Accelerated Lab Test Methodology for Steering Gearbox Bracket Using Fatigue Damage and Reliability Correlation

In the modern automotive sector, durability and reliability are the most common terms. Customers are expecting a highly reliable product but at low cost. Any product that fails within its useful life leads to customer dissatisfaction and affects the reputation of the OEM. To eradicate this, all automotive components undergo stringent validation protocol, either in proving ground or in lab. This paper details on developing an accelerated lab test methodology for steering gearbox bracket using fatigue damage and reliability correlation by simulating field failure. Initially, potential failure causes for steering gearbox bracket were analyzed. Road load data was then acquired at proving ground and customer site to evaluate the cumulative fatigue damage on the steering gearbox bracket. To simulate the field failure, lab test facility was developed, reproducing similar boundary conditions as in vehicle. Based on the damage analysis, customized lab test sequence was developed and field failure was simulated with the existing design samples. Reliability analysis was carried out and reliable life in lab test was correlated with the field. Lab cycle target for the intended vehicle life was derived by comparing the fatigue damage and reliability correlation. Improved design of steering gearbox bracket was validated in the same test conditions and compared with the life of existing design.