Stress Severity Factor Approach For Life Prediction Of Joints Under Vibration Loading

There are a large number of joints in engineering structures such as aerospace, transportation,and etal., which usually undergo vibration loading. Fatigue fracture is the main failure modes of thesestructures. Due to the discontinuity of the structure and complex loading-path, its anti-fatiguecapability falls sharply and directly. This has a great effect on fatigue life of the whole structuresystem. So further study on fatigue characteristics and life analysis methods of joints under vibrationloading have important theoretical significance and engineering application value.Firstly the mode test and random vibration fatigue test are done to the double row bolt test pieceon cantilever beam structure. Modal test is done with hammering method, random vibration fatiguetest is done in foundation vibration loading mode.In the same time the dynamic finite element analysis is done. According to the stress responsepeak of the power spectral density at the hole edge where is the dangerous point combined with thesurface quality factor and hole filling coefficient, the dynamic stress severity factor is. According tothe root mean square of stress at the hole edge combined with the surface quality factor and holefilling coefficient, stress mean square severity factor is defined. The numerical examples validate thattwo factors presented can provide good description of joint hole edge stress concentration underdynamic excitation.Then the stress severity factor (SSF) approach of vibration fatigue life of joints is proposed. Thedistribution characteristics of stress and root mean square stress distribution on the hole edge areobtained by fitting with different function. Based on the fatigue failure mechanism and the meanstress model, dynamic fatigue notch factor is defined, formed the SSF method of vibration fatigue lifeanalysis. The verification test shows that the method can predict the vibration fatigue life of jointswell.