Archives of Civil and Mechanical Engineering最新文献

This study investigates the cyclic behavior of steel beam-to-column connections incorporating a radially perforated plate damper (RPPD). A single experimental specimen was conducted to assess the structural response of the proposed damper, which consists of concentric steel plates with radial slits designed to induce controlled in-plane plastic deformation. The specimen demonstrated stable, symmetric hysteresis behavior with no pinching or degradation up to a rotation angle of 0.08 radians. The test results showed a peak energy dissipation capacity of 15.37 kJ and a maximum equivalent viscous damping ratio of 0.171. The RPPD sustained 38 cycles under increasing amplitude loading and achieved a cumulative plastic deformation index of 331. Finite element analysis closely matched the experimental observations in terms of moment capacity, strain distribution, and failure patterns. A parametric study involving 24 specimens was then carried out to evaluate the influence of damper geometry on the system performance. Increasing the number of radial strips from 2 to 12 led to a threefold improvement in moment resistance and energy dissipation. Strip thickness and width were found to play a critical role, with a 1.5-fold increase in thickness improving energy absorption by 45% and moment resistance by 60% while doubling the width enhanced both by over 200%. Shorter strips yielded better performance, with a 30% improvement in the moment and energy metrics observed when length was reduced by 1.5 times. The findings support the use of the proposed system as replaceable fuses for seismic energy dissipation and provide detailed guidance for their geometric optimization in structural applications.

Laser shock peening (LSP) markedly enhances the fatigue life of metallic materials but can degrade near-surface topography. This study develops a hybrid route that applies LSP followed by low-stress milling (LSP-LSM). The micro-removal depth (({delta }_{LSM})) is treated as a design variable for GH4169 to balance surface roughness reduction and retention of compressive residual stress (CRS). Guided by the indentation depth analysis of LSP, we experimentally quantify how the ({delta }_{LSM}) in LSP-LSM affects the surface integrity and high-cycle fatigue life of GH4169. LSP produces a CRS field extending to approximately 1 mm, with a maximum of approximately − 700 MPa within a subsurface layer near 300 μm, while increasing the surface roughness ({S}_{text{a}}) to 3.72 μm, a 68.3% increase compared with the untreated surface. In contrast, LSP-LSM reduces the minimum ({S}_{text{a}}) by 74.7% compared with LSP and by 57.4% compared with the untreated surface, increases the surface CRS by 287.4% and the maximum CRS by 37.0%, and shifts the stress peak toward the surface (CRS depth of approximately 700 μm). The fatigue life increases by 86.8% compared with LSP and by 192.2% compared with the untreated condition. LSP refines the surface grain size from approximately 254 μm to approximately 24 μm; LSP-LSM effectively retains this refinement at approximately 30 μm. Overall, an optimum ({delta }_{LSM}) of approximately 100 μm is identified under the present conditions. Building on these findings, the LSP-LSM route provides engineering guidance for GH4169 components and can be extended to curved and thin-walled geometries; evaluation of broader LSP/LSM settings and fatigue conditions will support component-level implementation.

Graphical Abstract

Additive manufacturing (AM) of titanium alloys offers significant benefits, including design flexibility and material efficiency; however, its poor surface quality often necessitates subsequent machining. Traditional cooling techniques have shown limited effectiveness, particularly with challenging materials like Titanium grade 2 (Ti-grade 2). In this study, graphene quantum dots (GQDs) were prepared using citric acid and employed as the minimum quantity lubrication (MQL) fluid, which was compared with MQL and cryogenic liquid nitrogen (cryo-LN₂) in the turning of Additive Manufactured-Titanium-grade 2 (AMed-Ti Grade 2). In addition, machine learning (ML) models, including multilayer perceptron (MLP), support vector machine (SVM), and random forest (RF), were utilized to predict machining responses [surface roughness (Ra), temperature (Tc), and flank wear (Vb)]. GQD–MQL demonstrated superior tool wear resistance by forming a stable tribo-film, minimizing Vb and crater wear. In contrast, MQL exhibited high wear due to inadequate lubrication, while cryo-LN₂ provided moderate control through effective cooling. However, in terms of Tc, cryo-LN₂ produced the lowest temperature in the cutting area when compared to other conditions. The ML models revealed that the MLP model accurately predicted Ra and Tc, whereas SVM outperformed the other models in predicting Vb.

