To address the complex and highly variable wheel–rail adhesion behavior on high-speed railway curves, this study establishes a numerical wheel–rail rolling contact model based on starved elastohydrodynamic lubrication (EHL) theory and Herschel–Bulkley rheological characteristics. The model validation yielded RMSE = 0.0228, MAE = 0.0217, MAPE = 11.80%, R² = 0.828, and a 95% confidence interval of the mean residual of −0.0298 to −0.0136. The study focuses on the initial operational phase after application, systematically quantifying the fluid-dynamic regulation mechanisms of water-based friction modifiers once a thin, starved lubricating film has been formed on the rail surface under curving conditions. By analyzing rail profiles (CHN60 and CHN60N), operating parameters, and track geometry, this study shows how adhesion behavior on curved track sections is governed by the coupled effects of contact mechanics and lubrication. As the outer rail superelevation increases from 0 to 70 mm, the adhesion coefficient decreases by approximately 15–25%, mainly because the reduced normal force shifts the wheel–rail interface toward the Stribeck transition regime. Increasing axle load from 14 t to 30 t reduces the dimensionless film thickness, but the enlarged contact area contributes to a more stable adhesion level, with an increase of about 12%. Compared with the CHN60 profile, the CHN60N profile exhibits better geometric conformity, producing a lubricating film that is 10–15% thicker and leading to a lower and more stable adhesion coefficient, decreasing from approximately 0.35 to 0.1. The results also identify a critical lateral displacement of around −4 mm, beyond which the contact radius becomes stable and the adhesion coefficient reaches a minimum plateau. These findings clarify the competing effects of fluid entrainment and metallic asperity contact, and provide quantitative guidance for friction management and friction modifier application on curved track sections.

Battery packs for new energy vehicles have evolved from simple load-bearing and protective assemblies into multifunctional safety structures integrating structural support, crash protection, thermal-runaway mitigation, flame retardancy, electrical insulation, electromagnetic interference shielding, waterproof sealing, and long-term reliability. Fiber-reinforced polymer composites are promising for upper covers, underbody shields, trays, cross beams, side frames, and local protective structures because of their low density, corrosion resistance, design flexibility, and functional-integration potential. However, composite-part performance is strongly governed by forming. Resin flow, impregnation, curing or cooling shrinkage, fiber orientation, filler dispersion, and interfacial bonding may induce voids, dry spots, resin-rich regions, delamination, warpage, and fiber waviness, thereby affecting load bearing, sealing, thermal protection, and durability. This review focuses on composite-forming technologies for new energy-vehicle battery packs. It summarizes component-level service requirements and material systems and compares representative forming routes, including sheet molding compound (SMC), prepreg compression molding/wet compression molding (PCM/WCM), resin transfer molding/high-pressure resin transfer molding (RTM/HP-RTM), vacuum-assisted resin transfer molding (VARTM), long-fiber thermoplastic direct processing (LFT-D), glass-mat thermoplastic (GMT), thermoplastic sheet forming, pultrusion, and multi-material joining. These routes are evaluated from six dimensions: material form, forming cycle, typical defects, representative mechanical performance, applicable components, and engineering maturity. The review further discusses defect mechanisms, performance effects, detection and control methods, and the roles of in-line monitoring, non-destructive testing, process simulation, machine learning, and digital twins in closed-loop quality manufacturing. Finally, engineering challenges are examined in multi-material joining, thermal-safety integration, low-carbon recycling, and standard certification. Composite-material battery-pack structures should therefore be developed as coordinated design and closed-loop manufacturing systems linking materials, processes, defects, performance, and validation.

Top-of-rail friction modifiers (TORFMs) act as transient interfacial films that regulate wheel–rail adhesion under rolling–sliding contact. Unlike permanent coatings, these films undergo continuous formation, depletion, and regeneration during repeated wheel passages. This study investigates TORFM-treated interfaces by combining laboratory rolling-contact tests with a starved non-Newtonian elastohydrodynamic lubrication (EHL) model. Experimentally, application dosage and viscosity were varied on a CL60 wheel–U71Mn rail pair, and the adhesion coefficient was measured as the validation quantity. Numerically, a model-based sensitivity analysis was used to examine how dosage-derived effective supply thickness, viscosity, and rheological index influence film formation and load sharing. The experiments show that increasing dosage alleviates inlet starvation and lowers initial adhesion, which then recovers toward dry-contact levels during repeated rolling. Increasing viscosity from 0.002 to 0.022 Pa·s reduced the minimum adhesion coefficient from 0.21 to 0.086, although excessive viscosity may prolong the low-adhesion stage. The rheological-index calculations (n = 0.7–1.0 around the measured formulation value n = 0.82) indicate that shear-responsive flowability can affect contact-zone supply and the film-supported load fraction; these rheological-index trends are model-based sensitivities rather than independently validated experimental effects. Overall, the results support a transient interfacial-film interpretation of TORFM-controlled adhesion and suggest that practical design should target a controllable medium-adhesion window (approximately 0.15–0.30 under the present laboratory conditions) rather than minimum friction alone.

