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Hu, F.-F.*; Qin, T.-Y.*; Ao, N.*; 徐 平光; Su, Y. H.; Parker, J. D.*; 篠原 武尚; 菖蒲 敬久; Kang, G.-Z.*; Ren, M.-M.; et al.
Journal of Traffic and Transportation Engineering, 25(2), p.75 - 93, 2025/04
To accurately predict the remaining lifetime of surface-strengthened railway axles, a damage tolerance method considering three-dimensional (3D) residual stresses was proposed. By taking the induction-hardened carbon steel S38C axle as an example, two-dimensional (2D) distribution characterization of residual strain and 3D residual stress measurement were performed through comprehensive application of the neutron Bragg-edge transmission imaging and angle-dispersive neutron diffraction experiments. A numerical method was employed to implant the 3D residual stress into the axle model, and the remaining lifetime of the full-scale axle was studied by coupling the measured load spectrum, press-fit loads, and residual stresses. Experimental results shows that, both axial and hoop directions present a compressive residual strain gradient layer of about 3 mm, with a maximum compressive residual strain of up to -4500 
in the surface layer, yet a maximum tensile strain of up to 1000 in the core. The maximum axial and hoop compressive stresses of the axle are about -500 MPa and -303 MPa respectively, while radial stresses overall fluctuate in the zero mean stress range. At depths beyond 4.5 mm from the surface layer, all three components are tensile stresses. The axle surface layer is subjected to compressive residual stresses, and crack propagation does not occur if the crack depth is less than 4.5 mm. Nevertheless, cracks propagate accelerates when the crack depth is greater than 4.5 mm. Different crack propagation depth thresholds lead to a larger calculated remaining lifetime for the residual stress-free condition than for the case where 3D residual stresses are taken into account. However, the axle remaining service mileage of the axle of 227000 Km under the most conservative conditions exceeds 3.5 non-destructive inspection (NDI) cycles, with a large safety margin. The experimental results can provide a scientific reference for the development and optimization of NDI cycles for surface-strengthened railway axles.
Hu, F. F.*; Qin, T. Y.*; Ao, N.*; Su, Y. H.; Zhou, L.*; 徐 平光; Parker, J. D.*; 篠原 武尚; Chen, J.*; Wu, S. C.*
Engineering Fracture Mechanics, 306, p.110267_1 - 110267_18, 2024/08
被引用回数：2 パーセンタイル：55.14(Mechanics)Non-destructive and quantitative mapping of gradient residual strain distribution in surface-hardened railway S38C axles could provide a positive reference for determining service lifetime and maintenance strategy. To tackle this concern, time-of-flight neutron Bragg-edge transmission imaging was employed by real axle samples with and without impacted crater. A novel and simple procedure to formulate the residual strain field was also developed in this work, with the transmission batch code in Appendix A. By mapping the global two- dimensional residual strains, it can be verified that the residual strains into the axle are uniformly distributed in the hoop direction. Subsequently, it was revealed that the axial and hoop residual strains, respectively in the cylinder and the long strip samples prepared from a real S38C hollow axle, indicated a gradient evolution distribution with a depth of 
8 mm, covering a range of -5500 1000 for axial strains and -6500 1000 for hoop strains. More importantly, the maximum compressive lattice strain of the cylinder sample was increased by 15.61%, and 22.35% at the impacting speeds of 100, and 125 m/s, respectively; and that of the long strip sample increased by 29.17%, and 43.70%, respectively. It can thus be concluded that lattice strains have redistributed around the impact crater, demonstrating the local alteration of the residual strain field. These new findings suggest the localized variation in residual strains should be taken into account while evaluating the service damage evolution of railway axles, especially those affected by high-speed impacts during operation.
