Abstract
The crack propagation of a center notched plate specimen in tensile creep under the plane stress condition was simulated by means of a finite element method on the finite strain theory. In the analysis, the restriction force of a nodal point in the triangular elements at the crack tip was removed whenever the strain at the point reached a critical value (i.e., the fracture strain). The distributions of creep stress and strain ahead of the propagating crack, the shape of the crack, and the relations between the crack propagation rate and the crack length, the crack tip stress, the net section stress or the elastic stress intensity factor were calculated. And the effects of the values of creep exponent, α, and fracture strain, ε*f, on the above quantities were clarified. The crack propagation rate was found to be proportional to the creep rate at the crack tip and inversely proportional to the slope of tangent of the creep strain distribution curve at the crack tip. The history of creep deformation made the slope of strain distribution ahead of the crack flat with the crack growth, resulting the acceleration of crack propagation rate especially in the region of relatively short crack length. The crack propagation rate changed approximately linearly against the net section stress, σnet, or the stress intensity factor KI, in a log-log diagram. For a given value of σnet/σg or KI/σg, the crack propagation rate was in proportion to the creep rate under the gross stress, σg, and in inverse proportion to the fracture strain of the material.
