Search Results (163)

Thin-walled laminated cooling plates integrate internal channels and pin-fin cores, producing reduced and spatially non-uniform stiffness that changes welding restraint and distortion. This study investigates stiffness-controlled plastic-strain evolution in laser butt welding of GH3230 laminated plates, with geometrically identical solid plates as reference. A coupled heat-transfer and thermo-mechanical finite element model was developed in MSC Marc using a composite Gaussian surface–volumetric moving heat source and temperature-dependent properties. The thermal solution was validated against near-weld thermal cycles and fusion geometry; mechanical predictions were evaluated by CMM distortion and residual-stress measurements. Both structures show comparable residual-stress magnitudes and spatial trends, indicating that residual stress is governed mainly by the local weld thermal gradient. In contrast, the laminated plate exhibits larger angular/bending distortion. Simulations show that, although the plastic-strain pattern is similar, the laminated plate develops higher peak plastic strain confined to a narrower band near the weld, with the transverse plastic strain dominating. Plastic strain–temperature paths reveal continued transverse plastic-strain accumulation during cooling with limited recovery, consistent with restraint redistribution induced by stiffness non-uniformity. An equivalent restraint–stiffness spring model explains this “narrower-but-stronger” plastic zone and links stiffness to yielding and residual plastic-strain magnitude, supporting distortion prediction and stiffness-informed control of welded laminated cooling plates. Full article

Vortex-induced energy dissipation is critical, yet its influence is frequently neglected in potential-flow analysis of wave interaction with thin-walled structures. This study revisits the parametrization of vortex-induced energy dissipation in potential-flow analysis, particularly for wave interaction with vertical, surface-piercing plates. The parametrization is derived by conceptually appending a short perforated region to the vortex-shedding edge of the plate. The underlying physical principle relies on the similarity between vortex shedding from a sharp edge and from an orifice. Two parameters are identified as important: the length of the perforated region and the quadratic loss coefficient associated with the pressure change. For practical applications, the value of the quadratic loss coefficient that is invariant of wave conditions is recommended for a given optimal length of the perforated region. The parametrization is validated using published results for a single plate, and its robustness is further demonstrated through applications involving two surface-piercing vertical plates with varying spacings. The findings of this study can find applications in using potential-flow theory to model plate-type wave breakwaters and wave interaction with thin-walled oscillating water column devices. Full article

Residual stresses are inevitably introduced during plate manufacturing and pre-processing (e.g., quenching and pre-stretching). However, springback prediction in creep age forming (CAF) is still frequently carried out by assuming an initially stress-free blank, which may lead to biased deformation–stress histories and tool compensation errors, hindering high-accuracy forming. This study aimed to close this practical gap by quantifying how inherited residual stresses affected the CAF springback of AA2219 double-curvature thin-walled parts. In this study, a multi-step finite element (FE) process chain covering quenching, pre-stretching, and creep age forming (CAF) was developed to investigate the evolution of the initial residual stress field and its influence on CAF springback. Surface residual stresses after quenching and after pre-stretching were measured by X-ray diffraction (XRD) to validate the FE models. The results show that, after quenching, the through-thickness residual stress exhibits a characteristic ‘compressive at the surfaces and tensile in the core’ distribution, and pre-stretching markedly reduces the residual stress level. During CAF, although the initial residual stress difference is largely equilibrated during loading, it affects springback primarily through differences in accumulated creep deformation. Incorporating the initial residual stress field reduces the springback error bandwidth from 9.59 mm to 3.51 mm (a 63.4% reduction) under the original die configuration. Additional simulations under a modified die curvature (geometric deviation ≈ 6 mm) demonstrate that the springback reduction remains at the millimeter scale, indicating that the proposed FE framework maintains a consistent predictive improvement across different curvature conditions. This work provides a theoretical basis and practical guidance for high-precision creep age forming. Full article

Aircraft structures are highly susceptible to fatigue damage, particularly in thin-walled aluminum alloy components such as skin panels. Damage in the form of holes or material loss drastically reduces fatigue life and compromises structural safety, which makes effective repair strategies essential. This study presents an experimental investigation into the fatigue performance of EN AW-2024-T3 aluminum alloy plates with central openings subjected to uniform shear. Repair nodes were applied using two approaches: conventional riveted metal patches and adhesively bonded composite patches. Variants of patch geometry, thickness, and diameter were evaluated to determine their influence on load transfer, buckling response, and fatigue life. The results show that central holes significantly shorten fatigue life, with a 20 mm hole causing a 67% reduction and a 50 mm hole causing a 95% reduction when compared with undamaged plates. Riveted metal patches restored only part of the lost performance, as stress concentrators introduced by fastener holes initiated new fatigue cracks. In contrast, adhesively bonded composite patches provided a substantial improvement, extending fatigue life beyond that of the riveted solutions, improving buckling shape, and delaying crack initiation. Larger patches, particularly those combined with metallic inserts, proved most effective in restoring structural functionality. The findings confirm the effectiveness of bonded composite repairs as a lightweight and reliable method for extending fatigue life and enhancing the safety of damaged aircraft structures. The study highlights the importance of patch geometry and stiffness in the design of repair nodes. Full article

