Von Mises Stress Research Articles

Biomechanical effects of FNS on femoral neck fractures based on different reduction quality: finite element analysis.

The femoral neck system (FNS) has been extensively studied and applied for the treatment of young patients with femoral neck fractures. The purpose of this study was to explore the biomechanical impact variations in reduction qualities on femoral neck fractures, considering factors such as tip-apex distance, the positioning of the bolt in the cortical corridor of the femoral neck, and bone mineral density. A randomly selected volunteer was recruited, whose clinical data on the femur were collected to establish finite element models for positive reduction, anatomical reduction, and negative reduction respectively. Based on the constructed models, different scenarios were established by varying the tip-apex distance, bone mineral density, and positioning of the bolt in the cortical corridor of the femoral neck. Under a vertical load of 2100N, the displacement and Von Mises stress (VMS) distribution of each group of models were evaluated through simulation testing. Under a load of 2100N, the maximum VMS values of the femoral neck system and femoral head was recorded during negative reduction, 968.85MPa and 80.09MPa respectively. In addition, factors influencing the negative reduction of FNS and the femoral head were identified to be the tip-apex distance > 10mm, the presence of osteoporosis, and the bolt positioned in the lower-middle to the third part of the cortical corridor of the femoral neck. The displacement and stress of negative reduction were greater than those of positive reduction and anatomical reduction when the tip-apex distance > 10mm, and the bolt was situated in the lower-middle to the third part of the cortical corridor of the femoral neck, and in the presence of osteoporosis. This means that we recommend positive repositioning over negative repositioning when anatomical repositioning is not clinically feasible.

Evaluation of the Biomechanical Effects and Stability of Titanium and Carbon Fiber-Reinforced Polyetheretherketone Mini Plates in Le Fort I Advancement Osteotomy Fixation Using Finite Element Analysis.

This study aimed to investigate the biomechanical properties of 60% carbon fiber-reinforced polyetheretherketone (Cfr-PEEK), which exhibits high mechanical strength and can address the limitations of titanium mini plates used in Le Fort I osteotomy. Models were created using the FEA method based on tomography images of adult individuals. A 5 mm maxillary advancement was applied to the models following Le Fort I osteotomy. Mini plates made of titanium and 60% Cfr-PEEK were used. Support was provided by the nasomaxillary and zygomaticomaxillary buttresses to fix a total of four L-shaped mini plates. Oblique loads of 125 N, directed from palatal to buccal, and a total of 250 N compression loads were applied to the central fossa of the premolar and molar teeth in the maxillary model at a 30° angle relative to the long axis of the teeth. Displacement values at the osteotomy line, Von Mises stresses in the mini plate-screws, and principal stresses in the bone were compared. Examination of stress values in the fixation systems of the models revealed higher stress values in the Cfr-PEEK model compared to the titanium model. However, these stresses did not reach levels that would deform the Cfr-PEEK fixation systems. Stress and displacement values in the bone were lower in the Cfr-PEEK model compared to the titanium model. According to the findings of our study, Cfr-PEEK represents a viable alternative to titanium for mini plate material in Le Fort I osteotomy, offering biomechanical advantages.

Yielding onset in FGM thick-walled spherical shells under thermo-mechanical loading

Based on von Mises yield criterion, a thermoelasto-plastic analysis of a thick-walled spherical shell composed of functionally graded material (FGM) subjected to internal pressure and thermal gradient is conducted in order to accurately predict the onset radius of yielding within the vessel wall. The modulus of elasticity, thermal conductivity and thermal expansion coefficients, and yield stress of FGM are assumed to follow power-law functions in radius according to Erdogan’s model. The equilibrium differential equation of the shell under thermo-mechanical loading in steady-state conduction heat transfer are derived analytically and then solved to determine through-thickness variations of the radial and circumferential stresses and radial displacement in elastic and perfectly plastic zones in the vessel wall. The presented approach leads to the definition of new formulation to predict the onset radius of yielding. Moreover, a neural network (NN) solution to reliable quantify the influence of all uncertain input parameters with respect to uncertain output parameter is utilized. The numerical results showed that for various FGM parameters and specific thermal gradient, the plastic zone can commence from inside radius, outside radius, simultaneously in both radii, or may be launched in the intermediate radius of the spherical shell wall.

