An extended structural stress method for predicting fatigue life of non-welded axle components 2020-01-0606
Leaking in a cover-pan of an axle assembly can result in severe durability issues. Preliminary tests of axle assembly for a fore-aft beaming test (replicating the load on the axle while accelerating or decelerating the vehicle) exhibited MPI indications of crack/leak adjacent to multiple bolt holes on the cover-pan. FEA results were able to capture the critical locations accurately. However, the crack initiation predictions were extremely conservative in nature due to the stress riser next to the bolted joints. Testing also indicated that a surface crack due to the bolt-edge-contact could withstand significant load cycles before a leak is formed (through thickness crack in the cover-pan). A unique simulation framework is implemented to perform the crack propagation life of the axle component. Traction structural stress method, build to predict the propagation life of welded components, was extended to predict the life of non-welded components. Unlike the welded components, mean-stress effect needs to be considered for predicting the propagation life. The test results from multiple axle designs indicate that the suggested method could predict the cover-pan life in a reliable manner.
Anoop Vasu, Shizhu Xing, Jifa Mei, William Webster, Scott Jacob, Jerry Chung, Ravi Desai