ELASTIC PLASTIC FATIGUE-CRACK GROWTH AND TEARING-INSTABILITY BEHAVIOR UNDER CYCLIC LOADS

Crack-growth behavior and tearing-instability characteristics under cyclic high stress were studied. The materials used in this study were STS42 carbon steel and A508 class 3 low-alloy steel. Tests were performed under both load-and displacement-control conditions. For a tearing-instability test, a high-compliance test apparatus was used. The cyclic J-R curve under lower initial J levels than JIC showed lower values than a monotonic J-R curve. A wide range of fatigue-crack growth rates (da/dN = 3-1 × 10-5 mm/cycle) can be evaluated by using the equation in which ΔJ and Jmax are used. In a high-compliance load system, it was shown that the critical J value at tearing instability under cyclic loading is almost equal to the value of J at an instability value under monotonic loading. © 1990.