The purpose of this study is to investigate the buckling behavior and failure mechanism of the boom of large-scale elevating jet fire trucks, so as to provide support for its safety design and service life improvement. In terms of research methods, a combination of double-version control tests and refined finite element simulations was adopted to carry out a systematic study. The research results show that the boom base plate exhibits typical sinusoidal wave buckling deformation when the load coefficient is between 0.45 and 0.5, and the wavelength is highly consistent with the theoretical prediction; under the critical load, the strain amplitude shows a significant nonlinear jump, which confirms the buckling mechanism of the coupling between geometric nonlinearity and material plasticity; under the ultimate load, the structure undergoes local buckling failure, the failure location is in good agreement with the simulation prediction, and the test results are highly consistent with the simulation results within the engineering allowable range, which verifies the reliability and applicability of the model. The research conclusion is the establishment of evaluation criteria for buckling failure of box-type knuckle arms: visible buckling waves appear, and the strain exceeds 40%. Based on this conclusion, optimizing the width-thickness ratio of the plate, strengthening the web constraint and improving the manufacturing process can effectively enhance the anti-buckling performance of the thin-walled box structure. Full article

The injection compression molding using dynamic mold control (ICM-DT) represents a promising technological approach to the manufacturing of highly filled, modified thermoplastic components with tight geometric tolerances. While the numerical prediction of flow states is, to date, predominantly based on the Cross–WLF modeling of viscoelastic characteristics of the melt, new material-related developments necessitate the assessment of process- and material-related boundaries. The present paper employs a highly filled graphite–polypropylene system, exhibiting a graphite mass fraction of 80%, for the quantitative comparison of Cross–WLF predictions and experimentally derived flow states. Based on coupled counter pressure-chamber high-pressure capillary rheometry (CPC-HCR) and counterpressurized viscometry (CPV) alongside the ICM-DT of thin-walled specimens, pressure-induced crystallization was identified to induce significant deviations from Cross–WLF predictions. Cross–WLF modeling strongly overestimates the processability of the applied graphite–polypropylene system under both injection molding (IM) and ICM regimes. We therefore observe a predominant influence of pressure-induced crystallization mechanisms in dynamic mold temperature process domains, in which the pressure-induced, crystallization-related exponential viscosity increase cannot be adequately modeled through both pressure-dependent and pressure-agnostic Cross–WLF models. The numerical approximation of flow states under dynamic mold temperature regimes hence necessitates the consideration of solidification-induced, self-intensifying pressure excursions. Full article

Cold-formed thin-walled steel (CFS) members were widely used in steel structures but faced challenges in meeting bearing capacity and assembly efficiency requirements as single-limb members. To overcome the above limitations, a promising fold-fastened multi-cellular steel panel (FMSP) was proposed. The FMSP eliminated the need for discrete self-drilling screws, instead utilizing a continuous mechanical fold-fastened connection, which enhanced structural integrity and assembly efficiency. This approach also provided greater flexibility to meet the design requirements of complex structural configurations. This study investigated the flexural behaviors of panels—a key mechanical property governing their structural behavior. A bearing capacity test was conducted on five FMSP specimens, focusing on the failure modes, bending moment–deflection curves, deflection distributions under representative loading levels, and flexural bearing capacities of the specimens. Refined finite element models (FEMs) of the specimens were established, and the stress and deformation distributions were further studied. The comparison results showed that the numerical results were in good agreement with the experimental results. Finally, the parametric analysis was carried out, and the influence of key parameters on the flexural behavior was revealed. Analysis results demonstrated that doubling the steel plate thickness increased the flexural capacity by 207%, while a twofold increase in panel thickness resulted in a 123% improvement. In contrast, increasing the steel strength from 235 MPa to 460 MPa yielded only a 61% enhancement. This research laid a solid foundation for promoting the application and investigation of FMSPs, thus achieving high industrialization and meeting the requirements of complex structural design. Full article

