Topology optimization of structures subject to self-weight loading under stress constraints

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Renatha Batista dos Santos ◽  
Cinthia Gomes Lopes
Keyword(s):  
Topology Optimization ◽  
Stress Constraints ◽  
Topological Derivative ◽  
The Self ◽  
Von Mises Stress ◽  
Stress Constraint ◽  
Content Type ◽  
Derivative Method ◽  
Von Mises ◽  
Weight Loading

PurposeThe purpose of this paper is to present an approach for structural weight minimization under von Mises stress constraints and self-weight loading based on the topological derivative method. Although self-weight loading topology has been the subject of intense research, mainly compliance minimization has been addressed.Design/methodology/approachThe resulting minimization problem is solved with the help of the topological derivative method, which allows the development of efficient and robust topology optimization algorithms. Then, the derived result is used together with a level-set domain representation method to devise a topology design algorithm.FindingsNumerical examples are presented, showing the effectiveness of the proposed approach in solving a structural topology optimization problem under self-weight loading and stress constraint. When the self-weight loading is dominant, the presence of the regularizing term in the formulation is crucial for the design process.Originality/valueThe novelty of this research work lies in the use of a regularized formulation to deal with the presence of the self-weight loading combined with a penalization function to treat the von Mises stress constraint.

Design of flexure hinges based on stress-constrained topology optimization

2016 ◽  
Vol 231 (24) ◽  
pp. 4635-4645 ◽  
Author(s):  
Min Liu ◽  
Xianmin Zhang ◽  
Sergej Fatikow
Keyword(s):  
Topology Optimization ◽  
Stress Concentration ◽  
Stress Constraints ◽  
Stress Constraint ◽  
Flexure Hinges ◽  
Weighted Sum Method ◽  
Stress Measure ◽  
Von Mises ◽  
Von Mises Stresses ◽  
Sharp Corners

Stress concentration is one of the disadvantages of flexure hinges. It limits the range of motion and reduces the fatigue life of mechanisms. This article designs flexure hinges by using stress-constrained topology optimization. A weighted-sum method is used for converting the multi-objective topology optimization of flexure hinges into a single-objective problem. The objective function is presented by considering the compliance factors of flexure hinges in the desired and other directions. The stress constraint and other constraint conditions are developed. An adaptive normalization of the P-norm of the effective von Mises stresses is adopted to approximate the maximum stress, and a global stress measure is used to control the stress level of flexure hinges. Several numerical examples are performed to indicate the validity of the method. The stress levels of flexure hinges without and with stress constraints are compared. In addition, the effects of mesh refinement and output spring stiffness on the topology results are investigated. The stress constraint effectively eliminates the sharp corners and reduces the stress concentration.

scholarly journals Topological Design of Multi-Material Compliant Mechanisms with Global Stress Constraints

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1379
Author(s):  
Jinqing Zhan ◽  
Yifeng Li ◽  
Zhen Luo ◽  
Min Liu
Keyword(s):  
Compliant Mechanisms ◽  
Stress Constraints ◽  
Von Mises Stress ◽  
Stress Constraint ◽  
Output Displacement ◽  
Topological Design ◽  
Global Stress ◽  
Von Mises ◽  
Moving Asymptotes ◽  
Structural Volume

This paper presents an approach for the topological design of multi-material compliant mechanisms with global stress constraints. The element stacking method and the separable stress interpolation scheme are applied to calculate the element stiffness and element stress of multi-material structures. The output displacement of multi-material compliant mechanisms is maximized under the constraints of the maximum stress and the structural volume of each material. The modified P-norm method is applied to aggregate the local von Mises stress constraints for all the finite elements to a global stress constraint. The sensitivities are calculated by the adjoint method, and the method of moving asymptotes is utilized to update the optimization problem. Several numerical examples are presented to demonstrate the effectiveness of the proposed method. The appearance of the de facto hinges in the optimal mechanisms can be suppressed effectively by using the topology optimization model with global stress constraints, and the stress constraints for each material can be met.

