An investigation into the Structural Impacts of Off-Road Manoeuvres on Rear Axle upper Link Mounting Bracket

Multi-link rigid axle suspension is widely used as a rear suspension system for body-on-frame SUVs. The upper link in a multi-link rear suspension plays a critical role in managing the vertical and longitudinal positioning of the axle, while the lower link ensures stability by regulating the axle's movement in the horizontal plane. This coordinated functionality of upper and lower link allows for controlled axle dynamics during compression and rebound, significantly enhancing ride comfort and improving vehicle handling characteristics. This study examines the failure of an upper link mounting bracket on the rear axle of an SUV during off-road events, despite no failures observed in other durability tests. Root cause analysis is conducted on failed samples to determine the specific reasons for failure only in off-road conditions. Additionally, the investigation focuses on understanding the dynamic loads experienced by the upper link during vehicle operation across various durability tracks, identifying their contribution to the observed failure. Using Road Load Data Acquisition (RLDA) techniques, loads at the mounting bracket location are measured while running the vehicle on different terrains. The acquired data enables to understand maximum stress acting on the bracket and which terrain is worst case for the bracket failure. The study further employs the finite element method (FEM) to develop a detailed FE model of the rear axle and upper link mounting bracket. The model is subjected to measured dynamic loads to analyse stress distribution and evaluate its impact on durability. Various design proposals are explored to enhance durability and mitigate stress concentrations, aiming to prevent structural failure. Based on the analysis, the study provides design improvement recommendations to ensure reliability and robustness. These insights are vital for manufacturers striving to produce high-performance SUVs capable of enduring demanding off-road manoeuvres and conditions.