A direct method for laboratory spectrum crack growth testing

Abstract In linear elastic fracture mechanics (LEFM), the fatigue crack growth rates are related to the elastic stress intensity factor range and the load ratio. However, this relationship is difficult to derive when the loading condition is of variable amplitude (spectrum loading). Attention is paid to the most encountered case of cracks growing in their own plane under mode I loading. A testing procedure is presented to directly evaluate the fatigue life of real cracks under spectrum loading. The direct method intrinsically has wide applicability. A separate communication will present an application of the method.