CRACK TIP PARAMETERS FOR CREEP‐BRITTLE CRACK GROWTH

Abstract

Crack growth histories for creep‐brittle aluminium alloy 2519‐T87 are simulated by controlling the rate of release of finite element nodes along the crack growth path using a variable time‐step, nodal release algorithm. While earlier experimental studies established little or no correlation between time‐dependent fracture parameters and the crack growth rate, a˙, during creep‐brittle fracture, the numerical results presented here indicate excellent correlation of the Ct parameter with a˙ during the quasi‐steady state crack growth regime. Differences in the experimental and numerical determination of time‐dependent fracture parameters are likely to be due to difficulties in experimental determination of the creep component of the load line deflection rate, V˙c , during creep‐brittle crack growth. A new quantity, K/rqc, is derived from time‐dependent fracture parameters to predict crack growth for transient, quasi‐steady state and steady state crack growth. However, Ct and K/rqc should only be employed as parameters for predicting creep‐brittle crack growth with an understanding of the couplings which exist between these parameters and the crack growth rate.