Geometrical Properties of Two Yield Criteria for Powder Metallurgical Materials
HUA Lin, QIN Xun-peng (School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China)
The yield criterion for powder metallurgical materials was a key basis of genera lized plasticity theory. Therefore, the basic forms of two important yield crite ria for powder metallurgical materials were introduced in the paper. Based upon the physical and mathematical analyses, it was deduced that the yield surfaces o f square yield function and linear yield function were elliptical sphere and hex agonal pyramid respectively. If powder metallurgical materials were changed into fully dense materials, then the elliptical sphere and hexagonal pyramid would e volve into cylinder and hexagon bar respectively. The yield properties in uni-a x ial elongation or compression, plane stress and plane strain were intensively re searched, the related yield track equations were derived and the geometrical for ms of the yield tracks were determined. Some relationships between the two yield criteria for powder metallurgical materials were revealed in detail.