Computational modeling of localized corrosion in steel pipelines supported by composite sleeves

Pitting corrosion is a worrying phenomenon in the oil industry representing a major threat that can lead to the reduction of the structural integrity of pipeline transportation networks. To prevent this corrosion risk, active cathodic protection with a potential maintained at – 850 mV Cu/CuSO4 is used as a coating protection system based on bituminous binders to isolate the steel from the corrosive soil environment in hydrocarbon transportation pipelines. In this work, we examine the clock spring repair method by applying composite paths including a numerical simulation on corroded tubes using ANSYS software. The approach involves analyzing the structure under three scenarios: without defects, after the introduction of elliptical simulated corrosion pits, and following repair with multilayer reinforcement using a composite sleeve. The results indicate that the stress distribution varies across each scenario. In the case of a structure with parabolic corrosion defects, the Von Mises stresses are unevenly distributed. The defect exhibits a peak stress that could lead to the propagation of corrosion pits, necessitating repair. Conversely, in the scenario where the corroded structure is reinforced with a composite sleeve, the maximum Von Mises stress is decreased to levels comparable to those of an uncorroded pipe, demonstrating the necessity and effectiveness of using composite sleeve reinforcement.

Biomechanical Effects of Different Spacing Distributions Between the Cemented Superior Boundary and Surgical Vertebral Superior Endplates After Percutaneous Vertebroplasty for Osteoporotic Vertebral Compression Fractures: A Three-Dimensional Finite Element Analysis.

Patients with osteoporotic vertebral compression fractures (OVCF) treated with vertebroplasty (PVP) are experiencing an increasing number of problems such as pain recurrence, mainly due to recompression fractures of the operated vertebral body within a certain period of time after the operation, which is closely related to the distribution of intraoperative bone cement. The aim of this study is to investigate the effect of different spacing distributions between the upper boundary of the cement and the upper endplate of the operated vertebra on the biomechanics of the operated vertebra after percutaneous vertebroplasty for OVCF using finite element analysis (FEA). One patient with L1 vertebral body OVCF was selected, and computed tomography (CT) of the thoracolumbar segment was performed. The CT data were extracted to establish an FEA model of the T12-L2 vertebral bodies. Bone cement was injected into the L1 vertebral body. Based on the spacing between the upper boundary of the bone cement and the vertebral body's upper endplates, the model vertebrae were divided into 0, 2, 4, and 6 mm spacing groups, and the human body's upright, flexion-extension, lateral flexion, and rotational positions were simulated. The biomechanical effects of different spacing distributions on the postoperative L1 vertebral body and the injected bone cement were evaluated. In this paper, we found that the Von Mises stress of the L1 vertebrae was the smallest when the spacing between the upper boundary of the bone cement and the vertebral body's upper endplates was 0 mm. The larger the spacing in a certain range between the upper boundary of the bone cement and the vertebral body's upper endplates, the greater the Von Mises stress of the L1 vertebrae. However, in the stress comparison of the injected bone cement, the Von Mises stress of the bone cement was greatest when the spacing between the upper boundary of the bone cement and the upper endplate of the vertebral body was 0 mm; the larger the spacing, the smaller the Von Mises stress. When the contact spacing between the upper boundary of the bone cement and the upper endplate of the vertebral body is 0 mm, it can effectively eliminate and transfer the pressure caused by the load, thus reducing the stress on the cancellous bone and further reducing the risk of vertebral refracture after surgery.

