Search Results (699)

Optimizing the structural stability of foundations is challenging in modern geotechnical engineering. This study investigated the mechanism of geocell-reinforced foundations through discrete element modeling based on transparent soil model tests. A three-dimensional particle flow code (PFC^3D) model was developed to investigate the micromechanical soil–geocell interactions in both unreinforced and geocell-reinforced foundations under strip loading. Particle displacement, contact force distribution, and structural deformation within the foundation system were analyzed to quantify the performance of geocell reinforcement. The results show that geocell inclusion enhances structural performance by 2.1 times compared to an unreinforced foundation, increasing the bearing capacity from 60.6 to 126.8 kPa at a defined bearing capacity criterion. The geocell walls act as rigid physical boundaries that microscopically intercept the lateral migration and horizontal extrusion of soil particles. The kinematic trajectories of soil particles beneath the loading plate are forced into a downward realignment, decreasing the displacement vector rotation angle from 42° in the unreinforced soil to 27° in the reinforced soil and effectively mitigating the heave of adjacent surfaces. Furthermore, the quasi-rigid three-dimensional network completely interrupts the continuous steep contact force chains inherent in unreinforced foundations. Concentrated vertical stresses are converted into horizontal components through interfacial friction and mechanical interlocking, resulting in the lateral redistribution of the applied load by a distance of approximately 0.06 m. The geocell–soil composite considered as a flexible raft foundation extends load dispersion and reduces average subsoil pressure. A coupled tension and compression stress state in the horizontal plane is developed within the geocell structure. Forces are channeled along rigid paths by elevated bending moments and stress concentrations at the cell junctions. These findings provide micromechanical insights into the performance of geocell-reinforced-foundation systems. Full article

Post-rotation jacking is a critical construction stage for load-path reconstruction and alignment adjustment in rotation-constructed bridges, particularly for ultra-wide double-deck composite girder systems. Taking a two-span continuous steel truss–concrete composite girder bridge with spans of 2 × 85 m as the engineering background, this study investigates the mechanical behavior during post-rotation jacking through theoretical derivation, finite element simulation, and on-site monitoring. Based on the force method of structural mechanics, a linear relationship between vertical synchronous jacking force and displacement is derived, and an analytical formulation for bearing reaction redistribution under laterally asynchronous jacking is established by considering the coupling effects of vertical bending, torsion, and transverse multi-bearing support. A full-bridge spatial finite element model was developed in MIDAS Civil NX 2024 V1.1 to analyze the redistribution of bearing reactions and the stress response of the concrete crossbeam under different jacking conditions. The results show that, for the investigated bridge, the jacking force–displacement response remains highly linear during synchronous jacking. The B-axis middle bearing is more sensitive to jacking displacement than the two side bearings, with its fitted stiffness being approximately 2.19 times the average stiffness of the side bearings. Eccentric jacking causes reaction concentration at the jacked point and reaction reduction at adjacent supports, and the magnitude of reaction variation increases approximately linearly with jacking displacement. When the transverse non-uniform jacking magnitude reaches 20 mm, a tensile stress of 0.3 MPa appears at the bottom flange of the concrete crossbeam; therefore, a project-specific stroke-difference limit of 20 mm is recommended for this bridge, while the actual construction achieved a stroke control accuracy of ±0.5 mm and a transverse elevation difference within 1 mm. Field monitoring results validate the proposed analytical and numerical methods. The Pearson correlation coefficients of the measured jacking forces with the finite element and theoretical results are 0.9987 and 0.9988, respectively, and the corresponding mean relative errors are 3.84% and 4.23%. For stress responses, the measured and calculated values show a strong correlation, with a Pearson correlation coefficient of 0.9980 and a mean relative error of 12.77%; the critical mid-span monitoring point shows a relative error of only 0.65%. The final bridge alignment deviation is controlled within ±3 cm. The overall mean verification coefficient is 0.968, with a 95% empirical agreement range of [0.888, 1.048], indicating that the proposed mechanical analysis framework and combined force–displacement control strategy can provide a useful reference for refined construction control of similar ultra-wide double-deck composite girder bridges with comparable span arrangement and transverse bearing layout. Full article

