Validation of SLA Control Arm Bushing Fatigue Life Under Multi-Channel Road Load Input

<div class="section abstract"><div class="htmlview paragraph">Continuing prior work, which established a simulation workflow for fatigue performance of elastomeric suspension bushings operating under a schedule of 6-channel (3 forces + 3 moments) road load histories, the present work validates Endurica-predicted fatigue performance against test bench results for a set of multi-channel, time-domain loading histories. The experimental fatigue testing program was conducted on a servo-hydraulic 3 axis test rig. The rig provided radial (cross-car), axial (for-aft), and torsional load inputs controlled via remote parameter control (rpc) playback of road load data acquisition signals from 11 different test track events. Bushings were tested and removed for inspection at intervals ranging from 1x to 5x of the test-equivalent vehicle life. Parts were sectioned and checked for cracks, for point of initiation and for crack length. No failure was observed for bushings operated to 1 nominal bushing lifetime. After 3 nominal bushing lifetimes, cracks were noted in several locations. Corresponding fatigue simulations considered rubber’s hyperelastic and fracture mechanical behavior (including strain crystallization effects), the nonlinear mapping from loads to strains, interpolation of the multichannel loading history to produce strain history using the Endurica EIE solver, and the computation of fatigue life using the Endurica DT incremental fatigue solver. The simulation indicated crack development at 2.0 nominal lives for cracks on the outside diameter of the flange end, 2.6 lives for cracks on the inside diameter of the flange end, and 4.8 lives for cracks in the center of the inner metal. Predicted crack development was in general agreement with observed crack development in terms of both location and duration, with some indication that crack precursors on the rubber-metal interface may be slightly larger than assumed based on characterization of the bulk rubber itself.</div></div>