ロックウェルかたさの誤差について : 第4報, 鋼球圧子の永久変形の影響

概要

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In the "Testing method of Rockwell hardness", JIS Z 2245 (1955), it is prescribed that the difference of diameter of a steel ball between two directions, the direction of loading and perpendicular to it, should not exceed 0.01mm. Permanent deformations were made in normal steel ball by indenting on materials hardness of which is over H_RB 100. The author made an experiment about the effect of this deformed steel ball on the hardness value of H_RB. The author have obtained the following results : Even with the same amount of permanent deformation, the effect differs according to the deformed form, in one case the errors ΔH_RB increase proportionally to H_RB of specimens, in other case ΔH_RB decrease, and in the third case ΔH_RB have little relation with H_RB. The author tried simple but reasonable consideration about the classification of these cases, applying the enlarged Meyer's law, and reached almost the same conclusion with the experiment. The author now conclude that the permissible limit of 0.01mm of amount of permanent deformation prescribed in JIS is too larger, and the permissible limit should be 0.02mm.
一般社団法人日本機械学会の論文
1961-04-25