Finite Element Stress Analysis Research Articles

Biomechanical evaluation of stress distributions at the implant-abutment complex and peri-implant bone around mandibular dental implants with different neck geometries and inclinations.

This study aimed to investigate the effects of the different dental implant neck designs, diameters, and inclinations, on the stress distributions at the mandibular crestal bone and implant-abutment complex, using three-dimensional (3D) finite element stress analysis (FEA) method. Finite element models of three-unit fixed partial dentures supported with two same length implants (10 mm), placed on the second premolar and second molar regions, were designed. Eight different models were designed according to the implants' neck designs (platform switching/traditional), diameters (4.1 mm/4.8 mm) and the tilting angles of the posterior implants (0°/15°). The anterior implants' widths were 4.1 mm and the neck design of the anterior implants matched the posterior implants. Two types of 100-N loads in vertical and 30° oblique directions were applied separately onto each central fossae and functional cusps of the fixed partial dentures crowns. Algor Fempro Software was used for the simulation and evaluation of the stress levels at the implant-abutment complex and the crestal bone. Stress levels measured at the crestal bone were found to be lower for the platform switching models. However, the platform switching design generated higher stress magnitudes within the implant-abutment complex. Inclined placement of posterior implants increased the amount of stress at the crestal bone around both implants. Biomechanically, selection of the largest diameter possible when using tilted platform switched implants may be recommended at the posterior mandible.

Influence of Occlusal Bite Forces on Teeth with Altered Periodontal Support: A Three-Dimensional Finite Element Stress Analysis.

Background:Masticatory forces generate various degrees of stress and strain in the periodontium of teeth which determine the clinical functions and load-bearing capacity of the teeth. There are few in vitro studies that have analyzed stress generated due to combined forces acting on the teeth. Thus, the objective of the present study was to do a comparative analysis of the influence of various stresses on the periodontal ligament and alveolar bone of maxillary central incisor with normal bone height and reduced bone height under simulated standard masticatory using finite element stress analysis.Methodology:A 3D model of the tooth was obtained with the help of ANSYS software. These models were subjected to various oblique forces, i.e., 100N and 235.9N, applied at 45° angle on the lingual surface of the maxillary central incisor and stress values were recorded in three dimensions. The results from FE analysis were analyzed using 3D Von Mises Criteria.Results:It was observed that in healthy periodontium; it was observed that among the periodontal structure studied, the maximum stress levels were exerted on root followed by cortical bone, cancellous bone, and PDL, irrespective of the force, as compared to the diseased periodontium, in which the bone height was reduced, the maximum stresses were on root followed by cortical bone, PDL, and cancellous bone.Conclusion:The main factor governing the success of any periodontal procedure depends on the height of the remaining bone and the amount of force exerted on to the tooth and the stress generated within the tooth. The finite element method could be of substantial importance in this respect as it can assess the stresses of various occlusal forces on the periodontal ligament, root, cortical bone, and cancellous bone of teeth in a periodontally healthy and diseased state.

Fatigue behavior of endodontically treated maxillary premolars with MOD defects under different minimally invasive restorations.

To analyze the stress distribution and subsequent fracture resistance of human maxillary premolars with mesial-occlusal-distal (MOD) defects restored with different minimally invasive restorations. Seventy non-carious human maxillary premolars were selected and divided into seven groups (n = 10). Ten teeth without further preparation served as control. The remaining teeth were endodontically treated and received three restorative patterns: inlays without cusp coverage (I), onlays with palatal coverage (O), overlays with both buccal and palatal coverage (Ov). Lithium disilicate glass ceramics (EM) and machinable composite resin (LU) were used for restoration. Specimens were tested under cycling loading with tongue direction of 45° for 1.2 × 106 cycles at a 50-N load and 2.0-Hz frequency. The survival time and two fracture mode classifications were assessed. Three-dimensional models of each group were designed. The magnitude and pattern of stresses were analyzed under the same condition of the in vitro test using finite element stress analysis. Although the overlay model pattern produced more favorable stress distribution, three restorative patterns restored with the same material had no difference in survival curves (P > 0.05). Only the survival curve of the EM-Ov group had no statistical difference with that of the control group (P > 0.05). EM groups presented mainly interface adhesive failure, while LU groups were mainly material cohesive failure. For the endodontically treated maxillary premolars with MOD defect, the lithium disilicate glass ceramic overlay pattern can reach the best restorative effect. Comparing with restorative pattern, restorative material had a greater influence on the minimally invasive restoration of posterior teeth.

