Archives of Civil and Mechanical Engineering最新文献

To address the growing need for sustainable construction materials and effective waste management, this study investigates the feasibility of incorporating ceramic waste powder (CP) and powdered eggshell (PES) as partial replacements of ground blast furnace slag (0–50% by weight) in geopolymer mortars (GPs). The experimental program employed Central Composite Design to analyze binary and ternary GPs, examining fresh properties, mechanical performance, physical characteristics, and freeze-thaw resistance. Microstructural and phase evolution were assessed using XRD, FTIR, and SEM/EDX techniques. Findings revealed that CP improved workability due to its slower reaction kinetics and sub-angular morphology. Moderate PES additions (12.5%) enhanced early-age strength (47.94 MPa), while CP incorporation up to 25% improved long-term strength (> 80 MPa). Balanced CP-PES combinations enhanced matrix density, reducing water absorption and improving ultra pulse velocity. Microstructural analysis confirmed the synthesis of C-(N)-A-S-H gels, with balanced Ca/Si and Al/Si ratios. Ternary mix (12.5% CP, 12.5% PES) exhibited superior freeze-thaw resistance, with strength and weight losses recorded at 14.52% and 1.25%, respectively. The optimized mixture (20.4% CP, 14.12% PES) achieved a desirability value of 0.91, demonstrating excellent performance across all properties. This research demonstrates the feasibility of incorporating industrial and agricultural waste into high-performance, frost-resistant geopolymer mortars, offering a sustainable alternative for cold-climate construction.

The utilization of industrial and construction wastes in binder and aggregate systems offers an effective pathway toward sustainable and eco-efficient construction materials. This study examines the mechanical and durability performance of expanded perlite-based alkali-activated lightweight composites (AALCs) incorporating waste tire aggregate (WTA) as a partial or full replacement for expanded perlite (EP) and brick powder (BP) as a supplementary binder with ground granulated blast furnace slag (GBFS). Eight mixtures were prepared with WTA at 0–100% (by volume) and BP at 0–10% (by mass), activated with 12 M NaOH and sodium silicate (SiO₂/Na₂O = 2.0). Specimens were thermally cured at 40 °C and 80 °C for 8 h, then tested for compressive and flexural strength, oven-dry density, thermal conductivity, sorptivity, freeze–thaw resistance, high-temperature stability (up to 350 °C), and 90-day sulfate resistance in 5% MgSO₄. The highest compressive strength (28.82 MPa) was obtained in the GBFS-only mix cured at 80 °C. Increasing WTA reduced strength but improved freeze–thaw and thermal performance; full EP replacement (100RB0) yielded the lowest strength (10.15 MPa at 40 °C) yet showed excellent freeze–thaw durability with only 3.84% loss. Incorporation of 10% BP enhanced sulfate resistance, with 25RB10 showing 13.63% strength loss versus 29.02% in the unmodified mix. Under thermal exposure, BP mixes retained up to 68% of strength at 250 °C, while all suffered ≥ 90% loss at 350 °C. Strong inverse correlations were observed between weight loss and compressive strength across durability tests (R² ≥ 0.90). Thermal conductivity ranged from 0.432 to 0.527 W/m·K, decreasing with WTA content. These findings confirm that optimized use of WTA and BP produces lightweight, durable, and eco-efficient AALCs, supporting circular economy goals through waste valorization.

This work concerns an experimental investigation of the Ti–25Nb and Ti–25Nb–1O (at%) SMAs in the initial stage of tensile deformation using acoustic emission (AE) and digital image correlation (DIC). The stress-strain responses of the considered SMAs are different. The Ti–25Nb SMA exhibits shape memory effect due to the stress–induced martensitic transformation from the cubic β phase to the orthorombic α″ phase. In the case of the Ti–25Nb–1O SMA, the addition of 1 at% of oxygen results in a nonlinear superelastic behavior with small hysteresis and an increased yield stress. The stress-induced phase transformation in the Ti–25Nb–1O SMA is hindered due to the addition of oxygen interstitials. The difference between the deformation mechanisms and the resulting mechanical behaviors of the SMAs was clearly reflected by the recorded AE signals and deformation fields. It was shown that the AE can serve to track the development of the stress–induced phase transformations in the Ti–25Nb and Ti–25Nb–1O SMAs during tension. The AE signals were correlated to the strain fields of the SMAs, which showed a Lüders–type deformation of the Ti–25Nb SMA and a distinct but still inhomogenous deformation of the Ti–25Nb–1O SMA. The results of this study show that DIC and AE techniques are effective tools for monitoring phase transformations of the Ti–25Nb and Ti–25Nb–1O SMAs during tensile loading.