Qin, T. Y.*; Hu, F. F.*; 徐 平光; Zhang, H.*; Zhou, L.*; Ao, N.*; Su, Y. H.; 菖蒲 敬久; Wu, S. C.*
International Journal of Fatigue, 185, p.108336_1 - 108336_13, 2024/08
被引用回数：9 パーセンタイル：93.27(Engineering, Mechanical)Gradient distribution of triaxial residual stresses to a depth of several millimeters is retained in middle carbon steel S38C axles after high-frequency induction hardening, which has become a critical concern for fatigue structural integrity. To address this, the axial, hoop, and radial gradient residual strains inside the axles were measured for the first time by advanced neutron diffraction. The SIGINI Fortran subroutine was then adopted to reconstruct the global initial residual stress field from the measured data. Experimental and simulation results show that residual stresses of about -520 MPa (axial), -710 MPa (hoop), and -40 MPa (radial) residual stress were retained below the axle surface. Subsequently, the fatigue crack propagation behavior of S38C axles was numerically investigated in the framework of fracture mechanics. The calculated results clearly show that the compressive residual stresses at a depth of 0?3 mm from the axle surface lead to a low crack growth driving force, and that fatigue cracks do not propagate as long as the crack depth is less than 3.7 mm for hollow S38C axles. These results further indicate that the maximum defect size allowed in routine inspections is acceptable from a safety and economic point of view. Accurate measurement and characterization of the global gradient residual stress field through experiments and simulations can provide an important reference for optimizing the mileage intervals of nondestructive testing (NDT) of surface defects in these surface-strengthened railway axles.
Zhou, L.*; Zhang, H.*; Qin, T. Y.*; Hu, F. F.*; 徐 平光; Ao, N.*; Su, Y. H.; He, L. H.*; Li, X. H.*; Zhang, J. R.*; et al.
Metallurgical and Materials Transactions A, 55(7), p.2175 - 2185, 2024/07
被引用回数：3 パーセンタイル：70.74(Materials Science, Multidisciplinary)High-speed railway S38C axles undergo surface induction hardening for durability, but are susceptible to fatigue cracks from foreign object impact. The neutron diffraction method was employed to measure the residual strain in S38C axles, obtaining microscopic lattice distortion data, for the gradient layer at a depth of 8 mm under the surface. The results showed that after induction-hardening, the microscopic lattice distortion had a gradient distribution, decreasing with the distance from the surface. However, in the case of impacting speed of 600 km/m, the average microscopic lattice distortion increased with the distance from the surface, reaching a maximum augmentation of 55 pct. These findings indicate a strong experimental basis, and improve our understanding of the relationship between macroscopic residual stress and decision-making, in regard to operation and maintenance.
Hu, F. F.*; Qin, T. Y.*; Su, Y. H.; Ao, N.*; Zhou, L.*; 徐 平光; Parker, J. D.*; 篠原 武尚; Wu, S. C.*
no journal, ,
High-frequency induction hardened S38C axles are widely applied in Japan Shinkansen and China bulletin trains. Due to well-designed surface treatment, these axles produce a large gradient change in the material structure from the axle surface to the core, resulting in a large-layer depth of residual strain and microhardness. It is well known that the residual strain of a real component is of great importance for its long-cycle service assessment, mainly at the reduced non-destructive detect interval and low maintenance cost. Fortunately, the neutron beam has a high penetrating capacity, which provides the advantage of using Bragg-edge transmission imaging to characterize the residual strain and microstructure inside large engineering components. In our study, ring shaped specimens of the axle were prepared. The neutron transmission imaging experiments were conducted at RADEN in J-PARC MLF under proposal Nos. 2022A0298 and 2023A0069. The obtained results reveal that the 0-5 mm area of the axle surface is compressive residual strain, while the core region is the combination of the tensile residual strain and the compressive residual strain. In the presentation, we will also analyze and compare the changes in residual strain and microstructure in defective S38C axles at various fatigue stages. We are expecting to employ pulsed neutron imaging data to assess the fatigue resistance of the axle.