A topology optimization algorithm based on topological derivative and level-set function for designing phononic crystals

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Rolando Yera ◽  
Luisina Forzani ◽  
Carlos Gustavo Méndez ◽  
Alfredo E. Huespe
Keyword(s):  
Topology Optimization ◽  
Level Set ◽  
Optimization Algorithm ◽  
Phononic Crystal ◽  
Phononic Crystals ◽  
Lagrangian Function ◽  
Topological Derivative ◽  
Content Type ◽  
Level Set Function ◽  
Set Function

PurposeThis work presents a topology optimization methodology for designing microarchitectures of phononic crystals. The objective is to get microstructures having, as a consequence of wave propagation phenomena in these media, bandgaps between two specified bands. An additional target is to enlarge the range of frequencies of these bandgaps.Design/methodology/approachThe resulting optimization problem is solved employing an augmented Lagrangian technique based on the proximal point methods. The main primal variable of the Lagrangian function is the characteristic function determining the spatial geometrical arrangement of different phases within the unit cell of the phononic crystal. This characteristic function is defined in terms of a level-set function. Descent directions of the Lagrangian function are evaluated by using the topological derivatives of the eigenvalues obtained through the dispersion relation of the phononic crystal.FindingsThe description of the optimization algorithm is emphasized, and its intrinsic properties to attain adequate phononic crystal topologies are discussed. Particular attention is addressed to validate the analytical expressions of the topological derivative. Application examples for several cases are presented, and the numerical performance of the optimization algorithm for attaining the corresponding solutions is discussed.Originality/valueThe original contribution results in the description and numerical assessment of a topology optimization algorithm using the joint concepts of the level-set function and topological derivative to design phononic crystals.

Improvement of a topological level-set approach to find optimal topology by considering body forces

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Meisam Takalloozadeh ◽  
Gil Ho Yoon
Keyword(s):  
Topology Optimization ◽  
Level Set ◽  
Thermal Loading ◽  
Topological Derivative ◽  
Optimization Process ◽  
Optimal Topology ◽  
Content Type ◽  
Body Forces ◽  
Applied Forces ◽  
Level Set Approach

Purpose Body forces are always applied to structures in the form of the weight of materials. In some cases, they can be neglected in comparison with other applied forces. Nevertheless, there is a wide range of structures in civil and mechanical engineering in which weight or other types of body forces are the main portions of the applied loads. The optimal topology of these structures is investigated in this study. Design/methodology/approach Topology optimization plays an increasingly important role in structural design. In this study, the topological derivative under body forces is used in a level-set-based topology optimization method. Instability during the optimization process is addressed, and a heuristic solution is proposed to overcome the challenge. Moreover, body forces in combination with thermal loading are investigated in this study. Findings Body forces are design-dependent loads that usually add complexity to the optimization process. Some problems have already been addressed in density-based topology optimization methods. In the present study, the body forces in a topological level-set approach are investigated. This paper finds that the used topological derivative is a flat field that causes some instabilities in the optimization process. The main novelty of this study is a technique used to overcome this challenge by using a weighted combination. Originality/value There is a lack of studies on level-set approaches that account for design-dependent body forces and the proposed method helps to understand the challenges posed in such methods. A powerful level-set-based approach is used for this purpose. Several examples are provided to illustrate the efficiency of this method. Moreover, the results show the effect of body forces and thermal loading on the optimal layout of the structures.

Hardening model of severe plastically deformed AA2024 by high-pressure torsion

2020 ◽  
Vol 11 (4) ◽  
pp. 591-603
Author(s):  
Fauziana Lamin ◽  
Ahmad Kamal Ariffin Mohd Ihsan ◽  
Intan Fadhlina Mohamed ◽  
Cheeranan Krutsuwan Nuphairode
Keyword(s):  
High Pressure ◽  
Simulation Model ◽  
High Pressure Torsion ◽  
Model Verification ◽  
Von Mises Stress ◽  
Rotational Axis ◽  
Content Type ◽  
Hardening Model ◽  
Von Mises ◽  
Stress Flow

