Developing a Robust Process for Design Margin Calculation Through Modal Scaling and Harmonic Analysis of Engine Mounted After Treatment System

Abstract: The last few years have seen an increase in the complexity of emission standards. This has caused OEMs to start using Exhaust Gas Processors (EGP) or Exhaust After Treatment Systems (EATS)in complex integration. These systems are usually mounted on vehicle chassis or engine body with the help of mounting straps or brackets. The arrangement of the system leads to road loads and/or engine vibrations being transferred and causing damage to its components. New BS VI engines need some AT (After treatment) components to be mounted directly on the engine and others to chassis. The components that are directly mounted on engine are called close couple AT system which are subjected to engine harmonic vibrations which falls under forced vibration criteria. Most of the AT system are subjected to random vibrations and industry has a well-defined procedure to address the problem, but for harmonic vibrations there is no specific approach. In order to optimize the structural durability of close couple AT system against HCF (high cycle fatigue) fatigue harmonic vibration, there is a need for well-defined test analysis correlation procedure. The objective of this work is defining and documenting a robust process for design margin through calculation modal scaling and harmonic analysis of close couple AT system through test analysis correlation activity. Analytical, numerical and testing data were compared and conclusions are drawn. More case studies can be added to this work in order to validate the test analysis correlation activity and boost the degree of confidence. Future study may include recording additional failure modes in addition to the harmonic HCF failure mode.