Abstract Magnetoelectric (ME) laminated composites exhibit strong coupling effects but remain difficult to model accurately when interfacial imperfections and time-dependent material behavior are present. Conventional micromechanical models typically assume perfect bonding and instantaneous responses, leading to discrepancies with experiments. This study develops two hierarchical micromechanical frameworks to predict the visco-magneto-electro-elastic behavior of 2-2 laminated composites with imperfect interfaces. A unit-cell model with a recursive time-integration scheme and a Mori-Tanaka model extended via the correspondence principle are formulated within a unified multiphysics constitutive framework. Interfacial effects are explicitly incorporated through a second-stage homogenization. The models are validated against experimental data, showing excellent agreement for dielectric, piezoelectric, and time-dependent creep responses. Results reveal that ME coupling exhibits pronounced time dependence governed by visco-electro-elastic effects and is highly sensitive to interfacial conditions. Even a thin interphase layer significantly reduces coupling efficiency, while optimal phase proportions enhance the response. The proposed framework provides a physically consistent and efficient tool for predicting realistic ME behavior and offers valuable insights for the design of advanced ME composites.
Abstract This study aims to clarify the vertical–horizontal coupled vibration mechanism of rolling mill rolls and to provide a mechanically interpretable model for vibration analysis and structural optimization. An extended Timoshenko beam element is developed for a flexible-roll finite element model, in which each node contains vertical and horizontal translational degrees of freedom together with the corresponding rotational degrees of freedom. Compared with conventional lumped-parameter, rigid-roll or single-plane beam models, the proposed formulation retains the distributed flexibility of the roll along the barrel direction and assembles bending stiffness, shear stiffness, rolling-zone contact stiffness and friction-induced tangential coupling into one global dynamic equation. Modal analysis, stability analysis, time-domain simulation, frequency-response analysis and field measurements are then carried out. The results show that lower-order modes are dominated by vertical motion, whereas higher-order local modes contain more pronounced horizontal vibration components. The flexible-roll model gives a smaller stability margin, and instability is more likely when the friction coefficient is negative and the coupling angle increases. The dominant response appears near the roll center and remains concentrated in the low-frequency range. Field measurements support the predicted trend that vertical vibration dominates the stable low-frequency response, while horizontal vibration mainly appears as an accompanying component induced by structural coupling and load transfer. The model provides a basis for offline stability assessment, vibration mechanism interpretation and structural optimization of rolling mills.
This study investigates the unsteady flow dynamics of a thin viscous fluid film over a heated variable horizontal stretching sheet, incorporating slip velocity and variable heat flux conditions. Using the Lie symmetry approach, new similarity transformations are derived by constructing a general linear combination of the admitted symmetries, leading to a reduced system of nonlinear ordinary differential equations containing arbitrary constant coefficients. It has been shown that the existence of these arbitrary coefficients enables control over the flow dynamics and heat transfer. The inclusion of slip and variable heat flux modifies the underlying Lie algebra, yielding novel solution structures compared to existing models. The reduced ordinary differential equation system is analytically treated via the homotopy perturbation method, revealing the influence of physical and control parameters on velocity and temperature fields. Shooting technique coupled with Runge-Kutta has also been implemented for a numerical validation of all the deduced analytical solutions. Graphical illustrations of these solutions reflect the modulation of flow and heat transfer characteristics enabled by the arbitrary Lie control parameters.
Recently, an advanced J-VAWT, featured by blades with a distinctive concave "J" profile, has been proposed. Previous numerical studies have reported varied performance outcomes for J-blades, with some indicating improvements and others showing negligible or negative effects. However, experimental evidence from carefully calibrated wind tunnel tests remains scarce to clarify the controversy. In this paper, the Taguchi analysis is performed to optimize the design of J-blades with the profile NACA0018. In this analysis, three control factors are considered, including the opening ratio, chord length, and blade thickness, for each of which there are five levels. In the optimization process, flow fields were simulated by the software Fluent to obtain the power coefficients of all 2D/3D models. With simply 25 simulation sets, the Taguchi analysis produced an orthogonal array of L25(53) to obtain the optimal design of the J-blades. For verification, both full-scale models of the closed-type and the optimally designed J-VAWT were experimented in a wind tunnel. The experimental results show that the use of J-blade may provide a performance gain of roughly 5% (7%) for Cp (Cm) at relatively low rotational speeds. In addition, the J-VAWT exhibited notably better self-starting capability. The present findings are applicable to small-scale VAWTs in the low-to-moderate Reynolds-number regime.
