scholarly journals Design and Shape Optimization of a Biodegradable Polymeric Stent for Curved Arteries Using FEM

2021 ◽  
Vol 7 ◽  
Author(s):  
Yasaman Baradaran ◽  
Mostafa Baghani ◽  
Morteza Kazempour ◽  
Seyed Kianoosh Hosseini ◽  
Morad Karimpour ◽  
...  
Keyword(s):  
Optimization Procedure ◽  
Optimization Method ◽  
Mechanical Tests ◽  
Middle Part ◽  
Pareto Set ◽  
The Other ◽  
Von Mises Stress ◽  
Middle Point ◽  
Radial Strength ◽  
Von Mises

Stent treatment has revealed safe and efficient outcomes for straight arteries, while it is still challenging for curved coronary arteries. On the one hand, a stent should be flexible enough to take the artery’s curvature with the least stress to the artery wall. On the other hand, it has to be strong enough to prevent any artery diameter reduction after the implant. In this work, the genetic algorithm multi-objective optimization method is exploited to provide a Pareto set and to design a curvature stent. The design has been performed based on the appropriate flexibility and radial strength design, depending on the characteristics of a particular case study. In the optimization procedure, flexibility and radial strength have been evaluated based on ASTM standard mechanical tests. These tests have been parametrically simulated using the finite element method. The strut curvature is formed by the spline curvature, whose middle point coordinates are two of the optimization variables. The other optimization variable is the thickness of the stent. Based on the Pareto set achieved from the optimization, five different stent designs have been proposed. In these designs, the middle part of the stent is stiffer (in the plaque aggregated) and benefits more radial strength rather than flexibility. At the stent’s extremes, where more deformation takes place, flexibility is weighted more than radial strength. These five design sets differ in their objective weight ratios. At the end of this research, their implementation in a curved vessel is simulated in ABAQUS/CAE, and von Mises stress distribution, maximum von Mises stress, and stent recoil after imposing the stent have been analyzed. The obtained Pareto front can also be a useful guide for physicians to design and manufacture customized stents for each patient.

Design improvement and fatigue analysis for a bicycle handlebar stem system using uniform design method and genetic algorithm

2020 ◽  
Vol 234 (11) ◽  
pp. 2266-2278
Author(s):  
Cho-Pei Jiang ◽  
Ching-Wei Wu ◽  
Yung-Chang Cheng
Keyword(s):  
Genetic Algorithm ◽  
Objective Function ◽  
Safety Factor ◽  
Uniform Design ◽  
Optimization Procedure ◽  
Bending Test ◽  
Von Mises Stress ◽  
Kriging Interpolation ◽  
Optimized Design ◽  
Von Mises

An integrating optimization procedure is presented to improve the von Mises stress and fatigue safety factor for a handlebar stem system in a bicycle system. The optimization procedure involves uniform design of experiment, Kriging interpolation, genetic algorithm, and nonlinear programming method. Using ANSYS/Workbench software and the ISO 4210 bicycle handlebar stem testing standard, the von Mises stress for the lateral bending test simulation and the fatigue safety factor for the fatigue test simulation is calculated. The von Mises stress and fatigue safety factor are combined into a single and integrated objective function, and Kriging interpolation is then used to create the surrogate model of the integrated objective function. When the integrating optimization procedure is used, the integrated objective function demonstrates that the von Mises stress for the optimized handlebar stem is reduced to 225 MPa and the fatigue safety factor increases to 1.796. This shows that the optimized design increases the strength of the handlebar stem. The proposed technique yields a handlebar stem with an optimized shape.

scholarly journals Análisis experimental y teórico del ensayo de adherencia capa – sustrato en un acero DIN UC1 tratado termoquímicamente por borurización

2020 ◽  
pp. 7-14
Author(s):  
J. Merced MARTÍNEZ-VÁZQUEZ ◽  
Arnulfo PÉREZ-PÉREZ ◽  
Gabriel RODRÍGUEZ-ORTIZ ◽  
Esperanza BAÑOS-LÓPEZ
Keyword(s):  
Surface Morphology ◽  
Layer Thickness ◽  
Industrial Application ◽  
Thermochemical Treatment ◽  
Boride Layer ◽  
The Other ◽  
Von Mises Stress ◽  
Adherence Test ◽  
The Times ◽  
Von Mises

In this work, the effect of the boronizing thermochemical treatment on the adherence and surface morphology of the boride layer formed in DIN UC1 steel was evaluated. The process was carried out by packing at the temperature of 1273 K, at the times of 4800, 6000, 7200 and 14400 seconds. The HRC adherence test based on the VDI 1398 standard, was simulated in COMSOL 5.0®; analysing the effect of the thickness of the boride layer and the roughness on the Von Mises stress, in addition to the stress on the indentation footprint; in which it was observed that by increasing the thickness of the layer from 22.2 to 37.8 µm the stresses increased, and therefore the adhesion of the layer on the substrate improved, which causes only the formation of microcracks. On the other hand, in the greater layer thickness (60.04 µm) the layer delaminates. Therefore, for an industrial application of DIN UC1 steel treated thermochemically by borurization, layer thicknesses up to 37.8 µm are recommended.

