Influence of load order effect on crack growth rate of different materials

In order to study the fatigue characteristics of the vertebral column joint under tensile load, it is necessary to understand the problem of crack propagation of the material under tensile load. Based on the extended McEvily model, the basic parameters of the extended McEvily model were determined by the constant amplitude fatigue load cycle test of AH36 marine high strength steel and Q235 low carbon steel under a stress ratio of 0.1. Simultaneously, the crack propagation rate tests of different load sequences were carried out. Then, based on the A.Bacilia model, the extended McEvily model was used to replace the Paris model, and the number of cycles of delay due to the “retardation effect” under single overload and overload/low load were calculated by the new model. The results were compared with the test datas to verify the adaptability of the new model. The errors of the two material models were about 10
^%
.