Methodology for Durability Evaluation of an Automotive Trailing Arm Damper Pin Using Road Load Spindle Acceleration

Suspension system is one of the most important systems in an automobile and the failure in the sub systems or parts would prove catastrophic. A semi-trailing arm (STA) suspension is an independent rear suspension system for automobiles where each wheel hub is located only by a large, roughly triangular arm that pivots at two points onto the chassis or the body. STA usually is subjected to three directional loads viz. vertical, longitudinal and lateral in service. The conventional methodology of validating the system is by applying multi-axial loads or by road load simulation consuming significant amount of time. In this paper an attempt is being made to validate the damper mounting pins by reproducing the damper loads locally instead of validating the entire system. STA was strain gauged at the critical locations and was mounted onto the vehicle. Accelerometer was mounted onto the wheel spindle and a displacement transducer (LVDT) was mounted parallel to the damper mounted to the body and the STA. The vehicle was run on the test tracks and the corresponding STA strain, spindle acceleration and damper displacement was recorded. The acceleration data was converted to velocity of the spindle which was then transformed to damper velocity. Range-mean histogram of the damper was plotted. Velocity vs damping force characteristics of the damper was generated. A test rig has been created where the actual damper has been replaced by a metal adapter and loads have been applied using a servo-hydraulic actuator. Forces corresponding to the observed velocities have been applied onto the pin and the corresponding strains have been recorded. These values were then compared to the vehicle level strains observed initially. This methodology reduces the test time and the complexity involved significantly.