予ひずみを施した7:3黄銅試験片の疲労限について

概要

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Either with the aim of studying the effect of the pre-strain one the fatigue strength of materials, or for the purposes of increasing fatigue strength, there have been investigators so many who have tested many materials with various amounts of pre-strain under repeated stresses, such push-pull, rotary or reversed bending, and reversed torsion with some of those having mean stress, and the results from these tests indicate that fatigue limit is generally increased by pre-strain. On the other hand, there have been reports that the fatigue limit of specimens that have been subjected to a small amount of pre-strain (just above yield point) drops below that of the original material. The above-mentioned facts are ascertained in this paper by the experiments with 7:3 brass specimens with electro-polished and pre-strained surface. The amount of pre-strain are 1.3, 5.3 and 8.7%. with 1.3% pre-strain, the fatigue limit decreases 8.3%. This phenomenon is explained by the fact that slips occurred in relatively weak grains on the surface of the specimen. the damage is retained and there is no artificial strengthening of the material. On the other hand, in the largely pre-strained state, the improvement by artifice is greater than the damaging effect due to the slip, and the fatigue limit is increased. By this consideration, the same phenomenon about notched prestrained specimens can also be explained.
社団法人日本材料学会の論文
1967-09-15