Search Results (221)

Multi-view fringe projection profilometry systems that integrate a telecentric projector with multiple oblique-view cameras offer unique advantages for inspecting high dynamic-range surfaces featuring densely packed, intricate microstructures. Nevertheless, such systems encounter fundamental calibration challenges, namely, sign ambiguity in the rotation matrices and truncated extrinsic parameters inherent to telecentric projector models, as well as difficulties in multi-view point cloud registration. This paper introduces a novel calibration framework with three principal contributions. First, we resolve the sign ambiguity by calibrating the telecentric projector under a quasi pinhole model and directly transferring the extrinsic sign conventions, thereby obviating the need for costly precision displacement stages or elaborate virtual targets. Second, we fix the axial-gauge freedom by constraining the origin of the projector coordinate system to lie on the XY-plane of the camera coordinate system. Third, we establish precise relative poses between all cameras and a designated reference camera, enabling unified multi-view point cloud registration directly within the projector coordinate frame, which substantially reduces alignment errors and accelerates data processing. Experimental results demonstrate marked improvements in accuracy: reprojection root-mean-square errors of 0.084 pixels for the cameras and 0.106 pixels for the projector, corresponding to in-plane spatial resolutions of 0.21 µm and 0.26 µm, respectively. The proposed method offers a robust solution for micron-level inspection in semiconductor packaging and precision manufacturing. Full article

Three-dimensional topological magnetic defects, such as Bloch points, are of significant interest for high-frequency spintronics due to their unique particle-like properties and effective inertial mass. We investigate the nucleation, stabilization, and driven dynamics of an isolated Bloch point in a ferromagnetic multilayer with alternating in-plane and perpendicular magnetic anisotropy. Using micromagnetic simulations, we show that a perpendicular magnetic field stabilizes a head-to-head Bloch point state, while a transient in-plane field pulse drives the defect into gyrotropic and nutation motion. To model the dynamics, we develop a collective-coordinate Lagrangian description of the Bloch point core. We further demonstrate that the time-dependent core displacement generates a transverse charge current via spin pumping and inherent spin-to-charge conversion within the multilayer system. The resulting current spectrum contains low-frequency and high-frequency components, including an intrinsic nutation mode in the gigahertz range. Our findings expand the capabilities for electrical control and identification of complex spin configurations, contributing to the development of active three-dimensional spintronic devices. Full article

This paper presents a stress-function-based finite element formulation for two-dimensional elastoplastic plane-stress problems with holes. The Airy stress function is used as the primary global unknown, and the resulting non-homogeneous biharmonic equation is discretized with the nonconforming Morley finite element. The stresses are obtained from the second derivatives of the discrete Airy function. Consequently, the differential equilibrium equations are satisfied inside each element, while interelement coupling is enforced through the Morley weak formulation. Plastic strains enter the governing equation through an element-wise weak-form contribution, which avoids the direct evaluation of their second derivatives. The local material response is described by associated von Mises plasticity with Kuhn–Tucker conditions and is integrated using cutting-plane and return-mapping algorithms. The formulation is applied to a perforated plate subjected to in-plane tension and compared with a classical displacement-based elastoplastic finite element model. The results show good agreement in the elastic stress concentration, yielding load, stress redistribution, and plastic-zone development. For the present benchmark, the Airy–Morley formulation is computationally competitive and provides a stress-function-based alternative for a restricted class of two-dimensional plane-stress problems. Full article

