Materials最新文献

This paper presents the results of research on minimizing welding distortion in a large-scale storage tank bottom made of S235JR steel with a diameter of 10,000 mm. The welding technology previously employed guaranteed flatness tolerances of the bottom plates in accordance with the EN 14015 standard at a ratio of T = 0.25% × D = 25 mm, where D represents the diameter of the tank bottom. The objective of this study was to investigate the possibility of reducing this value to the target level of ΔT = 0.2% × D = 20 mm. Two clamping system configurations, used to restrain the tank bottom plates during welding, were analyzed. Numerical simulations of both configurations were performed using the finite element method (FEM) in the SYSWELD software. For the selected clamping configuration, a physical simulation of the welding process was carried out, followed by an analysis of the distribution of welding-induced distortions in the storage tank bottom with respect to compliance with the required bottom plate flatness tolerance of 0.2% × D.

Thermosetting epoxy resins commonly used in wind turbine blades pose significant recycling challenges. This study addresses this limitation by using an eco-friendly, recyclable liquid polymethyl methacrylate (PMMA) resin to fabricate thermoplastic sandwich panels and by investigating their in-plane compressive buckling behavior. The experimental results demonstrated that the proposed PMMA thermoplastic sandwich panels exhibited improved in-plane compressive performance, with a 5.22% higher ultimate load than traditional epoxy counterparts. Furthermore, to investigate the effect of groove configuration on the buckling stability of composite sandwich panels, a finite element (FE) model for PMMA sandwich panels with initial geometric imperfections was established in this paper, and the reliability of the FE model was validated via compression and buckling tests. Finally, a Kriging surrogate model coupled with the NSGA-II algorithm was adopted to carry out multi-objective optimization, with groove parameters set as design variables. Based on the FE verification results, the optimized configuration (Point A) reduced the structural mass by 2.24%, while increasing the critical buckling load and shear modulus by 5.71% and 10.27%, respectively. Research on the buckling performance and groove configurations of PMMA sandwich panels, which can be applied to wind turbine blade webs and airfoils, can provide crucial data support for the engineering application of sustainable PMMA-based large-scale wind turbine blades.

Microwave-assisted recovery provides a potential approach for restoring fracture damage in asphalt mixtures, but previous studies have mainly focused on heating and curing conditions, while the role of the pre-heating fracture state remains less understood. This study investigated microwave-assisted fracture energy recovery from a damage-state regulation perspective by comparing a control asphalt mixture (CAM) with a basalt fiber-reinforced asphalt mixture (BFAM). Semi-circular bending (SCB) tests were combined with an L9 orthogonal design to evaluate three pre-heating conditions, target surface temperatures of 45-85 °C, and curing times of 6-24 h. Rather than directly enhancing binder recovery, basalt fiber reinforcement increased the initial fracture resistance and altered the relative fracture condition reached under a given external load. The recovery index RI ranged from 20.7% to 55.9% for CAM and from 35.2% to 82.3% for BFAM. Main-effects ANOVA showed that the pre-heating damage condition had the largest main-effect contribution within the adopted L9 framework, reaching 82.3% for CAM and 95.2% for BFAM, substantially exceeding those of target surface temperature and curing time. Under a comparable external load of approximately 2.5 kN, CAM reached the 70% P_max condition, whereas BFAM remained at the 40% P_max condition, with corresponding mean RI values of 42.8% and 76.9%. These results support a proposed conceptual damage-state regulation framework within the investigated material and experimental conditions, in which basalt fiber reinforcement preserves a more favorable pre-heating state and thereby greater recovery potential. The findings highlight the importance of improving fracture resistance and applying microwave-assisted treatment before extensive fracture development occurs, while broader validation is required before generalizing the proposed framework to other materials or field conditions.

