Moriya Oyane

Effect of Tool-Workpiece Contact Length on Lubrication in Metal Forming

Influence de la longueur de contact outil-piece sur la lubrification dans le formage des metaux

Residual Stresses in Copper Rod Manufactured by Hydrostatic Extrusion and Its Hardness

Hereunder is presented a report of hydrostatic extrusion of pure copper performed of commercial stuff at the extrusion ratios from 1.2 to 3.6, inclusive of the die angles from 20°to 90°. The residual stress distribution in it and its Vickers hardness distribution have also been determined.The residual stresses in it have been measured by Sachs method utilizing its drilling and chemical erosion. There have been found to exist, on the surface of the extruded rod, residual tensile stresses in its longitudinal and tangential directions. The longitudinal tensile stress decreases with increasing extrusion ratio. The die angle has little effect on the residual stress distribution at the extrusion ratio of 2.0.The hardness is determined as the mean of the values obtained in more than five experiments, and it is found that the value of hardness on the surface is larger than that at the center, and that this tendency becomes marked at low extrusion ratio and or at larger die angles. Theoretical calculation of hardness distribution is carried out assuming a velocity field, which gives a lowest extrusion pressure when upper bound solution is applid. The calculated hardness distribution is in fair agreement with the experimental results except for those at low extrusion ratios.

Plastic Deformation of Metals and the Octahedral Shearing Stress Theory (2nd Report)

The experiments were carried out to study the stress-strain relation in the metal under combined stress condition. In the case concerning the 1st report, the tubular specimens of 0·4%C steel with the open ends or the closed ends were at the first time deformed up to plastic range by internal oil pressure, which was removed soon, and then the specimens were subjected to tensile force in the axial direction. Experimental results : (1) The more severely the specimens with the closed ends were strained in the pressure tests, the greater the material was strain-hardened by the tensile strain except the non-prestrained specimen. (2) In the case of the specimens with the open ends, the elastic limits became lower with increase in the amount of the prestrain, while strain-hardening by tensile strain was greater in the range of large strain.