Volume 3, Issue 5 (May 2006)
Creep Crack Growth Predictions in Component Using a Damage Based Approach
This paper presents a numerical study of simulated creep crack growth (CCG) prediction in a compact tension [C(T)] specimen and a pipe component containing cracks. The results are compared to experimental data of the same consisting of creep crack growth tests of a carbon-manganese steel (C-Mn) tested at 360°C. The constitutive behavior for this steel is described by a power law creep model and the uniaxial properties are used in a damage based model to predict CCG. For comparison between CCG properties of the pipe and C(T) specimens, different reference stress methods were used to derive appropriate C* values. It has been shown that the global solution for collapse in the cracked pipes gives the best correlation with the C(T) data. On this basis CCG rates for pipe are higher than those for C(T) specimens at the same value of C*. The damage-based approach combined with a crack tip constraint model based on void growth is also used to predict the crack propagation rates in the pipe component using a two-dimensional finite elements (FE) mesh. Elastic-plastic-creep analyses are performed using a node debonding criteria to simulate and predict crack extension under plane stress and plane strain conditions. It has been found that CCG against time predicted from the FE under plane stress conditions is almost the same as those for the experimental data. Comparing C* derived from different reference stress methods to C* from FE analysis it has been found that C* from FE under plane strain condition correlates best with C* from the global reference stress solution. Consequently the main CCG difference between the C(T) and the pipe component is found to be due to the method of estimating C* and not due to constraint effects.