Validity of three engineering models for fatigue crack growth rate affected by compressive loading in LY12M aluminum alloy
(1. School of Mechanical and Power Engineering, Harbin University of Science and Technology, Harbin 150080, China;
2. Beijing Aeronautical Science and Technology Research Institute of COMAC, Beijing 100083, China;
3. Shanghai Aircraft Design and Research Institute of COMAC, Shanghai 200232, China;
4. Centre for Composite Materials and Structure, Harbin Institute of Technology, Harbin 150001, China)
2. Beijing Aeronautical Science and Technology Research Institute of COMAC, Beijing 100083, China;
3. Shanghai Aircraft Design and Research Institute of COMAC, Shanghai 200232, China;
4. Centre for Composite Materials and Structure, Harbin Institute of Technology, Harbin 150001, China)
Abstract: Based on the crack propagation mechanism of elastic-plastic fracture, a finite element analysis was performed upon the effect of compressive loading on fatigue crack tip stress field in LY12M aluminum alloy. By the validation of test data, two actual engineering models and a published double-parameter crack growth model, called Zhang-model, are all suitable in the case of negative stress ratio, and are used to describe the test data in the corresponding coordinate system. By comparing the degrees of linear correlation, R2, of each fitting line, it shows that Zhang-model is a better engineering method for life prediction of fatigue crack growth under negative stress ratio of aluminum alloy, some factors can be obtained from elastic-plastic finite element computation, and it will save a lot of funds in the new materials research.
Key words: fatigue life prediction; fatigue crack growth rate; compressive loading; aluminum alloy