Finite Element Analysis of Shape Memory Alloy Adaptive Trusses with Geometrical Nonlinearities

This contribution deals with the nonlinear analysis of shape memory alloy (SMA) adaptive trusses employing the finite element method. Geometrical nonlinearities are incorporated into the formulation together with a constitutive model that describes different thermomechanical behaviors of SMA. It has four macroscopic phases (three variants of martensite and an austenitic phase), and considers different material properties for austenitic and martensitic phases together with thermal expansion. An iterative numerical procedure based on the operator split technique is proposed in order to deal with the nonlinearities in the constitutive formulation. This procedure is introduced into ABAQUS as a user material routine. Numerical simulations are carried out illustrating the ability of the developed model to capture the general behavior of shape memory bars. After that, it is analyzed the behavior of some adaptive trusses built with SMA actuators subjected to different thermomechanical loadings.     

Bipotential versus return mapping algorithms: Implementation of non associated flow rules

Numerical implementation of constitutive laws involves specific incremental methods. The “return mapping” (Simo and Hughes, 1998) and the “bipotential” (de Saxcé, 1992) are one of those, associated respectively to two different classes of materials: the General Standard Materials (GSM) for the return mapping and the Implicit Standard Materials (ISM) for the bipotential.The objective of this paper is then to compare the implementation of those both methods in the case of non associated flow rules in plasticity.In the first section, the properties of the different previous material classes will be recalled and the methods of “return mapping” and “bipotential” will be detailed. The comparison of both methods is realised on the non linear kinematic hardening rule of Armstrong–Frederick (Armstrong and Frederick, 1966) in a second section and the details are given in a third part. The numerical implementation is realised in Abaqus/Standard 6.11 by the means of a UMat subroutine and the practical simple case of tension–compression is analysed in a last section.     

On a method of comparison for plate elements in finite element engineering software programs

The purpose of this paper is to propose a method for the evaluation of plate elements in the finite element engineering software comparatively to the Kirchhoff and Reissner plate theories. The method is based on the study of transverse deflection near a crack tip. A numerical work has been conducted for the shell elements in Abaqus software with different crack lengths and various thicknesses. The deflection can be written as a function of the exponent of the distance between the crack tip and one point along the crack. This exponent is accepted to describe the behaviour of finite elements.     

碳纤维增强铝合金板的抗冲击性能

采用ABAQUS/Explicit有限元分析软件对碳纤维增强铝合金层合板(CARAL)受低速冲击进行 数值模拟,研究其在承载过程中的动力响应及损伤。首先通过具体算例与文献中的结果相比较,验证了方法 的有效性;其次从试件的脱层和吸能等抗冲击角度对CARAL 进行分析,并与传统的纯碳/环氧树脂胶片 (CFRP)进行抗冲击对比分析,结果表明,CARAL具有较好的抗冲击性能。     

炭黑填充天然橡胶Mullins效应的仿真与计算分析

通过有限元分析软件Abaqus、Matlab数据拟合工具及单轴拉伸试验,研究了Yeoh本构模型、Ogden本构模型及伪弹性理论模型对炭黑填充天然橡胶的Mullins效应仿真效果及规律。结果表明,(1)对单轴拉伸主加载曲线的拟合,Ogden模型精度更高,而Yeoh模型随着炭黑含量的增加在小变形处的拟合效果变差;(2)提出了伪弹性参数与伸长比之间的关系,找到了一种快速计算伪弹性参数的方法,且精度良好,极大地提高了计算效率。     

FINITE ELEMENT MODELLING OF COMPLEX 3D STATIC AND DYNAMIC CRACK PROPAGATION BY EMBEDDING COHESIVE ELEMENTS IN ABAQUS

<正>This study proposes an algorithm of embedding cohesive elements in Abaqus and develops the computer code to model 3D complex crack propagation in quasi-brittle materials in a relatively easy and efficient manner.The cohesive elements with softening traction-separation relations and damage initiation and evolution laws are embedded between solid elements in regions of interest in the initial mesh to model potential cracks.The initial mesh can consist of tetrahedrons,wedges,bricks or a mixture of these elements.Neither remeshing nor objective crack propagation criteria are needed.Four examples of concrete specimens,including a wedge-splitting test,a notched beam under torsion,a pull-out test of an anchored cylinder and a notched beam under impact,were modelled and analysed.The simulated crack propagation processes and load-displacement curves agreed well with test results or other numerical simulations for all the examples using initial meshes with reasonable densities.Making use of Abaqus's rich pre/post-processing functionalities and powerful standard/explicit solvers,the developed method offers a practical tool for engineering analysts to model complex 3D fracture problems.     

一种TiNi合金本构在ABAQUS中的引入

从简化的Tang模型出发,基于塑性理论的假设把简化后的模型推广到了三维空间.利用ABAQUS/Standard模块所提供的材料本构接口程序UMAT把新的模型引入其中,以伪弹性TiNi合金板状试件的准静态拉伸实验为例,进行了数值模拟.通过对比实验中的物理量与数值模拟结果,说明了采用方法的合理性.     

基于Abaqus的剪切型阻尼器单元开发与应用

基于Abaqus软件平台,利用FORTRAN语言二次开发了一种剪切型金属阻尼器用户子单元(UEL)。通过与Abaqus软件库中用于近似模拟阻尼器的单元进行比较,验证了该用户子单元的正确性,为Abaqus软件二次开发提供了参考。与软件库自带的单元相比,该用户子单元参数输入简单,无需试算,动力分析下的滞回性能更明显。同时,本文对软件中的不同单元进行了探讨,为剪切型金属阻尼器的模拟提供了新的思路。     

Computation of leaky guided waves dispersion spectrum using vibroacoustic analyses and the Matrix Pencil Method: A validation study for immersed rectangular waveguides

The paper aims at validating a recently proposed Semi Analytical Finite Element (SAFE) formulation coupled with a 2.5D Boundary Element Method (2.5D BEM) for the extraction of dispersion data in immersed waveguides of generic cross-section. To this end, three-dimensional vibroacoustic analyses are carried out on two waveguides of square and rectangular cross-section immersed in water using the commercial Finite Element software Abaqus/Explicit. Real wavenumber and attenuation dispersive data are extracted by means of a modified Matrix Pencil Method. It is demonstrated that the results obtained using the two techniques are in very good agreement.     

含冲击损伤复合材料层板及加筋壁板剩余强度研究

应用含刚度折减的椭圆形弹性核模拟了层板的损伤问题,研究了复合材料层板及加筋壁板冲击后的剩余强度问题。利用含椭圆核各向异性杂交应力有限单元对损伤层板进行了应力分析,采用基于特征曲线概念的点应力判据预测了含损伤层板、加筋壁板的剩余强度;基于Abaqus用户子程序uel实现了该方法在工程中的应用,并讨论各种参数对剩余强度的影响。研究结果表明此方法是有效的。