Modal Analysis of Exhaust System to Optimize Mounting Hanger Location

Abstract

An exhaust system with a superior performance becomes unserviceable if its durability is insufficient, for example, due to excessive level vibrations. This excessive level of vibration caused by various excitation forces from engine and road surfaces are transferred on to the exhaust hangers which plays a vital role in clamping the exhaust systems in proper place, thus damaging the hangers much before its service life. Hence it becomes obligatory for NVH engineers to optimize the hanger location so that it undergoes minimum damage, thus increasing its durability. This paper presents a modal analysis approach for optimizing the hanger location using FEA and comparing the results with experimental modal analysis. For FEA technique, Hypermesh was used as a pre and post processor whereas Nastran was used as a solver. The methodology adopted here was to determine node and antinode points on the exhaust system so that the mounting hangers can be shifted to node points. Hence after the identification of critical frequencies, its mode shapes were analyzed to identify optimum hanger location. Further the results were compared by performing experimental modal analysis using LMS Data Acquisition System.