of osteoporotic vertebral compression fracture in the thoracolumbar segment, it was found that the deformation of three different bone cement distribution models above was not significantly different. In L1 cancellous bone, the Von Mises stress of the cementless lumbar spine group was significantly higher than that of the cemented group. Among the three groups of different bone cement injection situations, the Von Mises stress in the group of bone cement contacts with upper and lower endplates was the lowest, followed by the group of bone cement only contacts with upper endplates, and the highest Von Mises stress was the group that bone cement contacts neither the upper or lower endplates. In the comparison of bone cement stress, the Von Mises stress in the group of bone cement contacts with upper and lower endplates was significantly higher than the other two groups (upright 12.375 MPa, upright plus forward flexion 16.411 MPa, upright plus backward extension 16.801 MPa, upright plus left bending 13.425 MPa, upright plus right rotation 13.014 MPa), and the Von Mises stress in the group of bone cement does not contact with upper and lower endplates was the lowest. The bone cement contact with both upper and lower endplates can effectively absorb and transfer the stress level brought by the load, reduce the stress level of cancellous bone, and reduce the possibility of refracture of the operative vertebral body.

Mechanical behaviour of femoral prosthesis with various cross-section shape, implant configurations and material properties

The maximum Von-Mises stress analysis introduced by dynamic body load on hip implant was considered in this research. The different hip stem shapes including elliptical, circular and oval cross sections with various configurations and material properties including that of Ti-6Al-4V, Co-Cr-Mo and SS316L alloys were simulated by 3D computational analysis to evaluate the “stress-shielding effect” on the implant surface. In order to categorise the various shapes and materials based on “stress-shielding effect”, a factor called “stress distribution” (SD) was developed. Results showed that the highest Von-Mises stress levels are attributed to the elliptical cross-section, whereas oval cross-sections comprised the least figures with certain stem profiles. In terms of SD factor, titanium alloy with elliptical cross section indicated the lowest level, while the better results specified to the oval shape.

Cryo-Transferred Ultrathin and Stretchable Epidermal Electrodes.

A simple cryo-transfer method to fabricate ultrathin, stretchable, and conformal epidermal electrodes based on a combination of silver nanowires (AgNWs) network and elastomeric polymers is developed. This method can temporarily enable the soft elastomers with much higher elastic modulus and dimensional contraction through exploiting their glass-transition behaviors. During this process, a much higher Von Mises stress can be loaded on AgNWs than usual, and the generated strong grip force can facilitate the complete transfer of AgNWs. Afterward, the thawed AgNWs and elastomer composites quickly recover to their soft state at room temperature. The obtained ultrathin and soft electrode with a thickness of 8.4 µm and transmittance of 90.8% at a sheet resistance of 13.2 Ω sq-1 can tolerate a stretching strain of 70% and 50 000 repeated bending cycles, which meets rigorous requirements of epidermal applications. The as-prepared epidermal electrodes are effective and comfortable for electrophysiological signal monitoring, and while showing excellent performance exceeding the commercialized gel electrodes.

Multiphysics field coupling simulation for shell-and-tube heat exchangers with different baffles

Baffles are important components to control shell-side flow distribution and enhance heat transfer for shell-and-tube heat exchangers (STHXs). Based on multiphysics field coupling simulation, thermal–structural performance was studied for three types of STHXs with different baffles including segmental baffles, plain helical baffles and fold helical baffles. The results show that zigzag flow appears in STHXs with segmental baffles, and flow behavior is helical pattern in STHXs with helical baffles. Especially, much vortex and high velocity are generated in STHXs with fold helical baffles, where the shell-side pressure drop and Nussult number are the highest, and thermal enhancement factor (TEF) to evaluate thermal–hydraulic performance is also the largest. Although higher von-Mises stress distributes on the tube bundle, results of stress linearization at dangerous location in elastic stage show that membrane stress and sum of primary stress and secondary stress are both within range of corresponding stress intensity. Therefore, the comprehensive thermal–structural performance of STHXs with fold helical baffles is the best. The research can have a degree of theoretical guidance for design and choice of heat exchangers.