PurposeThis paper aims to evaluate the validity of bilinear hardening model to represent the stress flow of high-pressure torsion (HPT)-strengthened lightweight material, AA2024.Design/methodology/approachFinite-element HPT simulation was performed by applying a simultaneous prescribed displacement on the axial and rotational axis that is equivalent to 4 GPa pressure and 30° torsion. The material behaviour incorporates plasticity attributes with a bilinear constitutive equation that consists of elastic and tangent modulus.FindingsAs a result, the von Mises stress generated from the simulation is in good agreement with the experiment, indicating that the assumptions of plasticity properties applied for the FEM simulation model are acceptable. The model verification confirms the anticipated plasticity parameters’ effect on the generated von Mises stress. The disc centre also evidenced an insignificant stress increment due to the limited shear straining.Research limitations/implicationsA reliable hardening model would assist in understanding the stress flow associated with mechanical properties enhancement.Practical implicationsThe bilinear hardening model exhibits a satisfactory stress estimation. It simplifies the ideal strain variable hardening procedures and lessens the total computation time that is valuable in solving severe plastic deformation problems.Originality/valueAn integration of well-defined input parameters, concerning the hardening behaviour and the plasticity properties, contributes to the establishment of a validated HPT simulation model, particularly for AA2024. This study also proved that perfectly plastic behaviour is inappropriate to represent hardening in the HPT-strengthened materials due to the remarkable stress deviation from the experimental data.

3D fluid-structure interaction (FSI) simulation of new type vortex generators in smooth wavy fin-and-elliptical tube heat exchanger

2016 ◽  
Vol 33 (8) ◽  
pp. 2504-2529 ◽  
Author(s):  
Babak Lotfi ◽  
Bengt Sunden ◽  
Qiu-Wang Wang
Keyword(s):  
Heat Exchanger ◽  
Mechanical Behavior ◽  
Elastic Strain ◽  
Fluid Structure Interaction ◽  
Vortex Generators ◽  
Von Mises Stress ◽  
Fluid Structure ◽  
Content Type ◽  
Structure Interaction ◽  
Von Mises

Purpose The purpose of this paper is to investigate the numerical fluid-structure interaction (FSI) framework for the simulations of mechanical behavior of new vortex generators (VGs) in smooth wavy fin-and-elliptical tube (SWFET) heat exchanger using the ANSYS MFX Multi-field® solver. Design/methodology/approach A three-dimensional FSI approach is proposed in this paper to provide better understanding of the performance of the VG structures in SWFET heat exchangers associated with the alloy material properties and geometric factors. The Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are applied for modeling of the turbulent flow in SWFET heat exchanger and the linear elastic Cauchy-Navier model is solved for the structural von Mises stress and elastic strain analysis in the VGs region. Findings Parametric studies conducted in the course of this research successfully identified illustrate that the maximum magnitude of von Mises stress and elastic strain occurs at the root of the VGs and depends on geometrical parameters and material types. These results reveal that the titanium alloy VGs shows a slightly higher strength and lower elastic strain compared to the aluminum alloy VGs. Originality/value This paper is one of the first in the literature that provides original information mechanical behavior of a SWFET heat exchanger model with new VGs in the field of FSI coupling technique.

Finite element analysis (FEA) of polylactic acid/polypropylene carbonate (PLA/PPC) blends fixation plate for craniomaxillofacial surgery

2019 ◽  
Vol 10 (5) ◽  
pp. 678-691
Author(s):  
Intan Najwa Humaira Mohamed Haneef ◽  
Norhashimah Shaffiar ◽  
Yose Fachmi Buys ◽  
Abdul Malek Abd. Hamid
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Human Body ◽  
Healing Process ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Content Type ◽  
New Material ◽  
Fixation Plate ◽  
Von Mises