Computerized Generation and Finite Element Stress Analysis of Endodontic Rotary Files

Introduction: The finite element method has been extensively used to analyze the mechanical behavior of endodontic rotary files under bending and torsional conditions. This methodology requires elevated computer-aided design skills to reproduce the geometry of the endodontic file, and also mathematical knowledge to perform the finite element analysis. In this study, an automated procedure is proposed for the computerized generation and finite element analysis of endodontic rotary files under bending and torsional conditions. Methods: An endodontic rotary file with a 25mm total length, 0.25mm at the tip, 1.20mm at 16mm from the tip, 2mm pitch and squared cross section was generated using the proposed procedure and submitted for analysis under bending and torsional conditions by clamping the last 3mm of the endodontic rotary file and applying a transverse load of 0.1N and a torsional moment of 0.3N·cm. Results: The results of the finite element analyses showed a maximum von Mises stress of 398MPa resulting from the bending analysis and a maximum von Mises stress of 843MPa resulting from the torsional analysis, both of which are next to the encastre point. Conclusions: The automated procedure allows an accurate description of the geometry of the endodontic file to be obtained based on its design parameters as well as a finite element model of the endodontic file from the previously generated geometry.

Thermal-striping analysis methodology for sodium-cooled reactor design

Computational fluid dynamics simulations have been performed to study the applicability of engineering CFD methods for thermals striping analysis. Thermal striping is the fluctuating temperature profile in a solid caused by fluctuating fluid temperature, and the resulting thermal stresses cause high cycle fatigue and eventual material failure. This study presents the methodology for thermal striping analysis, including a transient conjugate heat transfer RANS simulation benchmarked against a sodium triple jet experiment. Multiphysics calculations are implemented to analyze the thermal stresses in the solid domain caused by the coupled heat transfer between the fluid and solid domains. Validation data from a liquid sodium triple jet experiment include time-averaged temperature measurements and power spectra of the temperature signal. The numerical results agree well with these experimental measures, demonstrating key features such as the dominant frequency of temperature fluctuations. The applicability of a low-cost wall treatment method is demonstrated, enabling key computational savings. Finally, the performance of two finite element stress analysis software packages is compared, and the validity of the lower-cost method is confirmed. These results demonstrate the applicability of engineering methods for computational thermal striping calculations, enabling thermal striping estimations in large fluid systems such as the core of a liquid metal-cooled nuclear reactor.

Finite element analysis of stress and distortion for welding reinforced structure of angular steel

A 3-D finite element model of residual stress and distortion in welded structure with square section for angle steel is developed based on thermal-elastic-plastic theory. The residual stress and deformation for welded structure under different conditions are calculated and their distribution characteristics are comparatively analyzed. Results show that, relatively larger stress is generated in and near the weld zone for the welded joint. With an increase in weld length, both equivalent stress and residual distortion increase accordingly, but the effect of weld length on welding residual stress is limited. Under the conditions of 20 mm, 50 mm and 100 mm long welds, the deformations of the three reinforced structures caused by 15000 Pa external load are 4.80mm, 4.79mm and 4.78mm respectively, indicating they have the similar bearing capacity.

Difference-based deep learning framework for stress predictions in heterogeneous media

Stress analysis of heterogeneous media, like composite materials, using Finite Element Analysis (FEA) has become commonplace in design and analysis. However, determining stress distributions in heterogeneous media using FEA can be computationally expensive in situations like optimization and multi-scaling. To address this, we utilize Deep Learning for developing a set of novel Difference-based Neural Network (DiNN) frameworks based on engineering and statistics knowledge to determine stress distribution in heterogeneous media, for the first time, with special focus on discontinuous domains that manifest high stress concentrations. The novelty of our approach is that instead of directly using several FEA model geometries and stresses as inputs for training a Neural Network, as typically done previously, we focus on highlighting the differences in stress distribution between different input samples for improving the accuracy of prediction in heterogeneous media. Our DiNN framework consists of three main modules: 1) a sample processing module that calculates the difference geometry and stress contours of each sample with respect to a reference contour extracted from the training samples, 2) an Encoder-Decoder module that predicts stress difference contours using geometry difference contours as input, and 3) a stress prediction module that combines the stress difference contours with the reference contour to construct the final prediction of stress contours. We evaluate the performance of DiNN frameworks by considering different types of geometric models that are commonly used in the analysis of composite materials, including volume fraction and spatial randomness. Results show that the DiNN structures significantly enhance the accuracy of stress prediction compared to existing structures, especially for composite models with random volume fraction when localized high stress concentrations are present.