Qin, T. Y.*; Hu, F. F.*; 徐 平光; Zhang, H.*; Zhou, L.*; Ao, N.*; Su, Y. H.; 菖蒲 敬久; Wu, S. C.*
no journal, ,
Gradient compressive residual stress with a depth of several millimeters exists in railway S38C hollow axles subject to surface induction hardening, which is a challenging problem for structural integrity assessment. To address this, the axial, hoop, and radial residual stress values inside the axles are measured by neutron diffraction technology. By integrating the limited neutron diffraction data, an innovative nodal stress based coordinate assignment (INSCA) approach was then proposed, to numerically reconstruct the global initial residual stress field in three dimensions for S38C axles. The comparison between simulations and experiments clearly show that approximately 515 MPa (axial), 710 MPa (hoop), and 43 MPa (radial) compressive residual stresses were retained underneath the induction hardened martensite layer, which also validates the newly-developed INSCA method. By including the measured axial- and hoop-direction residual stresses, the crack propagation behavior of railway S38C axles were investigated, in terms of fracture mechanics. It was clearly shown that the presence of compressive residual stress leads to a lower driving force of crack propagation, in terms of stress intensity factor range (
). Such smaller also indicates that this compressive residual stress can effectively prolong the service lifetime of high-speed railway axles subjected to induction hardening treatment.
Qin, T. Y.*; Zhang, H.*; Zhou, L.*; Ao, N.*; 徐 平光; Su, Y. H.; Wu, S. C.*; 菖蒲 敬久
no journal, ,
The S38C railway axles are developed for Shinkansen (Bullet Train) through high-frequency induction hardening and the residual stresses are introduced into the axle with a depth of several millimeters. Residual stresses seriously affect the fatigue mechanical strength and fatigue life of engineering structures, and the accurate determination and the optimization control of the three-dimensional (3D) residual stress distribution of high-speed railway S38C axles are increasingly necessary for improving the axle service life. Here, the residual stresses of the S38C axle samples were measured by using the RESA (residual stress analyzer) angle dispersive neutron diffractometer at JRR-3 (Japan research reactor No.3). The large axle samples were electro-discharge machined into: (a) 3 mmH
3 mmA20 mmR comb-shape stress-free coupons with a comb spacing of 1 mm to relieve the transformation induced residual stresses and determine the stress-free lattice spacing, d0; (b) sectioned bar sample 120mmA15mmR 15mmH) and sectioned fan sample (91mmR158mmH15mmA) to well measure the stress distribution in limited beam time. The residual stress distribution of the large axle samples was obtained in three directions (axial(A), radial(R) and hoop(H)) from the surface to the core. Unlike previous studies that only focused on the axial residual stresses of the axle, we found that the hoop residual stresses also have considerable values, which verified the necessity of 3D residual stress testing. Subsequently, according to the residual stress field and basic mechanical properties of the S38C axle obtained by experiments, the 3D residual stress field is reconstructed in the real axle by using an iterative technique. These results are much valuable to reveal the fatigue failure behavior of high-speed railway axles after surface strengthening and to optimize the non-destructive inspection interval.
Liu, J. J.*; Qin, T. Y.*; Hu, F. F.*; 徐 平光; Su, Y. H.; Wu, S. C.*
no journal, ,
The railway axles are critical components for high-speed trains, subject to complex fatigue loads from wheels, rails, and the car bodies, directly affecting service safety. Medium carbon steel S38C axles after high-frequency induction hardening retain a significant gradient of triaxial residual stresses down to a depth of several millimeters, raising concerns about their fatigue integrity. This study measures the axial, hoop, and radial residual strains within the axles for the first time using advanced neutron diffraction. Utilizing the SIGINI Fortran subroutine, we reconstructed the global initial residual stress field from the measured data, revealing residual stresses of approximately -520 MPa (axial), -710 MPa (hoop), and -40 MPa (radial) beneath the surface. We also investigated the fatigue crack propagation behavior of S38C axles through numerical modeling in the context of fracture mechanics, finding that compressive residual stresses within 0-3 mm of the surface reduce the driving force for crack growth, preventing propagation as long as the crack depth remains below 3.7 mm for hollow S38C axles. These results suggest that the maximum defect size allowed in routine inspections is safe.