"Effect of mid-root perforation and its repair on stress distribution and fracture resistance: a 3D finite element analysis and in vitro study".

to assess and compare the effect of mid-root perforation repair using Biodentine and Portland cement in single-rooted endodontically treated mandibular premolars in terms of stress distribution using finite element analysis (FEA) and fracture resistance test. In the FEA, an extracted human mandibular premolar tooth was scanned using cone beam computed tomography, and a 3-dimensional (3D) solid model was created. A sound tooth model (ST), an endodontically treated model (ET), an instrumented and mid-root perforated and repaired by Biodentine model (BM), and perforated and repaired by Portland cement model (PCM) were the 4 models simulated. A vertical force of 300N on the occlusal plane was applied. Evaluation of von Mises stress distribution and maximum displacement were investigated. In the fracture resistance in vitro study, 28 extracted premolars were selected and randomized into 4 groups, (n = 7), (A) is the negative control intact group, (B) is the positive control of endodontically treated group, (C) is mid-root perforated and repaired by Biodentine group and (D) is mid-root perforated and repaired by Portland cement. All Teeth were instrumented except for group A, group B was obturated while groups C and D were instrumented, perforated, repaired, and obturated. All groups were restored coronally except group A. Fracture force was measured; subsequently, the fracture repairability was evaluated. Finally, the data were statistically evaluated using one-way analysis of variance (ANOVA); the significance level was set at P ≤ 0.05 and the repairability of teeth after fracture was correlated to the maximum loading using Pearson's coefficient tests. In FEA, Maximum von Mises stress was descending assorted as 121.1MPa for ET, 115.6MPa for BM and PCM, and 109MPa for ST, and in the mid-root area or perforation site were 20MPa for PCM, 16.17MPa for BM, 10.16MPa for ET and 8.1MPa for ST while the Maximum Displacement was descending assorted as 0.0179mm for ET, 0.0169mm for BM and PCM and 0.0151mm for ST. In the fracture resistance test, Group A showed higher fracture resistance than other groups significantly. There was a non-significant difference between Groups B, C, and D. There was also an insignificant correlation between the maximum loading and the repairability of the tooth after fracture. FEA and fracture resistance test showed that the 2 repair materials are acceptable and recommended in iatrogenic mid-root perforation.

Coexistence of horizontal bone loss and dehiscence with the bundle and conventional fiber post: a finite element analysis

Horizontal bone loss (HBL) and dehiscence are common supportive tissue defects. This study evaluated the stress distribution in the presence of HBL or dehiscence and two types of fiber posts. Twelve premolars that were endodontically treated (Model-E), restored with conventional (Model-C), and bundle (Model-B) post were modeled. Bone defects were created as control (Model-1), with 4 mm (Model-4) and 8 mm (Model-8) HBL, and dehiscence involving two-thirds of the root (Model-D). HBL was included in all aspects of the models, while dehiscence was confined to the buccal aspect. The models were subjected to a 200 N force, and von Mises stress was analyzed. Model-B1 showed higher stress than Model-C1 but was more homogeneous. In Model-D, the stress was limited to the area without bone and only occurred at the buccal aspect. The highest stress was observed in Model-B8. The presence of a post caused a 2–5.8 times increase in stress. When the crown–root ratio was 1:0.8, stress was in the coronal two-thirds of the root, while at a ratio of 1:0.3, stress was distributed throughout the entire root. Bundle post with 8 mm HBL increased the stress 5.8 times. HBL resulted in stress extending beyond the marginal bone, while dehiscence did not.

Finite element analysis of two-level discontinuous cervical hybrid revision surgery strategy to reduce biomechanical responses of adjacent segments.