Fracture toughness of different adhesive/dentin interfaces analyzed by finite element stress analysis

Objectives: Study aimed to assess the fracture toughness of different dentin adhesive approaches and to evaluate the stress distribution at the bond interface during fracture toughness testing by finite element analysis. Materials and Methods: Specimens for chevron-notched beam fracture toughness (CNB) were prepared with dimensions of (3.0 mm × 4.0 mm × 20 mm) according to ISO 24370:2005 standard. Chevron notch was prepared at the adhesive–dentin interface using a highly polished stainless steel spacer. Four different dentin adhesives approaches were used total-etch 3 and 2 step and self-adhesives 2 and 1 step. A total of 60 specimens were prepared for each adhesive approach (n=15). Each specimen was loaded until failure in a 4-point bend test setup and the fracture toughness was calculated according to the ISO specifications. Finite element modeling of the specimens was carried out in order to analyze stress distribution during fracture toughness testing. Data were analyzed by one-way ANOVA followed by tukey‘s post hoc test with significant level at p < 0.001 level (p= 0.0001).. Results: Solobond plus 3-step etch-and-rinse showed the highest mean fracture toughness (1.78 MPam1/2) Whereas, Futurabond M+ 1-step self-etch showed the lowest value (1.13 MPam1/2). These finding were supported by finite element analysis which showed stresses to concentrate at the adhesive–dentin interface during fracture toughness loading and crack propagation. Conclusion: The adhesive approach has a strong effect on the fracture toughness of the adhesive–dentin interface. the 3-step etch-and-rinse approach showing the highest mean fracture toughness while 1-step self-etch approach showing the lowest value.

Finite element stress analysis of three-stage gear box

The stress analysis of the three-stage gearbox is carried out by finite element analysis method using the Ansys commercial program. The triple reduction helical gearbox is made of AISI 5115 Steel (16MnCr5) and AISI 8620. Static structural and rigid dynamic analyzes are performed in this work. The three-stage helical gearbox is a three-stage gearbox transmitting 0.5 kW at 1390 rpm with a reduction ratio of 127.99:1. After setting the boundary conditions for helical gears, the analysis is performed. Rotational velocity is given to rotating gears for static structural analysis. Analyzing these types of gearboxes to be produced enables the product to be produced more consciously with optimum design parameters with its right safety coefficients. After the static analysis, dynamic analysis is also performed using the modal analysis option of Ansys software. After the mode shape analysis and natural frequency analysis are performed, the operation frequency values of the gearbox are calculated by considering the input and output rpm values in the gearbox. These calculated values are compared with the normal operating condition to see if there will be any resonance in the gear box design during normal operating conditions.

Finite element analysis of stress and distortion for welding reinforced structure of angular steel used for power tower under load

Based on thermal-elastic-plastic theory, a three-dimensional numerical model of residual stress and distortion in L-shaped welding reinforced structure of angle steel used for power transmission tower is developed. The characteristics of residual stress distribution and deformation are numerically investigated, which are compared with the stress and deformation under the action of lateral compressive load. The research results show that, a large stress is generated in and near the weld zone. With enhancing the weld bead length, both equivalent stress and residual distortion have a growth, and the equivalent stress peak reaches 329Mpa, slightly lower than the yield stress of base metal, meanwhile the longitudinal residual stress peak is 399Mpa, higher than the yield stress of base metal. Under the action of 15000Pa lateral compressive load, the stress has no obvious change in the near weld zone of reinforce structure compared with that without load, and the distortion peak reaches 11mm.

A hygrothermal stress finite element analysis of laminated beam structures through hierarchical one-dimensional modeling

A new multi-field beam model based on Carrera’s Unified Formulation (CUF) is offered in this article to efficiently solve the hygro-thermal-mechanical problem of beam structures with high-fidelity. Several beam models have been hierarchically derived in the framework of CUF with consideration of the hygro-thermal stresses. By adopting the principle of virtual displacement, the element stiffness matrix can be derived into a compact form. The temperature and humidity profile is generated from the Fourier’s heat conduction and Fick’s law, respectively. With simply supported and cantilever configurations being adopted, hygro-mechanical and hygro-thermal-mechanical analyses are carried out for different beam slenderness ratios. Results are provided in terms of three-dimensional displacement and stress distributions. The proposed one-dimensional CUF-based beam model has been validated against traditional three-dimensional FEM-based solutions, and an excellent correlation has been achieved. It is found that an accurate result can be obtained through the proposed CUF-based beam model with reduced computational costs.