Carbon fiber-reinforced polymer (CFRP) composites are in urgent demand in the aerospace, new energy vehicle, and wind power sectors owing to their superior specific strength, specific modulus, and lightweight potential. However, molding defects, such as voids, dry spots, and delamination, arising from their anisotropy and weak interlaminar bonding, severely constrain their service performance. Advanced molding technologies represent the key to overcoming this bottleneck. This paper systematically reviews typical advanced molding technologies in the field of CFRP composites, including resin transfer molding (RTM) and vacuum-assisted resin transfer molding (VARTM) in liquid composite molding, autoclave molding and compression molding (CM) in prepreg molding, and automated fiber placement (AFP) and material extrusion (ME) in automated molding. From an integrated perspective of “technological evolution–process characteristics–defect mechanisms–optimization strategies,” this review summarizes the technical principles, development trajectories, and core advantages of each process, analyzes the formation mechanisms of typical defects, including voids, dry spots, delamination, wrinkles, warpage, and melt instability, and summarizes multidimensional optimization advances in process parameter regulation, numerical simulation, resin modification, equipment upgrading, path planning, and thermal management. Furthermore, the differences and complementarities among these processes in terms of molding precision, efficiency, cost, and applicable scope are compared. Finally, future development directions, including digital twins, green low-carbon manufacturing, ultra-large integrated structures, multi-process integration, standardized defect characterization, and low-cost collaborative design, are discussed. This paper aims to provide systematic theoretical references and technical support for the optimization and upgrading, process integration, and industrial application of advanced CFRP molding technologies.

To explore the effects of ultrasonic burnishing strengthening technology on the surface morphology and mechanical properties of 40Cr rods for hydraulic applications, a conical transition composite amplitude transformer was designed using ANSYS (Workbench 2024 R1) finite element analysis software, with a frequency of 18,158 Hz, an amplification factor (M_p) of 2.0, and a maximum stress of 122.9 MPa. The ultrasonic burnishing strengthening process was numerically simulated via ABAQUS finite element analysis software. Based on the single-factor analysis method, the influence of spindle speed, ultrasonic amplitude, and burnishing passes on the maximum residual compressive stress of the hydraulic rod was investigated, and key parameters such as surface roughness and microhardness of the rod before and after ultrasonic burnishing strengthening were comparatively analyzed. The results show that ultrasonic burnishing strengthening technology can reduce the surface roughness of the hydraulic rod, enhance its microhardness, and increase the depth of the plastic deformation layer. Ultrasonic amplitude and burnishing passes exert a significant influence on the maximum residual compressive stress on the rod surface, while the effect of spindle speed is relatively minor. When the ultrasonic amplitude is 10 μm, the spindle speed is 120 r/min, and the burnishing passes are 3, the surface residual compressive stress of the hydraulic rod reaches the maximum experimental value of 433.39 MPa. This study reveals the influence law of process parameters on the surface properties of rods for hydraulic applications, verifies the feasibility of the ultrasonic burnishing system, and provides a technical reference for improving the performance of rods for hydraulic applications.

The GH4202 nickel-based superalloy is widely used in aero-engine hot-section components, where surface integrity is critical to fatigue performance. This study combined Abaqus/Explicit 2023 single-shot simulations, single-factor experiments, and an L₁₆(4⁴) orthogonal array to evaluate the effects of shot diameter, peening duration, pressure, and impact angle. Qualitative single-shot simulation results show that an increase in the prescribed impact velocity leads to higher simulated compressive residual stress and plastic deformation, whereas the growth rate slows down significantly when the velocity exceeds 30 m/s. Orthogonal main-effect analysis indicated that pressure had the greatest effect on Ra, whereas duration had the greatest effect on HV0.1. The Pareto evaluation identified Runs 1, 6, 11, and 16 as non-dominated combinations. A₃B₃C₁D₂ (0.8 mm, 45 s, 0.2 MPa, and 45°) was selected as a representative intermediate compromise for characterization and independent confirmation. The confirmation batch yielded Ra = 0.243 μm and HV0.1 = 345.3 HV. Within the tested domain, the candidate ranges for subsequent validation were 0.6–0.8 mm, 30–45 s, 0.2–0.3 MPa, and 45–60°.