Hybrid surgery (HS) combined cervical disc arthroplasty (CDA) with anterior cervical discectomy and fusion (ACDF) is emerging, but its biomechanical effects as a revision surgery (RS) on adjacent segments were unclear. This finite element (FE) study aimed to investigate the biomechanical characteristics of HS to treat two-level discontinuous ASD in ACDF RS. A C2-T1 intact FE model was established and modified to a primary C5/6 ACDF model and five RS models. These RS models' segments C4/5 and C6/7 were revised using cage plus plate (C), zero-profile devices (P), and Bryan disc (D), respectively, generating C-C-C, P-C-P, D-C-P, P-C-D, and D-C-D models. In the intact and C5/6 ACDF models, a 1.0 Nm moment was used to produce the range of motion (ROM). A displacement load was applied to all RS models, to achieve a total ROM match that of the primary C5/6 ACDF model. In the P-C-P model, biomechanical responses including ROM, Intradiscal pressure (IDP), Facet joint force (FJF), and Maximum von Mises stresses of discs at segments C3/4 and C7/T1 were slightly lower than the C-C-C model. The biomechanical response parameters at segments C3/4 and C7/T1 of P-C-D, D-C-P, and D-C-D were smaller than those in C-C-C and P-C-P models. D-C-D had the most significant effect on reducing all biomechanical responses among all RS models in segments C3/4 and C7/T1. Moreover, the disc stress cloud maps showed that the maximum von Mises stress of the C3/4 disc was higher than that of C7/T1. D-C-D, P-C-D, and D-C-P are good RS choices for reducing the biomechanical responses, and D-C-D was the best choice. P-C-P can be the best recommendation when it does not meet the CDA indications. This study provided a biomechanical reference for hybrid surgical decision-making in the ACDF RS for preventing ASD recurrence.

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.

Zirconia endocrown with intracanal extension and zirconia posts on maxillary molars: in silicio study.

The study aims to evaluate the stress distribution on tooth and restoration of zirconia endocrowns with pulp chamber or intracanal extension and zirconia post performed maxillary first molar using finite element analysis. Three three-dimensional endodontically treated maxillary molars were modeled. Cortical bone and cementum were modeled 2 mm and 200 μm in thickness. Periodontal ligament at 250 μm thickness was constructed. Zirconia endocrown with pulp chamber extension of 2 mm (Model E+PCE), zirconia endocrown with intracanal extension of 4 mm (Model E+ICE), and zirconia post of 4 mm and crown (ZP) were modeled using software. All restoration models were placed on the maxillary molars. Models were subjected to 400 N loading from the three occlusal contact points. Von Mises stress was recorded. Expectingly, points where the stress was applied showed high stress compared to other regions of the models. The stress did not occur at the trifurcation in any of the models. For the stresses occurring in the restoration material, there were 14.67 MPa, 57.79 MPa, and 155.56 MPa, in Models E+PCE, E+ICE, and ZP, respectively. At the remaining dentin, these values were 47.04 MPa, 32.85 MPa, and 33.42 MPa in Models E+PCE, E+ICE, and ZP, respectively. Within the limitation of the study, zirconia endocrowns with intracanal extension exhibit more favorable stress distribution in both restoration material and dentin compared to zirconia posts and pulpal extension endocrowns. These findings suggest that endocrown with intracanal extension may be a better restorative option for reducing stress.

Finite element analysis of 2.5D packaging processes based on multi-physics field coupling for predicting the reliability of IC components

The 2.5D packaging technology is a high–performance method for electronic packaging. This study addresses the reliability issues of 2.5D packaging during the manufacturing process. A multi–physics field coupling Finite Element Method (FEM) has been developed, combined with sub–modeling techniques, to investigate the curing of underfill adhesive, the curing of Epoxy Molding Compound (EMC), and the reflow soldering between the interposer and substrate in a 2.5D packaging entity during various manufacturing procedures. The focus is on the thermo–mechanical–chemical behavior of viscoelastic components within the packaging structure, as well as the viscoplastic characteristics of the micro solder balls and microbumps. A systematic analysis is conducted on the warpage deformation and stress distribution of the 2.5D packaging at crucial time points. The results demonstrate that after curing, the overall warpage of the packaging exhibits a ‘concave’ warpage profile. Additionally, as the thickness of the EMC above the chip increases, the warpage value of the packaging also increases. The warpage value defined by linear elasticity is larger than that defined by viscoelasticity. The maximum Von Mises stress value in the key areas of the submodel is greater than the maximum Von Mises stress value in the corresponding key areas of the global model. After reflow soldering, the stress concentration in the micro solder balls occurs at the edge of the micro solder ball array. The maximum stress values for each component of the packaging are observed in the interface areas between the components. Packaging components that undergo the curing process have notably higher warpage and Von Mises stress values than those that do not undergo the curing process. The simulation method established in this study can accurately predict the warpage deformation and stress distribution state of 2.5D packaging, providing significant engineering application value for process optimization and reliability enhancement of 2.5D packaging in the production process.

