Improvement of Impact Fatigue Life of Sheet Valve

Abstract

Sheet valves used in a reciprocal compressor are subjected to a pulsation of impact force which k results in cracks forming at the tip during prolonged use, and sometimes chipping also occurs due to their connection with the cracks. In this study, the effect of geometrical improvement of the sheet valve on the impact fatigue life was investigated. The impact fatigue life was defined by the number of pulsations to crack initiation at the tip. Impact fatigue experiments were conducted using commercial steel sheet valves and three improved types of valves. A small upward bend in the valve tip increased the fatigue life considerably. An inclined cut at the valve tip did not result in a clear increase in fatigue life. On the other hand, scatterings in fatigue lives of improved valves were somewhat increased compared with that of commercial valves. Dynamic stress states are also investigated by FEM analysis.