The crack-modelling technique: optimization of parameters

The crack-modelling technique is a method for prediction of fatigue in comp onents using finite element (FE) analysis. The technique, which is based on the estimation of equivalent K factors fur stress-concentrators has had so me initial success in analysing components of complex shape, but this has r aised a number of questions about the potential accuracy of the method and its sensitivity to the choice of operating parameters. The present paper re ports on a systematic study using four different specimen types and one com ponent geometry Accurate estimates of equivalent K values are shown to be p ossible for both sharp notches and blunt notches, loaded in uniaxial tensio n or bending, using a very simple approach in which the stress distribution from the notch is compared to that from a standard cracked body. The metho d shows some sensitivity to the optimization routines used, and to some ext ent to the choice of the standard cracked body. It is relatively insensitiv e to mesh refinement and can be used with simple, elastic FE models.