Functionally graded (FG) graphene origami-enabled auxetic metamaterial (GOEAM) structures have gained significant attention in recent years owing to their exceptional mechanical properties. This paper presents an analysis of nonlinear vibration characteristics of FG-GOEAM beams, focusing on the influence of the coupling between damping and graphene origami (GOri) parameters. The effective material properties of the FG-GOEAM beams are determined using the genetic programming (GP)-assisted micromechanical model. The Kelvin-Voigt damping model is introduced, and the governing equations of the damped beam are derived using Timoshenko beam theory and von Kármán nonlinearity. Differential quadrature (DQ) method is employed to solve the nonlinear kinematic equations. A comprehensive parametric study is conducted to analyze the effects of GOri content, folding degree, temperature, and damping on the nonlinear vibration behavior of the FG-GOEAM beams. Numerical results demonstrate that damping alters the nonlinear vibration behavior of the FG-GOEAM beam by weakening the effects of GOri parameters. The dominant factor differs by FG distribution, with GOri content dominating in X-W_Gr distribution, whereas GOri folding degree dominates in U-W_Gr distribution. In X-W_Gr beams, increasing the damping coefficient reduces the enhancement of the nonlinear frequency caused by GOri content, with a maximum reduction of 7.81%. For U-W_Gr beams, damping weakens the frequency suppression associated with GOri folding degree, with the reduction declining to 4.57% at 100% folding degree. Additionally, when the bending and shear proportional constants are less than 2.5 × 10^–5 s, the maximum reduction in linear and nonlinear frequencies is approximately 2%, indicating that damping can be neglected under this condition.

This study employs laser-cold metal transfer (CMT) hybrid welding technology (with laser power accounting for 89.94%) to weld aluminum alloy 6082-T6 (AA6082-T6), and systematically investigates the effect of different butt gaps (0–0.15 mm) on weld forming quality, microstructure, and mechanical properties. Results show that 0.15 mm gap achieves optimal forming quality, with a porosity of only 1.64% (satisfying ISO 13919–2 Grade B). This is because although the melt pool mode at this gap is a keyhole mode, its Rayleigh jet instability is the weakest. Microstructure that as the butt gap increases to 0.15 mm, the partially melted zone (PMZ) decreases to 39.84 μm, the secondary dendrite arm spacing (SDAS) decreases to 5.01 μm, and partially equiaxed crystals form. These results are related to the increase in the cooling rate (CR). Additionally, scanning electron microscope (SEM) analysis shows that the Si element segregation and oxide inclusion phenomena are weakest under the 0.15 mm gap, which is consistent with the decreasing trend of SDAS. Mechanical properties show that the weld with a 0.15 mm butt gap has the best performance. Its average microhardness is 78.72 HV, ultimate tensile strength (UTS) is 213.83 MPa, elongation (EL) is 6.32%. Compared with the 0 mm gap weld, its UTS and EL increase by about 8% and 85%, respectively. And only the 0.15 mm gap weld achieves a UTS approaching 70% of the base material’s UTS. Fractographic analysis shows brittle-ductile fracture in the 0.15 mm gap weld, while other gap sizes show brittle fracture.

Spalling is a common dynamic damage phenomenon during blasting and excavation of underground projects, and the use of supporting structures is still the most effective engineering measure to control this type of disaster. This study investigates the spalling characteristics of Thin Spray-on Liner (TSL)-supported sandstone under dynamic loading using a Hopkinson pressure bar. Results demonstrate that increasing TSL thickness enhances impact resistance, necessitating higher impact pressures (0.30 MPa to 0.40 MPa) to induce spalling. TSL effectively attenuates reflected wave amplitudes, reducing spalling strength from 8.81 MPa to 7.20 MPa with increasing thickness. Furthermore, TSL reduces spalling events from two in unsupported specimens to one at 5 mm and 10 mm thicknesses, despite elevated impact pressures, and shifts spalling locations away from the free end, with distances increasing by 0%, 12%, and 65% for 5 mm, 10 mm, and 20 mm TSL, respectively. Both experimental and numerical simulation results reveal that the TSL has energy absorption properties under dynamic loading conditions, and the effect is most significant when the thickness reaches 10 mm; the enhancement of the energy absorption effect is gradually weakened with the further increase of the thickness. Compared to mortar support, TSL, at one-tenth the thickness, maintains structural integrity and superior adhesion, preventing interface failure and yielding greater spalling distances. These findings underscore TSL’s efficacy as a dynamic support material, offering significant potential for engineering applications.

A fracture toughness is one of the critical parameters for Pyrowear 53 steel which is widely used in planetary gears of aircraft vehicles. Due to a limited volume of planetary gears, it is impossible to directly assess their plain strain fracture toughness K_Ic. Therefore, the main aim of this study was to determine a formula correlating the plain strain fracture toughness K_Ic obtained for laboratory compact tension (CT) specimens having a thickness of B = 50 mm with smaller specimens (B = 10 mm) which can be prepared directly from planetary gears. For this reason, different force-based approaches were utilized considering conditional fracture toughness (K_Q), size-insensitive conditional fracture toughness (K_Qsi) and specimen strength ratio (R_sc) values calculated according to ASTM E399 standard. Four different sizes of CT specimens were analyzed, i.e. B = 50, 25, 16 and 10 mm. The K_IC value obtained for the B = 50 mm specimen was 101.7 ± 4.5 MPa m^1/2, while for the smaller specimen sizes, the K_Q value gradually decreased from 125.4 ± 10.0 MPa m^1/2 for B = 25 mm to 101.1 ± 3.0 and 86.6 ± 1.3 MPa m^1/2 for B = 16 and 10 mm, respectively. This trend was opposite to the commonly observed relation that the fracture toughness value increases for smaller specimen size with a higher plain stress region. The specimen size effect observed in the current work resulted from the methodology of determining the K_Q value based on a force P_Q defined at a point of 5% deviation from linearity of load-displacement curve. It has been shown that the fracture toughness of the Pyrowear 53 steel specimens exhibiting a rising R curve was more dependent on a ligament size.

