FRACTURE TOUGHNESS TEST BY IMPACT-FATIGUE METHOD

The crack tip stress intensity factor under impact-fatigue conditions expressed by the equation K_I=(AE/BW)~(1/2)·F(a/W) may be used as a measure of fracture toughness of materials on condition that a proper calibration of K_I with the compliance measurements is made. The fracture toughness values obtained by the above method are equivalent to the dynamic fracture toughness K_(Id) with loading rate of the order (?)=10~5kg/mm~(3/2)/sec, and would be valid as the critical crack length of the fracture surface of specimens are constrained within the range of a/W=0.36-0.6.The above method is simple and convenient for testing fracture toughness of materials. The testing results may be obtained directly from a ready made curve provided that the critical crack length on fracture surface has been predetermined. It can be recommended as a screen method in practical work.