To address the issues of low efficiency, high labor intensity, and susceptibility to damage during the manual harvesting of Volvariella volvacea, a mechanized harvesting device was developed to accommodate the growth characteristics of Volvariella volvacea. Thin-film sensors were used to measure the harvesting force values under both the bending method and the rotating method, incorporating two-finger and three-finger operation modes. The results indicated that the maximum force for the bending method was 4.60 N, while that for the twisting method was 2.91 N (peak values, n = 20 per method). The twisting method required less effort and posed a lower risk of damage. A four-suction-cup flexible end-effector was designed using silicone rubber material and equipped with a rotary cylinder. ANSYS 2022 R1 finite element simulation verified that under an applied force of 8 N, the surface stress on the Volvariella volvacea was less than 1.1489 MPa, meeting low-damage requirements. A Volvariella volvacea harvesting test rig was constructed, and performance tests were conducted. The results showed that the overall harvesting success rate was 96.65%, the damage rate was 2.03%, and the average time per harvest by the end-effector was 5.9 s. This study provides a theoretical foundation and technical support for the mechanized and intelligent harvesting of Volvariella volvacea, and is significant for promoting the high-quality development of the Volvariella volvacea industry. Full article

Fully integrated MITC4 (mixed interpolation of tensorial components) shells remain costly for large-deformation sheet-metal forming benchmarks at production mesh sizes. This paper presents a GPU-resident explicit MITC4 shell solver, implemented as a single CUDA pipeline in which co-rotational kinematics, assumed natural strain transverse shear, through-thickness J2 elasto-plasticity, and rigid-surface penalty contact remain in device memory. The study is positioned as computational verification and benchmarking for the Nakajima hemispherical-dome forming benchmark. Canonical shell tests verify the element kernel through membrane and bending patches and a force-driven cantilever, with the cantilever deflection agreeing with the MacNeal–Harder reference within about 2%. On the 10K-element Nakajima benchmark, the present solver agrees with Abaqus/Explicit with a mean von Mises error of 2.95% over 94% of specimen elements and a maximum shell thickness error of 2.08%. In the clamped/binder transition band, section-mean von Mises agrees to +1.0%, whereas section-maximum stress is under-predicted by 10.9%. A 50K-element Abaqus check remains bounded at 80 mm stroke, with section-mean von Mises differences of +0.6% globally and +0.4% in the transition band. For throughput, a separate 500K-element deck over 1.0 × 10⁻³ s and 15,808 steps give per-step speed-ups of 43.7×, 17.7×, and 13.5× versus 1-, 8-, and 32-core LS-DYNA MPP. Full article

Metamaterials with tailored structural architectures enable negative thermal expansion through geometric mechanisms that counteract constituent-level positive expansion. This study evaluates the thermomechanical performance and structural limits of polymer and hybrid NTE lattices. We systematically classify the dominant kinematic mechanisms, including bimetallic bending, rotational squares, and re-entrant honeycombs, and quantify the inherent trade-offs between effective thermal contraction, structural stiffness, and mass efficiency. The analysis demonstrates that reliance on idealized linear–elastic and rigid-lever models leads to significant predictive discrepancies when evaluating the physical response of polymeric and hybrid prototypes. We establish that these deviations are fundamentally governed by localized stress singularities at multi-material interfaces and the profound thermoviscoelastic softening of polymers as they approach the glass transition temperature ($T_g$). We conclude that accurate prediction of the cyclic lifespan and dimensional stability of these systems requires a transition to coupled multiphysics frameworks. Specifically, integrating temperature-dependent cohesive zone modeling and time–temperature superposition principles is essential for capturing interfacial delamination and thermal ratcheting in high-performance polymeric NTE metamaterials. Full article

Flapping-wing flight offers a promising solution for aerial mobility in low-density environments such as the Martian atmosphere, where conventional rotorcraft faces significant performance constraints. However, the coupled aerodynamic and structural mechanisms governing lift generation at low Reynolds numbers remain insufficiently understood. This study investigates the aeroelastic and unsteady aerodynamic behaviour of a bio-inspired flapping wing using an integrated experimental–numerical framework. High-speed imaging is employed to extract representative wing kinematics, including flapping frequency, stroke amplitude, and rotational motion. A geometrically scaled wing model is developed based on Reynolds number similitude and analysed using finite element methods to characterise its dynamic response. Aeroelastic behaviour is evaluated through modal transient simulations, while aerodynamic performance is assessed using both vortex-lattice modelling and computational fluid dynamics. The results show strong coupling between bending and torsional modes, with the structural response highly dependent on excitation frequency relative to the natural modes. Near-resonant conditions lead to amplified deformation and distinct phase relationships, while aerodynamic simulations reveal vortex-dominated lift generation. These findings provide a physics-based framework for the design and analysis of flapping-wing systems operating in low-Reynolds-number and low-density flight regimes. Full article

