Three-dimensional effects affecting the precision of lifetime predictions

A series of laboratory experiments on smooth and side-grooved compact specimens, as well as plates under tension with surface flaws, has been reevaluated by means of three-dimensional elastic-plastic finite-element analyses. Particular emphasis is laid on the calculation of the local crack-tip loading parameter, J, and of the local constraint factor, q. These parameters are correlated with experimental findings concerning initiation and stable crack propagation. A first-güss correlation between q and the slope of J(Delta a) curves is established. (IWM