Kohichi Tanaka

Fretting fatigue in SUP9 spring steel under random loading.

The fretting fatigue strength of SUP 9 spring steel under random loading was examined by clamping the contact pads of the same material. Random loading reduced the fretting fatigue strengths by a factor of 1.5. The linear cumulative damage rule held good for fretting fatigue under random loading. The relationship between the coefficient of the friction and the slip amplitude using root-mean-square values under random loading agreed well with that under constant loading. Prediction of fatigue life was made on the basis of the fracture mechanics analysis proposed in the previous paper, where the frictional force between the fretting pad and the specimen was taken into consideration. The predicted lives were in good agreement with the experimental results.

Effect of density on mechanical properties and ductile fracture in a high strength sintered steel.

Tensile tests and fracture toughness tests of high strength sintered steel have been carried out to investigate the effect of density on mechanical properties, fracture strain and fracture toughness JIC. Youngs modulus was measured in two ways including tensile test with extensometer and ultrasonic pulse time method. Experimental data for Youngs modulus, 0.2% proof stress, tensile strength, elongation, true fracture strain and JIC were presented simply in the form after Salak et al with narrow scatter. Theoretical predictions for Youngs modulus, where it is assumed that the porosity is distributed as independent spherical holes in a homogeneous and isotropic matrix, gave higher values than the experimental data in the lower density region. The predictions of fracture strain and JIC were successfully performed by using a void model with effective diameter d and spacing 1 and a fracture criterion of δ=λo (=1-d).