Railway Engineering Science (铁道工程科学)•2026•DOI: 10.1007/s40534-025-00419-y
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.
Nano-Micro Letters•2025•DOI: 10.1007/s40820-025-01746-9
Diamond, an ultrawide-bandgap semiconductor material, is promising for solar-blind ultraviolet photodetectors in extreme environments. However, when exposed to high-temperature conditions, diamond photodetector surfaces are unavoidably terminated with oxygen, leading to low photoresponsivity. To address this limitation, single-crystalline diamond nanowires (DNWs) embedded with platinum (Pt) nanoparticles were developed using Pt film deposition followed by chemical vapor deposition (CVD) homoepitaxial growth. During the CVD, Pt nanoparticles (approximately 20 nm in diameter) undergo dewetting and become uniformly embedded within the single-crystalline DNWs. Photodetectors fabricated with these Pt nanoparticles-embedded DNWs achieve a responsivity of 68.5 A W−1 under 220 nm illumination at room temperature, representing an improvement of approximately 2000 times compared to oxygen-terminated bulk diamond devices. Notably, the responsivity further increases with temperature, reaching an exceptional value of 3098.7 A W−1 at 275 °C. This outstanding performance is attributed to the synergistic effects of the one-dimensional nanowire structure, deep-level defects, the localized surface plasmon resonance effects induced by embedded Pt nanoparticles, and localized Schottky junctions at the Pt/diamond interface, which enhance optical absorption, carrier generation, and separation efficiency. These results highlight the significant potential of Pt nanoparticles-embedded DNWs for advanced deep ultraviolet detection in harsh environments, including aerospace, industrial monitoring, and other applications.
Chinese Journal of Mechanical Engineering•2025•DOI: 10.1186/s10033-025-01353-0
The huge impact kinetic energy cannot be quickly dissipated by the energy-absorbing structure and transferred to the other vehicle through the car body structure, which will cause structural damage and threaten the lives of the occupants. Therefore, it is necessary to understand the laws of energy conversion, dissipation and transfer during train collisions. This study proposes a multi-layer progressive analysis method of energy flow during train collisions, considering the characteristics of the train. In this method, the train collision system is divided into conversion, dissipation, and transfer layers from the perspective of the train, collision interface, and car body structure to analyze the energy conversion, dissipation and transfer characteristics. Taking the collision process of a rail train as an example, a train collision energy transfer path analysis model was established based on power flow theory. The results show that when the maximum mean acceleration of the vehicle meets the standard requirements, the jerk may exceed the allowable limit of the human body, and there is a risk of injury to the occupants of a secondary collision. The decay rate of the collision energy along the direction of train operation reaches 79%. As the collision progresses, the collision energy gradually converges in the structure with holes, and the structure deforms when the gathered energy is greater than the maximum energy the structure can withstand. The proposed method helps to understand the train collision energy flow law and provides theoretical support for the train crashworthiness design in the future.
Chinese Journal of Mechanical Engineering•2025•DOI: 10.1186/s10033-025-01316-5
This study decouples the material microstructure into matrix and void phases. The undamaged constitutive is derived from the matrix phase, while the void phase contributes to damage evolution. A constitutive model is established by coupling the two. According to the void-phase evolution during damage, a damage sequence interaction model is proposed. Tests on new vehicles and vehicles in service materials yield stress-strain curves of materials without and with fatigue damage and measure the apparent elastic modulus. The damage sequence interaction model accurately predicts the residual mechanical properties of undamaged materials. A trolley collision test validates the constitutive model. Collision simulations at 25, 36, and 48 km/h reveal that compared with undamaged models, the maximum vertical lift heights of moving vehicles with fatigue damage are 4.54%, 3.74%, and 9.17% lower, respectively, and the maximum longitudinal compressions of stationary vehicles are 4.76%, 14.53%, and 33.15% higher respectively. This research emphasizes the importance of considering fatigue damage in vehicle design and maintenance. The damage sequence interaction model has high engineering application value, applicable to vehicle safety checks and design, and provides a reference for improving relevant standards.
Chinese Journal of Mechanical Engineering•2025•DOI: 10.1186/s10033-025-01229-3
The exploration of titanium alloy applications in railway transportation aims to meet the newly emerged demand for vehicles that are lighter and more efficient. This research focuses on the potential of these materials to concurrently reduce vehicle weight and enhance efficiency, sustainability, and safety. Challenges faced include high production and processing costs, durability issues in harsh railway environments, and environmental impacts associated with alloy production. Research findings indicate that innovative alloy design and advanced processing techniques, such as powder metallurgy, additive manufacturing, and surface treatment, significantly improve the applicability of titanium alloys in railway applications. These methods substantially increase energy efficiency and safety. Additionally, advancements in environmentally sustainable practices in the production of titanium alloys address ecological concerns. As research progresses, the study and development of low-cost, high-performance titanium alloys highlight the need for more efficient and environmentally friendly manufacturing processes. Exploring new alloy compositions and applying emerging technologies in processing and manufacturing are key areas for future research. These advancements are expected to enhance the role of titanium alloys in revolutionizing railway transportation, aligning with global trends towards sustainability and performance improvement. This research underscores the significant potential contribution of titanium alloys to future efficient and eco-friendly rail travel.