Search Results (5,095)

The present study intends to evaluate the ratcheting of 304 stainless steel samples at room temperature, subjected to various loading spectra and holding times through the use of the combined Ahmadzadeh–Varvani (A-V) kinematic and Lee–Zavrel (L-Z) isotropic hardening rules. The nonlinear and time-dependent functions a_rec and R_rec were implemented in the hardening framework to account for the static recovery terms (SRTs) in the kinematic and isotropic hardening descriptions. The static recovery phenomenon promoted ratcheting in steel samples tested under asymmetric loading cycles with holding time peak/valley events. The static recovery phenomenon accounts for the restoration process, elevating the plastic deformation and reducing the number of cycles to material failure. The framework with the SRT enabled the prediction of material ratcheting involving the loading rate and dwell time at room temperature. Full article

Airfoil fin Printed Circuit Heat Exchangers (PCHEs) offer significant advantages in reducing flow resistance, promoting turbulence, and enhancing heat transfer performance due to their discrete fin configuration. However, compared with conventional continuous-channel structures, the geometric discontinuities and sharp trailing edges introduced by discrete fins tend to induce severe stress concentration at the fin roots, resulting in a more complex structural response. In this study, a PCHE core with NACA0020 airfoil fins is investigated. Finite element analysis combined with a sequential one-way thermo-structural coupling approach is conducted to characterize the fins’ stress and deformation behavior under high temperature and pressure. The plate region is evaluated based on the linear elastic stress criteria specified in ASME Boiler and Pressure Vessel Code Section III, while localized yielding regions such as the fin roots are assessed using an equivalent plastic strain indicator. Results indicate that the structural response of the PCHE core is dominated by pressure loading under the investigated operating conditions with ΔT = 18 °C and ΔP = 12.05 MPa, whereas thermal stress caused by constrained thermal expansion mainly modifies local stress distributions and has a limited effect on global deformation. Owing to the discontinuous support provided by discrete airfoil fins, the fin roots act as the primary load-transfer path and sustain higher stress levels. The maximum von Mises stress is observed at the trailing edge of the fin root on the high-pressure side, while the largest deformation occurs in the unsupported plate region and is governed by bending. Parametric analysis indicates that, within the investigated parameter range, a fully staggered fin arrangement promotes more uniform load distribution and exhibits the most favorable structural response. In contrast, increasing the fin chord length and relative thickness reduces the overall load-carrying capacity of the core. Finally, a power-law predictive correlation for the maximum total plate deformation was developed, showing that the parameter influence on plate structural response follows the order horizontal pitch (L_h) > vertical pitch (L_v) > channel etching depth (L_e) > staggered pitch (L_s). In contrast, normalized sensitivity analysis of the maximum fin-root von Mises stress shows the order staggered pitch (L_s) > horizontal pitch (L_h) > vertical pitch (L_v) > channel etching depth (L_e), indicating that global plate deformation and local fin-root response are governed by different structural mechanisms. Full article

Highway slopes susceptible to landslides are typically reinforced by vegetation cover and the application of concrete frame beams, but vegetation cover may degrade the accuracy of InSAR deformation monitoring. We installed artificial corner reflectors (CRs) on the frame beams and assessed the stability of the vegetated slope using finite element simulation constrained by InSAR deformation data. A study was conducted on a typical landslide-risk slope within the K87 + 391.5–K87 + 565 section of the Guihuang highway, which is reinforced with cast-in-place and prefabricated concrete beams. Experimental results demonstrate that two adjacent corner reflectors (CRs) on the two types of frame beams of the slope can be successfully identified, with deformation rates ranging from 0.1 to 0.4 mm/y, and the root mean square error (RMSE) of discrepancies between CR-InSAR measurements and slope displacement monitoring sensors is less than 0.3 mm. Meanwhile, the current strength reduction factor values for slopes reinforced with cast-in-place and prefabricated concrete beams, as constrained by InSAR multi-dimensional deformation, are 0.11 and 0.12, respectively which are much lower than the critical strength reduction factors of 1.28 and 1.22 corresponding to full coalescence of plastic strain from the slope toe to the slope crest, which indicates that the cast-in-place and prefabricated frame beams exhibit comparable support performance. Full article