This study employs a CFD approach using Fluent to establish a 2D axisymmetric airlift pump model. The Eulerian multiphase model and SST k-omega turbulence model are used to simulate three air injection modes: continuous, stepped and sinusoidal. Model validation was performed against experimental data. The effects of oscillation frequency (0-2 Hz) on gas holdup, liquid flow rate, efficiency, and hydraulic characteristics were systematically analyzed. Results show: (1) Oscillatory air injection significantly enhances pump performance. Sinusoidal injection at 1 Hz achieves a peak mass transport efficiency of 84%, a 34% improvement over continuous injection. (2) Stepped injection creates periodic large bubble clusters that strengthen local driving force but incur higher turbulent dissipation. Sinusoidal injection promotes uniform small bubbles and more stable liquid transport. (3) Vortex analysis indicates that stepped injection generates concentrated intense vortices in the riser mid-section, leading to uneven energy dissipation. Sinusoidal injection enhances gas-liquid mixing stability and reduces overall flow energy consumption. This work overcomes the conventional focus on continuous injection, elucidating the mechanism linking oscillation frequency and flow regime evolution. This work overcomes the conventional focus on continuous injection. It elucidates the underlying mechanisms connecting oscillation frequency and flow regime transition, establishing a theoretical foundation for optimizing airlift pump performance through gas-liquid interaction mechanisms. Furthermore, it provides critical parametric guidance for implementing oscillatory injection technology in engineering practice. The study holds significant value for both academic innovation and practical application in the design of gas-liquid transport systems for marine resource exploitation and related fields.
Composite stiffened panels are widely used in aerospace structures, where buckling under axial compression often governs structural design. This study presents a sizing optimization investigation of three representative composite stiffened panel configurations, namely hat-type, J-type and T-type stiffeners, aiming to enhance buckling resistance without increasing structural mass. A fully parameterized finite element model is established in Abaqus to perform linear eigenvalue buckling analysis and is validated through axial compression experiments, with discrepancies within 5%. For the hat-type stiffener, the web height, top width and web inclination angle are optimized; for the J-type stiffener, the web height, cap width and foot width are optimized; and for the T-type stiffener, the web height and foot width are optimized. Under a cross-sectional area constraint of +/- 2%, the optimization leads to a reduction in web height for all 3 configurations, a reduction in hat top width and J-type cap width, and an increase in the hat web inclination angle as well as the foot width of the J- and T-type stiffeners, thereby redistributing sectional dimensions to improve buckling resistance. A gradient-based NLPQLP optimization algorithm implemented in Isight is employed to maximize the first linear buckling eigenvalue. Within the linear eigenvalue buckling framework, the first eigenvalue (and the corresponding eigenvalue-based critical load) increases by 19.65%, 37.9% and 23.4% for the hat-, J- and T-type stiffened panels, respectively. These improvements indicate comparative sizing trends under the adopted idealized buckling metric and should not be directly interpreted as increases in ultimate load capacity. Comparative analysis highlights the distinct geometric sensitivities associated with different stiffener configurations.
The lightweight materials are highly suitable in the automotive, transportation, marine, defense, rail and other industrial sectors, due to their excellent strength-to-weight ratio. The environmentally friendly Friction Stir Welding (FSW) method was used in this work to produce solid-state joints with polygonal pin profiles. Weld trails were designed using an orthogonal array of L27 runs with five parameters each at three levels. AA6061/AA7075 Al-alloys in a dissimilar combination were processed using the polygonal pin profiles. The regression Eq. helps in developed the mathematical model to frame the relationship between input parameters to responses. In order to obtain precise F and P values the current work concentrated on determining the optimal condition by using predicted mean values of the outcomes. The experimental test results proved that, the highest values of Ultimate Tensile Strength, Yield Strength, Hardness and Flexural Strength of weld joint are measured as 237 MPa, 223 MPa, 122 HV, and 262 MPa respectively. The maximum joint efficiency of the sample 11, processed at a tool rotational speed of 900 rpm, weld speed of 20 mm/min, Tilt angle of 1o, offset of 1.5 mm and with a hybrid square profile is found as 87%, which is validated by American Welding Society (AWSD17) standards.
