Structural Validation of Hanger Brackets in Exhaust Systems: Correlation Between Virtual Simulation and Experimental Testing and Its Optimization

Since the last decades, the engineering design activity has shifted from manual drawings and dimensioning calculations to their computer-aided versions. Nowadays, in the industrial field, any manufactured product, as well as its characteristics and the operational processes necessary to build it, is designed and simulated in advance exploiting the computational capabilities of computers. By virtue of this technological improvement, design modifications are applied easily and their effects are checked instantaneously, allowing a reduction of the product development time. Once the iterative adaptation process has finished, the project is validated. Although virtual analysis results, manufactured goods have to be tested in a physical manner to confirm that the final objects comply with the imposed requirements. Here, a second validation arises. As a matter of fact, the two validation methods differ because of the impossibility of replicating identically the physical test in a virtual environment. To overcome this obstacle, simplifying assumptions are considered, but this unavoidably creates differences. The aim of this Thesis project is to analyze the two structural validation methods (experimental and virtual) to understand the dissimilarities and the effects that they exert on the correlation and to propose new validation procedures that provide more correlated results between the two methodologies. The present work is the summary of six months of internship within the Exhaust Systems R&D Testing department at Magneti Marelli S.p.A., an italian industry with worldwide diffusion devoted to the production of automotive components. The focuses of the investigation are the structural validation methods of hanger brackets in exhaust systems. After the introduction of the state-of-the-art methods adopted by the Company for the fatigue life validation in exhaust hanger brackets, a complete case study analysis provides the evidence of the inconsistencies related to the procedures. Different alternatives to the usual methods are proposed: evaluation of load levels on each bracket equivalent to the experimental driving test, different computational validation method based on structural vibrational analysis and identification of an average cumulative load curve, reveal to reduce the gap between the methodologies. Eventually, some guidelines for the verification and application of the innovative validation dispositions are proposed.