ポリスチレン粉体圧縮成形体の三軸圧縮特性

概要

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Powdered polystyrene which was prepared by grinding at a temperature of liquid nitrogen was compacted into a cylindrical shape for a triaxial compression test. These specimens having various void fractions n_0 were compressed at various confining pressures σ_3. The mode of fracture of the specimens changed with an increase in a3 or no from axial cleavage fracture to typical shear fracture, and then to shear fracture accompanied by consolidation. Yield loci were obtained from Mohr's stress circles using σ_3 and the axial stress σ_1 corrected by Taylor-Bishop's method. The yield criterion was expressed by τ^2 =μ_t^2σ^2+4σ_t(1+μ_t^2)(σ+σ_t), where τ is shear stress, σ is the normal stress, μ_t, is a constant, which is related to the sliding friction between particles and is close to the coefficient of effective internal friction, and σ_t is a constant corresponding to the tensile strength of the powder compact. The criterion can be related to the mechanisms of fracture of powder compacts. The second term of the criterion is larger than the :first one under the condition where n_0 and σ_3 are small ; in this case the specimens showed axial cleavage fracture which is characteristic of brittle materials. For larger values of n_0 and σ_3, on the other hand, the first term is larger than the second, and the specimens showed shear fracture.
社団法人日本材料学会の論文
1981-01-15