Number of Screws Affecting the Stability and Stress Distributions of Conventional and Locking Compression Plate: A Finite Element Study

The effectiveness of malleolar fracture fixation is still questionable. Internal fixator is the one of the treatment for treating this fracture. However, the analysis of various type of internal fixator is still lacking in the literature in terms of biomechanical characteristics and behaviour. Thus, the aim of the study was to compare the stability of locking compression plate (LCP) and one third tubular plate (OTT) in different configuration of screws. Computed Tomography (CT) images of bone was used to develop 3D model of fibula bone. The plate was constructed in Solidworks software and number of screws used were 3 and 5. Further, finite element study was conducted for both model. For LCP, the highest von Mises stress (VMS) observed at the plate for 3 screws was 484 MPa, whereas for 5 screws plate was 667 MPa. Besides, for OTT, the highest VMS at plate observed for 3 screws was 300.5 MPa, whereas for 5 screws plate was 127.5 MPa. Based on the results, it can be noted that the usage of 3 screws can causes a low VMS at plate compare to 5 screws. However, the relation is valid for LCP. For OTT, 5 screws constructs gave a low VMS than 3 screws constructs.

Biomechanical evaluation of tibial bone adaptation after revision total knee arthroplasty: A comparison of different implant systems.

The best methods to manage tibial bone defects following total knee arthroplasty remain under debate. Different fixation systems exist to help surgeons reconstruct knee osseous bone loss (such as tantalum cones, cement, modular metal augments, autografts, allografts and porous metaphyseal sleeves) However, the effects of the various solutions on the long-term outcome remain unknown. In the present work, a bone remodeling mathematical model was used to predict bone remodeling after total knee arthroplasty (TKA) revision. Five different types of prostheses were analyzed: one with a straight stem; two with offset stems, with and without supplements; and two with sleeves, with and without stems. Alterations in tibia bone density distribution and implant Von Mises stresses were quantified.In all cases, the bone density decreased in the proximal epiphysis and medullary channels, and an increase in bone density was predicted in the diaphysis and around stem tips. The highest bone resorption was predicted for the offset prosthesis without the supplement, and the highest bone formation was computed for the straight stem. The highest Von Mises stress was obtained for the straight tibial stem, and the lowest was observed for the stemless metaphyseal sleeves prosthesis.The computational model predicted different behaviors among the five systems. We were able to demonstrate the importance of choosing an adequate revision system and that in silico models may help surgeons choose patient-specific treatments.

Simulation Using Finite Element Analysis in the Optimization of Inflatable Bedpan Wall Thickness

The inflatable bedpan is designed to provide comfortable, convenient, safe, hygienic, efficient and easy to use to the patients and their caretakers. In order to investigate the suitability thickness of inflatable bedpan for the pressure inflow in bedpan tube, the analysis is done using Catia analysis. The static analysis work is carried out to inflatable bedpan cross section of polyvinyl chloride (PVC) and their relative performances have been observed respectively. The thickness 0.5 mm shows the highest Von Mises Stress which is 21100 kPa compared to 0.8and 1.0 mm thicknesses. The lowest Von Mises Stress observed at thickness 1.0 mm which is 2990 kPa. The less stress obtained can encourage perfect shape of the design. In this paper, by observing the result of static structure analysis obtained, 1 mm is suggested as best thickness to be used as an inflatable bedpan wall because it can withstand more pressure while maintaining its stability.

