No abstract

Damping characteristics degrade unavoidably in shock absorber's useful life. To study the effect of shock absorber degradation on NVH (Noise, Vibration and Harshness) performance of vehicles served in long term, double-action durability test was carried out on numerous shock absorbers. Afterwards, indicator diagrams and velocity characteristics of shock absorbers were obtained; damping coefficients were calculated at the pre-valve and postvalve opening. Based on the experimental result, a vehicle virtual prototype model was built by ADAMS/Car Ride. Then, vertical driver seat accelerations were measured, and weighted root-mean-square (RMS) accelerations were calculated at driver seat. In addition, influences of individual shock absorber degradation on vehicle high mileage performance were analyzed. The result shows that damping force degrades after durability test; the reduction rate of the weighted RMS acceleration is about 4.1%, while the increment rate is more than 7.5% at high mileage; the front-left shock absorber degradation causes a significantly worse vehicle NVH performance among the 4 individual one.