Abstract
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 Vicker's hardness distribution have also been determined.
The residual stresses in it have been measured by Sach's 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.
