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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, 11 Pages, 2024/00
被引用回数：0High-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.
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 3
320 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.
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 mmH3 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.
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.