Elasticized expanded polystyrene (EPS-T) is widely used as a resilient layer in floating floors, where dynamic stiffness is the key input for impact-sound prediction, while FEM modelling additionally requires elastic parameters and damping descriptions consistent with the adopted test or modelling configuration. This study investigates whether ISO-type dynamic stiffness testing and acoustic-response modal identification can provide consistent vibroacoustic parameters for EPS-T. Rectangular specimens of different thicknesses were tested for dynamic stiffness and damping using an ISO 9052-1-type setup. Additional cylindrical compression tests were used to examine apparent Young's modulus and Poisson's ratio, while impulse-excited acoustic responses of clamped specimens were combined with inverse FEM identification. The ISO-type dynamic stiffness decreased from approximately 53.3 MN/m³ for nominal 17 mm specimens to 27.0 MN/m³ for nominal 53 mm specimens. This trend was described by a compliance model with an effective Young's modulus of 2.04 MPa and an equivalent contact/support stiffness of 101.2 MN/m³. Acoustic-response inverse FEM gave consistent Young's modulus values, ranging from 1.77 MPa to 2.16 MPa, with a mean close to 2.05 MPa. Direct use of s' = E/h overestimated stiffness and underestimated predicted ΔL_w by approximately 2-5 dB. The two routes provided consistent estimates of the effective modulus, but this consistency applies only to modulus identification and not to direct stiffness conversion or damping transfer.

The combined elasticity, processability, and recyclability of thermoplastic elastomers (TPEs) has enabled their widespread adoption across diverse industrial sectors. In particular, TPEs have emerged as attractive alternatives to chemically crosslinked elastomers, contributing to extended product lifetimes and reduced waste generation. Their performance arises from the presence of physical, reversible crosslinks, which allow the integration of elastomeric behaviour with thermoplastic reprocessability. This review provides an overview of recent advances in ABA thermoplastic elastomer (TPE) design, focusing on three major classes: styrenic block copolymers, acrylic-based TPEs, and emerging bio-based systems, with particular emphasis on the latter. Special attention is given to structure-property relationships and the influence of molecular architecture on thermomechanical behaviour. Styrenic block copolymers remain the most established class, offering well-defined phase-separated morphologies and tuneable mechanical properties. Acrylic-based TPEs have attracted increasing interest owing to their superior thermal and oxidative stability and versatile molecular design. We also discuss recent progress in bio-based TPEs derived from renewable resources, which aim to reduce reliance on fossil feedstocks without compromising performance. Finally, we examine current challenges and future perspectives, highlighting the need for sustainable synthetic strategies and advanced TPEs with lower environmental impact.

Diamond has emerged as a promising ultrawide-bandgap semiconductor material for next-generation electronics because of its unique combination of a wide bandgap, high critical electric field, superior carrier transport properties, exceptionally high thermal conductivity, and strong chemical and radiation stability. Over the past two decades, progress in crystal growth, substrate engineering, surface control, dielectric integration, and device fabrication has advanced diamond electronics beyond early proof-of-concept demonstrations. The review connects material properties, growth, doping, defects, and figures of merit with reported performance in hydrogen-terminated field-effect transistors, MOSFETs, Schottky and p-i-n diodes, and related power-device architectures. Emerging opportunities in ultraviolet photodetectors, multifunctional electronics, and memory-oriented diamond devices are also briefly considered. Among the device classes reviewed, diamond diodes currently show the strongest evidence of high-voltage capability, whereas transistor development remains constrained by threshold-voltage control, normally off operation, contact resistance, interface stability, and reliability. Diamond is therefore more likely to complement than replace established SiC and GaN technologies, particularly in specialized high-field, high-temperature, radiation-rich, and chemically demanding applications. Broader deployment will require scalable low-defect wafers, reliable n-type doping, stable interfaces and contacts, and more cost-effective manufacturing.

This study presents a comparative evaluation of the wear performance of three hot-work tool steels-WCLV (1.2344), Uddeholm Unimax, and Uddeholm QRO 90 Supreme-for die forging applications. The materials were characterized in terms of hardness and bulk chemical composition using Vickers hardness testing and X-ray fluorescence spectroscopy. Tribological behavior was investigated using ball-on-disc tests, while industrial performance was assessed by analyzing forging punches after the production of 16,250 components. Surface degradation was quantified using optical profilometry and three-dimensional roughness parameters. Measured hardness values were 591 HV for WCLV, 622 HV for QRO 90 Supreme, and 639 HV for Uddeholm Unimax. The average friction coefficients were 0.88, 0.92, and 0.77, respectively. Unimax also exhibited the lowest volumetric wear, reaching 0.04683 mm³ (R19 mm) and 0.03384 mm³ (R22 mm), compared with 0.08646-0.13095 mm³ for WCLV and 0.09598-0.13635 mm³ for QRO 90 Supreme. This corresponds to approximately 45-70% lower wear relative to the other steels. Industrial trials confirmed improved surface stability of Unimax punches after service. The observed trends are consistent with differences in alloying content and the expected microstructural response associated with chromium and molybdenum additions. Overall, Uddeholm Unimax demonstrated the most favorable balance of hardness, friction behavior, and wear resistance.

