A Consideration on the Low-Cycle Fatigue Life of Bellows : The Fatigue Life under Completely-Reversed-Deflection Cycles

Abstract

In this paper, a method is treated which predicts the low-cycle fatigue failure of bellows subjected to completely-reversed loading, with use of the solution procedure employing the finite difference technique proposed previously by the authors for the large deflection problems of elastic-plastic shells of revolution. Namely, a procedure is discussed which estimates the low-cycle fatigue life, applying the plastic strain range under cyclic loading assessed by the elastic-plastic analysis to the Manson-Coffin equation. A U-shaped bellows subjected to deflection-controlled cyclic loading is taken as an example for the fatigue life analysis, and comparison is made with the corresponding experimental results to ascertain the appropriateness of the present method. Moreover, the fatigue lives predicted by other methods are compared with those by the present method, and fairly good agreement is recognized between the fatigue lives by the modified Langer equation which takes account of the strain concentration factor obtained from the elastic-plastic analysis and the experimental ones.