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Using a finite element approach, a technique for optimization of an exhaust system design was developed. This technique involved the creation of the parameterized model, implementation of the loading and finally the optimization of the model. In the creation of the finite element model, pipe elements were used. Parameters were assigned to the structure using coordinate relations between nodes, instead of the positions of the nodes in coordinate space. The model was then verified using modal analysis. A random vibration analysis was used as a loading criterion for the model, as well as static gravitational loading. The optimization of the design focused primarily on the shape characteristics of the structure and secondarily on each component thickness. Using only thickness parameters, a 15% reduction of the weight of the system was achieved, with an additional 2-3% decrease in weight possible through shape optimization.

Catalytic converters are typically constrained and cushioned by an intumescent mat material that is critical to the durability of the ceramic and metallic substrates. In an effort to reduce costs and improve designs, this work attempts to develop and verify a material model for the mat that can be utilized in predictive analysis. Test data are used in conjunction with the finite element program ABAQUS™ to create both a hyperfoam and a user-defined material model. These models will be verified and compared by modelling with ABAQUS the specimens and test conditions used to generate the data.

Non-linear FEA models are applied to three different catalytic converters, with the objective of predicting structural parameters such as shell deformation, push-out force, and mounting-system contact pressure under various conditions. The FEA modeling technique uses a novel constitutive model of the intumescent mat material typically found in ceramic-monolith converter designs. The mat constitutive model accounts for reversible and irreversible thermal expansion, allowing for the prediction of the one-way converter deflection observed in hot durability tests. In addition to this mat material model, the FEA methodology accounts for elastic and plastic shell deformation, contact between materials, and a three-dimensional temperature field in the shell and mat. For each of three designs, predictions are presented for converter canning, heat-up, and cool-down (i.e., post-heating) conditions.