Stress Distribution Around Two Dental Implant Materials with New Designs: Comparative Finite Element Analysis Study

2021 ◽  
Vol 4 (1) ◽  
pp. 19
Author(s):  
Faaiz Alhamdani ◽  
Khawla H. Rasheed ◽  
Amjed Mahdi
Keyword(s):  
Stress Distribution ◽  
Dental Implant ◽  
Cancellous Bone ◽  
Stress Level ◽  
The Other ◽  
Von Mises Stress ◽  
Uniform Stress ◽  
Element Analysis ◽  
Other Hand ◽  
Von Mises

Background: The introduction of modified thread designs is one of the research areas of interest in the dental implantology field. Two suggested Buttress and Reverse Buttress thread designs in TiG5 and TiG4 models are tested against a standard TiG5 Fin Thread design (IBS®). Purpose: The study aims to compare stress distribution around the suggested designs and Fin Thread design. Methods: Three dental implant models: Fin Thread design, and newly suggested Buttress and Reverse Buttress designs of both TiG5 and TiG4 models were tested using FEA for stress distribution using static (70N, 0°) and (400N, 30°) occlusal loads. Results: The main difference between the suggested Buttress design and Fin Thread design lies in the overload (400N, 30°) condition. Maximum Von Mises stress is less in Buttress design than Fin Thread design. On the other hand the level of Von Mises stress over the buccolingual slop of the cancellous bone in Fin Thread design liess within the lowest stress level. The suggested Reverse Buttress design, on the other hand showed almost uniform stress distribution in both TiG4 and TiG4 models with maximum Von Mises stress higher than the elastic modulus of cancellous bone in overload (400N, 30°) condition. Conclusion: The suggested TiG4 Buttress design might have a minor advantage of stress level in cases of stress overload. In contrast, Fin Thread design shows minimal stress over the buccolingual slop of the cancellous bone. The suggested Reverse Buttress design might be more suitable for the D1 bone quality region with the advantage of almost uniform stress distribution

Optimization of a Bend-Twist-and-Sweep Compliant Mechanism

2014 ◽  
Author(s):  
Joseph Calogero ◽  
Mary Frecker ◽  
Aimy Wissa ◽  
James E. Hubbard
Keyword(s):  
Compliant Mechanism ◽  
Twist Angle ◽  
High Stress ◽  
Peak Stress ◽  
The Other ◽  
Optimal Designs ◽  
Von Mises Stress ◽  
Loading Conditions ◽  
Objective Functions ◽  
Von Mises

The overall goal of this research is to develop design optimization methodologies for compliant mechanisms that will provide passive shape change. Our previous work has focused on designing two separate contact-aided compliant elements (CCE): one for bend-and-sweep deflections, called the bend-and-sweep compliant element (BSCE), and another for twist deflection, called the twist compliant element (TCE). In the current paper, all three degrees of freedom, namely bending, twist, and sweep, are achieved simultaneously using a single passive contact-aided compliant mechanism. A new objective function for a contact-aided compliant mechanism is introduced and the results of the optimization procedure are presented. A bend-twist-and-sweep compliant element (BTSCE) can be inserted into the leading edge spar of an ornithopter, which is an avian-scale flapping wing un-manned air vehicle. The multiple objective functions of the optimization problem presented in this paper are: for upstroke, maximize tip bending and sweep deflections, maximize twist angle, and minimize the mass and peak von Mises stress in the BTSCE, and for downstroke, minimize tip bending and sweep deflections, minimize twist angle, and minimize the mass and peak von Mises stress in the BTSCE. This allows a designer to select a CCE from a set of optimal designs to accomplish all three displacement goals. The BTSCE was modeled using a commercial finite element program and optimized using NSGA-II, a genetic algorithm. The results for a single angled compliant joint (ACJ) for quasi-static upstroke loading conditions are presented. Two optimal designs are discussed and compared, one with a moderate peak stress and moderate deflections, the other with a high peak stress and large deflections. The optimization results are then compared to the previous results for the two independent CCEs. A design study showed that the angle of the ACJ needs to be obtuse to achieve a positive twist angle during upstroke, and an acute contact angle reduces peak stress. The deflection objective functions were relatively insensitive to eccentricity for upstroke and downstroke compared to the other parameters, and a high stress penalty was paid for any gains in deflection. The downstroke objective functions were relatively insensitive to all parameters compared to the upstroke objective functions, and were much smaller in magnitude. The optimization showed that under simplified upstroke loading conditions, the BTSCE with a single ACJ allowed bending deflection near 30% of the length of the BTSCE, twist angle near 0.14 radians, and sweep deflection near 5% of the length of the BTSCE.