This case study benchmarks a novel design approach for assessing the survival function of nonlinear nonstationary dynamic systems subjected to combined stochastic, nonstationary environmental loadings, with a particular focus on offshore engineering and naval architecture. The proposed design methodology benchmarks a novel log-integral (4-parameter generalized Weibull) extrapolation scheme of the Integrated Cumulative Distribution Function (ICDF) for accurate modeling of failure or damage probabilities aboard an operational Floating Production Storage and Offloading (FPSO) unit. The proposed design approach provides a robust tool for reliability and safety assessment of operational vessels and offshore structures in adverse deep-water conditions, particularly in ocean-wave environments. Predicted design values have been cross-validated against a 4-parameter Weibull distribution parametric fit. The combination of ICDF and onboard sensor measurements may provide offshore engineers with a robust framework for enhancing the reliability analysis of marine structures under dynamic, rapidly changing loading conditions.The primary novelty of this study lies in combining full-scale hot-spot stresses, measured by onboard-installed sensors using a novel integral ICDF extrapolation scheme, which is particularly suitable for design purposes when the underlying dataset is representative yet limited in size. A novel formulation of the fundamental design concept, such as Most Probable Maximum (MPM), for a non-Gaussian process with clustering (narrow-band) effects is presented, expressed as a memory-modified mean up-crossing rate in a practical engineering context.
Deep geotechnical engineering requires grouting technology to ensure project safety. However, the interlayered geological conditions of layered rock formations make grouting effectiveness difficult to predict and guarantee. Therefore, it is of significant practical value to investigate the diffusion mechanism of grouting within layered rock masses further. First, this study developed a true triaxial grouting physical testing system to reveal the influence of water-to-cement ratio (W/C) and injection rate on grout diffusion. The evolution of acoustic emission characteristics under different grouting parameters was compared and analyzed. Furthermore, potential fracture mechanisms within layered rocks were identified through moment tensor inversion. The results indicate that cement slurry spreads more readily within weak layers at low injection rates and W/Cs, facilitating generation of multiple small-scale fractures. Peak fracturing pressure exhibits a positive correlation with the injection rate and a negative correlation with W/C. Acoustic emission localization results indicate that higher injection rates facilitate slurry diffusion perpendicular to weak layers. Furthermore, a hydraulic-mechanical-damage coupled model for simulating grouting in layered rocks was developed using COMSOL Multiphysics software. By numerical simulation, the regulatory mechanisms of weak layer dip angle and in-situ stress on dominant diffusion directions were revealed. Compared results revealed that when longitudinal stress was the maximum principal stress, a steeper weak-strength layer inclination tended to confine slurry within high-strength layers. However, the initial cracking pressure first decreased then increased with weak layer inclination, approaching its minimum at 45 degrees. This work systematically investigates the fracture mechanism induced by grouting in layered rocks by integrating laboratory physical tests with numerical simulations that account for weak layer dips and in-situ stress fields. The relevant findings and insights provide valuable practical references for underground geotechnical engineering.
Stainless steel (SS) 316 is extensively used in aerospace, marine, and nuclear industries because of its superior mechanical properties and corrosion resistance. Nevertheless, its microstructure and mechanical behavior are greatly affected by welding-induced thermal cycles. In this research, the influence of Tungsten Inert Gas (TIG) welding on the microstructural development and mechanical properties of analogous SS316 weldments is explored. A multi-pass (two-pass) TIG welded process was used, and the weld joints were characterized by microstructural characterization, tensile testing, microhardness testing, and infrared (IR) thermography. IR thermography was used to record temperature gradients during welding at various stages, indicating heat buildup and thermal gradients influencing microstructural development. Microstructural analysis indicated columnar dendrites in the fusion zone and grain coarsening in the heat-affected zone (HAZ). Mo and Cr segregation in inter-dendritic areas was seen, and these can affect corrosion resistance and mechanical performance. Tensile test results revealed that the weld joints had an ultimate tensile strength (UTS) of 636-640 MPa with minor fluctuations because of heat build-up. Among the three tensile-tested specimens, two exhibited failure in the HAZ. However, specimen 3 failed just adjacent to the weld zone, suggesting that localized heat input at the commencement of welding influenced the failure location. Microhardness analysis revealed a hardness value of 94-99 HV in the weld and 97-99 HV in the HAZ, which followed grain refinement and thermal effects. The results of this research offer significant information on the optimization of welding parameters to improve joint performance, ensuring the reliability of SS316 components in critical applications.
