板の前方押出し加工のモデル実験

抄録

The model experiments of direct extrusion through the wedge-shaped dies have been executed. The material of the specimen is acetyloid, and four kinds of dies have been adopted, whose dimensions are: die half angle 15°, 10°and 0° and reduction ratio 1/4 and 1/2. The square grid lattice (0.5mm interval) are traced on the specimen and the photo-plastic isochromatic patterns and grid paterns are taken on the films. The fringe-order of the point on the central line of the vicinity of the die entrance always remains in zero fringe-order and the point is suppressed by the hydrostatic pressure. The distribution along the central line of the fringe-order and of the difference of the principal strains of the die (15°, 1/2, symmetry) has been measured. The latter vanishes on the above mentioned point.
The method of visioplasticity has been applied. By the measurement of the displacement vector of each material point on the grid lines, the strain-rate pattern has been obtained. According to the Lévy-Mises plastic equation the pattern of the directions of the principal shearing stress has been calculated. On the other-hand the slip-line field has been obtained in the case of the friction angle 7°. The two patterns are comparatively in good agreement. The analysis of the stress distribution is yet to be made.