Ni-based single crystal (NBSC) superalloys employed as turbine blades are generally vulnerable to elevatedtemperature fretting fatigue (FF) damages during services. To prolong lifetime, ultrasonic surface rolling (USR) was adopted to NBSC in this study, with its FF performance investigated at 650 degrees C. Results reveal that USR induced a wave texture with reduced roughness and a heterostructure layer characterized by gradient slip trace (ST) network on DD6 surface. These modifications enhance the surface microhardness by 68.6% and yield compressive residual stress (CRS) with amplitude of 941.25 MPa, thus raising FF lifetime by 210.6% compared to as-received sample. During FF test, the wave texture considerably mitigates surface stress concentration and protects the sample bulk from the direct contact of the pad, while CRS effectively reduces the actual stress and compels the inward migration of crack source. These alleviate the synergistic damages from the fretting and fatigue components. Besides, the octahedron-dominated ST networks facilitate dodecahedral slip activations to accommodate cyclic plastic strains, and serve as skeletons to collect free dislocations to fulfill recrystallizations. Slip mode transitions and intense recrystallizations in USR sample require additional dissipated energies. Unlike common rafting in FF-failed as-received sample surfaces, the gradient ST networks manipulate crack propagations through the formations of inclined gamma'-raft domains. Frequent crack deflections elevate the critical fracture thresholds and consequently extend FF lifetimes. The findings provide new insights to understand the deformation mechanisms of DD6 during FF and guide their anti-FF designs.
Radio-frequency (RF) and microwave dielectric ceramics are key materials for high-frequency electronic devices. Among them, perovskites outperform conventional dielectrics due to their high quality factor ( Q = 1/dielectric loss) and exceptional reliability. However, their practical application is limited by the trade-off between Q & times; f and the temperature coefficient of resonant frequency ( rf ), as well as by their high densification temperature ( >= 1500 degrees C). Here, a synergistic strategy combining B-site complex-ion modification with composite sintering-aid engineering is proposed. The optimized 95CZT05CMN composition exhibits excellent microwave dielectric properties of dielectric constant sr = 32.4, Q & times; f = 34,240 GHz, and rf = + 16.8 ppm/ degrees C at 1540 degrees C. More importantly, the 5G1L0.5C-modified ceramics can be densified at 950-1050 degrees C while retaining favorable dielectric properties ( sr = 27.3-31.9, Q & times; f = 12,920-13,400 GHz, rf = -6.1 to -11.6 ppm/ degrees C), together with a high flexural strength of 212 MPa. Furthermore, a C-band dielectric resonator antenna delivers radiation efficiency above 85%, while multilayer ceramic capacitors (MLCCs) fabricated show excellent C0G-type stability ( AC / C25 degrees C within +/- 0.3%) and a dielectric loss of similar to 0.06% at 1 MHz. These results establish a viable route toward low sintering temperature, low-loss and thermally stable CaZrO3 -based perovskites for advanced RF and integrated electronic applications. (c) 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
This study presents a modelling framework for dynamic response analysis of a differential elliptical gear transmission system (DEGTS) under multi-source excitations. In novel piston power devices, the variable transmission ratio of elliptical gears couples internal time-varying meshing parameters with external cylinder torque, complicating quantitative prediction. A bending-torsional coupled model accounts for time-varying meshing stiffness (TVMS), composite transmission error, backlash, cylinder torque excitation, and inertial torque arising from non-uniform motion. It examines how these excitation parameters modulate system response. Root mean square (RMS) and coefficient of variation (Cv) characterize response amplitude and dispersion, respectively. Results show that these parameters affect the two characteristics differently. Increasing input speed from 100 to 400 r/min raises the RMS and Cv of relative meshing displacement by 3.7% and 28.6%, respectively, whereas increasing cylinder torque fluctuation amplitude from 1 to 4 N m raises them by 11.8% and 11.0%, respectively. Raising mean cylinder torque from 2 to 8 N m increases the RMS by 278.8% but reduces Cv by 23.6%, implying that a higher mean load suppresses relative dispersion. When composite transmission error amplitude and backlash increase from 10 to 40 mu m, the RMS increases by 25.9% and 8.2%, respectively, and Cv by 41.3% and 23.8%, respectively; both also amplify components within the meshingfrequency band and its sidebands. Experimental results validate predicted trends, periodic characteristics, and dominant frequency components. The proposed framework provides a practical tool for multi-source coupled dynamic analysis and parameter design of non-circular gear transmissions.
Abstract The mechanical degradation of Q420 bridge steel in arid, deicing-salt environments poses a major threat to structural integrity and economy. This study combines experimental and numerical analysis to elucidate the fracture mechanism under combined atmospheric and salt corrosion. Specimens exposed for 0–60 days underwent quasistatic tensile tests and scanning electron microscope fracture analysis, revealing three decisive pit types. These findings directly guided the development of three finite element models, including a uniform corrosion model and models with explicit pit geometries. Results showed post-60-day corrosion elevated stress concentrations by over 33%. The modified void growth and stress-weighted damage models, incorporating these pitting parameters, achieved fracture displacement predictions with ≤ 6 % error, validating their accuracy as representations of the fracture process. This integrated approach not only shifts the failure analysis paradigm from conservative uniform-corrosion assumptions to morphology-aware prediction but also provides engineers with validated tools for quantitative residual life assessment.
Urban road networks are vulnerable to extreme disasters, where secondary disasters frequently exacerbate primary impacts. To enhance lifecycle resilience, this study proposes a distributionally robust optimization (DRO) framework integrating pre-disaster reinforcement with post-disaster restoration scheduling. We formulate a two-stage DRO model: the first stage determines reinforcement strategies to mitigate capacity degradation, while the second stage schedules limited repair resources. To characterize spatially correlated impacts, we propose a concentric scenario generation scheme that represents the progressive expansion of network damage. In addition, we construct a decision-dependent ambiguity set to characterize distributional uncertainty under incomplete disaster information. To improve computational tractability, we develop a constraint generation algorithm, which iteratively identifies binding constraints. Extensive computational experiments are conducted on randomized networks, the Sioux Falls benchmark, and the Beijing Miyun road network. Results highlight the superior out-of-sample performance of the proposed DRO model and quantify the value of distributional robustness in resilience-oriented transportation planning.