MPFEM investigation on densification and mechanical structures during ferrous powder compaction

Metal powder compaction is a crucial process in powder metallurgy, significantly affecting the final properties of compacts. However, the quantitative characteristics of multi-scale mechanical structures and the microscopic densification behavior, taking into account the influence of friction conditions, remain unclear. This study utilises a two-dimensional multi-particle finite element method to analyse the ferrous powder compaction. The evolution of powder densification, powder deformation and multi-scale mechanical behaviour under different friction coefficient conditions are analyzed quantitatively and qualitatively. Results reveal that powder densification occurs in distinct stages, with lower friction coefficients promoting greater powder densification, as observed from relative density and coordination number. Additionally, as the axial strain increases, plastic strain gradually rises whilst roundness decreases. Higher friction coefficients are associated with higher equivalent plastic strain but lower powder roundness. The Von Mises stress exhibits different stages of increase with the increment of axial strain. Powders with lower friction coefficients exhibit lower levels of Von Mises stress. As axial strain increases, the number, length, strength and direction coefficient of force chains undergo different evolution processes. Force chains exhibit longer length, fewer numbers, lower strength and lower direction coefficients at lower friction coefficients.

Appropriate sagittal positioning of femoral components in total knee arthroplasty to prevent fracture and loosening.

This study aimed to investigate the optimal sagittal positioning of the uncemented femoral component in total knee arthroplasty to minimize the risk of aseptic loosening and periprosthetic fracture. Ten different sagittal placements of the femoral component, ranging from -5 mm (causing anterior notch) to +4 mm (causing anterior gap), were analyzed using finite element analysis. Both gait and squat loading conditions were simulated, and Von Mises stress and interface micromotion were evaluated to assess fracture and loosening risk. During gait, varied sagittal positioning did not lead to excessive Von Mises stress or micromotion. However, under squat conditions, posterior positioning (-4 and -5 mm) resulted in stress exceeding 150 MPa at the femoral notch, indicating potential fracture risk. Conversely, +1 mm and 0 mm sagittal positions demonstrated minimal interface micromotion. Slightly anterior sagittal positioning (+1 mm) or neutral positioning (0 mm) effectively reduced stress concentration at the femoral notch and minimized interface micromotion. Thus, these positions are deemed suitable to decrease the risk of aseptic loosening and periprosthetic femoral fracture.

Nonlinear Finite Element Analysis of Bone–Implant Contact in Three Short Dental Implant Models with Varying Osseointegration Percentages

Objectives: Dental implants have become a cornerstone of restorative dentistry, providing a long-lasting method for tooth replacement. The degree of osseointegration has a significant effect on biomechanical stability at the bone–implant contact (BIC), determining the continued efficacy of these implants. However, the exact consequences of changing osseointegration levels on different implant designs, especially in bones with variable densities, are not well known. Methods: This study used 3D finite element analysis (FEA) to look at the biomechanical performance of three short dental implants: BioMet 3iT3, Straumann® Standard Plus Short-Regular Neck (SPS-RN), and Straumann® Standard Plus Short-Wide Neck (SPS-WN). This paper tested the implants at four stages of osseointegration: 25%, 50%, 75%, and 100% in both high-density (bone type III) and low-density (bone type IV) cancellous bone. It also created and examined realistic CAD models under static occlusal loading conditions to assess stress distribution and major strains at the bone–implant contact. Results: The study discovered that as osseointegration increases, von Mises stress and principal strains go down significantly for all implant types. The SPS-WN implant had the lowest strain values, especially for bone with low density. These reductions demonstrate increased mechanical stability as the bone–implant interface becomes more capable of dispersing mechanical stresses, minimizing the potential for localized deformation and bone resorption. Conclusions: The results highlight the importance of achieving optimum osseointegration to reduce mechanical stress and increase the lifespan of dental implants. The SPS-WN type implant performed better in biomechanical tests than the others, especially when bone conditions were not ideal. This makes it a great choice for clinical applications that need long-term implant success.

