はめあい軸の疲労強度に及ぼすひずみ時効の影響

概要

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In order to clarify the effect of strain-aging on fatigue strength, rotating bending tests were made on interference fitted car axles, φ12 mm and φ50 mm, aged after cold surface rolling as well as on those subjected to warm surface rolling. The results obtained are as follows; (1) The microstructure of specimen was hardly changed by aging, but the surface hardness was increased by 1.1 times in comparison with the cold rolled specimen due to strengthening of ferrite. (2) The surface compressive residual stress of the aged specimen was 400 MPa and the depth of hardened layer was 4 mm. Then in comparison with the cold rolled specimen, the residual stress was decreased by 50 MPa and the depth of hardened layer increased by 2 times. (3) The maximum value of fatigue strength of the press-fitted specimen of φ50 mm was obtained at 300℃ aging. The value was 216 MPa, 1.1 times in comparison with the cold specimen and 2 times in comparison with the normalized specimen. Because of the size effect, the fatigue strength of the φ50 mm aged specimen was decreased by 0.9times in comparison with the φ12 mm aged specimen. (4) The fatigue strength of the aged specimen was closer to that of the warm surface rolled specimen than that of the cold rolled one.
1983-09-15