Dimensionless Load—Displacement Relation and Its Application to Crack Propagation Problems

The dimensionless load () and load‐point displacement (û) are introduced to discuss crack propagation problems. The −ũ relation for the case of equilibrium crack propagation in any linear elastic material is demonstrated to lie on a single universal fracture curve independent of the material. The concept of the universal −ũ relation is extended to yield a direct and simple form of the dimensionless total energy ( eq (α)) which is applicable to many types of instability problems for crack extension, when the shape factor ( Y ) of the specimen is known as a function of crack length ( a ). In addition, by applying the deviation of the experimentally observed —ũ curve and the theoretical universal fracture curve, the evaluation of the nonlinear fracture resistance parameter of a polycrystalline graphite material, as an example, was demonstrated.