Cumulative probability distribution characteristics of Fatigue and Strength of Engineering Plastics : PEEK

Abstract

We had clarified the relationship of fatigue strength reduction factors K_f of engineering plastics PBT, PEEK, PC between strain concentration factor K_ε in the region of high- and low-cycle fatigue. In this study, we have proposed new design method of calculation on the basis of the size-effect defined on the ratio of standard smooth fatigue specimen to damaged area of structures size. In order to obtain the new conceptual size-effect : S, low- and high-cycle fatigue tests carried out on 100 smooth specimens made of super engineering plastics :PEEK. As the results of those experiments and calculations, it is clarified that life-size-effect :S_life is N_f0^0.81 for large structure, N_f0^1.30 for small structure, and strength -size-effect :S_st is ⊿ε₀^0.69 for large structure, ⊿ε₀^1.53 for small structure.