Qualitative analysis of the influence of the non-linear material characteristics of flexible adhesive on the performance of lap joints

This paper discusses the issue of a lap joint in the form of a thin film attached to a rigid base with the use of a layer of flexible adhesive exhibiting a non-linear constitutive relation between shear stress and distortional strain, which is approximated by the second-order power law. Similarity theory is used to perform a qualitative analysis of the influence of magnitude of non-linearity on the performance of the system. The introduced similarity numbers are proposed to be used in formulation of simple design tools. The analysis is performed by solving the derived governing equations for characteristic cases in a numerical way combining the fourth-order Runge-Kutta algorithm and iterative shooting ruled by a steepest descent method. The results are compared with the results of the plane stress finite element analysis. It can be observed that within considered models the influence of the material non-linearity is of minor importance and in some cases it may be almost entirely surpassed by local effects resulting from boundary conditions. For relatively small load intensity it becomes negligibly small.

Research on the coupling effect of the composite slope geometrical parameters

Purpose. To analyze the coupling effect between composite slope geometrical parameters. Methods. The slope angle and excavation depth are coupled with load which is waste dump in this case. Several models were created and analyzed to capture their coupling effect and interactions using FLAC/Slope. Findings. When the slope angle and excavation depth are coupled with a load such as that of a waste dump, the factor of safety decreases. But a suitable dumping position can prove vital to enhancing stability. The primary cause of this phenomenon is that the stresses induced by the waste dump decrease as the dump is moved away from the crest of the slope and the stress induced within the zone of active wedge beneath the dump reduces on the reference slip plane. Hence, it can be said that the position of the waste dump in the formation of a composite slope plays a key role in enhancing stability. Factor of safety have the same influence pattern for all parameters induced by stress as that of influence rule. The results obtained from the finite element stress analysis are the same with those obtained for the slope stability analysis. Originality. The current research presents for the first time the coupling effect of the composite slope geometrical parameters and the results of finite element stress analysis, which are similar to those of slope stability analysis. Practical implications. The current research results can be used to effectively analyze and design the composite slopes in soft rocks specially in surface mines.

Evaluation of Zirconia-Ceramic Crowns Applied to Implants Placed in the Maxilla at Different Angles by Finite Element Stress Analysis

Evaluation of Zirconia-Ceramic Crowns Applied to Implants Placed in the Maxilla at Different Angles by Finite Element Stress Analysis

超声速导弹弹头热应力的有限元分析

超声速导弹弹头热应力的有限元分析

Finite Element Analysis of Residual Stress in TC4/TC11 Titanium Alloy Gradient Material Produced by Laser Additive Manufacturing

Finite Element Analysis of Residual Stress in TC4/TC11 Titanium Alloy Gradient Material Produced by Laser Additive Manufacturing

Finite element and experimental study of the residual stresses in 2024-T3 Al alloy treated via single toroidal roller burnishing

This article presents the outcomes of finite element (FE) simulations and X-ray stress measurements of residual stresses in high-strength 2024-T3 Al alloy introduced via the single toroidal roller burnishing (STRB) process. In terms of the deforming toroidal roller geometry, STRB is particularly suitable for deep rolling. A 3D FE model was developed using the flow stress concept, and the actual STRB kinematics was simulated to evaluate both hoop and axial residual stresses. The FE model was validated through a comparison of FE and X-ray residual stress distributions. The effects of the burnishing force, feed rate, and number of passes on the residual hoop and axial stresses were studied. It was established that increasing the feed rate leads to a decrease in the residual hoop stresses and an increase in the residual axial stresses. The greater burnishing force increases the compressive zone depth and only slightly increases the surface residual stresses. The FE and X-ray stress analyses confirm the effectiveness of STRB of 2024-T3 Al alloy to introduce significant residual compressive axial and hoop stresses.

Finite element stress analysis of Aramany class I maxillectomy defect with single- and two-piece closed bulb obturators.