Transformer fires within indoor substations constitute severe hydrocarbon fire scenarios characterized by rapid heat release rates and extreme peak temperatures, posing a critical threat to the structural integrity of steel frameworks and power grid stability. To rigorously assess structural safety under such conditions, this study employs a sequential thermal-mechanical coupled numerical methodology combining Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA). Focusing on a 110 kV indoor substation, the research simulates the transient, non-uniform temperature fields induced by transformer oil combustion and analyzes the thermo-mechanical response of key steel components. Furthermore, the protective efficacy of two non-intumescent coatings (Material A and Material B) with distinct thermal conductivities is systematically evaluated. Computational results elucidate significant thermal stratification, with upper-level structures sustaining exposure to temperatures exceeding 1500 K. Unprotected steel components subjected to direct flame impingement exhibit severe stress concentrations and plastic deformation, reaching their load-bearing limit within 4825 s. The application of fire-retardant coatings markedly enhances fire resistance; a 5 mm layer of Material A (λ = 0.20 W/(m·K)) extends the time to failure to approximately 9390 s. Notably, increasing the thickness of Material A to 20 mm, or alternatively employing a 10 mm layer of Material B (λ = 0.10 W/(m·K)), effectively mitigates thermal stress concentrations. This ensures structural deformation remains within safe limits throughout a 3 h (10,800 s) fire duration. This study provides a theoretical basis and quantitative engineering references for the optimal fire protection design of substation steel structures. Full article

This study investigates the influence of adhesive type on the bond performance between CFRP plates and steel interfaces through static tensile double-shear tests. Three types of adhesives (Araldite 420A/B, 2015-1, Sikadur-30CN) were tested under four bond lengths. The results indicate that adhesive strength significantly affects failure characteristics, with distinct material performance differences observed. Bond length influences the stress distribution, enhancing dispersion while potentially altering damage progression. High-performance adhesives exhibit superior shear resistance and fracture energy due to improved viscous properties, whereas moderately plastic adhesives achieve adaptive deformation and durable bonding by enhancing the flow and substrate contact. These findings provide a theoretical basis for material selection in CFRP-strengthened steel structures and offer actionable guidance for structural repair engineering applications. Full article

One-way joist slab floor systems are commonly favored in modern residential building applications due to their efficiency in architectural and structural design processes. However, a significant number of such buildings experienced heavy damage or collapse mechanisms during the catastrophic earthquakes in Türkiye since they are more vulnerable due to some uncertainties in the design and construction stages. In this regard, although well-known seismic codes such as Eurocode, IBC, and ASCE do not impose additional requirements for the design of structural systems with joist slabs, the seismic codes of some Mediterranean basin countries regulate the ductility levels, use of shear walls, and member/system-based specific requirements. In the present study, the impact of shear wall quantity on the seismic behavior of reinforced concrete buildings with one-way joist slabs was investigated in five-story structural systems, which were basically similar in terms of the slab properties and layout but have different overturning moment ratios (α_M = 0.75, 0.60, 0.45, 0). In this context, a total of 88 bi-directional nonlinear time history analyses were conducted on four structural systems, which were highly representative of buildings in the earthquake zones of Türkiye, under real earthquake ground motions. Hence, the seismic behavior demands—including story displacement, inter-story drift and plastic deformations, distributions of plastic hinges, and member-based performance levels—were discussed by the overturning moment ratio that is directly associated with the shear wall quantity in the system. It can be concluded that when these buildings are jointly designed with the shear walls and frames of a high ductility level—through the capacity design principles—the stipulated performance objective can be successfully achieved. While the shear wall quantities ranging from 0.45 to 0.75 did not have a significant impact on the member-based damage across all floors, the frame-only system was found to be inadequate for controlling the lateral deformations due to insufficient stiffness under design-based seismic events. Full article

Two-dimensional (2D) materials are promising candidates for nanoscale wear-protective coatings. The mechanisms governing their tribological behaviour (i.e., friction and wear) are material-dependent. In this work, we use atomistic molecular dynamics simulations to investigate nanoscale sliding, friction, and lithographic tracks in two 2D materials, graphene and MoS${}_2$, both placed on a SiO${}_2$ substrate. Our results reveal fundamentally different deformation mechanisms in the two materials, where deformation comes as a consequence of applied normal load. MoS${}_2$ deforms via the formation of a stable out-of-plane pucker beneath the contact, enabling efficient absorption and elastic redistribution of mechanical energy within the coating as well as simultaneous reduction of plastic deformation of the underlying material. Wear prevention in the substrate comes at the cost of localised damage to the MoS${}_2$ layer along the sliding path once it reaches the rupture point. On the contrary, graphene exhibits strongly localised deformation due to its high in-plane stiffness and atomic thickness, leading to plastic deformation of the underlying material and mitigating layer damage. These findings provide clear design guidelines for 2D coatings in nanotribological applications, and highlight layered materials, such as MoS${}_2$, as particularly effective for wear protection. Full article