To investigate the static behavior of UT-type assembled semi-rigid joints and the effects of bolt pretension loss, two representative joint configurations, UT250 × 150 and UT400 × 200, were studied by combining full-scale tests with refined finite element analysis using ABAQUS. Pure bending, bending-shear, and constant-axial-force-coupled loading conditions were considered, with particular attention paid to the effects of single-bolt and multiple-bolt pretension loss on moment capacity, initial rotational stiffness (K_y), interface slip, and the failure mode of the joints. The results show that the UT-type joint mainly fails through concentrated plastic yielding in the joint zone, and its ultimate moment (M_u) is 12.3–18.7% higher than that of a conventional bolted-welded joint, satisfying the design principle of “strong joint and weak member”. Loss of pretension in a single bolt has only a limited influence on the yield moment (M_y) and ultimate moment (M_u), with a maximum reduction of 8.0% in the ultimate moment (M_u) under negative pure bending; however, it causes clear degradation in the initial rotational stiffness (K_y), and pretension loss in the upper bolt produces a greater stiffness reduction than loss in a single lower bolt, with a maximum reduction of 33.43%. Multiple-bolt pretension loss exhibits a pronounced coupling effect. Simultaneous loss in lower bolts on the same side is the most unfavorable case, leading to a maximum stiffness reduction of 67.78% (coupling coefficient of 1.17), whereas diagonal loss is relatively controllable and generally keeps the stiffness reduction within 7%. When the axial compression ratio does not exceed 0.3, the mechanical response of the joint remains relatively stable, and the adverse effect of pretension loss can be alleviated to a certain extent; further increases in the axial compression ratio accelerate the degradation of both stiffness and load-carrying capacity. The present study provides a useful reference for the design optimization, construction quality control, and in-service maintenance of UT-type semi-rigid joints. Full article

CuZn39Pb3 leaded brass is one of the most widely used alloys in machining. Despite its good machinability, there is a lack of information in the literature on the effects of surface cold working on the surface microhardness, microhardness profile, introduced residual stresses, microstructure, and the operating behaviour of machined components. This article reveals the capabilities of conventional diamond burnishing (DB) (implemented under flood-lubrication conditions) to improve the surface integrity and high- and mega-cycle fatigue strength of CuZn39Pb3 cylindrical components such as axles and shafts. The results show that both the smoothing and hardening DB processes achieve mirror-like surfaces, introduce significant residual compressive stresses at depths greater than 0.5 mm, and significantly increase the fatigue strength in the high- and mega-cycle regions compared to the reference condition (turned and polished specimens). However, the surface microhardness is weakly affected by the degree of surface cold working. Given the almost identical microhardness profiles and the equivalent distribution in depth of the introduced residual stresses by the two DB processes, the possible reason for the more pronounced effect of the hardening process on the fatigue strength lies in the thicker affected layer and the reduced negative skewness introduced by this process. Full article

This study introduces and characterizes a family of quilling-inspired S-shaped unit-cell architectures intended as building blocks for mechanical metamaterials. In contrast to conventional lattice designs based mainly on straight struts, the proposed geometries use continuous curved elements inspired by paper quilling, enabling deformation mechanisms dominated by bending, rotation, and progressive opening of the curved members. By translating quilling’s coiled and spiraled patterns into engineered geometries, nine distinct S-shaped unit cells were fabricated by fused deposition modeling and tested experimentally under uniaxial tensile loading. Finite element analysis was performed to reproduce the tensile response and to assess the influence of geometry on stiffness, stretchability, and energy absorption. The results show that relatively small changes in radii, span lengths, angular distribution, and symmetry produce significant differences in mechanical response. Compact configurations such as S2, S3, and S5 exhibit high stiffness and limited elongation, whereas S9 shows the highest compliance and stretchability. The results indicate that these quilling-inspired architectures provide a tunable design space and have strong potential for applications in energy absorption, adaptive structures, and lightweight load-bearing systems. Full article

