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Regeneration capability of a wall-flow monolith type diesel paticulates filter with an electric heater was studied. To prevent filter crack generation and unburned particulates accumulation, a precision controller was added to the test equipment to reduce thermal load. In order to control the supply of oxygen to potentially prevent cracking, a second air feeder was also added. Furthermore, to ignite the accumulated particulates uniformly and propagate extensively to burn accumulated particulates completely a newly improved heater unit was employed. Repeated regeneration tests were conducted with cars on a chassis dynamometer. Though crack generation and unburned particulates accumulation were reduced considerably, satisfactory prevention could not be achieved. Therefore a parameter study using regenerative burning and thermal stress analysis model was carried out.

A method of fatigue life estimation for the spot-welds of vehicle body structures by means of Finite Element Analysis (FEA) was studied. 6 general forces applied to a nugget of spot-weld under multiaxial loads were determined and the Nominal Structural Stress (σns) was calculated from them. It was confirmed that fatigue strength of the spot-welds under various multiaxial loads could be estimated universally by using σns. Based on the theory of elasticity of plates, stress of spot-weld nugget was analyzed. The theoretical equations for determining the principal stress at the nugget edge from6 general forces acting on a nugget were derived. And the principal stress was defined as the σns. The value of σns was determined by FEM that used a solid model and compared with the theoretical calculation value. They agreed quite well. Fatigue tests of DC specimens under various multiaxial loads (shear plus cross tension and tensile shear plus torsion) were conducted.