Investigation of tearing instability phenomena in ASTM A106 steel

An experimental investigation was performed to evaluate tearing instability theory by varying the applied tearing modulus, T/sub applied/, so that fracture instability would be initiated at various levels of stable crack extension. This is an extension of past investigations of tearing instability theory in that crack extension was monitored continuously using the dc potential drop technique, enabling the applied and material tearing moduli to be calculated at the point of instability. The results of this investigation indicate that, in most cases, fracture instability occurred when the difference between the applied and material tearing moduli was on the order of 10%. Variations in the load versus displacement records of the specimens near maximum load due to local instabilities and friction in the load train precluded measurement of a smooth applied tearing modulus curve.