Search Results (3,451)

This study develops and validates a finite element model for round-ended concrete-filled steel tubular (CFST) columns subjected to combined compression–bending–shear loading using ABAQUS. Based on the calibrated model, the mechanical behavior of such members is thoroughly analyzed, including lateral bearing capacity, axial force evolution, and interaction mechanisms. The influences of key parameters, such as shear-span ratio, axial load ratio, cross-sectional aspect ratio, concrete strength, and steel yield strength, on the bearing capacity are systematically investigated. Furthermore, a calculation method for predicting the ultimate bearing capacity is proposed based on the section equivalent approach. The results demonstrate that the loading direction relative to the principal axes significantly affects structural performance: long-axis loading leads to higher bearing capacity and improved ductility, whereas short-axis loading reduces the ultimate capacity by an average of 49%. As the shear-span ratio increases, the ultimate lateral capacity gradually decreases. For shear-span ratios between 1.0 and 3.0, the long-axis loaded specimens exhibit pronounced compression–bending–shear failure modes. Variations in the axial load ratio notably influence both lateral capacity and axial force distribution; both bearing capacity and ductility decrease with increasing axial load ratio, although the effect on ultimate capacity remains minor when the axial load ratio does not exceed 0.4. Full article

Ultra-high-strength steel sheets were joined by forge joining during hot stamping. This study investigated the influence of punch cross-sectional shape and punch tip inclination shape on joint strength through experiments and finite element simulation, with applications in hat bending. The experiments systematically evaluated various punch geometries by varying the punch’s cross-sectional shape and the aspect ratio of rectangular punches. A second set of experiments focused on the influence of punch tip inclination shape. These experiments examined a rectangular punch with a slope. Joint strength is primarily assessed by measuring the tensile shear load. Finite element simulation was used to analyze joining mechanisms, investigating contact pressure and surface expansion rate distribution. The results from the experiments consistently indicated that, for a constant cross-sectional area, punch shapes with a larger punch perimeter on the upper sheet yielded a higher tensile shear load, though the changing inclination shape of the rectangular punch tip did not lead to an observed improvement in joint strength. Finite element simulation analysis revealed that punch shapes promoting a uniform distribution of contact pressure and surface expansion rate across the joint area tended to exhibit higher joint strength compared with the same punch cross-sectional area but less uniform distribution, a tendency that was more pronounced for the distribution of contact pressure than for the surface expansion rate. Full article

In the automotive industry, the most critical factor affecting dimensional stability during the forming of Advanced High-Strength Steels (AHSSs) is the springback phenomenon. This study systematically investigates the springback behavior of four distinct dual-phase steel grades (DP450, DP600, DP800, and DP1000) in U-shaped body-in-white (BIW) structures across 180 distinct scenarios. The experimental design varied sheet thicknesses (1.2, 1.6, 2 mm), die clearance angles (5°, 10°, 15°), and bending radii (R6, R8, R10, R12, R14). Numerical simulations using Autoform R8 were validated against Atos 3D optical scanning data, achieving values exceeding 0.90 for all grades. Quantitative validation metrics showed exceptional fidelity for lower-strength grades with error margins below 1.1%, while the maximum deviation was limited to 3.1% for the ultra-high-strength DP1000 grade. The findings demonstrate that while increasing material strength substantially intensifies springback, the strategic augmentation of sheet thickness and optimization of die radius effectively mitigate these deviations, thereby enhancing process stability. Full article

Lodging is a major constraint to rice productivity and grain quality. The mechanical strength of basal internodes, particularly bending resistance (BDR), is a critical determinant of lodging resistance. In this study, we evaluated the BDR of the third and fourth basal internodes (BDR3 and BDR4) in a diverse panel of 340 rice accessions. A genome-wide association study (GWAS) identified three QTLs significantly associated with BDR3, which were defined and designated as qBDR1, qBDR4, and qBDR5. Further analysis revealed that OsWRKY102 on qBDR1 was identified as a key candidate gene. Haplotype analysis revealed distinct allelic variations between subspecies, with the elite haplotypes (Hap.1 and Hap.4) contributing to superior lodging resistance, while Hap.2 was predominantly found in lodging-susceptible Japonica accessions. CRISPR/Cas9-mediated knockout of OsWRKY102 in the ZH11 background resulted in a significant reduction of more than 50% in both BDR3 and BDR4 compared to the wild type. Detailed phenotypic characterization of the oswrky102 mutants revealed a substantial decrease in cellulose content and culm diameter, accompanied by an increase in culm wall thickness. These findings demonstrate that OsWRKY102 maintains culm mechanical strength by promoting radial expansion and cellulose accumulation. Biomechanical analysis further suggests that culm diameter and cellulose content are more critical for bending strength than wall thickness. Our results elucidate the regulatory role of OsWRKY102 in coordinating culm morphology and cell wall composition, providing a valuable genetic target for molecular breeding of high-yielding, lodging-resistant rice varieties. Full article

