The State-of-the-Art Methodology to Compute the 3-D Stress Intensity Factors for Arbitrary Shaped Cracks in Complex Shaped Structures.

In present research, engineering softwares that can perform highly efficient and accurate fracture analyses based on the finite element method (FEM) is being developed. The developed softwares will drastically shorten time and labor cost to perform the fracture mechanics analyses. Structural integrity problems have been recognized as the major concerns by engineers in power plant, civil engineering, aerospace and ship-architectural industries. One of the scenario leading to structural failure is that (1) cracks from in the structure, (2) they propagate through the structure under the applied stress and (3) unstable crack propagation lading to catastrophic structural failure occurs. In this scenario, it is very important to detect the structural defects by non-destructive inspection (NDI) techniques and to predict how the existing cracks propagate through the structure. Thus, the remaining service life of damaged structure can be predicted. The major tool to perform the residual life prediction analysis is the finite element method (FEM). Once FEM analysis is performed for the damaged structure, fracture mechanics parameter such as the stress intensity factor is evaluated and it characterizes the severity of crack tip deformation field. Rate and direction of crack propagation are predicted based on the stress intensity factor. In this research we aim at developing softwares that can automate the fracture mechanics analysis by coupling the (1) automatic mesh generation software, (2) finite element program for large scale analysis and (3) a new virtual crack closure-integral method (VCCM) [1] for evaluating the stress intensity factor based on tetrahedral finite elements. Among them the VCCM technique is the key technology. In the presentation, the VCCM for quadratic tetrahedral finite element is described first and the-state-of-the-art mesh generation software called VENUS [2] and the use of free mesh method (FMM) [3] are discussed. [ABSTRACT FROM AUTHOR]