This paper presents an experimental investigation of a demountable hybrid timber–carbon-reinforced concrete (CRC) wall system with a reversible mechanical connection detail based on embedded transport anchors, screwed steel angle brackets, and full-thread screws. The study addresses a wall concept in which a thin externally mounted CRC plate contributes to lateral load transfer through discrete reversible connection points rather than through a bonded or cast-in-place composite interface. Four full-scale wall specimens were tested under horizontal shear loading and a nominal vertical preload of $92\mathrm{kN}$ in an adapted in-plane shear test arrangement. The maximum horizontal loads ranged from $19.7$ to $22.7\mathrm{kN}$, with a mean value of $21.2\mathrm{kN}$ and a coefficient of variation of $5.9\%$. For the three specimens with complete displacement records, the head displacement at maximum load ranged from $33.7$ to $45.8\mathrm{mm}$. The initial wall stiffness $K_{0.05-0.15}$ ranged from $1.93$ to $2.80\mathrm{kN}/\mathrm{mm}$, whereas the stiffness evaluated between $0.2F_{\max }$ and $0.4F_{\max }$ ranged from $0.52$ to $0.67\mathrm{kN}/\mathrm{mm}$. Normalized to the reference width of the tested configuration, the maximum horizontal load was $15.8$ to $18.2\mathrm{kN}/\mathrm{m}$. Damage initiated locally in the CRC anchorage zones, especially at the corner anchors, and progressed from first cracking to local concrete spalling. The governing failure mode was local concrete failure in the anchorage zones, accompanied by deformation of the steel angle brackets, while no critical damage was observed in the timber joints. The results demonstrate the feasibility of the investigated reversible timber–CRC connection concept for transferring in-plane shear forces in the tested configuration, but further tests are required before general design recommendations can be derived. Full article

Accurate measurement of the 6-DOF motion responses of marine floating structures is essential for structural safety assessment and operational decision-making. To address the critical issues of integration drift in inertial navigation systems, susceptibility of GNSS to sea-surface multipath effects, and deployment complexity of binocular vision systems, this paper proposed a 6-DOF motion measurement method for floating structures based on monocular vision and natural feature point tracking. This method eliminates the reliance on artificial cooperative targets and auxiliary sensors, instead utilizing the inherent surface textures of the floating structures as feature sources. Stable feature point tracking is achieved through multi-strategy cascaded detection and the pyramidal KLT optical flow algorithm. RANSAC geometric consistency verification is introduced to eliminate outlier matches, retaining only identical physical points between two consecutive frames for motion estimation. In-plane translations and $RZ$ angle are extracted from the similarity transformation, while $RX$ and $RY$ angles are estimated using principal component analysis of the covariance matrix of the feature point set. The depth-direction displacement is linearly mapped from variations in the scale factor. Subsequently, two series of physical model tests under different conditions were conducted to validate the measurement accuracy and robustness of the proposed method on different floating structures. The results demonstrate that the proposed method can accurately capture the motion attitudes of floating structures, maintaining a consistently high inlier ratio exceeding 80% in regular waves and averaging 85.2% in irregular waves, with a reprojection error of less than 0.05 pixels. The NRMSE for the primary motion directions are all below 10%, and the dominant frequency errors are essentially zero. It offers advantages such as low cost, easy deployment, and strong robustness, thereby providing valuable technical support for field monitoring of marine floating structures. Full article

Deployable reflector antennas demand high geometric precision; the Ruze equation directly links surface error to RF gain. Arc-shaped CFRP ribs are vulnerable to thermal deformation, as their curvature converts in-plane expansion into out-of-plane displacement, which symmetric laminates cannot suppress. Classical laminate theory (CLT) underestimates the coefficient of thermal expansion (CTE) of cross-ply laminates by factors of 1.75–2.38 for the laminate configurations investigated in this study, causing up to 79.4% of displacement prediction errors in symmetric designs. Here, we present an asymmetric laminate that overcomes both limitations. The upper skin (nine plies) and lower/web skins (seven plies) from the same prepreg batch create a CTE mismatch (Δα = 6.30 × 10⁻⁷ K⁻¹), activating coupling stiffness to generate a thermal moment opposing curvature-driven displacement. Because both skins share identical batch history, CTE prediction errors cancel through common-mode rejection. Compared with the symmetric design, the asymmetric design achieved a 50.4% reduction in thermal deformation (from 210 µm to 104 µm) and improved FEA accuracy from 79.4% error to 4.8% error under experimental schemes. The method uses only conventional 0/90° prepreg and standard autoclave processing, with the upper-surface ply count as the sole design variable for a given section’s geometry, establishing retained coupling stiffness as a practical route to dimensional stability in curved space structures. Full article