Glass fiber-reinforced epoxy composites were modified with carbon nanotubes (CNTs), Al₂O₃, and TiO₂ nanoparticles to comparatively evaluate their influence on tensile, flexural, and low-velocity impact performance within an integrated experimental–numerical framework. Nanoparticles were incorporated at controlled weight fractions to identify dispersion-controlled reinforcement regimes and the onset of heterogeneity-driven mechanical transitions. Among all formulations, 0.5 wt% CNTs provided the most pronounced static mechanical enhancement, increasing tensile strength to 419.50 MPa (≈21% improvement over the reference GF laminate) and flexural strength to 230.23 MPa (≈26% increase). In contrast, impact performance exhibited a non-monotonic evolution; the highest absorbed energy (9.64 J) was observed at 2 wt% CNTs, indicating that dynamic energy dissipation mechanisms do not necessarily scale proportionally with static strength gains. Oxide-filled systems demonstrated stiffness-dominated behavior, where increasing filler content amplified elastic mismatch and progressively reduced strength despite modulus enhancement. Finite element simulations conducted in ANSYS LS-DYNA (MAT_022) reproduced global stiffness trends within the dispersion-controlled regime. Tensile strength predictions agreed within 0–9% at optimal CNT loading, whereas larger deviations (up to ~33%) emerged under bending-dominated loading in oxide-rich systems, reflecting amplified sensitivity to microstructural heterogeneity. The coupled evolution of stiffness–strength decoupling (SSDI) and FEM deviation (η) enabled identification of a Composite Heterogeneity Threshold (CHT), defined as the nanoparticle concentration beyond which stiffness enhancement no longer translates into proportional strength or toughness improvement. Beyond this threshold, dispersion-induced heterogeneity not only reduces mechanical efficiency but also marks the boundary of homogenized continuum model adequacy across static and dynamic loading conditions. Full article

Fracture toughness is a very important mechanical attribute that affects the strength of rail steel used in high-speed rail systems. This study tests the measurement uncertainty that comes with measuring the plane strain fracture toughness (K_IC) of R350HT rail steel. We used the Single-Edge Bend (SEB) specimen to do fracture toughness testing. We used the Guide to Expressing Measurement Uncertainty (GUM)-based method to figure out how much uncertainty came from measuring the load, the crack opening displacement (COD), and the specimen’s shape and figuring out the crack length. At a 95% confidence level (k = 2), the combined standard uncertainty was found to be 0.881 MPa·m^1/2, which is the same as an expanded uncertainty of 1.761 MPa·m^1/2. The measured fracture toughness value of 40.59 ± 1.76 MPa·m^1/2 meets the standards for rail steels. The results show how important it is to include measurement uncertainty in conformity assessment methods for safety-critical railway components. They also provide an experimentally proven framework for accurate mechanical property evaluation. Full article

Lightweight design and crashworthiness of protective structures are critical for battery safety in electric vehicles (EVs). This study addresses the limited research on cross-sectional shape design of high-strength steel double-cell roll-formed tubes (DCRFTs), widely used in EV bumper beams, battery boxes, and electric bus frames. A parametric design method is proposed based on three parameters: middle flange offset (o), upper deflection angle (α), and lower deflection angle (β). Under the constraints of constant cross-sectional height and enclosed area, this method systematically generates diverse shapes, including square, trapezoid, hexagon, re-entrant hexagon, and various hybrid shapes. Validated finite element models were employed to analyze the deformation modes and crashworthiness of DP980 steel DCRFTs under idealized lateral three-point bending with simple supports. The results indicated that the re-entrant hexagon section reduced maximum deformation (Disp) by 2.95%, peak crushing force (PCF) by 9.53%, and improved crushing force efficiency (CFE) by 13.88% compared to the baseline square section. The parametric study and sensitivity analysis confirmed that the offset (o) was the most critical parameter, contributing over 80% of the variance in Disp, PCF, and CFE. Multi-objective optimization using an RBF surrogate model and the NSGA-II algorithm yielded Pareto optimal solutions. Compared to the baseline, three representative solutions achieved Disp reductions of 11.83–25.10% and CFE improvements of 15.63–22.26%, each with distinct trade-offs among objectives. This work establishes a methodological framework for parametric cross-section design of roll-formed profiles; its extension to realistic boundary conditions will further facilitate practical EV protective structure design. Full article

