A New Model for Crack Growth Prediction Under Random Loading

초록

The load interaction effect in variable amplitude fatigue test is a very inportant issue for correctly predicting fatigue life. Some prediction methods for retardation are reviewed and the problems discussed. A new model that combines overload plastic zone, residual stress consideration together with Elber's closure concept is proposed to fully take account of the load-interaction effects including both over-load and under-load effects. The model used a simple yet very powerful experssion to calculate U factor cycle by cycle. The Calculated crack growth rate da/dN and the predicted a-N behavior compared well with test points. Applying this new model to complex load sequence is explored here. The best prediction is given by the newly proposed Chen-Lee model. Simulations of tests show the improvement of the new movel over other models.