HT有限元在Ⅰ、Ⅱ与Ⅲ型复合弹性断裂问题中的应用

APPLICATION OF HT FINITE ELEMENT METHOD TO MULTIPLE CRACK PROBLEMS OF MODEⅠ,Ⅱ AND Ⅲ

  • 摘要: 探讨了HT有限元应用于Ⅰ、Ⅱ和Ⅲ型复合裂纹的弹性断裂问题。分析了Ⅲ型弹性断裂问题的HT有限元方法及高阶奇异性应力强度因子KΙΙΙ,同时,对Ⅰ和Ⅱ型断裂问题的HT有限元原理及断裂强度因子KΙ和KΙΙ的计算也进行了阐述。特别地,在计算三个强度因子时,引入了一种新的方法——附加试函数法,它主要用于满足裂尖特殊的边界条件,提高了三个奇异应力强度因子的精确性与可靠性。最后,根据HT有限元计算结果,讨论了奇异应力强度因子无量纲化系数K/Kc随裂纹单元特殊T函数项数、细划单元数、单元高斯点数及裂尖不同附加试函数的变化规律;获得了应力强度因子精确度和可靠度,并与其它有限元结果进行了比较,阐述了此方法的优越性。

     

    Abstract: The paper presents a multiple fracture analysis of mode Ⅰ, Ⅱ and Ⅲ problems by Hybird-Trefftz (HT) finite element element. Since the approach employs regular T-complete functions that satisfy the governing equation, the procedure is much simpler and its accuracy should be better than that of general finite element. HT method can be viewed as a powerful computational tool in dealing with the singular crack problems. The paper focus on the applications of HT finite element method to mode Ⅰ, Ⅱ and Ⅲ fracture problems in elastic field. In particular, a series of special element models are presented to represent those elements containing a crack, which can accurately satisfy the fracture behavior of elements on crack faces. Furthermore, auxiliary functions are adopted near crack tips to improve computing accuracy at the same time. The performance of the proposed finite element formulations is assessed by an case of arbitrary elastic three-dimension mass with an arbitrary side crack, which can be simplified as pure mode Ⅰ, Ⅱ and Ⅲ fracture problems, respectively. In contrast with conventional finite or boundary element model, the effect of numbers of T-complete functions, the mesh density, the number of Gauss points and the auxiliary functions near crack tips on the accuracy of the solution are discussed. The numerical assessment indicates that the proposed HT finite element formulation is ideally suitable for the analysis of mode Ⅰ, Ⅱ and Ⅲ fracture problems, and may be applied to engineering problem as well.

     

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