Fiber-Reinforced Polymer (FRP)-laminated composite materials are increasingly recognized as a transformative solution for future structural applications, due to their exceptional properties, such as lightweight, superior fatigue life, corrosion resistance, and ease of manufacturing. These advantages make them highly suitable for innovative applications in various sectors, including aerospace, automotive, marine, energy and defense. As one of the load-carrying members, the composite laminated plate structures are widely used in aircraft structures, such as the fuselage, wing and tail. These thin-walled structures will buckle under compressive or shear loading, which is a major consideration in the structural design process. Due to their high specific strength, laminated FRP composite structures are gaining increasing attention and are widely used in advanced lightweight structures. However, to fully exploit the large post-buckling reserves of FRP structures, their damage behavior and failure modes must be well understood. In this study, a progressive failure analysis based on ANSYS finite element (FE) simulations has been carried out to predict the nonlinear response and failure characteristics of a laminated composite plate under compressive loading. The FE-based progressive failure analysis utilized shell elements based on the Classical Laminate Plate Theory (CLPT) to calculate the in-plane stresses. The failure model employed the 3D failure criterion LaRC04 for damage detection and the stiffness degradation model for damage propagation in an FRP-laminated composite plate structure. The analysis results are found in close agreement with the published simulation and experimental results. This study has proposed an efficient methodology to accurately predict the post-buckling response, i.e., failure modes and collapse loads of laminated FRP composite constructions under compressive loading. Full article

This article investigates the structural resistance of thin-walled steel sections classified as Classes 1 to 4 under Eurocode 3. The study focuses on flexural capacity, and takes into consideration the effects of local buckling and the bimoment. Although Class 1 and 2 sections can develop complete plastic resistance, Class 3 sections are limited to elastic behavior prior to local instability. For Class 4 sections, effective width methods are employed to account for the reduction in strength due to early local buckling. Based on Eurocode formulations, these approaches are extended to incorporate the influence of the bimoment, which is significant in thin-walled open sections under non-uniform torsion. A comparative analysis between analytical models and numerical simulations is presented, with an emphasis on how the bimoment alters stress distributions and reduces the effective widths of slender plates. The results underscore the necessity of including these effects in the structural design of thin-walled members, particularly for open profiles subjected to bending and warping. Full article

The Qianlong Tripitaka preserved in the Capital Museum is a distinctive large-scale wood block printing plates of the Qing Dynasty. It represents a unique type of Chinese documentary wooden heritage preserved in a dry museum environment, which has rarely been subjected to comprehensive physicochemical analysis, resulting in an inadequate understanding of their deterioration processes. This study applied a comprehensive multi-analytical method to investigate the deterioration of the scripture plates. The findings indicate that the Qianlong Tripitaka shows typical structural deformation, chemical depolymerization, and a decline in structural integrity and stability. Scanning Electron Microscopy (SEM) and Computed Tomography (CT) revealed thinning and the distortion of cell walls, reduced density, and partial collapse of tissue structures. Thermogravimetric Analysis (TGA) indicated lower decomposition temperatures and higher inorganic residues, while a Brunauer–Emmett–Teller surface area analyzer (BET) showed diminished surface area, expanded pores, and compromised connectivity. Moisture content analyses verified significant water loss, contributing to brittleness and susceptibility to microbial degradation. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) analyses revealed considerable hemicellulose degradation, the disruption of cellulose crystallinity, and relatively stable lignin. This study highlights the value of a multi-analytical strategy for assessing the deterioration of wooden cultural heritage, providing a transferable framework for similar documentary wooden artifacts. Full article

Achieving reliable implant stability in type IV (D4) bone remains a clinical challenge due to its thin cortical plates and low trabecular density, which increase the risk of early failure. Novel osteotomy techniques such as osseodensification and the OsseoShaper have been proposed, yet their effects when combined with different implant macrogeometries are not fully understood. This in vitro study evaluated forty osteotomies in standardized polyurethane foam blocks simulating D4 bone density. Three site preparation protocols—conventional osteotomy, osseodensification, and OsseoShaper—were combined with two implant macrogeometries (parallel-walled conical and tri-oval tapered designs). Insertion torque (IT) was measured using a calibrated digital torque meter, and implant stability was assessed by resonance frequency analysis (ISQ). Intraoperative thermal changes were monitored with infrared thermography under constant irrigation. Statistically significant differences were observed among groups (p < 0.05). Osseodensification with parallel-walled implants achieved the highest stability, whereas osseodensification with tri-oval implants showed the lowest. Although osseodensification produced the greatest thermal increase, all values remained below the 47 °C osteonecrosis threshold. Within the study’s limitations, both the osteotomy technique and implant macrogeometry significantly affected stability and thermal outcomes, with osseodensification plus parallel-walled implants providing the most predictable performance in D4 bone. Full article

