DURABILITY COMPARISON AND LIFE PREDICTIONS OF COMPETING MANUFACTURING PROCESSES: AN EXPERIMENTAL STUDY OF STEERING KNUCKLE

The objective of this research program was to compare fatigue performance and assess fatigue life of steering knuckles made from three materials of different manufacturing processes. These include forged steel, cast aluminum, and cast iron knuckles. Fatigue behavior is a key consideration in design and performance evaluation of steering knuckle, since it is subjected to repeated loading during its service life. Forging process was considered as the base for investigation and other processes were compared to it, mainly due to the high volume of forged steel vehicle components. Strain-controlled monotonic and fatigue tests of specimens machined from the three knuckles were conducted. From these experiments, monotonic as well as baseline cyclic deformation and fatigue properties were obtained and are compared. In addition, a number of loadcontrolled fatigue component tests were conducted for the forged steel and cast aluminum knuckles. Finite element analysis of the steering knuckles was also conducted to obtain stress and strain distributions in each component. Based on the results of specimen testing and finite element analysis, life predictions were performed. The predicted lives are then compared with the experimental component test results.