To promote the application of lightweight aggregate concrete in sulfate-rich environments, the evolution of its interfacial bonding behavior with normal concrete (NC) had to be clarified. Therefore, the direct shear test was employed to investigate the interfacial bonding behavior of full lightweight ceramsite concrete and NC in a sulfate environment. The experimental parameters included sulfate concentrations and erosion times. The interfacial behavior was assessed based on failure modes, load-slip curves, shear strength, shear stiffness, and fracture energy. The results showed that at concentrations of 5 wt% and 7 wt%, the failure mode of the specimens shifted unfavorably as erosion continued. With the increase of erosion time, the interfacial shear strength and fracture energy firstly increased and then significantly decreased to form an inflection point, and the increase of concentration led to an earlier appearance of the inflection point. The interfacial fracture energy was much more affected by sulfate than the interfacial shear strength. After 150 days of erosion, the fracture energy K value decreased to 49.8%–57.5%. In addition, equations for the evolution of interfacial shear strength, shear stiffness, and fracture energy were established.

In this work, influence of the variant of the Ti grade 4 plastic deformation with multi-pass hydrostatic extrusion (HE) on its microstructure and mechanical properties was studied. The emphasis was placed on the correlation between the extrusion pressure curves and the microstructure of produced rods after subsequent extrusion passes. The qualitative and quantitative microstructure characterization was performed with SEM/EBSD and orientation imaging in TEM. The mechanical properties were assessed in static tensile test. The results revealed that dynamic recrystallization during three-pass HE allowed to obtain bimodal microstructure consisting of elongated grains and a fraction of ultrafine defect-free equiaxed grains facilitating the plastic deformation. Adding a fourth extrusion pass produced highly deformed microstructure, as the temperature was insufficient to activate recrystallization processes. In this way, the highest mechanical strengthening was obtained inhibiting the extrusion process represented by nonuniform pressure curves. Application of recrystallization annealing to sustain uniform and stable plastic deformation represented by smooth extrusion curves, enabling to obtain relatively high plasticity of the final product. It has been demonstrated that optimization of extrusion path by selection of cross-sectional reduction or application of recrystallization annealing leads to obtaining either large mechanical strengthening or increased plasticity, depending of intended application.

Under conditions of single-sided moisture transfer, concrete displays an uneven distribution of internal relative humidity and creep deformation along its cross-sectional height. This heterogeneity is further intensified by the inclusion of recycled coarse aggregate. In this study, a non-uniform creep model was proposed for recycled concrete under such moisture-transfer conditions. A thermomechanically coupled finite element model was developed to simulate the long-term deformation of recycled concrete, and its accuracy was validated against experimental data. The investigation quantitatively evaluated the effects of key parameters—including the recycled coarse aggregate replacement ratio, loading duration, and humidity boundary conditions—on the non-uniform creep behavior. By incorporating the internal relative humidity profile into a standard uniform creep model, the authors derived an improved distribution model that considered the influence of humidity boundary conditions. Results indicated that both the recycled coarse aggregate replacement ratio and loading duration played crucial roles. Specifically, increasing the replacement ratio from 0 to 100% led to a 39.8–41.4% increase in the top surface creep coefficient and an 86.7–99.6% increase in creep curvature. Moreover, extending the loading period from 90 days to 50 years resulted in a 32.9–79.5% increase in the top surface creep coefficient while simultaneously reduced creep curvature by 34.0–90.0%. The proposed prediction model accurately calculated the creep deformation in recycled aggregate concrete under conditions of single-sided moisture transfer, effectively mitigated prediction inaccuracies caused by moisture gradient effects.

