Random Vibration Fatigue Tests To Prove Integrity Of Cantilevered Attachments On Compressor Shells

Many Air Conditioning and Refrigeration hermetic compressor shells are designed with cantilevered attachments such as control valves. These attachments are subject to several sources of loading such as shell pressure, external tube load or vibration. One of the most common failure modes yet the least predictable is fatigue due to vibration at the joint with the shell. The purpose of the paper is to provide a method for developing an accelerated random vibration test, which can be used to efficiently evaluate the joint reliability for these cantilevered compressor shell attachments. By assuming a simple cantilever beam model, the cumulative fatigue damage can be estimated at the joint from the relative displacement at the beam-ends. The cumulative damage from a bench test is compared to the measured vibration of operating compressors subject to a representative sample of the compressor application. Finally a random vibration fatigue test is developed at higher-than-service loads to accelerate the test and reduce test cost. This fatigue test includes the specification of test load spectra, test duration and pass criteria that represents an acceptable probability of failure in the market place.