Prof. YAN Jinghan | Publications & Academic Profile | SinoTechIntel

Research Publications & English Decoded Briefs

Showing 2 publications

Railway Engineering Science (铁道工程科学)•2026•DOI: 10.1007/s40534-025-00419-y

Multiscale Investigation on Fatigue Crack Growth and Remaining Useful Life of Bogie Frame Materials Under Service-Induced Damage

This study quantifies the degradation of fatigue crack growth (FCG) resistance in high-speed train bogie frame materials after long-term service. Full-scale frame fatigue tests, multiaxial FCG experiments, and finite element simulations were integrated to determine equivalent crack loading conditions. Digital image correlation captured surface displacement fields for stress intensity factor calculation. Comparative testing of as-welded (AW) and base metal (BM) regions before and after service revealed substantial reductions in remaining useful life: 70.54% for AW and 22.31% for BM. Crack-tip strain responses increased by more than twofold in AW and 1.44 times in BM after service, indicating diminished crack growth resistance. Microscopic fracture surface analysis showed more secondary cracks, unstable crack paths, and blurred fatigue striations in post-service materials, particularly in the AW region. Phased array ultrasonic testing detected no macroscopic defects, yet microstructural deterioration was evident. These findings establish a quantitative link between service-induced damage and fatigue performance degradation, supporting region-specific residual life assessment strategies for bogie frames. The experimental protocol, grounded in actual service loading spectra, improves the accuracy of remaining useful life prediction and provides a reliable basis for maintenance decision-making in high-speed rail operations.

Read Full Analysis→Download Authentic PDF

Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报)•2025•DOI: 10.1007/s12613-024-3032-3

Texture, residual stress and mechanical properties of 7039-T6 thick plate Al alloy with MIG-welded laminar tearing

7039 Al alloys are widely used in armor vehicles, given the material’s high specific strength and fracture toughness. However, laminar tearing in the thickness plane of the base metal (BM), specifically in the normal direction (ND) and rolling direction (RD) plane, was occasionally observed after the welding of thick plates, resulting in premature material failure. A vertically metal-inert gas (MIG)-welded laminar tearing component of a 30 mm thick plate was analyzed to determine the factors associated with this phenomenon. The texture, residual stress, microhardness, and tensile properties were also investigated. The results indicated that the crack extended along the RD as a transcrystalline fracture and terminated at the BM. The grains near the crack grew preferentially in the (001) crystal direction. Furthermore, the tensile strength (83 MPa) and elongation (6.8%) in the RD were relatively higher than those in the ND. In particular, the primary factors for crack initiation include stronger texture, higher dislocation density, increased Al7Cu2Fe phases, lower proportion of small-angle grain boundaries, and varying grain sizes in different regions, leading to the fragile microstructure. The higher residual stress of the BM promotes the formation and extension of cracks. The restraining force due to fixation and welding shrinkage force transformed the crack into laminar tearing. Preventive measures of laminar tearing were also proposed.

Read Full Analysis→Download Authentic PDF