Instance segmentation in heterogeneous waste scenes remains challenging due to object variability, deformable shapes, partial occlusion, and large appearance differences across packaging types. This study presents a YOLOv11-based deep learning framework for mixed plastic waste instance segmentation, developed to connect visual perception with reliable material quantification. The framework integrates curated instance-level annotations, strict split isolation, multi-stage optimization, training strategy ablation, and seed-robustness analysis to support reproducible model selection. Experimental results on a held-out test set show that the optimized model achieves a mask mAP@50:95 of 0.9337, indicating strong segmentation performance under heterogeneous waste-scene conditions. To extend the analysis beyond standard vision metrics, the framework incorporates a physics-informed mask-to-mass module that converts predicted masks into class-specific mass estimates using geometric calibration and material priors. Applied to a representative stream of 1253 detected objects, the system estimated a total plastic mass of 15.48 ± 1.08 kg, corresponding to a theoretical H₂ potential of 0.41 ± 0.04 kg and a greenhouse-gas avoidance of 34.57 ± 4.15 kg CO₂e. Overall, the proposed framework extends waste-scene understanding beyond vision-level assessment toward physically grounded, data-driven decision support for smart material recovery systems. Full article

Aiming at the difficult problem of floor heave control in deep coal mine roadways, this paper took the 1224 transportation roadway of Shuguang Coal Mine in Shanxi as the engineering background and carried out the first underground industrial test of floor-slotting pressure relief technology by using special slotting equipment. The aim is to reveal the energy transfer law of the floor rock mass during slotting pressure relief and clarify its inherent connection with stress redistribution and floor heave deformation control. The research adopts a combination of theoretical analysis, numerical simulation, and field tests to systematically explore the energy accumulation characteristics of the floor and the induced mechanism of floor heave. Results show that the maximum energy accumulated in the floor after roadway excavation reaches 6.0 × 10⁵ J, which is the fundamental cause of floor heave. After optimizing the slotting parameters (depth 2.5 m, width 0.2 m), numerical simulation indicates that the surrounding rock stress concentration zone migrates to the deep part, the energy peak shifts down by 2.5 m, the floor plastic zone expands, and the range of the high-energy zone shrinks. Field test results show that the floor heave amount decreases from 30 cm to 20 cm, with a reduction rate of 33%. This study reveals the synergistic mechanism of “energy transfer–stress regulation–deformation control”, verifies the effectiveness and feasibility of the slotting pressure relief technology in the floor heave control of deep, high-stress roadways, and provides a guarantee for the safe and efficient advancement of the working face. Full article

Rock–fill composite slopes formed during the transition from underground to open-pit mining in metal mines are highly susceptible to interface hydraulic weakening and sudden sliding under intense rainfall, mainly due to the permeability contrast between the two media. Taking the Shizhuyuan Mine as a case study, a coupled hydro-mechanical numerical model was developed in ABAQUS 2025 to investigate slope stability under different rainfall patterns and interface strength degradation scenarios. The spatiotemporal evolution of seepage and deformation fields was examined in detail, with particular attention given to the variation of the safety factor, the distribution of pore water pressure along the interface, and the characteristics of interface slip. The results show that: (1) the deterioration of the hydraulic condition within the slope is governed by the water-blocking effect of the interface and the infiltration threshold of the surface layer. Under the same total rainfall, prolonged low-intensity rainfall is more likely than short-duration intense rainfall to produce sustained deep infiltration, and the factor of safety decreases from the initial 1.369 to 1.173 (0.005 m/h, 288 h) and 1.255 (0.02 m/h, 72 h), respectively, indicating that the former exerts a more pronounced weakening effect on slope stability. (2) Slope instability exhibits a clear interface-controlled pattern. Regardless of the degree of parameter degradation, the base of the plastic zone consistently develops along the rock–fill interface, accompanied by extensive plastic deformation within the overlying fill material. (3) Failure initiates at the slope toe where the mechanical equilibrium along the rock–fill interface is first disturbed. Under the combined influence of topographic conditions and the water-blocking effect of the interface, rainfall infiltration tends to converge toward the slope toe and form a local high-pore-pressure zone, resulting in a marked reduction in the effective normal stress at the interface. Once the local shear stress exceeds the shear strength, yielding is triggered first at the slope–toe interface, which then induces plastic deformation in the overlying fill material and ultimately leads to overall slope instability. Full article