Purpose The internal fixation plate of bone fractures by using polylactic acid (PLA) has attracted the attention of many researchers, as it is biodegradable and biocompatible to the human body. However, its brittleness has led to implant fracture. On the contrary, polypropylene carbonate (PPC), which is also biodegradable and biocompatible, has an excellent elongation at break. The purpose of this paper is to compare the PLA fixation plate with the new fixation plate made up of PLA/PPC blends by using finite element analysis (FEA). Design/methodology/approach The mandible bone from CT data set and fixation plate was designed by using the MIMICS, Amira and Solidworks softwares. Abaqus software was used for FEA of PLA/PPC fixation plate applied on the fractured mandible bone. A model of mandibular bone with a fracture in the body was subjected to incisor load. The analysis was run to determine the von Mises stress, elongation of the fixation plate and the displacement of the fractured gap of PLA/PPC blends fixation plate. Findings The von Mises stress predicted that all the blend compositions were safe to be used as a fixation plate since the stress values were less than the yield strength. In addition, the stress value of the fixation plate was gradually decreased up to 20 percent when the amount of PPC increased to 30 percent. This indicates that the stress shielding effect was successfully reduced. The elongation of the fixation plate was gradually increased from 11.54 to 12.55 µm as the amount of PPC in the blends increased from 0 to 30 percent, thereby illustrating that the flexibility of the fixation plate was improved by the addition of PPC. Finally, the measured displacement of the fractured gap for all compositions of PLA/PPC blends fixation plate is less than 150 µm, which proves the likely success of fracture fixation by using the PLA/PPC blends. Research limitations/implications An optimum solution of PLA/PPC blends and another new material such as compatibilizer need to be introduced in the blends in order to improve the performance of PLA/PPC blends as a new material for a fixation plate. Besides, by using the same method of producing PLA/PPC blends, longer durations for in vitro degradation of PLA/PPC blends are essential to further understand the degradation behavior of the blends applied in the human body. Finally, it is also important to further test the mechanical strength of PLA/PPC blends during the degradation period to know the current strength of the implant in the healing process of the bone. Practical implications PLA fixation plate and screw can commercially be used in CMF surgery since they reduce cost because of the elimination of secondary surgery to remove the fixation plate and screw after the healing process. Social implications It is hoped that the advantages of this research will ensure the market of PLA product to continue expanding in medical application. Originality/value This study is one of the alternative ways for the biomedical researchers to improve the elongation break of PLA. Currently, many researchers focus on polymeric materials such as PLA, poly(glycolic) acid and polydioxanone blends, which were extensively being used in CMF surgery. However, the work on PLA/PPC blends to be used as one of the materials for the CMF fixation plate is very limited, if any. PPC, the proposed material for this research, will improve the mechanical performance of PLA fixation plate and screw to become more sustainable and flexible when applied on human mandible bone.

scholarly journals Combined shape and topology optimization for minimization of maximal von Mises stress

2017 ◽  
Vol 55 (5) ◽  
pp. 1541-1557 ◽  
Author(s):  
Haojie Lian ◽  
Asger N. Christiansen ◽  
Daniel A. Tortorelli ◽  
Ole Sigmund ◽  
Niels Aage
Keyword(s):  
Topology Optimization ◽  
Von Mises Stress ◽  
Shape And Topology Optimization ◽  
And Topology ◽  
Von Mises

Design of Stress Constrained SiC/SiC Ceramic Matrix Composite Turbine Blades

2020 ◽  
Author(s):  
Robert J. Boyle ◽  
Pritheesh Gnanaselvam ◽  
Ankur H. Parikh ◽  
Ali A. Ameri ◽  
Jeffrey P. Bons ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Turbine Blades ◽  
Ceramic Matrix Composite ◽  
Aircraft Engine ◽  
Stress Constraints ◽  
Time Frame ◽  
Von Mises Stress ◽  
Efficiency Improvement ◽  
Low Aspect Ratio ◽  
Von Mises

Abstract The structural and aerodynamic performance of a a low aspect ratio SiC/SiC CMC High Pressure Turbine blade was determined. The application was a NASA notional single aisle aircraft engine to be available in the N+3, beyond 2030, time frame. The notional rpm was maintained, and to satisfy stress constraints the annulus area was constrained. This led to a low span blade. For a given clearance low span blade are likely to have improved efficiency when shrouded. The efficiency improvement due to shrouding was found to strongly depend on the axial gap between the shroud and casing. Axial gap, unlike clearance or reaction, is not a common parameter used to correlate the efficiency improvement due to shrouding. The zero clearance stage efficiency of the low aspect ratio turbine was 0.920. Structural analyses showed that the rotor blade could be shrouded without excessive stresses. The goal was to have blade stresses less than 100 MPa (14.5 ksi) for the unshrouded blade. Under some not very restrictive circumstances, such as blade stacking, a one-dimensional radial stress equation accurately predicted area averaged Von Mises stress at the blade hub. With appropriate stacking radial and Von Mises stresses were similar.

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