Mechanical Behaviour of Auxetic Microstructures Using Contact Mechanics and Elastoplasticity

2016 ◽  
Vol 681 ◽  
pp. 100-116
Author(s):  
Georgios A. Drosopoulos ◽  
Nikolaos Kaminakis ◽  
Nikoletta Papadogianni ◽  
Georgios E. Stavroulakis
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Topology Optimization ◽  
Contact Mechanics ◽  
Compliant Mechanisms ◽  
Nonlinear Finite Element Analysis ◽  
Nonlinear Finite Element ◽  
Numerical Homogenization ◽  
Element Analysis ◽  
Optimization Formulation

The design of novel mechanical microstructures having auxetic behaviour is proposed in this paper using techniques of topology optimization for compliant mechanisms. The resulting microstructure can be modified in order to cover additional needs, not included in the topology optimization formulation. Classical structural optimization, contact mechanics, homogenization and nonlinear finite element analysis are used for this step. Thus, the modified microstructure or composite is studied with numerical homogenization in order to verify that it still has the wished auxetic behaviour. Finally, nonlinear finite element analysis shows how the auxetic behaviour is influenced by unilateral contact between the constituent materials, large displacements and elastoplasticity.

scholarly journals Multiresolution Topology Optimization of Large-Deformation Path-Generation Compliant Mechanisms with Stress Constraints

2021 ◽  
Vol 11 (6) ◽  
pp. 2479
Author(s):  
Joseph Reinisch ◽  
Erich Wehrle ◽  
Johannes Achleitner
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Nonlinear Finite Element Analysis ◽  
Stress Constraints ◽  
Nonlinear Finite Element ◽  
Path Generation ◽  
Element Analysis ◽  
Multiresolution Topology Optimization

Topology optimization is a powerful numerical tool in the synthesis of lightweight structures and compliant mechanisms. Compliant mechanisms present challenges for topology optimization, as they typically exhibit large displacements and rotations. Path-generation mechanisms are a class of mechanisms that are designed to follow an exact path. The characteristics of compliant mechanisms therefore exclude the validity of linear finite-element analysis to ensure the proper modeling of deformation and stresses. As stresses can exceed the limit when neglected, stress constraints are needed in the synthesis of compliant mechanisms. Both nonlinear finite-element analysis as well as the consideration of stress constraints significantly increase computational cost of topology optimization. Multiresolution topology optimization, which employs different levels of discretization for the finite-element analysis and the representation of the material distribution, allows an important reduction of computational effort. A multiresolution topology optimization methodology is proposed integrating stress constraints based on nonlinear finite-element analysis for path-generation mechanisms. Two objective formulations are used to motivate and validate this methodology: maximum-displacement mechanisms and path-generation mechanisms. The formulation of the stress constraints and their sensitivities within nonlinear finite-element analysis and multiresolution topology optimization are explained. We introduce two academic benchmark examples to demonstrate the results for each of the objective formulations. To show the practical, large-scale application of this method, results for the compliant mechanism structure of a droop-nose morphing wing concept are shown.

The Stiffness Model of Leaf-Type Isosceles-Trapezoidal Flexural Pivots

2008 ◽  
Vol 130 (8) ◽  
Author(s):  
Pei Xu ◽  
Yu Jingjun ◽  
Zong Guanghua ◽  
Bi Shusheng
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Rigid Body ◽  
Compliant Mechanisms ◽  
Nonlinear Finite Element Analysis ◽  
Nonlinear Finite Element ◽  
Leaf Segment ◽  
Element Analysis ◽  
Leaf Type ◽  
Stiffness Model

A leaf-type isosceles-trapezoidal flexural pivot can be of great practical use for designing compliant mechanisms. The analysis of load-deflection behavior for such a pivot is essential to the study of the mechanisms that are comprised of them. Based on the analysis of a single special loaded leaf segment, a pseudo-rigid-body four-bar model is proposed. The four-bar model is further simplified to a pin-joint model for some simple applications. The accuracy of both models is demonstrated by comparing results to those of nonlinear finite element analysis. At last, the two models are applied to analyze the cartwheel hinge as an example.

Simulation Study on Armor-Piercing Effect of Armor-Piercing Bomb

2013 ◽  
Vol 456 ◽  
pp. 55-59
Author(s):  
Ren Bin Zhou ◽  
Xue Bing Liao ◽  
An Qing Ming ◽  
Yong Feng Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Simulation Study ◽  
Nonlinear Finite Element Analysis ◽  
Nonlinear Finite Element ◽  
Analysis Program ◽  
Element Analysis ◽  
Aluminum Target

Studying the armor-piercing effect of armor-piercing bomb that attacks aluminum target is essential, because the target can be considered the simulation of the actual fight equipment. Based on the hypothesis about building the fraction field, the armor-piercing effect of armor-piercing bomb is analyzed, and the velocity and the intruding depth parameter model of armor-piercing effect are established. Taking a certain armor-piercing bomb as example, the intruding processes of armor-piercing effect are simulated by using the nonlinear finite element analysis program LS-DYNA, while aluminum target simulates the wall of combat equipment in two different conditions. At last, the finite element simulated results are given and analyzed that agree with the experiments.

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