Search Results (696)

To address the challenges of bedding separation and large deformation in deep gob-side roadways with composite roofs under the influence of stress deviation and weak interlayers, this study takes the 1692(1) rail roadway of Pansan Coal Mine as the research object. By combining numerical simulation, theoretical analysis, and field testing, the study thoroughly investigates the evolution patterns of the plastic zone in the surrounding rock and the mechanisms governing delamination. The results demonstrated that stress deviation induces shear failure of weak interlayers and causes bedding separation at the early excavation stage, which subsequently transforms into tensile failure and leads to coal pillar instability. The principal stress deviation angle determines the expansion direction of the plastic zone, while the thickness and number of weak interlayers are positively correlated with the degree of bedding separation. It is concluded that the coal pillar strength is a critical factor for bedding separation control. Based on these findings, a combined control scheme of “strengthening coal pillars, restraining shear damage, improving coordinated deformation” is proposed. Field engineering practice confirms that this proposed scheme effectively restrains the expansion of the plastic zone and ensures the long-term stability of the roadway. Full article

This study investigates the seismic response of a natural draft reinforced concrete cooling tower subjected to spatially varying earthquake ground motion, with particular emphasis on nonlinear material behavior, damage evolution, and stiffness degradation. The analysis is based on a constitutive description of concrete using the Concrete Damaged Plasticity (CDP) model, enabling the representation of tensile cracking, compressive crushing, and irreversible plastic deformation under cyclic dynamic loading. Two structural configurations of the lower shell region–a locally thickened shell and a bottom ring-stiffened solution–are examined from the perspective of material performance and damage control. Spatially varying seismic excitation is defined using a real earthquake record from the Carpathian Flysch region, with wave passage and incoherence effects calibrated from in-situ measurements. Nonlinear time-history analyses, performed to capture the coupling between material degradation mechanisms and global structural response, demonstrate that the seismic performance of the cooling tower is controlled primarily by local material behavior rather than global dynamic characteristics. Spatial variability of ground motion activates complex deformation modes, leading to pronounced tensile damage, plastic strain accumulation, and stiffness degradation in the lower shell region. The structural variant with thickened lower zone of the shell exhibits extensive material deterioration, including the formation of a continuous plastic zone and irreversible deformation associated with damage localization. In contrast, the ring-stiffened configuration effectively limits damage propagation, reduces plastic strain by up to 80%, and maintains predominantly elastic material response with significantly lower stiffness degradation. The bottom ring stiffener is shown to provide superior performance by mitigating damage evolution of the concrete structure under spatially non-uniform seismic loading. The study highlights the critical role of advanced constitutive material modeling in capturing the realistic seismic behavior of reinforced concrete shell structures and demonstrates that structural strengthening strategies should be evaluated based on their ability to control material degradation mechanisms. Full article

The construction of single-story industrial halls in high-seismicity regions requires reliable beam-to-column connections to ensure adequate structural stiffness and strength. This paper investigates the emulative performance of a rigid precast beam–column connection utilizing threaded couplers and grouted corrugated steel sleeves. An experimental pro-gram was conducted on five scaled specimens—one monolithic reference and four pre-cast—subjected to quasi-static cyclic loading. The objective was to verify if the precast system achieved emulative behavior. Experimental results confirm this goal was fully achieved: the precast specimen exhibited a maximum recorded force nearly identical to the value recorded for the monolithic reference. Furthermore, the total dissipated energy for the precast joint had only a marginal 2.6% difference from the monolithic reference. Results demonstrate that the proposed solution provides emulative behavior consistent with monolithic casting. Specifically, the specimens achieved plastic deformation capacities exceeding 3%, surpassing current seismic design code requirements. While smaller diameter rebars (D14) experienced tensile failure at approximately 3% to 4% drift due to strain localization, specimen with larger D25 bars reached 4% drift without major damage. This paper concludes that the connection is suitable for seismic applications provided large diameter rebars (≥20 mm) are used. Full article