The Impact of Stress Distribution on The Electrical Performance of Different Silver Stretchable Conductive Ink Pattern Using FEA Simulation

Stretchable conductive ink has been widely investigated to be used in the fabrication of stretchable electrical devices. Experimentation methods to test the mechanical and electrical behaviours of the stretchable conductive ink composite are commonly applied; however, not much of the computational approach has been scrutinized to validate the results further. This paper employs the finite element analysis method to investigate the relationship between the stress and strain distribution of the stretchable conductive ink with the highest strain obtained. This research validates the past experimentation works of different patterns of stretchable conductive ink for its stretchability and electrical performance. The maximum Von Mises stress (VMS) and maximum principal strain of the stretchable conductive ink played a significant role in determining its electrical performance, rather than the localisation of high stress and strain at specific locations within the stretchable conductive ink pattern. Zigzag pattern exhibited the lowest maximum stress and strain concentration at 57.826 MPa and 4.05% while straight pattern suffered the highest respective values at 118.143 MPa and 10.39%. The lower maximum Von-Mises stress and principal strain contributed to a better stretchability which is indicated by a higher strain rate prior to electrical conductivity.

Sustainable rubber nanocomposites for hydrogen sealings: Impact of carbon nano-onions and bio-based plasticizer

Additives play a crucial role in modifying and enhancing the properties of rubbers, improving mechanical strength, thermal stability, and chemical resistance to make them more suitable for various applications. The rubber industry faces challenges related to high resource consumption and toxic emissions, which are further impacted by the use of performance-enhancing additives. In hydrogen storage systems, tailored additives are required for rubbers to withstand elevated temperatures and high pressures, preventing hydrogen-induced swelling, a major cause of sealing failure. Herein, a novel form of carbonaceous material, carbon nano-onions (CNOs), and the bio-based plasticizer additive epoxidized soybean oil (ESO) are utilized in conventional silica-filled nitrile butadiene rubber (NBR) nanocomposites to develop low-carbon manufacturing high pressure hydrogen resistant O-rings for sealing applications. The results reveal that the incorporation of CNOs increases the crosslinking density (vc), assisted by ESO, in silica-filled NBR nanocomposites. While the conventional adipate-based plasticizer and ESO were found to be susceptible to high pressure hydrogen exposures, ESO demonstrated sustained compressive sealing properties with increase in von-Mises stress and in elevated thermo-oxidative conditions over time. The results of the life cycle assessment (LCA) recommend ESO for low-carbon manufacturing in rubber processing over conventional plasticizer.

Analysis of Wind Turbine Towers subjected to Blast Loading

The research work in this paper mainly focuses on the dynamic simulation of a High strength steel wind turbine tower subjected to blast loading in increasing order, conducted by using ABAQUS. The analysis of the wind turbine tower evaluates the response and performance of the structure when subjected to blast load levels in the form of TNT charges ranging from 500 kgs to 2000 kgs applied at the base and at the top of the tower respectively. The study focuses mainly on the key parameters such as Von Mises stress, displacement, and reaction forces in which the results indicate that the High strength steel wind turbine tower passes the Von Mises stress limit up to a blast load of 1500 kgs at the base but fails under higher loads of 1750 kgs and 2000 kgs respectively where stresses of the wind turbine tower exceeds the tensile strength of the material. Moreover, at the top of the tower, the structure fails at a low charge of 500 kgs demonstrating its vulnerability to the blast load. Displacement of the wind turbine tower surpasses its recommended limit for TNT charges beyond 1500 kgs at the base with a maximum displacement of 129.49 mm at 2000 kgs. The maximum reaction force recorded was 2890 KN at a TNT charge of 1750 kgs. The study concludes by revealing the findings of the limitations of High-strength steel wind turbine towers under extreme blast conditions and throws spotlight on the need for structural reinforcement or alternative designs and hybrid towers for the wind turbine for improved performance and use in high-risk environmental zones.

