Effect of crack closure on gear crack propagation

Computational and experimental studies were performed in order to investiga te the propagation of cracking in a spur gear tooth. The stress intensity f actors were numerically calculated by the definition of weight functions an d by finite element analysis. The influence of the hardness and the residua l stress was evaluated and a computational procedure, based on crack tip op ening displacement, was defined in order to assess the crack closure effect . Different propagation laws were adopted and life predictions were made. E xperimental results were obtained by using special equipment with which it is possible to carry out fatigue tests on gear teeth. These results were co mpared with the life predictions. The comparison clearly indicates the impo rtance of residual stresses, hardness and, particularly when the loads appl ied are lower, the crack closure effect. (C) 2001 Elsevier Science Ltd. All rights reserved.