Abstract:
For Mode I fatigue crack propagation under cyclic loading, a peridynamic fatigue crack growth model that accounts for crack tip cyclic elastoplastic effects was developed based on bond-based peridynamic theory and a bond residual life damage model. The Neuber rule and the Ramberg-Osgood constitutive relation were introduced to correct the local cyclic bond strain near the crack tip by considering elastoplastic effects, while a crack growth criterion based on the fracture ratio of candidate bond groups was adopted to improve the conventional crack propagation mechanism governed by the failure of a single critical bond. The applicability of the proposed model was validated against fatigue tests on cracked aluminum alloy plates and Q345E steel specimens. On this basis, the effects of the bond breaking ratio threshold, crack geometry, initial crack length ratio, and global stiffness evolution were investigated. The results show that the bond breaking ratio threshold is a key parameter governing crack growth determination and fatigue life prediction accuracy, and good agreement with experimental results is achieved when the threshold
ηc is set to 50%. Crack geometry significantly affects the crack growth rate, with the double-edge cracked plate exhibiting faster crack propagation than the center-cracked plate, mainly because the difference in crack tip cyclic bond strain between the two configurations increases from 4.0% to 12.7% as the crack propagates. The initial crack length ratio
a0/
w also has a pronounced influence on crack growth; as
a0/
w increases from 0.3 to 0.7, the crack tip cyclic bond strain is substantially amplified, promoting accelerated crack propagation. In addition, the residual global stiffness exhibits nonlinear degradation during the fatigue process and shows a clear stage dependent correspondence with the evolution of crack tip cyclic bond strain. The proposed model provides a new analytical approach for simulating fatigue crack propagation and predicting fatigue life of materials subjected to cyclic loading.