An Approach for Dynamic Response Correlation of Exhaust System between Measurements and FE-Simulations 2010-01-1569

Study and design of the lifetime durability of mechanical components in an automotive exhaust system becomes a challenging task today for engineers. During the investigation, both experimental tests and finite element simulations are used for the investigation under dynamic engine excitations. For the dynamic finite element analysis, the experimental system must be simplified as a linear mathematic model and real boundary conditions are idealized. Due to this simplification, the dynamic behavior of the finite element model may strongly deviate from that in operational conditions. To gain insight into the dynamic behavior of exhaust systems from simulations, the finite model must be modified based on experimental results.

As known the harmonic response is related to modal shapes and engine loads. Therefore, modifications of the finite element model can be done from these two aspects. Tenneco has developed an approach for correlation between measurements and FE simulations with respect to the harmonic response in full exhaust systems. In this approach model updating and input load compensation are combined. To evaluate the dynamic response correlation between measurements and FE simulations, the Modal Assurance Criterion (MAC) is used which gives a global number between 0 ~ 1 for how good the correlation is between the two. By use of this approach, MAC values are improved and the validation process of the finite element simulation is speeded up. Tenneco has been making efforts to validate FE simulations with respect to computational speed and robustness. This tool provides an important contribution to this objective.