Path Independent Integral to Creep Crack and Crack Energy Density

Abstract

The crack energy density εJ-integral which is the path independent expression of εare applied to creep problem and it is shown that εand its differential coefficient with respect to time εst are valid parameters to creep crack without any restriction on constitutive equation. The contents are as follows; (1) εand εst are introduced as creep crack parameters and it is shown that εst can be evaluated by path independent integral εJst obtained by differentiating εJ with respect to time. (2) It is pointed out that J'-integral (C*-parameter) can be evaluated by newly-introduced ε'Jst which is a path independent integral even to non-steady state creep, and the physical meaning of J' is clarified based on ε'Jst. Also the relation between εst and J' is discussed ant the role of J' is made clear. (3) The validities of εand εst as creep crack parameters are numerically verified through finite element analyses.