Stress Analysis in Automotive Vacuum Booster

The reliability of automobile brake components is a very important issue from the point of view of safety. This thesis presents a combined experimental and numerical stress analysis of a vacuum booster. The booster consists of a thin-walled, closed shell that contains a diaphragm and a mechanical control system. The master cylinder which provides hydraulic pressure to the components on the wheels, is mounted directly on the booster shell using threaded bolts. The booster under consideration developed crack near one of these bolts during an endurance test. The numerical stress analysis conducted here demonstrated that significant stress concentration can be present on the booster shell near these mounting bolts. The numerical model was validated by direct comparison of meridional strains to experimental measurements at selected locations. The results also showed that increasing the wall thickness of the booster by 25% would allow the booster to successfully complete the endurance test.