Recognizing human actions from static images in complex industrial environments remains challenging due to insufficient feature representation and high computational complexity. This issue is particularly critical in power-grid safety monitoring, where improper worker postures (e.g., bending, climbing, falling) can lead to severe accidents and personal injuries, necessitating automated monitoring systems that operate reliably on resource-constrained edge devices. This study proposes a bio-inspired lightweight recognition framework that integrates an improved YOLO-Pose model with a gated recurrent unit (GRU) network. The scientific motivation is grounded in the observation that the human musculoskeletal system achieves highly efficient motion perception through three key mechanisms: hierarchical muscle coordination providing intrinsic rotation invariance, proprioceptive feedback enabling real-time error correction, and selective neural gating reducing redundant information transmission. These biological principles directly inspire our technical contributions: polar-coordinate encoding provides rotation invariance, three-stage filtering mimics proprioceptive feedback, and GRU gating mirrors selective information propagation. Unlike prior approaches that treat pose-based action recognition as a generic computer vision problem, this work explicitly incorporates anatomical structural constraints into the computational pipeline. The framework addresses three research gaps: (1) existing methods lack biomechanically derived invariance properties; (2) GCN-based approaches use fixed topologies that fail to adapt to occlusion patterns; (3) the trade-off between model complexity and accuracy remains unsatisfactory for edge deployment. Experiments on the self-constructed SKPose dataset demonstrate that the proposed method achieves 95.04% accuracy, outperforming ST-GCN by 3.67 percentage points and 2s-AGCN by 1.94 percentage points, with an inference speed of 48 FPS on 8.7 M parameters in underground power-grid environments and provides practical support for biomimetic perception systems and industrial safety monitoring. Full article

Burnishing technologies are a cheap and effective means of improving the surface integrity (SI) and performance of metal components. However, there is practically no information about the integral influence of the preceding turning process on the initial (pre-burnishing) SI. This study answers the question of how the white layer resulting from flank wear on the cutting insert in pre-turning affects the SI and fatigue limit, and determines the extent to which subsequent diamond burnishing (DB) is able to improve the SI and rotating bending fatigue limit of normalised, quenched and high-temperature-tempered C45 steel. The (DB)–SI–fatigue limit correlation was investigated using a holistic approach that took into account the effects of the dynamic pattern of flank wear on the initial SI. An explicit relationship was established between the flank wear, the affected surface layer structure and the fatigue limit. Increasing flank wear to the 60th minute intensified the formation of a gradient layer with finer and thinner grains that formed a texture. As a result, a synergistic effect was observed from turning with an insert operating for 60 min and subsequent DB, which maximised the fatigue limit (741 MPa). After 60 min, the structure of the affected layer changed qualitatively towards the formation of a nanostructured (white) layer, which reversed the trend, worsening the fatigue behaviour. As the thickness of the white layer increased, the fatigue limit was sharply reduced to below 560 MPa after the 90th minute. Regardless of the degree of flank wear, DB significantly improved the SI characteristics and increased the fatigue limit after turning with a worn insert, although the absolute dimensions of the positive DB effect depend on the initial SI and fatigue limit due to pre-turning. To achieve a synergistic effect, the cutting insert should be replaced with a new one after every 60 min of operation. Full article

A generalized eigenvalue formulation is developed for the free vibration analysis of anisotropic rectangular plates with rotationally restrained edges using the finite integral transform method. For free vibration problems, casting the governing equations into a generalized eigenvalue problem is particularly advantageous because it enables the direct and systematic extraction of multiple natural frequencies and their associated mode shapes within a unified framework, while avoiding the need for assumed trial functions or solution searching near initial guesses. In the present study, a two-dimensional sine integral transform is introduced into the governing equation of anisotropic plates with bending-twisting coupling, and the mechanical description of rotationally restrained boundary conditions is incorporated simultaneously, thereby converting the original partial differential boundary value problem into a generalized eigenvalue problem. The corresponding analytical solution is then established through the finite integral transform framework. The accuracy and reliability of the proposed method are verified through comparisons with finite element results and published data. Based on the obtained analytical solution, the effects of boundary conditions, rotational stiffness coefficients, aspect ratio, and key stiffness components on the vibration characteristics of anisotropic rectangular plates are further examined. The present study provides an effective analytical framework for free vibration analysis of anisotropic plates with nonclassical rotational restraints and offers theoretical support for the dynamic design and optimization of advanced composite plate structures. Full article

