A new criterion for drillpipe multiaxial fatigue damage

A fatigue damage model is developed. The effects of stress state and mean stress are considered in the new model. The model does not require a cycle counting method. The model is evaluated by using the multiaxial fatigue data. The results indicate that the model can satisfactorily correlate the experimental results for a wide range of materials and loading conditions. Moreover, the developed criterion can be used to predict the drillpipe life.