High-performance alkali-free accelerators require a mechanistic understanding of interactions between inorganic accelerants and organic modifiers. Although aluminum sulfate (AS) promotes rapid ettringite (AFt) formation, uncontrolled crystallization leads to coarse microstructures and instability from AFt-to-AFm conversion. Here, a molecular-scale synergistic mechanism is identified in which an amide regulates AS-driven hydration. The amide controls nucleation and growth of AFt and C-S-H via chemisorption on C₃A/C₃S and complexation with Ca²⁺. Within the tested mixing proportions, the high-aluminum-sulfate and moderate-amide combination achieves the highest early strength (17.05 MPa at 1 day) via constructing an interlocked AFt/C-S-H skeleton, whereas excessive amide suppresses crystallization and low AS accelerates AFt-to-AFm conversion, reducing long-term performance. In-situ XRD, thermal analysis, and microscopy confirm a denser, more stable microstructure (27.37 MPa at 10 days) with minimal 28-day strength loss (17.38 MPa). Density functional theory shows an adsorption hierarchy of amide > AS species > H₂O, explaining its dominant surface-modifying role. This study provides a framework for designing cement accelerators with balanced early strength and durability.

The use of manufactured sand (MS) as a substitute for natural sand or quartz sand in the production of ultra-high-performance manufactured sand concrete (UHPMC) represents a critical approach to alleviating the shortage of high-quality aggregates and promoting low-carbon development. However, after steel fibers and steel rebars are introduced into this material system, the synergistic working mechanism and damage evolution characteristics of the resulting ultra-high-performance manufactured sand-reinforced concrete (UHPMRC) beams under flexural loading remain largely unexplored. Acoustic emission (AE) technology, owing to its high sensitivity to the initiation and propagation of microcracks, enables real-time dynamic monitoring of UHPMRC beams throughout the entire process from the elastic stage to fracture failure, thereby providing an effective means to reveal the internal performance degradation law. Accordingly, this study conducted simultaneous AE monitoring on small-scale reinforced beams under four-point bending and investigated the effects of MS replacement ratios (0%, 50%, 100%) and steel fiber contents (1.0%, 1.5%, 2.0%). Results show that UHPMRC beams with 100% MS replacement and 1.5% steel fiber content achieve optimal performance. Compared to 0% MS specimens, those with 100% MS exhibit superior early stiffness, ductility, and flexural capacity due to the combined effects of steel fibers and MS. Beams with 2% steel fiber content experienced fiber clustering, reducing bridging capability and promoting earlier cracking relative to those with 1.5% fibers. AE energy parameters accurately identified cracking and characterized crack propagation in UHPMRC beams. Increasing MS content raised the proportion of shear cracks while reducing tensile cracks. The highest shear signal proportion occurred at 1.0% steel fiber content. These findings provide a valuable reference for the design of sustainable high-performance reinforced-concrete structures using manufactured sand.

High-temperature graphitization inevitably compromises the surface polarity and resin wettability of polyacrylonitrile (PAN)-based high-modulus carbon fibers (HMCFs), creating a long-standing trade-off between fiber modulus and interfacial adhesion that restricts its applications. Here we report a tension-temperature synergy to overcome this limitation. HMCFs were fabricated at 1700-2100 K under axial tensions of 0-70 N, and the resulting microstructures and surface activity were characterized by X-ray diffraction, Raman spectroscopy, dynamic contact angle testing, and microdroplet debond measurements. Temperature dominates crystallite coarsening and surface-active carbon (Sac) concentration, whereas tension enhances axial lamellar orientation without inducing appreciable grain growth. At constant temperature, two competing effects, both slight crystallite growth and radial lamella rearrangement, keep Sac stable under varying tension. Fibers processed at 1900 K with 60 N tension achieve a modulus of ~350 GPa, equivalent to that of the 2100 K/10 N sample, while delivering a 13.5% higher Sac, elevated surface energy (26.3 mN·m^-1), and 37.9% stronger interfacial shear strength (IFSS). The Sac parameter exhibits strong correlations with surface energy and IFSS. This one-step in situ thermal strategy eliminates post-treatment and offers an industrially viable route to HMCFs with balanced modulus and intrinsic interfacial bonding.