Abstract
PU Bump stop fitted on a rear shock absorber is critical for the ride comfort, handling and structural integrity of two wheelers. Bump stop failure will lead to overload and mechanical failure of structural components. Hence durability proving of PU bump stop is very critical. Component level test is the most cost effective and time efficient method of the durability proving. In this paper, fatigue damage based method for PU bump stop durability evaluation at component level is demonstrated. The challenge in the study was load duty cycle measurement for the bump stop having nonlinear stiffness. This difficulty was overcome by developing a clever instrumentation setup using a washer type load cell. The measurement method offers significant advantage over displacement based method used for load estimation. The uncertainty in load estimation was found to be of order greater than 50% for displacement based estimation. This uncertainty can have serious repercussion on the design and durability requirement of bump stop. In the final stage of the study, test specification was developed for the target durability based measured duty cycle loads and component level SN generated experimentally. Results of the lab test samples were compared against field test samples to validate the methodology implemented. Good field to lab correlation was observed based on the analysis. The PU bump stop under evaluation was also found to meet the durability requirements.