1)

Improvement of Metal Fatigue Strength by Grain Refinement and Residual Stresses

Keisuke TANAKA1)

AbstractThe paper presents various methods to improve the fatigue strength of metals by reducing the grain size and introducing the residual stress. Based on the recent understanding of fatigue mechanisms, the quantitative analysis of the effects of material grain size, micro defects and the residual stress on the fatigue strength of metallic materials is described. The current state-of-art of the nondestructive measurement of the residual stress using X-rays, synchrotron and neutrons is reviewed. Possible future developments of the technology to improve the fatigue strength are proposed.

1.

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67

1) 理工学部

1) Faculty of Science and Technology

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W fK

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(1) (mean stress model)

(2) (point stress model)

(3) (fictitious crack length model )

Fig. 2

II(1)(2) area(3)

Fig. 1. Relation between fatigue strength and grain size.

Fig. 2 Reduction of fatigue strength by defects.

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材料組織の微細化と残留応力による疲労強度の向上 名城大学理工学部研究報告 No.48 2008

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Fig. 3(a). A fatigue crack in fine-grained steel.

Fig. 3(b). Distribution of stress around fatigue cracak.

69

材料組織の微細化と残留応力による疲労強度の向上 名城大学理工学部研究報告 No.48 2008

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[14]

70

材料組織の微細化と残留応力による疲労強度の向上 名城大学理工学部研究報告 No.48 2008

（原稿受理日　平成 19 年 9 月 25 日）