METHOD DETERMINING DURATION OF GROWTH DELAY OF FATIGUE CRACK AFTER OVERLOADING Russian patent published in 1997 - IPC

FIELD: testing. SUBSTANCE: sample during test is subjected to cycle two-axes tension or to tension-compression and fatigue crack is grown. When crack reaches preset length sample is loaded with overload with reference to maximal level of cyclic loading before overload. After this load is decreased and then loading is continued to new overloading. Tension stress opening edges of crack should be same before and after overloading. For determination of value of delay zone of crack length of crack in section within which decrease of skewing caused by plastic deformation after overloading and number of loading cycles corresponding to it tale place should be measured. There is proposed relationship to determine dimension of zone of plastic deformation at moment of overloading which includes measured height caused by plastic deformation achieved by moment of overloading and polar angles used in Irwin equations for description of dimensions of zone of plastic deformation. EFFECT: increased accuracy of determination of growth delay of fatigue crack.