Plastic design enables efficient structural systems by exploiting controlled inelastic deformation and force redistribution. While mature in steel structures due to stable ductility and well-defined yielding, its extension to reinforced concrete (RC) remains challenging because cracking, stiffness degradation, confinement dependency, and progressive damage govern deformation capacity and collapse mechanisms. This paper presents a state-of-the-art review of optimal plastic design methodologies for RC structures by tracing the evolution from classical plasticity theory to modern damage-informed, reliability-oriented, and sustainability-driven formulations. A systematic and structured literature review of more than 90 peer-reviewed journal articles (1990–2025) was conducted using Scopus, Web of Science, and ScienceDirect. The selected studies are classified by structural system type, plastic analysis approach, constitutive modeling strategy, and strengthening technique, including CFRP and hybrid fiber systems, optimization framework, and uncertainty treatment. The review highlights how nonlinear elasto-plastic and damage–plasticity models improve the prediction of plastic hinge development, redistribution, and failure-mode transitions, and how metaheuristic optimization, topology optimization, surrogate modeling, and machine learning are increasingly used to manage discrete design variables and computational cost. Reliability-based methods (e.g., FORM/SORM and simulation) are shown to be essential for quantifying deformation-capacity uncertainty and ensuring consistent collapse-prevention performance. A comparative assessment of nine plastic design methodologies is also provided, identifying their core assumptions, limitations, and domains of applicability within a structured evaluative framework. Remaining challenges include robust deformation-capacity prediction, reproducible calibration of damage models, and integration of life-cycle sustainability criteria within reliability-constrained plastic optimization. Future research directions are proposed toward multi-objective reliability-based design, durability-informed plastic modeling, and hybrid physics-informed AI-assisted workflows. Full article

Different from isothermal amplification, for polymerase chain reaction (PCR), highly reliable valving for PCR chamber, significantly shortened thermal cycling time, and concise multiplexed detection are always challenges for microfluidic-based devices. Here, we present a real-time, centrifugal, plastic microfluidic chip for multiplexed PCR detection specifically based on the mechanism of cooperating valving. To achieve consistent amplification, a concise dual-valving strategy was developed. Instantly melted wax is centrifuged and completely filled into the narrow channel and hole to act as the compact wax valve. Meanwhile, an elastic and sticky membrane is depressed to seal the hole to act as the membrane valve. The wax valve is protected by the membrane valve from being damaged by both mechanical deformation and thermal corroding caused by the hot vapor with high pressure from the PCR chamber. A double-sided heating strategy is adopted to reduce the thermal cycling time; meanwhile, a balanced mechanism is used to achieve real-time amplification by rotating the centrifugal chip between the heating and detection positions in turn. As a proof-of-concept, the performance of the centrifugal chip with four parallel units is demonstrated by successfully detecting purified DNA templates or the extracted DNA templates from cells as well within 20 min. Full article

The prediction model for collision damage to a ship’s side structure plays a crucial role in the design phase. In traditional analytical methods, the bow of the striking ship is often simplified as a rigid body, with the majority of studies focusing on spherical or ellipsoidal bows. This paper focuses on wedge-shaped bows. First, numerical simulation analysis reveals that when the stiffness of the striking ship’s bow is relatively close to that of the struck ship’s side structure, accounting for the elastic–plastic deformation of the bow significantly affects the prediction results of collision damage to the struck ship. Building upon the rigid-body analytical prediction model (RAPM), further consideration of the elastic–plastic deformation of the striking ship’s bow leads to the development of a prediction model that accounts for the coupled collision damage process between the bow and the side structure (CDPM). Comparisons with simulation results and predictions from RAPM demonstrate that CDPM captures the physical process of collision damage more accurately, thereby proving the superiority of this approach over RAPM. Full article

This study investigates the influence of preliminary severe plastic deformation on the efficiency of ion-plasma nitriding (IPN) and the formation of a nitrided layer in 12Kh18N10T austenitic stainless steel. Two types of surface mechanical treatment were compared: vibro-impact ball mechanical treatment (VIMT) and ultrasonic nanocrystalline surface modification (UNSM). After the preliminary treatments, the samples were subjected to ion-plasma nitriding at 500 °C for 10 h using ammonia (NH₃) as the working gas. The phase composition, microstructure, elemental distribution, surface roughness, microhardness, and scratch resistance were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) analysis, profilometry, instrumented indentation, and progressive scratch testing. The results show that both types of preliminary treatment promote the formation of a nitrogen-enriched diffusion layer. The UNSM-treated samples exhibited more pronounced peak broadening and shifting in XRD patterns, indicating a higher level of lattice distortion and nitrogen supersaturation. The maximum nitrogen concentration in the near-surface region reached 15.56 wt.%. Microhardness increased significantly after nitriding for both treatments. Under the selected processing conditions, the UNSM + IPN samples demonstrated a thicker diffusion layer, lower surface roughness, and higher critical loads in scratch testing, indicating improved resistance to surface damage compared with VIMT + IPN samples. The obtained results highlight the important role of the defect structure formed during preliminary treatment in controlling nitrogen diffusion and the resulting mechanical and tribological properties of ion-plasma nitrided austenitic stainless steel. Full article