Comparison of Torque Transmitting Shaft Connectivity Using a Trilobe Polygon Connection and an Involute Spline

2000 ◽  
Vol 122 (1) ◽  
pp. 130-135 ◽  
Author(s):  
Zella L. Kahn-Jetter ◽  
Eugene Hundertmark ◽  
Suzanne Wright
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
The Other ◽  
Von Mises Stress ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Principal Compressive Stress ◽  
Torque Transmission ◽  
Von Mises ◽  
Involute Spline

The results of a finite element analysis of a trilobe polygon shaft connection used as an alternative for a spline for torque transmission is presented. These results are compared to the results of a finite element analysis previously performed on an involute spline. It is shown that the tensile stress in the polygon shaft is significantly smaller than in the involute spline and is smaller than all the other stresses in both the shaft and the hub in the polygon connection. Furthermore, the magnitudes and distributions of the maximum principal compressive stress, the shear stress, and the Von Mises stress are nearly the same on the shaft and the hub. It appears that polygonal connections can be more advantageous than splined connections because of lower stresses and the lack of stress concentrations typical of splines. [S1050-0472(00)00601-2]

Effect of Dielectric Materials on Stress-Induced Damage Modes in Damascene Cu Lines

2003 ◽  
Vol 795 ◽  
Author(s):  
Jong-Min Paik ◽  
Hyun Park ◽  
Ki-Chul Park ◽  
Young-Chang Joo
Keyword(s):  
Mechanical Properties ◽  
Hydrostatic Stress ◽  
Three Dimensional ◽  
Dielectric Materials ◽  
The Other ◽  
Von Mises Stress ◽  
X Ray Diffraction ◽  
X Ray ◽  
Von Mises ◽  
Low K

ABSTRACTVarious low-k materials are being pursued as dielectric materials for future interconnects. However, poor thermo-mechanical properties of low-k materials cause tremendous reliability concerns, thus the proper materials for integration with Cu are not suggested yet. In this study, the line width and spacing dependence of damascene Cu lines embedded by TEOS and low-k materials (CORAL) was analyzed using x-ray diffraction. Generally, the hydrostatic stress of Cu/TEOS was greater than that of Cu/CORAL, while the opposite for von-Mises stress. Using a three-dimensional finite analysis (FEA), the effect of low-k materials on the stress and its distribution in via-line structures of dual damascene Cu interconnects was studied. In the case of Cu/TEOS, the hydrostatic stress was concentrated at the via and on the top of the lines, where it was suspected that the void would nucleate. On the other hand, in the via-line structures integrated with organic low-k materials, large von-Mises stress was maintained in the via. Therefore, the deformation of via, rather than voiding, may be the main failure mode in the interconnects with low-k materials.

The multi-objective optimization of the damaged aircraft trailer based on a dynamic model

2017 ◽  
Vol 232 (11) ◽  
pp. 1481-1493
Author(s):  
Zhenyu Hong ◽  
Xiaoli Yu ◽  
Zhenpeng He ◽  
Guichang Zhang
Keyword(s):  
Lightweight Design ◽  
Optimization Method ◽  
Von Mises Stress ◽  
Load Force ◽  
Multi Objective Optimization ◽  
Optimal Method ◽  
Multi Objective ◽  
Suspension Model ◽  
Von Mises ◽  
Response Method

A damaged aircraft trailer is an essential piece of airport emergency rescue equipment which is made up of frames and multiple suspensions. As a load–force transferring mechanism, the suspension bears heavy loads which can cause fatigue damage. Therefore, reducing the maximum stress of the suspension is necessary to improve the vehicle performance. Besides, lightweight design should be considered to reduce energy consumption. Thus, lighter suspension which can bear more pressure is the optimization objective of this research. A multi-objective optimization method was carried out to analyze the suspension arm of a damaged aircraft trailer. Firstly, to investigate the dynamic characteristics and the reliability of the damaged aircraft trailer, a detailed three combined damaged aircraft trailers model was built. Based on the flexible-rigid coupled method, dynamic simulation of the damaged aircraft trailer was conducted in MSC.ADAMS. Then a suspension model was established, and the stress under different loads was measured to verify the accuracy of the finite element suspension arm model by experiments. Based on the design of experiment method, the effect of suspension arm parameters were obtained to build the approximate models. Besides, the influences of some effect parameters on optimal objectives were analyzed based on the surface response method. During the optimization process, a non-dominated sorting genetic algorithm II was adopted to optimize the mass and stress of the suspension arm. The results show that the mass of the suspension arm is reduced from 146.81 kg to 126.69 kg, which is a reduction of 14%. The maximum von Mises stress is changed from 325 MPa to 297 MPa, which is a decrease of 8.6%. This optimal method can be extended to the overall vehicle, which has an important significance in the whole damaged aircraft trailer characteristics improvement design.

