Studies and Applications of Three Kinds of Calculation Methods by Describing Damage Evolving Behaviors for Elastic-Plastic Materials

By means of bidirectional combined coordinate system, three kinds of calculation methods are proposed with respect to the damage evolving rate and the life of elasticplastic material, which include the singleparameter method, the ratio method and the multiplication-method. In this work a lot of new calculation equations are given; a new concept on the all around material constant is provided, which has functional relations with each of the typical material parameters: the fatigue strength coefficient óf, the fatigue strength exponent b'1, the fatigue ductility coefficient ɛ'f, the fatigue ductility exponent ć1, the average stress, the average strain, critical loading time and so on. In addition, an example of a carpart is given, and some comparisons of calculation results are made. The calculation methods will have practical significance in avoiding the unnecessary fatigue tests, saving time, manpower and capital, as well as providing the convenience for engineering applications in a certain degree.