This study presents an experimental investigation into a novel hybrid strengthening system for reinforced concrete (RC) beams that combines externally bonded carbon-fiber-reinforced polymer (CFRP) sheets with a spray-applied polyurea coating (Linex XS-350). Seven beams were tested under four-point bending to evaluate the effects of two main parameters, CFRP thickness and single vs. double layers, and polymer coating configurations, i.e., none, thin with 2 mm, thick with 4 mm, and embedded. The coating was intended to act as an elastic confinement layer that mitigates peeling stresses and enhances CFRP concrete bond performance. The results demonstrated significant improvements in strength, ductility, and strain capacity for coated specimens compared with CFRP-only beams. The inclusion of Linex increased the ultimate load by up to 24% in single-layer beams and 20% in double-layer beams, while bottom-fiber strain at failure increased by more than fivefold, indicating enhanced CFRP utilization. The uncoated beams failed prematurely by CFRP peeling, whereas the coated and embedded specimens transitioned to CFRP rupture with more gradual and ductile behavior. The combined use of multiple CFRP layers and polymer coating produced the most effective performance, with the double-layer embedded configuration (B7) achieving the highest load, strain, and energy absorption. The findings confirm that integrating polyurea coatings with CFRP can effectively delay debonding and significantly improve the reliability and toughness of strengthened RC members, offering a practical solution for more resilient structural retrofitting. Full article

Benefiting from their outstanding porosity, considerable specific surface area, and natural flexibility, cellulose nanofibers (CNFs)/MOF materials have emerged as competitive candidates for advanced flexible energy storage devices. However, conventional CNFs/MOFs aerogels or films often suffer from poor recoverability under compression, bending, and folding, accompanied by severe plastic deformation that compromises the cycling and structural stability of devices. To address this issue, we report a rationally designed flexible PU/CNFs/ZIF-8/PANI composite foam with an interconnected micro-mesoporous structure. Using polyurethane foam as a soft substrate and CNFs/ZIF-8 as building blocks, the composite was fabricated through a combined strategy of impregnation, in situ ZIF-8 growth, hot-pressing, and in situ aniline polymerization with simultaneous etching of the ZIF-8. The incorporation of carboxylated CNFs enhances the hydrophilicity of the PU skeleton. This, in combination with the hot-pressed framework, establishes an interconnected 3D network, thereby effectively preventing the agglomeration of active materials. Meanwhile, the hierarchical pores derived from the sacrificial ZIF-8 template provide abundant electroactive sites, accelerate ion transport, and facilitate high PANI loading. By virtue of this synergistic architectural effect, the resultant electrode achieves a high specific capacitance of 449 F/g at 0.2 A/g, with 97% capacitance retention after 2000 cycles at 5 A/g. Furthermore, the composite foam demonstrates excellent mechanical flexibility, with a tensile strength of 0.87 MPa and an elongation at break of 230%. This work offers a feasible approach for developing high-performance flexible supercapacitors and provides novel perspectives for the rational design of portable energy storage devices. Full article

Rock fracture behavior is strongly influenced by grain size and boundary effects, which complicate the determination of fracture parameters and the interpretation of size-dependent failure. This study investigates the fracture behavior of sandstone and diorite within the framework of the boundary effect model (BEM) using three-point bending tests, acoustic emission (AE), and digital image correlation (DIC). By varying the prefabricated crack length, different values of the structural geometric parameters a_e were obtained, and the fracture toughness K_IC and tensile strength f_t were identified by regression analysis. The results show that K_IC = 0.6841 MPa·m^0.5 and f_t = 4.5625 MPa for sandstone, whereas K_IC = 2.7233 MPa·m^0.5 and f_t = 21.8218 MPa for diorite. Increasing the prefabricated crack length reduces the peak load and prolongs the pre-peak damage evolution stage. Diorite, with a larger average grain size, exhibits higher AE energy release, a higher proportion of high-energy AE events, and a larger fracture process zone (FPZ) than sandstone. Moreover, the AE energy distribution along the crack propagation direction shows a distinct “three-stage” characteristic, consistent with the non-uniform distribution of local fracture energy g_f predicted by boundary effect theory. The results indicate that BEM can reasonably characterize the fracture behavior of rocks with different grain sizes, and the identified material parameters can be used to construct a BEM-based structural failure curve for estimating nominal failure stress over a wider range of structural geometric parameters. Full article

