張り出し成形における延性破壊機構のフラクトグラフィによる研究

概要

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The ductile fracture mechanism of the in-plane stretching of 70/30 brass, OFHC copper, and 1100-O aluminum sheet alloys have been examined on the basis of fractography and modified M-K analysis. Dimples, which are a large number of elongated dimples and a small number of equiaxised dimples, and ripples are observed on every fracture site. The profiles of fracture are slant type for brass, cup-and cone type for copper, and chisel point type for aluminum. Observations of matched fracture sites by scanning electron microscope and on flow-line by optical microscope lead to the conclusion that the elongated dimples are shear dimples formed by a shear rupture toward the sheet thickness. The final strain conditions of the neck are almost identical to those assumed in the modified M-K analysis, indicating that the observed width of the fractured site is less than the theoretical one when the neck is reached under the plane-strain condition. These ductile fracture mechanisms are explained in terms of the shear deformation and dimple.
1987-07-25