Accurate prediction of welding-induced deformation is essential for dimensional control in large-scale ship block construction. In production design, transverse shrinkage directly governs the cutting allowance and shrinkage margin among various deformation modes. The inherent strain framework is widely used due to its computational efficiency, but the interaction between the implementation of equivalent loads and geometric nonlinearity has not been systematically investigated. This study evaluates two conventional loading representations: the equivalent nodal force method and the equivalent thermal load method, under both linear and geometrically nonlinear analysis formulations. In linear elastic analysis, both representations are equivalent and successfully provide identical, stable in-plane shrinkage predictions because both methods utilize input loads formulated from the same target inherent deformation. However, in shipbuilding practice, a geometrically nonlinear formulation is frequently required to capture large-displacement behaviors or structural instabilities in thin-walled assemblies. When geometric nonlinearity is introduced into these shrinkage predictions, a critical discrepancy emerges depending on the load implementation: the equivalent nodal force method violates the physical basis of shrinkage prediction by introducing unwanted out-of-plane deformation artifacts. This is a numerical artifact arising from the interaction of localized artificial compressive stresses with the stress-dependent geometric stiffness matrix. In contrast, the equivalent thermal load method is robust and always preserves the target in-plane shrinkage without any undesired out-of-plane geometry. Therefore, even though both methods are robust in the linear regime, the equivalent thermal load method is recommended when a geometrically nonlinear formulation is involved to ensure numerical consistency and reliability in production design. Full article

Conventional masonry infill walls can significantly alter the seismic response of framed buildings and often produce damage patterns incompatible with resilience-based seismic design. Dry-jointed sliding masonry wall systems have therefore emerged as deformation-tolerant alternatives that accommodate drift through controlled interface motion rather than damage accumulation. This study investigates the sequential in-plane (IP) and out-of-plane (OOP) behavior of such systems considering wall thickness, openings, and boundary detailing. Six full-scale specimens were tested, including thick- and thin-wall reference specimens, thick-wall specimens with window openings, and thin-wall specimens with door openings. IP performance was evaluated using global hysteretic and energy-based response parameters, whereas OOP behavior was assessed through load–displacement response, an equivalent acceleration index, and selected image-based displacement fields. The results show that IP drift was mainly accommodated through distributed sliding along horizontal interfaces and local block rotation, without diagonal compression strut formation or brittle cracking, even at drift ratios up to approximately 3.5%. Wall thickness improved IP strength, stiffness, shear resistance, and cumulative energy dissipation, while openings mainly affected deformation compatibility and load-transfer continuity. Under OOP loading, wall thickness and boundary continuity increased stiffness and capacity while enabling resistance mobilization at smaller displacement levels. As inertia-based comparison indicators, boundary-enhanced thick- and thin-wall specimens reached equivalent acceleration capacities of 3.41 g and 1.64 g, respectively. Overall, the system reduced IP damage accumulation, but adequate OOP stability requires appropriate wall thickness, unit geometry, and boundary detailing. Full article

The in-plane shear performance of carbon fiber-reinforced polymer (CFRP) composites is critical for structural design but is challenged by significant property scatter. This study aims to achieve individualized prediction of the complete shear stress–strain curve for each composite specimen using only a single early-stage digital image correlation (DIC) strain field. Systematic in-plane shear tests were conducted on 45 laminated carbon fiber/epoxy specimens with synchronized full-field DIC data and macroscopic load–displacement records. A lightweight encoder–decoder convolutional neural network was developed, taking a single DIC strain contour map at 0.2% global strain as input and mapping it directly to the full-range stress–strain curve up to failure for that specific specimen. Data augmentation and Dropout regularization mitigated the small-sample challenge. The proposed model achieved strong predictive performance across the five-fold cross-validation yielded a mean R² of 0.926 ± 0.022 and a mean RMSE of 6.37 ± 1.14 MPa for stress. Individual specimen predictions on the test set yielded an average R² of 0.945, with a minimum of 0.821, confirming robust capability across scattered properties. Residual analysis elucidated error characteristics across deformation stages. This research provides a novel paradigm for non-destructive, early-stage individualized assessment of composite mechanical properties, with applications in structural health monitoring and probabilistic design. Full article

