失效评定图在典型船体结构完整性评估中的数值应用研究

Numerical Application of Failure Assessment Diagram to Integrity Assessment of Typical Hull Structures

失效评定图是对带裂纹结构进行完整性评估的一种有效工具。但是失效评定图目前主要基于解析公式应用于简单构件的完整性评估,尚未在船体等复杂结构中得到广泛应用。为了扩展失效评定图在船体等复杂结构领域的应用,基于虚拟裂纹闭合法和虚拟截面闭合法,在有限元软件ABAQUS子程序UEL平台上编写三维界面单元,可通过一步线弹性计算快速准确得到失效评定图中的断裂比和载荷比,完成失效评估工作。以带裂纹的典型Nishihara模型为验证算例,使用三维界面单元和全局分析法分别进行完整性评估。计算结果表明,两种方法得到较为一致的结果,同时表明三维界面单元操作简便,计算效率高,具有较好的工程应用价值。

The failure assessment diagram( FAD) had widely known as a useful tool to perform failure assessment of cracked structures. However,FAD had been only applied to simple structures based on analytical formulae. For the methodology based on analytical formulae,FAD had not been applied to complex hull structures. To meet this challenge,a 3-D interface element was built based on the virtual crack closure technique and virtual section closure technique with subroutine U EL in the commercial finite element software ABAQ U S. The interface element could obtain fracture ratio and load ratio simultaneously in the frame of linear elastic analysis within a single step. The capacity of the proposed interface element was assessed based on the cracked N ishihara specimen( N ST-3). The results obtained from the interface element were compared to those obtained by the global analyses. The comparison indicates that the proposed interface element is accurate. N o convergence troubles are encountered. In addition,the interface element is simple to operate and efficient. Therefore,the interface element makes a very useful tool to perform failure assessment based on FAD by engineers.