Quantifying the creep crack-tip constraint effects using a load-independent constraint parameter Q*

In this work, a load-independent creep constraint parameter Q* was introduced, and its load-independence was confirmed by 3D finite element analyses of six different cracked specimens. A fixed distance r=0.2 mm ahead of crack tips was chosen to define the Q*. In addition, the parameter Q* was used to quantify the in-plane constraint induced by crack depths, specimen widths and loading configurations and the constraint effects induced by specimen thicknesses. The results revealed that the values of Q* increased with increasing the crack depths (a/W ≤0.5) and specimen thicknesses and decreased with increasing the width-thickness ratio W/B of specimens. Furthermore, the highest constraint level occurred in the CT specimen while the lowest occurred in the CCT specimen.