Mesh-Dependence in Local Approach to Creep Fracture

Mesh-dependence and its regularization in the local approach to creep fracture based on continuum damage mechanics and finite element method are discussed. The essential causes of the mesh-dependence are elucidated first in some detail. Then, the process of damage localization and its effects on the mesh-dependence are discussed by performing finite element analysis of a plate in uniform state of stress. The stress sensitivity in damage evolution equations is shown to be one of the major causes of the mesh-dependence. Finally, besides the non-local damage theory often employed in local approach, three new possibilities, including the stress limitation method and that of the modified stress sensitivity in the damage evolution equation, to secure the convergent results are proposed. The validity and the limitations of these methods are elucidated and compared with each other by analyzing creep fracture process of an axisymmetric thick-walled tube.