1 Several kinds of Calculation Methods on the Crack growth Rates for Elastic-Plastic Steels Yangui Yu* Zhejiang GuangXin New Technology Application Academy of Electromechanical and Chemical Engineering Hangzhou, 310007, China * gx_yyg @126.com Abstract Research interdependent correlations among various calculations models, relationship between their calculations parameters, and relationship between their materials constants in equations on strengths and life predictions, which are elastic-plastic steels with cracks. Thereby obtain and suggest to adopt several new calculations models and their calculations methods on crack propagation rates, which are respectively suitable for calculations of crack propagation rates under different stress ratio loading, or are suitable for calculations under symmetrical and unsymmetrical cyclic loadings, the work stresses less than or greater than the yield limit. Also the material constants 2B in new models are defined as comprehensive material constants and give also out their physical meaning and geometric significances that are having a function relation with other parameters. Moreover provide yet a calculation example of crack propagation rate. Anticipate that the works will be having practical significances for fatigue - damage - fracture tests to save experimental times, fund inputs and to expand engineering applications. Keywords Elastic-Plastic-materials, Comprehensive material constants, Crack growth rate, Calculation methods 1. Introduction In the engineering fields, loading conditions are very complicated. In the engineering designs and calculations, there are a lot of calculating models are applied. In traditional design methods, for their calculating parameters, for their material constants adopted in the models, in addition to some key calculating parameters, in addition to some limited materials constants which are showing the material properties, they must be by means of the experiments to take data. However there are also some of the traditional calculating models, their calculating parameters and material constants had been already extensively applied, which had been derived usually from the relationships between various calculation parameters or from the relationships between all kinds of material constants, afterwards again applied to engineering design calculation and analysis. The same, for including cracks structures and materials undergone to very complicated loadings, the calculations on their strengths, crack propagation rates and service life, in all kinds of calculation models also must refer to many calculation parameters and material constants, but these required parameters of designs and calculations got from experiments are always limited. In fact, between these calculations parameters or between these materials constants each other, there are also usually some functional relations. So that to research and analyze these calculations models, their calculations parameters and materials constants, of course, some new models and their parameters and constants can also be derived from them and would be applied to designs and calculations in engineering. The author researches various strengths, crack propagation rates and life calculations models, to analyze and find interdependent relationships between the various calculation parameters and all kinds of material constants, proposes respectively several new calculation models and calculation methods for the elastic-plastic steels with cracks. But also puts forward specially the new concepts of comprehensive material constants and their calculation methods, its purpose is in combination
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