Strong chiral responses in planar dielectric metasurfaces are important for polarization-selective nanophotonic devices, but achieving large and reversible circular dichroism (CD) in simple dielectric structures remains challenging. This work proposes a symmetry-broken silicon metasurface that realizes near-infrared chiral response based on bound states in the continuum (BICs). The unit cell consists of a silicon nanoblock with two through-air grooves. The in-plane displacement of the air grooves breaks the C₂ rotational symmetry and splits the BIC-related polarization singularity into two circularly polarized points (C points) with opposite handedness. By further introducing out-of-plane tilting, one of the C points is shifted to the Г point, enabling spin-selective coupling between normally incident circularly polarized light and the quasi-BIC mode. Reversing the out-of-plane tilt switches the sign of CD, with values reaching −0.98 and 0.98, approaching the theoretical limits of ±1. Under oblique incidence, the structure can also exhibit near-limit CD responses. Finally, by introducing graphene, the structure achieves tunable circular-polarization-selective absorption, with the absorption of CD approaching the theoretical limits of ±0.5 for the coupled system. This work provides a new design idea for compact chiral nanophotonic materials by using symmetry breaking to control spin-selective quasi-BIC coupling and tunable chiral absorption. Full article

This paper focuses on the characterization of the micro-leakage channel geometry in the flange-gasket rough contact interface of hazardous chemicals transport vehicles. This work represents the first step in a multi-physics simulation framework for optical-fiber-based micro-leakage monitoring. Directly establishing a full-scale contact model from micron-scale rough peaks and valleys to the decimeter-scale flange structure would lead to extremely high computational costs; a nonlinear contact model based on quasi-representative volume element (quasi-RVE) and quasi-periodic boundary condition (quasi-PBC) is proposed in this paper. Quasi-RVE refers to a local region selected from the overall rough surface. Unlike a traditional RVE that requires strict geometric periodicity, the quasi-RVE is only approximately consistent with the overall surface with respect to key morphological parameters and volume parameters. Quasi-PBC only imposes in-plane displacement compatibility constraint on the relative side boundary without imposing periodic constraints in the peak-valley height direction. In this paper, the average interface gap and its distribution are selected as the geometric descriptors of the micro-leakage channel, and the reliability of the contact model is verified by comparing with the existing experimental and numerical results. On this basis, the influences of surface roughness, gasket material and loading conditions on the geometric characteristics of the micro-leakage channel are further analyzed. The results show that the lower stiffness gasket is easier to fit with the rough flange surface under the same load conditions, so as to obtain a larger contact area and a smaller average gap. The quasi-RVE contact model established in this paper can effectively reduce the computational scale of contact analysis of the rough sealing interface, and provide reliable channel geometric information for subsequent micro-leakage fluid simulation and optical fiber signal response simulation. Full article

