Creep damage and life analysis of anisotropic materials (Q5946992)

Based on generalizations of Norton's secondary creep law and Markman-Grant life rule, the author analyzes the title prolbem on the hypothesis of one-dimensional damage anisotropy. The multiaxial tertiary creep analysis starts from tensorial damage and constitutive equations for strain rates which use the Jaumann derivative of tensor-dependent stresses and a fourth-order anisotropy tensor. The strain tensor is represented by means of a symmetric tensor of rank two with scalar-valued coefficients. Canonical representations of strain are given as expansions in stress tensor with coefficients dependent upon Jaumann derivatives and anisotropy tensor. An ample exposition concerns the irreducible sets of invariants and generators for stresses. Due to the involved intricacy, the author resorts to simplified equations in which new tensors result from multiplication of stresses. This leads to manageable stress-strain equations. Performed experiments with thin metallic pipes under tension, torsion and internal pressure, as well as with rolled metal sheets in biaxial tension justify the results.