Plasticity modeling at elevated temperatures is highly nonlinear and multivariate in nature; the accurate prediction of the strain hardening behavior is challenging. To address this issue, this study investigates the mechanical properties of AA6061-T6 round bars when exposed to high temperatures to assess their plastic behavior and thermal stability. Tensile tests over 25–250 °C were performed at a fixed strain rate of 0.001/s to avoid confounding between temperature and strain rate; constitutive parameters were calibrated at this reference rate. The Johnson–Cook (JC), Zerilli-Armstrong (ZA), Khan-Huang-Liang (KHL), Lim-Huh (LH), and artificial neural network (ANN) models were utilized to model the true stress-plastic strain behavior at different temperatures. Finite element analyses were conducted to compute the reaction force using ABAQUS/Explicit VUMAT subroutines with all the analytical and ANN models. These models were evaluated for their accuracy in replicating experimental tensile behavior under high temperature. The analytical results showed that the ANN model has higher prediction accuracy, achieving a determination coefficient of 0.99998, whereas those of the JC, ZA, KHL, and LH models were found to be 0.9608, 0.7351, 0.9129, and 0.9614, respectively. The FEA results showed that the ANN model accurately illustrates the load capability, with the best agreement among the analytical models. The results highlight the robustness and predictive capability of the ANN model, making it a reliable tool for modeling intricate stress–strain relationships under high temperature.

In this paper, the effect of hafnium, titanium, and molybdenum addition on the microstructure and properties of the aluminide layers deposited by using a chemical vapor deposition process on IN 713C nickel superalloy substrate was discussed. A multi-component aluminide diffusion layer containing Ni–Al, Al–Ti–Ni, and hafnium-rich phases was successfully formed by aluminizing IN 713C nickel superalloy. Subsequently performed corrosion resistance tests confirmed the beneficial effect of the aluminide layer deposited on IN 713C as compared to substrate material. Anticipating improved mechanical response of coated material, density functional theory calculations were performed. It was found that a single Hf/Ti/Mo atom prefers to be positioned within the Al sublattice in the NiAl, and Ni₃Al phases. This justifies the presence of the experimentally observed Ni₃Hf phase in the Hf-enriched IN 713C. The Hf modification effects on the NiAl, and Ni₃Al were further discussed based on the changes of the elastic constants C_ij, bulk modulus B, and shear modulus G. The presence of Hf in NiAl causes a decrease of phase’s C₁₂ and C₄₄ values, and increase in the C₁₁ value. It was found that Hf modification of the Ni₃Al causes a decrease in the C_ij values and a slight decrease of phase’s B/G ratio, indicating a less ductile character of modified phase decohesion.

This study investigates the mechanical, thermal, and durability performance of one-part geopolymer foam concrete (GFC) incorporating boiler ash (BA) as a partial replacement for fly ash (FA) and polypropylene fibers (PPF). Nine distinct mixtures were prepared with varying BA replacement levels (0%, 10%, and 20%) and PPF contents (0%, 0.5%, and 1%). Comprehensive testing was conducted to evaluate compressive and flexural strength, thermal conductivity, porosity, water absorption, sorptivity, freeze-thaw resistance, and high-temperature durability. The experimental results indicate that replacing FA with BA enhances the geopolymer matrix’s mechanical and durability properties through improved gel formation and matrix densification. The optimal mixture, containing 20% BA and 0.5% PPF, achieved a 41.52% increase in compressive strength compared to the reference mixture (0% BA, 0% PPF). This mixture also exhibited the lowest porosity (23.82%), water absorption (16.76%), and sorptivity (8.28%), along with the highest thermal conductivity (0.619 W/mK). However, mixtures with higher BA and PPF contents experienced reduced high-temperature resistance, with strength losses of 16.2% and 27.1% observed at 400 °C and 900 °C, respectively. Durability assessments revealed significant improvements in freeze-thaw performance. The optimized mixture demonstrated minimal weight loss and significant compressive strength gains after 15 freeze-thaw cycles. Microstructural analysis confirmed the synergistic effects of BA and PPF in enhancing the matrix’s densification, reducing pore connectivity, and bridging micro cracks. Additionally, BA’s high calcium content contributed to the formation of dense C-S-H and C-A-S-H gels, which played a crucial role in enhancing strength and reducing permeability. This study underscores the potential of BA as a sustainable alternative to FA in GFC production, highlighting its role in waste valorization and environmental sustainability. The findings provide valuable insights for optimizing BA and PPF content in GFC formulations, promoting their application in eco-friendly and high-performance construction materials.