The upscaling of turbines in the offshore wind industry has been unprecedented, as compared to 5–6 MW rated turbines 10 years ago. A typical 20–26 MW rated turbine in modern commercial applications (MingYang MySE 18.X-20 MW installed in 2025 and 26 MW prototype by Dongfang Electric tested in 2025) has been demonstrated. This scaling has been made possible by increasing rotor diameters (>250 m) and hub heights (>150–180 m) to achieve capacity factors of up to 55–65%, annual energy generation of more than 80 GWh/turbine, and significant decreases in levelised cost of energy (LCOE) to current values of up to 63–65 USD 2023/MWh globally averaged in 2023 (with minor variability in 2024 due to market changes and new regional areas). The paper analyses turbine upscaling over three levels of hierarchy, including turbine scale—rated capacity and physical aspect, project scale—multi-gigawatts of farms, and market scale—the global pipeline > 1500 GW level, and combines techno-economic evaluation, structural evaluation of loads, and infrastructure needs assessment. The upscaling has the advantage of reducing the number of turbines dramatically (e.g., 500 to 67 turbines in a 1 GW farm, as turbine size is increased to 15 MW) and balancing-of-plant (BoP) CAPEX (turbine-to-turbine foundations and cables) by some 20 to 30 percent per unit of capacity, and serial production learning rates of between 15 and 18% per doubling of capacity. But the problems that come with the increase in ultra-large designs are nonlinear increments in mass and load (i.e., blade-root and tower-bending moments), logistical constraints (blades > 120 m, nacelle up to 800–1000 tonnes demanding special vessels and ports), supply-chain issues (rare-earth materials, vessel shortages increase day rates by 30–50%), and technology limitations (aeroelastic compounded by numerical differences between reference 5 MW, 10 MW, and 15 MW models), it becomes evident that there is a significant increase in deflections of the tower and blades and platform surge/pitch responses with continued increases in power levels, but without a correspondingly mature infrastructure. The regional differences (mature ports of Europe vs. U.S. Jones Act restrictions vs. scale-up of vessels/manufacturing in China) lead to the necessity of optimisation depending on the context. The analysis concludes that, to the extent of mature markets with adapted logistics, continuous upscaling is an effective business strategy and can result in 5 to 12 percent further reductions in LCOE, but beyond that point, gains become marginal or even negative, as risks and costs increase. The competitiveness of the future depends on multi-scale/multi-market-based approaches—modular-based families of turbines, programmatic standardisation, vibration control innovations, and industry coordination towards supply-chain alignment and standards. Its major strength is that it transcends mere size–cost relationships and shows how nonlinear structural processes, aero-hydro-servo-elastic interactions, and bottlenecks in logistical systems are becoming more determinant of the efficiency of ultra-large turbines. The study demonstrates that upscaling turbines has LCOE benefits through the support of associated improvements in installation facility, supply-chain preparedness, and structural vibration control potential, based on the comparisons of quantitative loads, techno-economic scaling trends, and regional market differentiation. Full article

Longitudinal shuttle-shaped concrete-filled steel column with cruciform sections (LSS-CFST-CS) is highly valued by architects and structural engineers for its distinctive appearance and significant architectural impact in spatial steel structures. However, there are currently no available studies addressing the buckling behavior, load-carrying capacity, and strength design methods of such structures. This study numerically investigates the elastic buckling behavior, load-carrying capacity, and design methods of LSS-CFST-CS under axial compression, as well as under combined axial compression and bending moment. First, closed-form solutions for the elastic buckling load under axial compression are derived for a pinned–pinned tapered concrete-filled steel column (TCFST) with cruciform sections and standard LSS-CFST-CS, respectively. The resulting solutions are validated against finite element (FE) numerical results from a wide range of LSS-CFST-CS examples, and the corresponding buckling modes are examined. Next, a unified expression for the elastic buckling load under axial compression is established for both types of TCFST and standard LSS-CFST-CS. Finally, a parametric study incorporating initial geometric imperfections is conducted to investigate the load-carrying capacity of LSS-CFST-CS and to quantify the influence of key parameters on stability capacity. On this basis, design recommendations for the stability capacity are proposed for axial compression and combined axial compression and bending moment of LSS-CFST-CS, respectively. Full article