Thin steel plates with stiffeners are widely employed in several branches of engineering, combining mechanical strength with low weight and serving as both structural and cladding components. However, the influence of the side-wall inclination angle of hat-stiffeners on the stiffness distribution and deflection patterns of steel plates remains insufficiently explored. This study conducts computational modeling to evaluate the deflection of thin steel plates reinforced with hat-stiffeners. The plates were considered simply supported and subjected to a uniformly distributed load. The Constructal Design method and the exhaustive search technique were employed, allowing for geometric evaluation and optimization. A fraction corresponding to 30% of the plate volume was removed and redistributed to generate longitudinal hat-stiffener geometries by varying its side-wall angle and thickness. The smaller base of the hat-stiffeners was imposed as a geometric constraint and therefore kept fixed. The results indicate a nonlinear trend between the side-wall angle, the moment of inertia, and the resulting deflection, leading to a new geometrical pattern that connects the angular inclination to the overall stiffness behavior of the plate. Angles between 105° and 130° provided the best performance, reducing the maximum deflection by 93.72% compared with the reference plate and improving it by around 7.5% relative to previous studies. These findings illustrate how geometric configuration can enhance performance in line with Constructal Design principles. Full article

Phased array technology can be realized with directional control with fixed beam steering. However, its directionally dependent beam pattern limits the efficiency of suppressing undesirable distance interference. This paper presents a guided wave frequency diverse array-based damage location method for thin-walled structures. Firstly, a guided wave frequency diverse array signal model is derived with a relatively small frequency increment that can achieve distance–direction two-dimensional focusing. Secondly, three types of receiving arrays, including a monostatic array, following array, and symmetric array, are constructed to achieve the maximum damage-induced signal amplitude. Finally, a two-dimensional multiple signal classification (MUSIC)-based damage location method is applied for damage imaging in thin-walled structures. Simulations on an aluminum plate and the experiments on an epoxy laminate plate demonstrate the validity and effectiveness of the proposed method. Full article

The aim of this study was to investigate microstructure and the mechanical and operational characteristics of thick and thin walls 3D-built by electron beam additive manufacturing (EBAM). In addition, the milling parameters (rotation speed, feed, and cutting width) were optimized based on simultaneous assessments of Ra roughness on the machined surfaces and material removing rate values. The wall dimensions did not exert a noticeable effect on their chemical compositions, as compared with the original wires used for 3D printing. In comparison, the strength characteristics of the wrought steel (cold-rolled plate) were higher due to finer grains, with both ferrite content and dislocation density being greater as well. In the 3D building process, multiple thermal cycles gave rise to the formation of elongated columnar grains, reducing the strength characteristics. The corrosion rate of the wrought steel was almost twice those of the 3D-printed blanks because of the higher content of both ferrite and twins. By assessing the machinability of the EBAM-built blanks using the stationary milling machine, the cutting forces were comparable due to similar mechanical properties (including microhardness). To improve the removing rate values and reduce the cutting forces, it is recommended to enhance the cutting speeds while not increasing the feeds. For the semi-industrial milling machine, both linear multiple regression and nonlinear neural network models were applied. An integrated approach was proposed that rationally determined both additive manufacturing and post-processing parameters based on a combination of express assessment and analysis of the mechanical, operational, and technological characteristics of built products within a single laboratory complex. Full article

This study presents an analytical model to reduce the impact of wave-induced forces on a vertical seawall by introducing a floating elastic plate (EP) located at a specific distance from two bottom-standing porous structures (BSPs). The hydrodynamic interaction with the EP is described using thin plate theory, while the fluid flow through the porous medium is described by the model developed by Sollit and Cross. The resulting boundary value problem is addressed through linear potential theory combined with the eigenfunction expansion method (EEM), and model validation is achieved through consistency checks with recognized results from the literature. A comprehensive parametric analysis is performed to evaluate the influence of key system parameters such as the porosity and frictional coefficient of the BSPs, their height and width, the flexural rigidity of the EP, and the spacing between the EP and BSPs on vital hydrodynamic coefficients, including the wave force on the seawall, free surface elevation, wave reflection coefficient, and energy dissipation coefficient. The results indicate that higher frictional coefficients and higher BSP heights significantly enhance wave energy dissipation and reduce reflection, in accordance with the principle of energy conservation. Oscillatory trends observed with respect to wavenumbers in the reflection and dissipation coefficients highlight resonant interactions between the structures. Moreover, compared with a single BSP, the double BSP arrangement is more effective in minimizing the wave force on the seawall and free surface elevation in the region between the EP and the wall, even when the total volume of porous material remains unchanged. The inter-structural gap is found to play a crucial role in optimizing resonance conditions and supporting the formation of a tranquility zone. Overall, the proposed configuration demonstrates significant potential for coastal protection, offering a practical and effective solution for reducing wave loads on marine infrastructure. Full article