To evaluate the stress on the surrounding structures of Aramany class I maxillectomy defect restored with different obturator prostheses. Definitive three-dimensional (3D) finite element (FE) model of Aramany class I defect rehabilitated with single- and two-piece closed bulb obturator prostheses was constructed based on patient computed tomography (CT) using a software. Unilateral defect restored with tripodal design single-piece closed bulb obturator was used as FE model 1- and two-piece magnet retained closed bulb obturators as FE model 2. Finite element analysis (FEA) with three different load (150N, 200N and 250N) applications was used to calculate the equivalent von Mises stress. A least stress value of 62.28MPa was observed in two-piece closed bulb design with 150N force, and highest stress value of 104.15MPa was observed in single-piece obturator with application of 250N force. Minor difference in stress distribution pattern was observed between single-piece obturator and two-piece obturator, and stress value was comparatively lesser in two-piece than single-piece obturator. The stress pattern, distribution and numerical values increased with increase in magnitude of forces. More stress was observed on the lateral slopes of obturator closer to defect than in other areas of the obturator.

Determination of the critical length of the crack-like flaws and its effect on safety

Methodologies of API 579 have been widely accepted as the de-facto standard guideline for fitness for service assessment on crack-like flaws in pressure equipment. For different purposes and needs, the evaluation is divided into three levels, from critical length estimation in level 1, use of the failure analysis diagram (FAD) in level 2, to performing finite element stress analysis in level 3, that is from simplified to accurate. It is generally considered safe as long as the crack is smaller than the critical crack, but not all of them are actually the case. Therefore, it is very important to study the physical meaning behind the critical crack and understand the conservativeness of it.In this study, numerous examples of critical cracks determined according to API 579 Level 1 were put into Level 2 analysis for comparison. Each case is mapped onto the FAD of level 2 analysis to see its position and distance from the borderline between safe and danger zones. A huge amount of examples covering the majority of possible scenarios, including the geometry, thickness, inner diameter, pressure and half-length of the flaw, depth of the crack, crack tip and crack bottom, as a whole, there are 960 cases to be analyzed.Results show that cracks on the circumferential direction of the cylindrical and spherical vessels are distributed tightly in a small area far from the borderline on the FAD diagram. In these cases, the vessel is actually not as dangerous as the critical crack implies, since most of the points lie quite far from the danger zone. As for the longitudinal cracks of a cylindrical vessel, the results are scattered around, and three data points are located outside the allowable zone. The peculiar results are partly due to a discrepancy of interpolating procedure as the influence coefficient is being computed. Through this study, it is also found that the cumbersome process of estimating the critical crack length can be greatly simplified for longitudinal cracks in a cylindrical vessel.

Abstract 16111: Clinical Application of Deep Learning for Stress Analysis of Ascending Thoracic Aortic Aneurysms

Introduction: Current guidelines for elective surgery of ascending thoracic aortic aneurysms (aTAAs) use aneurysm size as primary determinant for risk stratification of adverse events. Biomechanically, dissection may occur when wall stress exceeds wall strength. A widespread method for stress analysis is structural finite-element analysis (FEA). Patient-specific aortic geometries are easily obtainable and stress distributions can potentially predict risk of dissection. However, FEA is a time-consuming and difficult procedure. To bypass this issue, a recent study has developed the first deep learning (DL) approach for a fast and accurate estimation of aortic wall stress distributions. Hypothesis: In this study, we assessed the hypothesis that this deep learning approach can be applied to a large clinical dataset. Model performance was measured by comparing FEA and DL stress predictions in parallel. Methods: Patients with aTAA (n = 169) were studied. Patient-specific aneurysm geometries were obtained from ECG-gated computed tomography. Shapes were represented by hexahedral meshes with 9648 nodes and 6336 solid elements. FEA peak wall stresses and stress distributions were determined using LS-DYNA software with user-defined fiber-embedded material models under systolic pressure. The DL model was implemented in Julia and consisted of unsupervised and supervised learning algorithms. Training was performed on a training set of 152 shapes and testing set of 17 shapes with 10-fold cross-validation. Mean absolute error (MAE) and absolute error of peak stress values (APE) were used to compare DL model predictions with FEA values considered to be ground truth. Results: Average stress values predicted by our DL model were 175.64 ± 4.17 kPa and 95.69 ± 2.15 kPa in the circumferential and longitudinal direction, respectively. We computed a MAE of 5.06 ± 1.08 kPa and APE of 2.58 ± 1.39 kPa in the circumferential direction and MAE of 4.51 ± 0.98 kPa and APE of 2.32 ± 1.84 kPa in the longitudinal direction. Conclusions: DL model trained exclusively on clinical data was able to accurately predict stress distributions on complex aortic geometries. Fast and accurate stress predictions will facilitate real-time clinical applications for the risk assessment of aTAAs.