Biomechanical Evaluation of Magnesium-Based Resorbable Metallic Screw System in a Bilateral Sagittal Split Ramus Osteotomy Model Using Three-Dimensional Finite Element Analysis

The aim of this study was to evaluate the stress distribution of a magnesium (Mg)-based resorbable screw system in a bilateral sagittal split ramus osteotomy (BSSO) and to compare its biomechanical stability with those of titanium (Ti)-based and polymer (IN)-based systems. A 3-dimensional BSSO model (10-mm advancement and setback) was constructed with Mimics. Bicortical screw fixation using Ti, IN, and Mg screws was performed with 4 different geometries of fixation. With an occlusal load of 132 N on the lower first molar, the von Mises stress (VMS) distribution was calculated using ANSYS. The VMS distribution of Mg was more similar to that of Ti than to that of IN. In all cases, the highest VMS was concentrated on the screw at the most posterior and superior area. Stress was distributed mainly around the screw holes (cancellous bone) and the retromolar area (cortical bone). In the advancement surgery, fixation with 5 Mg screws (5A-Mg, 99.810 MPa at cortical bone) showed biomechanical stability, whereas fixation with the same number of IN screws did not (5A-IN, 109.021 MPa at cortical bone). In the setback surgery, although the maximum VMSs at cortical bone for Mg, IN, and Ti were lower than 108 MPa (yield strength of cortical bone), Mg screws showed more favorable results than IN screws because the maximum VMSs of Mg at cancellous bone were lower than those of IN. The Mg-based resorbable screw system is a promising alternative to the IN-based system.

Effect of intervertebral disc degeneration on biomechanical behaviors of a lumbar motion segment under physiological loading conditions

The consideration of biomechanical alterations due to intervertebral disc (IVD) degeneration is crucial for the accurate analysis of spine biomechanics. In this study, finite element (FE) models of the L4-L5 motion segment with full coverage of the degeneration grades from healthy IVD to severe degeneration were developed. The effects of IVD degeneration on spine biomechanics were analyzed under physiological loading conditions using compressive forces and bending moments. The FE models of all degeneration grades were consistent with published data in terms of the ranges of motion. Severe IVD degeneration showed lower inter-segmental rotations in flexion-extension and lateral bending, lower intradiscal pressure in all motions, higher facet joint forces in lateral bending and axial rotation, and higher von-Mises stress in annulus ground substance in all motions versus the healthy IVD. These findings could provide fundamental information for understanding the characteristics of the biomechanical behaviors of degenerated lumbar motion segments.

Simulation Analysis on Wear-Resistance of Roller with Concave Surface

Three dimensional finite element model of roller and sheet rolling process was first built according to roller and flattening sheet rolling wear characteristics by using ANSYS/LS-DYNA software. Total 10 rolling models including 1 smooth surface and 9 non-smooth surfaces were established to compare with wear resistance characteristics difference. Simulation results showed that comparing with smooth surface roll sample, the non-smooth roller surface with concaves possessed had higher Von Mises stress value with non-uniform fluctuation at mean value in favor of enforcing rolling sheet fluidity. On the other hand, some air concentrated on concave circumjacent area will low adhesion wear appearance between plate and roller. Thirdly, Concave on the roller surface was also able to protect from sliding at friction interfaces. It was these factors above that were in favor of improving wear resistance capability of the rollers. The result of the model tests and the simulation are identical.

Three-dimensional finite element analysis of effect of root canal taper and post on tooth stress distribution

To evaluate the effect of root canal taper and post on tooth stress distribution. Three-dimensional finite element models of human mandibular first molar with root canals prepared with 35# K file, ProTaper and Profile were established. The tooth were restored with fiber-resin, stainless steel and silver amalgam posts respectively. A vertical load on tooth occlusal surface was simulated. Marc software was used to analyze and calculate the stress distributions in the tooth restored with three kinds of different root canal posts, especially the in the cervical part and root. Different tapered root canals had no obvious influence on stress distribution in all three different posts. Stress distribution of stainless steel post located at the cervical and middle part of distal root, the highest Von-Mises stress was about 45 MPa. Stress distribution of silver amalgam post located at the orifice of root canal and pulp fundus, the highest Von-Mises stress was about 16 MPa. Stress distribution of fiber-resin post had no obvious stress concentration. Fiber-resin post is the most ideal root canal post. Stainless steel post causes remarkable stress concentration in the root, which may raise the possibility of root fracture.