Molecular dynamics investigation of nano-polishing on silicon carbide substrate with rough topography using a rotating diamond abrasive

To achieve low-damage polishing on silicon carbide substrates utilizing a rotating diamond abrasive, the molecular dynamics model for nano-polishing is established. The nano-polishing simulation of silicon carbide substrates with both smooth and rough topographies is conducted using the diamond abrasive at two different velocity ratios. The constructed MD models are compared with existing models to assess the influence of abrasive rotation and substrate topography. The results provide valuable insights into the nano-polishing. Firstly, improving substrate smoothness and increasing abrasive rotation can effectively reduce von Mises stress, force, temperature, and amorphous layer thickness. Secondly, the atomic motion within silicon carbide substrates is affected by abrasive rotation and substrate topography, thus altering the removal mechanism. Finally, the differences in friction coefficient between the constructed MD models and existing models arise from atomic adhesion and plie-up phenomena.

Stress Distribution in Proclined Anterior Teeth of Pediatric Patients With and Without Mouthguard Use: A 3D Finite Element Analysis.

Traumatic dental injuries related to sports are a significant concern, as they can have severe physical and psychological impacts on children. Using mouthguards is essential, particularly in sports like skating, where high-impact forces are common. The study aimed to evaluate how stress is distributed on the teeth and surrounding bone in children with proclined anterior teeth when a force of 614.12 N was applied to two different regions of the jaws. The evaluation was conducted using finite element analysis (FEA), both with and without the use of a mouthguard. A 3-dimensional finite element analysis (FEA) model was constructed using a cone beam computed tomography (CBCT) scan of a 12-year-old male patient. An average standardized force of 614.12 N was calculated, based on the average weight of children aged 11 to 13 years and the average speed of 13.4 m/s with which the children skate. The force was applied in two different directions and areas of the jaws: a lateral blow, perpendicular to the crown and root with the maxillary and mandibular teeth in occlusion (between the first molar and second premolar), and a blow obliquely at the pogonion point on the chin. Static simulations were then performed for four realistic scenarios-two with mouthguards and two without mouthguards. The Von Mises stresses were evaluated under all conditions. When the applied force was directed laterally, the stress values observed were 126.76 MPa with a mouthguard and 140 MPa without a mouthguard. When the force was applied to the chin region, the stress values were 37.997 MPa with a mouthguard and 40.67 MPa without a mouthguard. The use of a mouthguard in children is beneficial for protecting teeth and surrounding structures, especially in cases of proclined anterior teeth, as it helps dampen the generated stresses.

Biomechanical significance of intervertebral discs on growthplate stresses in scoliotic trunks following unilateral muscle weakening: A hybrid approach of finite element and musculoskeletal modeling.

This study aimed to ascertain the relevance of intervertebral discs (IVD) in the stress distribution on growthplates (GPs) of a trunk model with adolescent idiopathic scoliosis (AIS) following a unilateral weakening of muscles. A thoracolumbar spine finite element (FE) model of a young female healthy and an AIS spine comprising GPs linked to the T12 through sacrum vertebrae. Two scenarios of including (FEI) and excluding (FEE) IVDs were considered. Then, using optimization-driven musculoskeletal models of the AIS and healthy trunks, the FE models were examined under subject-specific muscle forces and gravity loads. Results of this study demonstrate that when IVDs included in the FE model, an increase, ranging from 0.2 to 1.7 MPa, with the highest value occurring at the apex of the AIS model, in the von Mises stresses in the GPs. The ratio of 1.5 was found for the maximum von-Mises stress value on the most tilted GP in the FEI over the FEE model. Unilateral paralysis of muscles caused a reduction of 50% and 63% in the von Mises stress ratio of the concave-over-convex side of the most tilted GP in the FEI and FEE models of the AIS spine with healthy muscles, respectively. The intradiscal pressures, found for FEE and FEI models, assented to recent in-vivo investigations. Nonetheless, employing IVDs in the simulations provides an indispensable tool to anticipate the effects of neuromuscular disorders on GP stresses in an AIS spine and predict deformity progression during growth.