In this work, experimental studies were conducted on the damage failure of laminated composite laminates under low-velocity impact and compressive failure behavior under compression after impact. The study primarily investigated the effects of stitch density, impact energy, and laminate thickness on the damage behavior of composite laminates. The experimental results indicate that at impact energies of 10 J, 15 J, and 20 J, the stitched specimens demonstrated higher impact resistance. When the stitch density was 10 × 10 mm, the average maximum impact force of the stitched specimens increased by 13.14%, 15.83%, and 21.48%, respectively, compared to the unstitched specimens. This was mainly attributed to the resin threads formed by the stitches, which enhance the through-thickness strength of the laminate, with the strengthening effect being positively correlated with stitch density. Under 20 J, the strength of the three groups of specimens with different stitching densities increased by 9.24%, 14.58%, and 21.48%, respectively, compared to the unstitched specimens. Under lower impact energies, the bending stiffness of the laminate itself was sufficient to resist the impact force, resulting in minimal differences in residual displacement among different specimens. Furthermore, the study found that under identical impact energy, stitch thread significantly suppressed delamination damage in thin specimens, whereas its effect on thick specimens was comparatively limited. The stitching also had a positive effect on the residual compressive strength of the specimens. Under 20 J impact energy, compared to the unstitched specimens, the residual compressive strength of the three groups of stitched specimens increased by 6.52%, 17.71%, and 27.48%, respectively. The mode of compression after impact failure also differed: unstitched laminated specimens mainly exhibited delamination damage, with cracks propagating along the width direction, while stitched laminated specimens demonstrated strength failure. Under axial compression, stress was released at the stitching points, leading to small-scale cracks along the fiber direction at these locations. Overall, the stitching process effectively enhances the impact resistance of laminated boards. Higher stitching density correlates with greater compressive residual strength, with this effect being more pronounced in thin-plate specimens. Full article

Fiber-reinforced concrete has proved to be viable in improving the mechanical characteristics of structural elements to the flexural and shear stresses. The concrete cubes, prisms, and cylinders were standardized, cast and cured after 28 days to assess the baseline mechanical characteristics. Beam specimens were made of different types of fibers, lengths, and different volumetric contents and then subjected to controlled shear tests in which the crack initiation, propagation, and deformation were accurately measured. The experimental data proved that the addition of fibers was highly beneficial in terms of the mechanical performance of concrete. Basalt fibers enhanced compressive strength by up to 20.8 percent and tensile strength by 30.8 percent, whereas steel fibers had the best flexural strength with a maximum compressive and bending strength of 47.2 MPa and 6.56 MPa, respectively, at optimum dosage. Polypropylene fibers also improved performance, but in a lesser manner. The fiber addition served well to reduce the width of cracks and retard crack propagation, thus enhancing load-bearing capacity. These results show that dispersed fiber reinforcement that uses steel and basalt fibers is a practical solution to improving the dispersion of concrete in terms of durability and load-bearing capacity. The research will help guide the selection of fiber and the content in the reinforced concrete work to offer more robust and sustainable solutions to building. Full article

Ultra-high-performance concrete (UHPC) has been widely investigated for its superior strength and durability; however, despite extensive research on fibre reinforcement, limited attention has been given to validating fibre surface modification strategies at the structural scale. Improvements in fibre–matrix bonding are commonly demonstrated through single-fibre tests, with limited evidence of their translation into the mechanical performance of UHPC elements. This study investigates the influence of bioinspired surface-modified steel fibres on the mechanical behaviour of UHPC, focusing on whether interfacial enhancements lead to measurable structural-scale performance gains. Steel fibres were coated under mild aqueous conditions and incorporated into UHPC at a volume fraction of 1%. Compressive strength was evaluated at 7, 14, 28, 56, and 90 days, while flexural behaviour was assessed at 7 and 28 days using three-point bending tests on notched beams and four-point bending tests on prisms. The incorporation of surface-modified fibres resulted in consistent strength enhancement at all curing ages. Compared with mixes containing uncoated fibres, compressive strength increased by approximately 15% at 7 days and remained 5–7% higher at later ages up to 90 days. More pronounced improvements were observed in flexural performance, with coated specimens exhibiting up to 51% higher peak load at 7 days and 29–32% higher peak load at 28 days in both bending configurations. These results demonstrate that fibre surface modification effectively enhances both early-age and long-term mechanical performance of UHPC, confirming that interfacial bond improvements are directly translated into structural-scale response. The findings highlight fibre surface engineering as a practical approach for improving the mechanical efficiency of UHPC without altering mix composition or fibre dosage. Full article