Study Of Crack Propagation And Fatigue Life Based On Virtual Crack Closure Technique

Fracture mechanics has been widely practiced in different engineering areas, such as structure engineering, mechanical engineering, rock and soil engineering, aerospace engineering, naval architecture and ocean engineering, nuclear power engineering, oil and gas pipelines. However, only few fracture problems have analytical solutions, many engineering problems should be solved by numerical methods.In the present work, some numerical techniques based on FEA in fracture mechanics are reviewed first, for instance, extrapolation technique for stress intensity factors, equivalent domain integral technique for J-Integrals, virtual crack extension technique for strain energy release rates. Then, virtual crack closure technique (VCCT), which is simple and straightforward, and is not sensitive to the FEA mesh size, was discussed in detail. Based on VCCT, a fracture and fatigue element, named as VCCT fracture element and VCCT fatigue element, were developped in conjunction with commercial FEA software ABAQUS by its user-defined element(UEL) feature. The VCCT fracture element was validated to be accurate in calculating stress intensity factors by comparation to the analytical solution of three-point bend specimen, and it was proved to be convenient to simulate the crack propagation by the DCB specimen. The VCCT fatigue element was validated by comparation to the existing experimental data obtained from center crack panels.This method could be a powerful tool for engineers to study the fracture and fatigue problems in engineering structures.