功能材料双轴拉伸十字板试件的优化设计

在对Demmerle和Boehler提出的一个基于试件实验区应力标准差的数学判据进行修正的基础上,将这一判据应用于有限元方法中,通过 ABAQUS有限元软件计算出试件实验区的应力分布,结合Powell优化设计方法,实现了对各向同性形状记忆合金材料双轴拉伸十字板试件的最优化设计.优化设计所得试件的应力位移分布图与原有的Kelly试件迸行了比较,结果表明经过优化的试件在满足双轴试验要求方面有了明显的改进.同时验证了在各向同性材料下优化所得的试件同样适用于各向异性材料.最后,对形状记忆合金相变过程在试验区中引起的应力应变变化进行了数值模拟,其结果表明优化试件完全能够满足记忆合金材料双轴实验的要求.

OPTIMAL DESIGN OF BIAXIAL TENSILE CRUCIFORM SPECIMENS FOR SMART MATERIALS

A mathematically well-defined criterion proposed by Demmerle and Boehler is modified in this paper, in order to realize an objective evaluation of the stress state in the test section of biaxial tensile cruciform specimens. This criterion is based on the standard deviations of the values of the stresses in the test section, taking the homogeneity of the stress fields, the compatibility of the obtained stresses with the nominal stresses and possible stress concentrations into consideration. By using this criterion, an optimization procedure for design of cruciform specimens is developed in terms of the finite element analysis. This procedure is used to realize the optimization of the cruciform specimens for isotropic materials such as Shape Memory Alloys. The performances of the optimized specimen are by far better than those of the specimen by Kelly. In particular, the stress and displacement fields in the central test section exhibit an excellent homogeneity and the maximum Von Mises stress corresponds to the central part of the test section. Thus, the experiment data obtained with such an optimized specimen are realistic and can be employed for the identification of constitutive laws.The performance of the obtained optimized specimen design is also examined for anisotropic materials in off-axes tests and a good result is obtained. Furthermore, after integrating a proposed three-dimensional constitutive model into finite element software ABAQUS, the transformation behavior of CuAlNi under biaxial loading is simulated by using the optimized specimen.