S-N equation and E-N equation over all-life range of composite material

Two new equations of the S-N curve equation and the E-N curve equation were presented. These equations with four parameters, have better physical properties than those with two or three parameters. By means of the optimization method of correlation coefficient, the parameter estimation formulas and numerical solutions of these equations were established. Finally, two application examples of these equations were given. From these examples, it is shown that the equations are not only of excellent fitting effect, but also convenient for application.