Ultrasonic impact treatment (UIT) is widely employed as a post-weld treatment to enhance the fatigue performance of welded joints through the introduction of surface plastic deformation and compressive residual stresses. While its beneficial effect on fatigue life when applied at an earlier stage is well established, the influence of UIT on aged structures remains controversial in the literature. This study investigates the effect of UIT on the corrosion performance of S355 steel welded T-joints after accelerated corrosion-induced aging. As-welded (AW) and UIT-treated T-joints were subjected to salt spray exposure, followed by detailed microstructural and surface analyses to assess corrosion morphology and damage evolution. The results show that UIT induces significant surface plastic deformation and microstructural refinement in the weld toe region without promoting preferential corrosion aging or accelerated degradation. The aging behavior of UIT-treated joints, following accelerated environmental exposure, is comparable to that of the AW condition, with corrosion rates decreasing from 3.27 and 3.28 mm/year at 42 days to 1.32 and 1.26 mm/year at 126 days for AW and UIT specimens, respectively. These results indicate that the compressive residual stresses and surface modifications introduced by UIT do not adversely affect material durability. These findings clarify the role of UIT under such exposure conditions and demonstrate that UIT can be applied as a post-weld treatment to improve fatigue properties without compromising the long-term performance of structural steel welded joints. Full article

High-load sliding components, including gun barrels, are susceptible to accelerated wear and damage due to coupled thermal-mechanical stresses and reciprocating frictional conditions. Therefore, enhancing their operational lifespan requires the application of wear-resistant coatings with high melting points for effective surface protection. In this study, Ta-10W alloy coatings were deposited on CrNi3MoVA steel substrates through electricspark deposition, focusing on deposition voltage as a critical parameter. Experimental results indicate that the Ta-10W coatings are primarily composed of α-Fe, α-Ta₂O₅, δ-Ta₂O₅, α-Ta(W), and Fe-W intermetallic phases. An increase in deposition voltage facilitates enhanced melting and mass transfer, thereby promoting solid solution and oxidation strengthening, which results in improved hardness. However, higher voltages also induce defects such as porosity and microcracks. Hardness measurements and friction-wear tests demonstrate that coatings deposited at 80 V exhibit optimal performance, attaining the highest hardness (~753 HV) and a friction coefficient similar to that at 60 V. Conversely, the friction coefficient increases at 100 V due to defects and coating spalling. The wear mechanism transitions from adhesive wear at 60 V to adhesive wear with minor plastic deformation at 80 V and ultimately to spalling wear at 100 V. Finite element thermomechanical simulations reveal that increasing voltage significantly elevates the equivalent interfacial stress (600–1150 MPa), thus correlating with the propensity for microcracks to propagate into longitudinal semi-penetrating cracks at elevated voltages. This study establishes a theoretical foundation for optimizing electricspark deposition process parameters and contributes to the reliability design of Ta-W alloy coatings. Full article

This study investigates nanoscale material removal behavior and its correlation with subsurface damage of (100)-oriented β-Ga₂O₃ subjected to single-point diamond scratching across a range of normal loads. Using multi-scale characterizations, we elucidate the load-dependent transition from elastic deformation to plasticity-dominated removal and, ultimately, to brittle fracture. Under low-load conditions, β-Ga₂O₃ exhibits a fully plasticity-dominated removal mechanism, characterized by smooth groove formation with surface pile-up and a crack-free subsurface containing only dislocations and stacking faults, suggesting that ductile-regime processing is achievable under appropriate mechanical conditions. As the normal load increases, the material enters a ductile–brittle transition regime, where plastic flow coexists with the initiation of micro shear cracks, accompanied by unstable fluctuations in the friction coefficient. Under high-load conditions, extensive brittle fracture becomes dominant, characterized by severe subsurface mixed cracking and large-scale material spalling. This research contributes to a deeper understanding of the machinability of β-Ga₂O₃ materials with high hardness and brittleness in ultraprecision surface processing. Full article

