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YU Yangui
Zhejiang Guangxin New Technology
Application Academy of Electromechanical
and Chemical Engineering,
Hangzhou 310012, China
LIU Xiang
School of Information and Electronic
Engineering,
Zhejiang Science and Technology
University,
Hangzhou 310023, China
ZHANG Changsheng
TAN Yanhua
Computer Science and Engineering
College,
Wenzhou University,
Wenzhou 325027, China |
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FATIGUE DAMAGE CALCULATED BY
RATIO-METHOD TO METALLIC MATERIALS WITH SMALL CRACK UNDER
UNSYMMETRIC CYCLIC LOADING
Abstract:
Based on the standpoint to take for the crack size also to be a damage variable like the damage variable, by means of the two-directions coordinate system, several new calculation equations on the small crack growth rate are suggested for describing the elastic-plastic behavior of some metallic materials. And the estimation formulas of life are also suggested relative to varied small crack size at each loading history, which is unsymmetric cyclic loading. In the calculation method, as a loaded stress-strain parameter to adopt the ratio with plastic strain range to elastic strain range, and as the material constants using the typical material parameters in damage calculation expression, a new concept of the compositive material constant, which has functional relation with the typical material constants, average stress, average strain, critical loading time is given out. In addition, the fatigue damage of a part of car is put up to calculate as an example, its calculation results are accordant with the Landgraf’s equation, and calculation precision is more rigorous, so could avoid unnecessary fatigue tests and will be of practical significance on saving times, manpower and capitals, as well as the convenience for engineering applications.
Key words:
Ratio-method Unsymmetric cycle Typical material constant Small crack Growth rate
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