The Zircaloy-4 alloy is a key structural material for nuclear reactor cores. However, its behavior under warm deformation conditions and during phase transformations requires in-depth investigation to improve technologies for producing ultrafine-grained (UFG) structures using severe plastic deformation methods. This work presents a comprehensive study of the rheological properties, phase stability, and microstructural evolution of the alloy in the temperature range from 20 to 950 °C at strain rates of 0.5 and 15 s⁻¹. The experimental part included plastometric testing, dilatometric analysis, and microstructural characterization. It was established that the optimal window for plastic deformation corresponds to warm deformation at 650 °C. Dilatometric analysis confirmed that heating to 650 °C ensures the preservation of a stable initial α-phase structure, since the formation of secondary phases and the α→β transformation are initiated at higher temperatures, namely 694 °C (onset) and 847 °C (completion). At 650 °C, the deformation resistance decreases by approximately 70% compared to cold processing, while the strain-rate sensitivity of the flow stress is minimized. EBSD analysis showed that deformation under these conditions leads to intensive grain fragmentation via mechanisms of dynamic recovery and the initial stages of continuous dynamic recrystallization. The decisive role of the kinetic factor was demonstrated: reducing the strain rate to 0.5 s⁻¹ promotes the formation of a finer and more homogeneous grain structure. In contrast, high strain-rate deformation (15 s⁻¹) results in coarser grains and increased non-relaxed intragranular residual stresses. The obtained results provide a physical basis for optimizing thermomechanical processing regimes and can be used to produce UFG structures in zirconium alloys without the risk of phase degradation. Full article

Modern performance-based bridge design seeks to control damage in specific failure modes in order to balance safety and economy, particularly in high-seismic regions where inelastic and ductile deformation is expected to occur, both in the structure and soil, allowing potential reduction in seismic demand through fuse elements. In short-span bridges, abutments strongly influence longitudinal response, whereas transverse performance depends largely on seismic components such as shear keys and other energy-dissipation devices. Thus, performance assessment requires explicit representation of their hysteretic behavior. This study presents a numerical evaluation of the damping provided by common elements in typical bridge systems, using as reference damage observations from bridges affected by recent interface earthquakes in Mexico. Three-dimensional finite-difference models were developed, and nonlinear response-history analyses were performed to simulate ductile behavior and energy dissipation. The Sig3 hysteretic model available in FLAC^3D was used for abutments and foundation soils, while shear keys were represented as nonlinear springs. The results established a relationship between plastic deformation and energy dissipation, showing that incorporating the hysteretic behavior of both soil and sacrificial structural components enhanced the seismic bridge performance assessment, and led to more reliable and cost-efficient designs when inelastic deformation capacity was explicitly included in the numerical simulations. Full article

Under long-term cyclic loading, the cumulative plastic deformation of unsaturated sandy subgrade is a key control factor for the pavement’s service performance. However, its evolution mechanism and quantitative characterization still lack a universal model. In this study, based on the GDS dynamic triaxial system, a series of cyclic tests were conducted under different conditions: matric suction from 0 to 90 kPa, net confining pressure from 30 to 120 kPa, dynamic stress amplitude from 60 to 240 kPa, and compaction degrees of 87–96%, reaching a total of 10,000 cycles. The results reveal that the permanent deformation of unsaturated sandy subgrade material evolves through three stages: fast, slow, and stable. The deformation is exponentially negatively correlated with matric suction, net confining pressure, and compaction degree, and exponentially positively correlated with dynamic stress amplitude. A coupling prediction model was developed by embedding matric suction and compaction degree factors into the Karg model. This model incorporates net confining pressure, dynamic stress amplitude, matric suction, and compaction degree. By using a normalized master curve method, the permanent deformation curves under different working conditions were compressed into a unique dimensionless function. The parameters have clear physical significance and allow for a unified description across stress, suction, state, and soil types. Experimental data, along with data from the literature, were used to validate the model, showing prediction errors of less than 10% and R² > 0.95. The model provides a simple, high-precision, and transferable theoretical tool for long-service-life subgrade deformation control. Full article