Microwave pretreatment is an effective method for weakening rocks in mining and civil engineering applications. Understanding the dynamic fracturing behavior of microwave-treated rocks is crucial for optimizing microwave-assisted mechanical rock breakage in excavation. In this study, granite disc samples were subjected to microwave irradiation for durations ranging from 0 to 10 min, followed by dynamic splitting tensile tests using the Split Hopkinson Pressure Bar (SHPB) apparatus. Rock surface temperatures were measured using an infrared camera, and internal damage was evaluated through nuclear magnetic resonance (NMR). The results demonstrated that microwave treatment significantly reduced the dynamic splitting tensile strength of granite. The increase in porosity was negatively correlated with the macroscopic strength of the rock. Interestingly, some samples without visible macro-cracks exhibited more extensive internal damage than those with visible cracks. High-speed imaging revealed that, as the microwave irradiation time increased, the rock’s impact fracturing behavior transitioned from being primarily controlled by microwave-induced cracks. Based on these findings, a novel microwave-assisted rockburst prevention and control method is proposed.

Strongly reinforced composite dowels (SRCD) is a new structural solution that enables the creation of new types of steel–concrete hybrid sections in bridges. It was developed in Poland in 2021 to build a new kind of hybrid bridge, in which the webs made of normal concrete are to be only 20 cm thick, which is less than allowed by the current regulations for designing structures with a composite dowels shear connection. The design solution assumes the use of such a high density of bars in the vicinity of steel dowels that brittle mechanisms of concrete failure (pry-out cone) will be eliminated while ensuring such a degree of confinement of the concrete dowel core that the failure mechanism can be classified as close to the currently adopted shear failure mechanism. The target concept of design, the scientific basis of which is presented in this paper, is therefore completely different to the present one. Instead of two criteria for concrete failure in the form of pry-out cone and shear, there will be only one criterion in the form of shear with a reduced confinement effect. It is emphasized that the obtained load-bearing capacity will be significantly greater than calculated from the current pry-out criterion, which always decides when designing a bridge structure. It is noted that under the proposed concept, two separate issues were simultaneously recognized, linked, and solved: the first concerns a narrow concrete web and the hypothetical pry-out cone perpendicular to the surface of the steel web, and the second concerns the pry-out cone from the bottom of the web.

The heterostructured medium Mn steels are fabricated via tailoring the schedule of cold rolling reduction and subsequent intercritical annealing in the present study. The strengthening mechanism of hetero-deformation induced (HDI) hardening in the heterostructured steels is revealed, and the interplay between cold rolling reduction and formation of morphological heterostructure and its effect on the mechanical properties are clarified. The heterostructure concurrently compromising the granular and lath-typed microstructures is obtained in the intercritically annealed medium Mn steels with the cold rolling reduction of 40% and 60%. The formation of heterostructure should be attributed to the occurrence of partial recrystallization in the sites with strain concentration within the as-cold-rolled samples. The heterostructured steels exhibit enhanced mechanical properties in comparison to their homogeneous counterpart, which should be originated from the joint effect of the HDI hardening and enhanced transformation-induced plasticity (TRIP) effect. The mutual constraint between the lath-typed and granular microstructures facilitates the accumulation of GNDs in the soft domain, producing significant HDI hardening. The volume fraction of lath-typed microstructure is closely dependent on the cold rolling reduction and further plays an important role in the mechanical properties. An ideal heterostructure can be obtained in the steel through cold rolling reduction of 60% + intercritical annealing at 665 °C for 1 h. During deformation, the soft domains (lath-typed microstructure) can be rigidly constrained by the hard domains (ultrafine-grained granular matrix), promoting the multiplication of GNDs and thus leading to the significant HDI hardening and the enhanced TRIP effect. It is of great significance that the heterostructure can be introduced in the medium Mn steel to achieve enhanced mechanical properties by adopting the appropriate processing schedule of cold rolling and intercritical annealing.

This study presents the development and validation of finite element models aimed at integrating thermal predictions with Warehouse Management Systems (WMS) for optimizing logistics operations. The research introduces both one- and two-dimensional heat transfer models, each tailored to specific operational needs. The one-dimensional model is designed for rapid calculations, making it suitable for integration into WMS, while the two-dimensional model provides more detailed insights required for model calibration and validation. These models account for the heat transfer between adjacent coils by estimating the effective ambient temperature based on the temperatures of neighboring coils. Validation against thermographic measurements confirmed the models’ accuracy and demonstrated the one-dimensional model’s suitability for real-time WMS applications. Future work will focus on enhancing the computational efficiency of these models through parallel processing, making them viable for full-scale warehouse simulations.