A Method to Determine the Safety Coefficient in Fatigue of Compressor Valves

This paper proposes a method of evaluating the fatigue life of a refrigeration compressor reed valve, given the applied stresses as might be computed by a valve simulation. Mean and alternating values of equivalent stresses (e.g. Von Mises) are plotted in the Haigh diagram. Various choices of models are considered for the safe area of the diagram. This method takes into account surface finish, thickness, ultimate tensile strength and residual stresses related to the strip valve material and process used to obtain the parts. For a given level of confidence, it is possible to predict a safety coefficient, the ratio between admissible stress and applied stress. (]" VonMises (]"rum (]"Max ae aR t Ra (J"adm s NOMENCLATURE equivalent Von Mises stress minimum stress amplitude maximum stress amplitude mean stress amplitude alternating stress amplitude stress ratio number of cycle to failure fatigue limit reversed bending stress at N cycles fatigue limit fluctuating bending stress, minimum stress=O at N cycles bending fatigue strength at N = 2 10 , 50 %probability of fracture tensile strength elastic limit residual stress strip valve thickness surface roughness admissible stress safety coefficient factor Fifteenth International Compressor Engineering Conference at Purdue University, West Lafayette, IN, USAJuly 25-28, 2000 429