EFFECTS OF HYDROSTATIC PRESSURE ON THE RATE OF FATIGUE CRACK GROWTH

— Fatigue crack growth rate data have been obtained, for both positive and negative R stress ratios, in pressurised and unpressurised oil and in inert argon gas. Expected results show that for negative R the rate data should be correlated against the tensile stress intensity range. For tension‐compression loading constant hydrostatic pressure has a detrimental effect increasing the tensile stress intensity range. For tension‐tension loading constant hydrostatic pressure has a beneficial effect decreasing crack growth rates. A simple theoretical model has been proposed which describes these trends.