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Su, Y. H.; 及川 健一; 篠原 武尚; 甲斐 哲也; 堀野 孝*; 井戸原 修*; 三阪 佳孝*; 友田 陽*
International Journal of Fatigue, 174, p.107729_1 - 107729_12, 2023/09
被引用回数：3 パーセンタイル：84.61(Engineering, Mechanical)A novel procedure, double induction quenching (DIQ), effective for improving the fatigue strength of gear products, has been used for producing gears with steep gradients of compressive residual stress generated in the tooth surface. We performed a Bragg edge imaging experiment at a pulsed neutron source to determine the spatial distribution of the {110} lattice spacing (d
) and the broadening of the {110} Bragg edge (w) on the DIQ gear product after tooth-bending fatigue tests to which different loading cycles were applied. No significant difference occurred in the d and the wat Hofer 's critical section of the teeth with different loading conditions within the accuracy of data analysis. However, we detected a decrease in the w and changes in the residual lattice strain distribution in the axial direction along the tooth root directions at the opposite side of Hofer 's critical section for both teeth after 3
10 
and 810 cycles, relieving the compressive residual stresses during the fatigue process. The residual stress close to the gear tooth surface determined by X-ray diffraction using sequential polishing showed a slight relaxation and redistribution from the tensile side in the hoop direction, complementary to the neutron Bragg edge imaging.
Zhang, H.*; Wu, S. C.*; Ao, N.*; Zhang, J. W.*; Li, H.*; Zhou, L.*; 徐 平光; Su, Y. H.
International Journal of Fatigue, 166, p.107296_1 - 107296_11, 2023/01
被引用回数：4 パーセンタイル：59.01(Engineering, Mechanical)Abnormal damages in railway axles can lead to a significant hazard to running safety and reliability. To this end, a surface treatment was selected to effectively inhibit fatigue crack initiation and growth. In this study, a single edge notch bending fatigue test campaign with artificial notches was conducted to elucidate the fatigue crack non-propagation behavior in railway S38C axles subjected to an induction hardening process. The fatigue cracking behavior in the gradient structure was revealed by optical microscopy, electron backscatter diffraction, and fractography. The microhardness distribution was measured using a Vickers tester. The obtained results show that the microhardness of the strengthening layer is nearly triple that of the matrix. Owing to the gradient microstructures and hardness, as well as compressive residual stress, the fatigue long crack propagates faster once it passes through the hardened zone (approximately 2.0 mm in the radial depth). Thereafter, local retarding (including deflection, branching, and blunting) of the long crack occurs because of the relatively coarse ferrite and pearlite in the transition region and matrix. Totally, this fatigue cracking resistance is reasonably believed to be due to the gradient microstructure and residual stress. These findings help to tailor a suitable detection strategy for maximum defects or cracks in railway axles.
Lejeail, Y.*; 笠原 直人
International Journal of Fatigue, 27(7), p.768 - 772, 2005/00
被引用回数：25 パーセンタイル：62.53(Engineering, Mechanical)流体温度ゆらぎによる構造物の熱疲労現象は熱流動と構造の両分野に亘る複雑な問題であり、従来その評価にはナトリウムモックアップテストが必要であった。本問題に対する解析による設計法を確立するため、CEAとJNCは評価法の開発を行ってきている。流体温度ゆらぎに対する構造健全性に対して、流体から構造への伝達過程で生じる温度ゆらぎの減衰作用が重要な役割を果たすことが知られている。その減衰の大きさは周波数に依存することから、評価法検証のために周波数制御ナトリウム試験データを用いたベンチマーク問題を計画した。一つはCEAから出題されたもので、温度が周波数制御された平行流を受ける管と平板の温度および疲労評価に関する問題である。もう一つのJNC出題の問題は、周波数制御された垂直ジェットを受ける平板の評価に関するものである。両者の実験の疲労評価結果が比較された。