Thin rectangular plates, due to their small thickness relative to length and width and their high strength-to-weight ratio, are widely used in structural elements such as ship hulls, bridge decks, and aircraft wings. They are prone to nonlinear buckling under compressive forces, especially under biaxial in-plane compressive loading with large displacements, where linear theories often fail and membrane stresses complicate analysis. This study aimed to formulate a general mathematical equation for buckling analysis of thin rectangular isotropic plates with large displacements subject to biaxial in-plane forces using the Ritz potential energy functional method, and incorporates both geometric and material nonlinearities. Based on the formulated general equation, a specific equation for an all-round simply supported (SSSS) plate was developed using polynomial displacement shape function to determine the stiffness characteristics. Numerical values for critical buckling and post-buckling loads under biaxial compression for a square plate case were obtained. To validate these results, a comparison with values in the literature was made and the results show high consistency. The uniaxial buckling deviations ranged 0.047–0.10%, while undeformed biaxial buckling coefficients across varying aspect ratios and loading ratios (n = Ny/Nx) showed near-zero differences. From the two studies used for comparison, the maximum deviation is 24.42% and the minimum deviation is 1.12%. This indicates that the new model is adequate. Also, the adequacy of this new equation can be judged based on the simplicity of the formulation, and the closed agreement of the obtained numerical results with established results in the literature. This research enhances theoretical understanding of nonlinear buckling in thin plates and offers practical insights for improving structural reliability and efficiency in civil, mechanical, aerospace, and marine engineering. Therefore, the conclusion is that the model is suitable for buckling and post-buckling analysis of thin rectangular isotropic plates. Full article

Acoustic emission (AE) is a vital non-destructive technique for monitoring damage in materials, yet its simulation via the Discrete Element Method (DEM) has historically been limited to material-scale analysis. This research presents a novel application of block-based DEM to simulate AE signals in masonry structures at the structural scale under quasi-static in-plane loading. Using a simplified micro-modeling approach, the study first validates the method by monitoring crack initiation and AE energy in single mortar bed joints under tensile and shear conditions. The methodology is then scaled to a large-scale masonry wall panel (1.835 × 1.170 × 0.15 m³) subjected to monotonic shear loading. A critical finding is the influence of local damping; a reduced damping ratio of 0.3 is recommended to preserve the kinetic energy necessary for capturing clear velocity signals. Numerical results show strong agreement with experimental force-displacement and cumulative AE energy curves, confirming the model’s robustness. Furthermore, frequency analysis of the simulated signals successfully distinguishes between tensile and shear failure modes. This study fills a significant gap in the literature by demonstrating that DEM is an effective predictive tool for structural-scale failure analysis and AE monitoring in heterogeneous masonry. Full article

Flexible honeycomb skins offer a promising route for achieving continuous shape adaptation in morphing aircraft. In practical service, however, the skin must simultaneously accommodate large in-plane deformation while maintaining sufficient out-of-plane load-bearing capacity, which poses a fundamental design challenge. To address this trade-off, this study investigates an SMA-based U-shaped honeycomb under combined tensile deformation and aerodynamic pressure. A parametric finite element model incorporating SMA superelasticity is established, and an automated Abaqus–modeFRONTIER framework is developed for multi-objective optimization under dual loading conditions. The curvature radius, parallel-segment length, and middle-beam length are selected as design variables. The optimization objectives are defined as minimizing the maximum local strain under a prescribed tensile displacement and reducing the Z-direction displacement under aerodynamic loading as an indicator of out-of-plane bending resistance. The resulting Pareto front reveals the trade-off between flexibility and load-bearing capacity, and the sensitivities of the key geometric parameters are analyzed. Compared with the initial design, a representative optimized solution reduces the maximum local strain by 58.5% and the Z-direction displacement by 61.3%. These results provide a numerical basis for the design of SMA-based flexible skins for morphing aircraft. Full article

This study comprised an experimental investigation of the in-plane performance of composite floor slabs under out-of-plane effects. Two composite floor slabs were subjected to pure in-plane loading, and in-plane and out-of-plane coupled loading, respectively. The study analyzed crack patterns, failure modes, and load–displacement curves, and evaluated how out-of-plane effects influenced in-plane performance. The test results indicated that both specimens exhibited a typical shear-tension failure mode, forming diagonal shear cracks. The specimen with out-of-plane loading exhibited a trend for lateral development of the shear cracks. The load–displacement curves of the two specimens showed obvious strength degradation, stiffness degradation, and a pinching effect. By comparing the two specimens, it could be observed that at a small out-of-plane displacement angle, the in-plane ultimate bearing capacity of a specimen was not significantly weakened; however, as the out-of-plane displacement continued to increase, the in-plane bearing capacity of the specimen decayed more rapidly. Full article