Abstract: Based on plenty of tensile-compressive overload test,a formula of overload shut-off ratio γ SR ,the parameter which takes account of reducing overload retardation effect by compressive load,is proposed.For delermining the value of overload shut-off ratio γ SO of single overload,a test method is suggested here as well.It is shown that the prediction of crack propagation life with the parameter γ SR involved in is well correlated with the test results of random load spectra.

Key words: tensile- compressive overload, overload rat io, crack propagation