To further improve the mechanical properties of shotcrete in coal mine roadways, end-hooked steel fibers and chopped basalt fibers were selected. Based on the optimal mix ratios identified in existing research, steel–basalt hybrid fiber shotcrete (SBFC) specimens were prepared. Dynamic impact tests under different impact loads and various hybrid fiber contents were conducted using an SHPB. The microstructure was characterized using SEM and XRD. The results show that the dynamic compressive stress–strain curve of steel–basalt hybrid fiber shotcrete can be classified as elastic deformation stage, plastic yield stage, and post-peak failure stage. The incorporation of hybrid fibers reduces the elastic deformation and plastic yield stage, and the post-peak failure stage under active confining pressure shows elastic aftereffect characteristics. The dynamic compressive strength, dynamic elastic modulus, and deformation modulus increase with the increase in impact pressure and fiber content. When there is no confining pressure, the maximum dynamic compressive strength, dynamic elastic modulus, and modulus of deformation of SBFC4 reached 53.1 ± 2.2 MPa, 4.51 ± 0.3 GPa, and 2.55 ± 0.1 GPa, respectively, representing increases of 37.20%, 264.01%, and 59.37% compared with the control group. The dynamic compressive strength increases with the average strain rate, demonstrating a favorable strain rate effect. The energy–time history curves can be roughly divided into initial, growth, and stable stages. Under the same impact load conditions, as the fiber content gradually increases, the incident energy, dissipated energy, and energy utilization rate of the specimens all show a gradual upward trend. SEM and XRD results show that steel fibers and basalt fibers maintain good bonding with the cement matrix, contribute to the formation of gel and crystalline products within the specimens, effectively delay the initiation and propagation of cracks, and thereby improve the mechanical properties of the concrete specimens. Full article

Ductility dip cracking (DDC) remains a persistent challenge in multipass welds of high-chromium nickel-based alloys used in the nuclear power generation industry. While dynamic recrystallization (DRX) has been observed to arrest DDC crack growth and has been associated with weld regions that experience less DDC, there exists no quantitative relationship between the extent of recrystallization in a microstructure and DDC susceptibility. This research examines the influence of intragranular carbides on DRX behavior and establishes an experimental relationship between DDC susceptibility and extent of recrystallization in high-chromium nickel-based weld metals, novel contributions for this alloy system. In this work, the DRX behavior of the weld metal of high-chromium nickel-based filler metals (FM-52, FM-52M, FM-52i, and FM-52xl) was investigated under controlled thermo-mechanical conditions, and its effect on DDC susceptibility was established. Weld metal specimens were subjected to uniaxial deformation at 1100 °C to a true strain of 2% at strain rates of 10⁻³/s and 10⁻⁴/s using a Gleeble 3800^TM. Recrystallization was quantified using electron backscatter diffraction (EBSD) via grain orientation spread (GOS) analysis and dislocation–precipitate interactions were examined using transmission electron microscopy (TEM). Strain-to-fracture (STF) testing at 950 °C was employed to assess DDC susceptibility as a function of the extent of recrystallization and grain surface area. All tested weld metals exhibited increased recrystallization and grain refinement, as the strain rate decreased from 10⁻³/s to 10⁻⁴ s. The FM-52i weld metal specimens exhibited the highest grain refinement under high temperature deformation, followed by the FM-52xl, FM-52, and FM-52M weld metals with a percent reduction in average grain surface area of 51.22%, 41.66%, 35.48%, and 24.40%, respectively. The FM-52i weld metal specimens also exhibited the highest recrystallization response, followed by FM-52M, FM-52xl, and FM-52 weld metals at 75%, 40%, 39% and 21% recrystallized, respectively. Weld metals containing strong carbide formers experienced higher recrystallization responses than those without due to precipitate–carbide interactions. All tested weld metals experienced drastic reductions in DDC response with increasing extent of recrystallization and decreasing average grain surface areas. DRX in STF specimens was observed to facilitate uniform plastic strain accumulation, lowering overall DDC susceptibility compared to non-recrystallized specimens. Full article