Hu, F. F.*; Qin, T. Y.*; Zhang, R.*; Ao, N.*; He, L. H.*; Su, Y. H.; 徐 平光; Wu, S. C.*
no journal, ,
The S38C railway axles demonstrate excellent fatigue resistance owing to the large-layer depth compressive residual stress in the hardened surface. However, during fatigue crack propagation, the residual stress may occur the stress relaxation problem, which results in a reduction of the damage tolerance capacity and the service lifetime. To tackle this concern, the time-of-flight neutron scatter methods, including the Bragg-edge transmission imaging and neutron diffraction, were employed to quasi-in-situ study the residual strain and RS relaxation during the fatigue crack advance with single-edge notch bending samples. The BET experimental results show that lattice parameters will change as the crack grows, which then leads to a decrease in residual strain. Moreover, it was discovered from the neutron diffraction test that all three RS components decrease as the crack propagation. The CRS in the axle surface layer is almost fully released when the crack propagates to the matrix material zone.
media笠松 良崇; 豊嶋 厚史; 浅井 雅人; 塚田 和明; 羽場 宏光*; 石井 康雄; 當銘 勇人; 西中 一朗; 秋山 和彦*; 菊永 英寿*; et al.
no journal, ,
タンデム加速器を用いて
Cm(
F, 5
)反応により合成した105番元素
Db(T
=34s)の0.89M HF/0.3M HNO水溶液中における陰イオン交換挙動を迅速イオン交換装置を用いて調べた。周期表上で同族元素であるNb, Ta, 擬似同族元素Paの陰イオン交換挙動もHF/HNO水溶液系で詳細に調べた。それぞれの結果の比較からDbの挙動が本実験条件下でTaの挙動とは大きく異なり、NbやPaの挙動に比較的近いことがわかった。
混合水溶液中における化学挙動笠松 良崇; 當銘 勇人; 豊嶋 厚史; 塚田 和明; 浅井 雅人; 石井 康雄; 西中 一朗; 佐藤 哲也; 篠原 伸夫; 永目 諭一郎; et al.
no journal, ,
原子力機構タンデム加速器施設において、Cm(F,5)反応によりDb(半減期:34秒)を合成し、
線測定装置結合型イオン交換分離装置(AIDA)を用いて0.89M HF/0.3M HNO混合水溶液中における陰イオン交換挙動を調べた。また、
Ge(F,
), Gd(F,)反応により
Nb(14.3分), 
Ta(6.76分)を合成し、同様に陰イオン交換挙動を調べた。その結果、今回の実験条件において陰イオン交換樹脂に対する吸着能の順列がTa
NbDbとなることがわかった。
Zhou, L.*; Zhang, H.*; Qin, T. Y.*; Ao, N.*; 徐 平光; Su, Y. H.; He, L. H.*; Parker, J. D.*; 篠原 武尚; 菖蒲 敬久; et al.
no journal, ,
The neutron diffraction is widely applied to evaluate various microstructures and residual stresses while the neutron Bragg-Edge imaging is increasingly employed to obtain 2D mapping. Here, the microstructure and residual strain in induction-hardened S38C steel railway axles were complementarily measured by using the GPPD time-of-flight power diffractometer at CSNS (China spallation neutron source), the RESA angle dispersive neutron diffractometer at JRR-3 and the RADEN energy-resolved neutron imaging system at J-PARC. The full neutron patterns from GPPD about the gradient microstructure were Rietveld analyzed, and the related parameters from the surface to the core were found in good consistence with the microstructure mapping from RADEN. The 3320 mm
comb-shape d0 samples were used on RESA, and the residual stress distribution in three directions was evaluated successfully. These results suggest a complementary use of various neutron instruments is valuable in engineering.
