Application of shell vibration theory to automotive muffler design and development

The muffler shell of an automotive exhaust system can cause numerous NVH (Noise, Vibration and Harshness) issues such as radiated noise, buzzing, rattling and implosion. In general, the problems are detected and solved after the mufflers are built and assembled in a vehicle, which are expensive and time consuming to correct at that stage. It would be beneficial to develop an analytical technique to predict the vibration behavior of a muffler shell during the early stages of exhaust system design. In this paper, shell vibration theories are investigated by comparing the solutions with the results from modal tests and finite element analysis. Utilizing these theories, an analytical model to predict the natural frequencies and mode shapes of muffler shells with circular cross section, elliptical cross section and cross section with two constant radii has been developed. A novel approach for accurately predicting the natural frequencies of muffler sections with two constant radii is also presented in this paper. Case studies are presented to demonstrate that the theoretical analysis can be applied effectively to predict and solve NVH issues of muffler shells.