Catalytic Converter Design from Mat Material Coupon Fragility Data

Automotive catalytic converters must provide a very high level of mechanical and thermal durability to maintain performance during their 100,000 to 150,000 mile life expectancy. The work reported herein characterizes the converter as a base (can) excited spring (mat material) supported mass (substrate). A mat material coupon test apparatus was developed for the purpose of providing parameter data for the converter model in the form of stiffness and material loss factor data as a function of shear deflection across the mat. An intumescent mat material was chosen and its dynamic properties evaluated for a range of converter operating parameters. The mat material response properties were placed into a mat material database as a function of gap bulk density, substrate temperature, and temperature gradient across the mat. A series of canned converters employing the intumescent mat were then tested to provide frequency response data for comparison to corresponding predictions employing the mat material database and a proposed converter model.

It was found that the mat material exhibited a non-linear response with respect to shearing deformation exhibiting decreased stiffness and increased loss factor with increased shearing deformation. However, the mat material non-linear behavior could be adequately represented using a linearized single-degree-of-freedom (SDOF) system representation about the system resonant frequency. This research effort has resulted in new mat material test and converter design procedures to meet component extended life requirements.