抄録
In order to determine the yield criteria for metal powder undergoing compaction and to ascertain the effect of shear stress on the densification, triaxal compression tests were made on iron, copper and aluminium powders under hydrostatic confining pressure up to 600 MPa. The yield criteria for these powders changed gradually from a Mohr-Coulomb type at low hydrostatic confining pressure under 200 MPa to a Tresca type with increasing the confining pressure. The angles of internal friction measured on iron, copper and aluminium powders at low confining pressure were 14.7°, 13°and 9.7°respectively. During triaxial compacting, these powders were densified abruptly at the outset of yielding and successively densified through three stages, and the mean normal stress required to obtaining the compact of a given density was 50-65% lower than that in the isostatic compaction. The structure of produced compact showed a remarkable plastic deformation of particles in the shearing direction.
