Analysis of Front Suspension Ball Joint Separations in Motor Vehicle Crashes

In crash analyses, components or component assemblies are evaluated to identify if they were damaged as a result of the crash or if they lost function prior to the crash. Determining the circumstances that cause a component to become disabled can be useful when evaluating the cause of a crash. This study focuses on spherical ball joints commonly used in automotive suspension systems. Analyses can include the evaluation of the ball joint itself, the surrounding components, evidence at the scene, and the circumstances of the specific crash. In this study, the causes and conditions for a ball joint separation are analyzed, in part, through both component level testing and full vehicle testing. Laboratory tests were performed on upper ball joint assemblies where loads were applied in multiple directions and the residual damage to the components was measured and documented. Full vehicle testing was performed to analyze vehicle response to suspension ball joint separations on independent front suspensions. A lower ball joint separation test was conducted with the staged ball joint separation occurring as the vehicle was being operated. An upper ball joint separation test was conducted by disconnecting the upper ball joint prior to testing and evaluating the modified vehicle response to driver inputs. Residual damage to suspension, components, and the test surface were analyzed as well. Case studies of ball joint separations are presented and compared to the controlled test results.