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It is essential to attain accurate understanding of vehicle service loads for customer usage and to reflect this understanding into development test conditions established to ensure strength and durability. The Road Load Standardization Subcommittee* of the Japan Society of Automotive Engineers (JSAE) Fatigue and Reliability Committee has therefore employed direct measurement and new analytic methods in an attempt to quantify Japan-wide on road service load data. This quantified data has been used as the basis to standardize road loads for a wide range of vehicle categories. The following were major considerations in the implementation of this research: Employment of a 6 degree of freedom (6DOF) wheel force transducer (increased measurement accuracy) Identification of load from road input vs input from driving operation generated.

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.