Optimization of Turbine Disk Profiles by Metamorphic Development

2002 ◽  
Vol 124 (2) ◽  
pp. 192-200 ◽  
Author(s):  
Jing-Sheng Liu ◽  
Geoffrey T. Parks ◽  
P. John Clarkson
Keyword(s):  
Hoop Stress ◽  
Thermal Loading ◽  
Axial Stress ◽  
Optimization Method ◽  
Geometric Constraints ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Metamorphic Development ◽  
Turbine Disks ◽  
Von Mises

A novel topology/shape optimization method, Metamorphic Development, is applied to an axisymmetric thermo-elasticity design problem. Based on solid modeling and finite element analysis, optimal profiles of minimum mass turbine disks are sought by growing and degenerating simple initial structures subject to both response and geometric constraints. Radial stress, axial stress, hoop stress and von Mises stress are analyzed throughout the optimization and a constraint is imposed on von Mises stress everywhere in the disk. The optimal structures are developed metamorphically in specified infinite design domains using both quadrilateral and triangular axisymmetric finite elements. Comparisons are made of the results obtained for different optimization scenarios: (a) with and without thermal loading; (b) with and without centrifugal body forces; (c) with and without a fit pressure on the inner surface of the hub; and (d) operating at different rotational speeds.

Effects of Strain Rate on the Stress Propagations in Bonded Shrink Fitted Joints Under Impact Push-Off Loadings

2011 ◽  
Author(s):  
Lijuan Liao ◽  
Toshiyuki Sawa ◽  
Takashi Kobayashi ◽  
Yasuhiro Goda
Keyword(s):  
Strain Rate ◽  
Adhesive Layer ◽  
Rate Sensitivity ◽  
Middle Part ◽  
Experimental Results ◽  
Von Mises Stress ◽  
Deformation Behaviors ◽  
Von Mises ◽  
Structural Adhesive ◽  
Good Agreement

The effects of the strain rate sensitivity on the stress propagations of bonded shrink fitted joint, in which a ring is fitted using an adhesive layer at the middle part of a shaft, subjected to impact push-off loadings are examined. The plastic flow deformation behaviors of structural adhesive under some strain rates are examined experimentally. In addition, the stress wave propagations in the joint are analyzed using finite element method (FEM). The experimental results show that the yield stress of the adhesive increases as the strain rate increases nonlinearly. It is observed that the maximum equivalent von Mises stress occurs in the adhesive layer at the upper interfaces, which causes the rupture of the joint based on the numerical calculations. Furthermore, the strain responses obtained from numerical and experimental methods are compared with each other. A fairly good agreement is obtained between FEM calculations and experiments. In addition, the joint strength is predicted by impact energy using experimental results, which is about 20.85 J in the present study.

Topology Optimization of Compliant Mechanisms Using Hybrid Discretization Model

2010 ◽  
Author(s):  
Hong Zhou
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Diagonal Element ◽  
Initial Guess ◽  
Von Mises Stress ◽  
Stress Constraint ◽  
Hybrid Discretization

Hybrid discretization model for topology optimization of compliant mechanisms is introduced in this paper. The design domain is discretized into quadrilateral design cells. Each design cell is further subdivided into triangular analysis cells. This hybrid discretization model allows any two contiguous design cells to be connected by four triangular analysis cells no matter they are in the horizontal, vertical or diagonal direction. Topological anomalies such as checkerboard patterns, diagonal element chains and de facto hinges are completely eliminated. In the proposed topology optimization method, design variables are all binary and every analysis cell is either solid or void to prevent grey cell problem that is usually caused by intermediate material states. Von Mises stress constraint is directly imposed on each analysis cell to make the synthesized compliant mechanism safe. Genetic algorithm is used to search the optimum and avoid the need to choose the initial guess solution and conduct sensitivity analysis. The obtained topology solutions require no postprocessing or interpretation, and have no point flexure, unsmooth boundary and zigzag member. The introduced hybrid discretization model and the proposed topology optimization procedure are illustrated by two classical synthesis examples in compliant mechanisms.

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