Research And Realization Of Impact Fatigue Life Test System For Valve Leaves In Small Hermetic Reciprocating Compressors

Valve leaves are the key parts of hermetic reciprocating compressors and also the vulnerable components.Failure of valve leaf will cause serious problems of compressor.So,the quality and precision of valve leaves had great influence on energy saving performance and lifetime of small hermetic reciprocating compressors.This paper presented a test system that intended to analysis and evaluate of impact fatigue life of valve leaves used in small hermetic reciprocating compressors.Valve leaves were mainly subjected to bending stresses and impact stresses during work condition,therefore bending fatigue strength and impact fatigue strength of valve leaves played a deterministic role.Bending fatigue strength could be examined in commercial fatigue testing devices.As valve leaf was a light and thin elastomer,impact fatigue life were needed to be investigated in a special impact fatigue testing system.Usual sensors cannot be set on valve leaf.So,noncontact measurement is applied and detection method with signal models used is adopted.This paper presented an accelerated test system with both hardware and software,which contains a noncontact incentive system,a data acquisition system,a control module used to control the working state of incentive system and a fatigue detection system to evaluate the valve leaf’s impact fatigue life.Firstly,an incentive system was designed to simulate real work condition for valve leaf.Secondly,a data acquisition system was built to collect the sound signal while valve leaf was being under test.Simultaneously,the system could control the working state of incentive system so that test could be terminated automatically once fatigue was detected.Finally,fatigue detection system was designed to detect fatigue of valve leaf.Fatigue detection was the key point of this test system.Fast Fourier Transform(FFT)and Wavelet Packet Transform(WPT)were applied to analyze sound signal,both of which were effective in detecting the damage through analyzing the feature vector.Facts showed that the test system provided a feasible approach to evaluate impact fatigue life for valve leaf manufacturing.