Mechanical Strength of a Metallic Catalytic Converter Made of Precoated Foil 900505
Recent developments have shown the feasibility of catalytic converters with metallic substrates having increased endurance strength. However, drawbacks still exist similar to those found in converters with ceramic substrates. This paper discusses a method of manufacturing which avoids these drawbacks by rolling straight and corrugated foils into a cylindrical or oval form. In this case, the foils are precoated with support material and a catalyst layer, thus, fixing of the substrate by brazing or welding is not feasible.
Results of a research program to develop a pin-type mechanical bracing, which pierces the substrate, are described. Load distributions from foil to pin are calculated. The principles of fracture mechanics and plastic limit analysis are used to predict cracking and yielding type failure of foils adjacent to the pin. Different pin shapes are compared both theoretically and experimentally.
In experiments, crack propagation is tracked by making inspection holes into the substrate and unknown fracture mechanics material parameters can be calculated from test data. As a result it is found that, by special design of the pin, it is possible to control the fracture mode and rate of the foil substrate, and to stay below the crack propagation threshold value.
Both the laboratory and in-field tests have proven that the presented mechanical pin-type bracing, provides adequate strength, and allows the full utilization of the many advantages of the metallic catalytic converter.