Efficient gas drainage in deep coal seams is critical for safe mining, yet the coupling between plastic damage evolution in borehole surrounding rock and seepage characteristics remains a key barrier to improving drainage efficiency. This study established a dual-porosity model that couples gas diffusion–seepage with elastoplastic coal deformation and conducted numerical simulations under various stress states. Triaxial tests were conducted to support the stress–deformation–permeability trends used in the numerical analysis. The simulation results showed a strongly nonlinear positive correlation between plastic damage and in situ stress, and the damage scale under uniform stress was well described by an empirical quadratic fit. The lowest and most symmetric damage occurred at a lateral pressure coefficient of 1.0, whereas deviations from this value changed the damage morphology, produced uneven gas pressure distributions, and formed high-velocity seepage zones favorable for directional drainage. Plastic damage exerted dual effects on drainage, with moderate damage enhancing permeability and high stress suppressing far-field seepage. Experiments revealed that confining pressure was the dominant factor affecting permeability and that it suppressed both deformation and seepage, whereas gas pressure was kept constant and was not treated as an independent variable in the experimental design. These findings provide support for optimizing gas drainage parameters in deep coal seams. Full article

Molecular dynamics simulations were performed to investigate the nanometric cutting of polycrystalline oxygen-free copper using a single-crystal diamond tool. The effects of grain size, tool geometry (rake angle and edge radius), cutting speed, and ambient temperature on atomic migration, dislocation activity, and tool wear were systematically analyzed. The results indicate that material removal is dominated by cutting-induced amorphization and the formation of hcp-coordinated defect structures, while dislocation activity governs plastic deformation and cutting force fluctuations. A damaged subsurface layer, composed of amorphous structures, hcp-coordinated defects, and residual dislocations, is formed beneath the machined surface. Increasing grain size reduces grain-boundary-induced stress concentration and suppresses subsurface damage. A larger rake angle facilitates chip removal and reduces damage, whereas a larger edge radius intensifies dislocation activity and amorphization. Higher cutting speeds reduce lattice distortion and subsurface damage but increase stress concentration on the tool. Elevated temperature enhances atomic mobility, promoting amorphization and subsurface deformation while accelerating tool wear. These findings provide insight into the nanometric cutting behavior of polycrystalline copper and offer guidance for optimizing process parameters to improve surface integrity and tool life. Full article

This study aims to enhance the damage controllability and overall seismic resilience of assembled underground structures under earthquake actions. To achieve this, three types of prefabricated roof–sidewall composite joints are proposed based on the design concepts of cogging for force transfer and local strengthening. These include the high-strength bolt–cogging–grouting sleeve joint (HCG), the prestressed steel strand–cogging–grouting sleeve joint (PCG), and the UHPC–cogging–grouting sleeve joint (UCG). Following the principle of positioning joints in regions of low structural stress, four 1/4-scale reinforced concrete (RC) specimens were designed and fabricated, including one cast-in-place (CIP) reference specimen and three precast RC specimens. Quasi-static tests were carried out to systematically evaluate the seismic behavior and internal force distribution of each specimen. Numerical validation was also performed using ABAQUS. The results show that both UHPC and a reasonable application of prestressing can effectively inhibit crack initiation and damage propagation at the joint seams. When the composite joints are positioned outside the plastic hinge region, they provide a reliable load transfer path for the reinforcement. The HCG and UCG joints significantly enhance the load-bearing capacity and energy dissipation capacity of the specimens. Their ductility and energy dissipation both achieve a seismic performance equivalent to that of the CIP specimen. Furthermore, damage in these specimens is predominantly confined to the designated plastic hinge region of the roof. This effectively mitigates shear damage in the roof–sidewall connection zone (RSC). Although the PCG joint improves the initial stiffness of the specimen, its energy dissipation capacity and ductility are reduced. It also causes damage to be transferred to the RSC. This leads to increased shear deformation and premature shear failure in this zone. Consequently, both UHPC and a reasonable application of prestressing can be used for the prefabrication of underground structures. Positioning the joints outside the roof plastic hinge zone can effectively achieve the seismic design goal of “strong joint, weak component”. 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