白點状缺陷に關する研究 (IX) : 白點状缺陷發生を困難ならしめる條件について

概要

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In former experiments, the condition to form easily the flake-like defects has been studied. But in this experiments the condition to impede the flake formation is studied. The results are summerized as follows : (1) Notch engraved on the side of tensile and bending test piece impede the flake formation. (2) On the fracture of pickled Izod and Charpy test pieces, no flake-like or fish-eye-like defects are appeared. (3) On the fracture of pickled tensile test pieces, no defects are also appeared, if it be broken by shockness. But if the same test piece be broken more slowly (for example, by the Amsler testing machine), the flake-like defects appear clearly. From this experiment the flake formation of the pickled test piece is affected remarkably by its breaking speed. (4) This result suggest us that the action of outer stress is to assist the concentration of supersaturated hydrogen at the supermicroscopic holes in the mosaic boundary or similar substructure or others, and both, inner stress of concentrated molecular hydrogen and outer stress are the essential factors for flake formation.
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