Search Results

The converter assembly consists of a ceramic monolith with racetrack cross-section, a suitable “springy” mat wrapped around it and a clam-shell steel can to contain and guard these components against road hazards. The process to effect this assembly is rather dynamic and introduces directional loads onto the monolith in view of the anisotropic stiffness of the can. If these loads exceed certain values, they may cause failure of the monolith either by crushing it or by shearing it. In this paper we analyze the stiffness of various components of converter assembly, determine the load distribution around the monolith, and modify the design of can and monolith to make the load distribution more favorable. It is concluded that the converter assembly can be optimized and the failure of monoliths, if any, eliminated during closure. The present monoliths do not suffer from such failure.

Ceramic honeycomb structures have been used successfully as catalyst supports in gasoline-powered vehicles for the past ten years. They are currently the leading candidate for trapping and oxidizing the carbonaceous particulate emissions in diesel-powered vehicles. In both of these applications the long term durability of the ceramic substrate is of prime importance. This, in turn, depends on the physical properties of cellular structure, cyclic nature of service loads and design of the mounting assembly. This paper examines the nature and dependence of both the mechanical and thermal stresses in the substrate on its geometry, properties, mounting parameters, and the operating conditions. It also compares the observed failure modes with those predicted by the theory. The paper concludes with a set of recommendations for optimal systems design and acceptable operating conditions which will promote the long term durability of the ceramic substrate.