As floating offshore wind turbines (FOWTs) scale towards 10 MW+ capacities, suppressing wave-induced rotational resonance becomes critical for system survivability. This study introduces an optimized, highly symmetrical four-float semi-submersible platform, explicitly tailored to support the DTU 10 MW wind turbine and paired with an orthogonal four-point mooring system. Using three-dimensional linear potential flow theory via ANSYS AQWA, comprehensive frequency- and time-domain hydrodynamic evaluations were conducted. To address the inherent limitations of inviscid potential flow assumptions, an empirical added-damping method was implemented. Quantitative results demonstrate a drastic reduction in motion responses: the peak Response Amplitude Operator (RAO) for heave decreased by 68.6% (from 1.945 m/m to 0.610 m/m). Most notably, the peak RAOs for the critical rotational degrees of freedom—pitch and roll—were reduced by over 92% (from 2.080 °/m and 2.216 °/m to ~0.168 °/m, respectively). Ultimately, compared to traditional asymmetric three-float concepts, this novel symmetric omnidirectional layout provides a more uniform restoring stiffness. The resulting suppression of pitch and roll resonance results in a profound reduction in tower-base bending moments and gyroscopic loads, thereby significantly enhancing the dynamic stability, safety margins, and fatigue life of the 10 MW FOWT under extreme survival sea states. Full article

This paper investigates the low-cycle behaviour of Concrete-Filled steel Tubes (CFTs) subjected to cyclic pure bending, a loading condition representative of large bridge and building girders. A 3D finite element model is developed in Abaqus/Explicit, combining a ductile damage law for the steel tube and Concrete-Damaged Plasticity for the infilled concrete, and is calibrated against large-scale cyclic bending tests on circular and square CFT beams. An automated Python scripting framework is then used to perform a systematic parametric study on members made of standard code-based materials, varying diameter-to-thickness ratio and span length over a wide range of practical configurations. Constant-amplitude chord rotations are imposed, and the nonlinear response is tracked in the plastic range while material damage evolves. The hysteretic behaviour is quantified in terms of cumulative plastic strains, dissipated energy and the degradation of reaction force and bending moment after 25 cycles. The results show that geometric parameters strongly affect the cyclic response: within the investigated loading layer, configurations with $D_e=100$ mm generally exhibit strength degradation values between about 10% and 60%, whereas for $D_e=400$ mm the degradation typically ranges between 50% and 100%, with most cases falling in the moderate-to-severe degradation domain. At the same time, larger diameters and thicker tubes generally lead to an increase in dissipated energy, while longer members tend to show lower energy dissipation but also reduced degradation. The study therefore provides a reproducible computational framework and comparative performance trends for the assessment of low-cycle cyclic response in CFT beams under a prescribed loading protocol. Full article

The production of fiber-reinforced polymer composites using 3D printing technology offers significant potential and opportunities for industrial applications. However, current dimensional limitations in 3D printing necessitate the use of joining techniques to obtain larger components. Recently, innovative strategies such as friction stir spot welding (FSSW) have attracted considerable attention for joining polymer composites due to their ability to produce strong joints with relatively low heat input (solid-state welding). Nevertheless, it is important to understand how the fibers present in fiber-reinforced polymer composites influence material flow and welding performance during the FSSW process. In this study, glass fiber-reinforced polylactic acid (PLA-GF) composite samples produced using a 3D printer were joined by means of FSSW. Five different tool rotational speeds (900, 1200, 1500, 1800, and 2100 rpm) and three different plunge rates (10, 20, and 30 mm/min) were employed during the welding process. Mechanical tests were performed on the welded joints to investigate the relationship between the welding parameters and the resulting mechanical properties. In addition, microstructural analyses were conducted to examine the formation of welding defects. The results revealed that three distinct zones were formed in the material after the FSSW process: the stir zone, mixed zone, and shoulder zone. Defects were observed in the mixed zone of the samples exhibiting relatively lower mechanical properties. The highest tensile force was achieved at a plunge rate of 20 mm/min and a rotational speed of 900 rpm. The highest bending force, on the other hand, was obtained at a plunge rate of 30 mm/min and a tool rotational speed of 2100 rpm. Full article