This study addresses the optimization of blasting parameters for narrow gold vein. A PFC2D numerical model was built based on an underground metal mine in China. A systematic simulation of blasting were conducted under 3 borehole layouts (square, zigzag, and quincunx) using 9 blast hole network parameters. The relationships among excavation ratio, fracture number, and peak particle velocity (PPV) at the free surface were studied. The findings show that the blasting effect is energy-dominated; Inadequate rock fragmentation arises from insufficient energy to fracture the rock mass when the number of fractures is less than 2800 and the PPV is less than 15 m/s. There is more underbreak when the weight or hole spacing is increased. A comprehensive multi-index study indicates the quincunx borehole layout as the ideal pattern, with the best parameters being a burden of 0.6 m and a hole spacing of 0.6 m. Field tests revealed that this improved technique results in regular blast cavity, homogeneous fragmentation, and near alignment with the planned contour. For the safe and effective blasting extraction of narrow veins when confined, this research offers a useful reference.
The strain energy can be divided into changes in volume and distortions in shape. Distortions in shape are a significant contributing factor to material failure. Therefore, this paper transforms global stress constraints into distortion energy constraint based on the level-set method to optimize the structure design. First, the large and complex stress constraints are transformed into a distortion energy constraint, which is based on the theory of distortion energy causing material yield. Next, due to the challenges in extracting distortion energy from the elements and ensuring design safety, the more easily extractable strain energy constraint is used as a substitute for the distortion energy constraint. Finally, four numerical examples serve to demonstrate the effectiveness and practical applicability of the proposed approach.
This study investigates the influence of aspect ratio on the aerodynamic characteristics of a finite-length square cylinder with free ends using computational fluid dynamics simulations at a Reynolds number of 6000. Aspect ratios from 12.5 to 2 are analyzed, revealing crucial insights into aerodynamic behavior under varying conditions. At an aspect ratio near 8, a major wake reorganization occurs, marking the dominant transition in the wake structure. Higher aspect ratios result in periodic shedding of coherent tip and spanwise vortices, forming a von K & aacute;rm & aacute;n vortex street. As the aspect ratio decreases, tip vortices migrate toward the leeward side, disrupting spanwise vortices and reducing vortex shedding. Below an aspect ratio of 8, steady loops of tip and spanwise vortices form, suppressing periodic shedding. The drag coefficient peaks at an aspect ratio of 12.5 and declines with decreasing aspect ratio, while the root mean square lift coefficient reaches zero below an aspect ratio of 6.5. The Strouhal number indicates no periodic vortex shedding below an aspect ratio of 4.5. Pressure distribution analysis reveals intricate patterns and changes in high-pressure regions. These findings highlight the crucial role of aspect ratio in aerodynamic behaviors, providing valuable insights for optimizing square cylinder designs in various engineering applications.
Under alternating axial external forces, threaded fasteners are prone to fatigue failure. At present, the main focus is on improving material strength to optimize fatigue resistance; most of these methods have greatly increased the cost. Plastic strengthening is a traditional method that does not increase the cost, is easy to operate and can effectively improve the fatigue resistance. Without changing the fastener, the fatigue resistance can be enhanced to a certain extent by simply pre-tightening it beyond the target clamping force and then untighten it to the target clamping force. However, currently there is no clear specification for the maximum pre-tightening force that exceeds the target clamping force. Too strong or too weak maximum pre-tightening force may cause micro-cracks in the fastener or fail to be effectively strengthened. In addition, the strengthening mechanism of the threaded structure has not been clearly explained. This study, the relationship between the strengthening level and the using conditions is clarified through experiments and finite element stress analysis, and the plastic strengthening mechanism is revealed, which is also of guiding significance for the plastic strengthening of other structures.
With the advancement of micro-nano fabrication technology, microbeam-based biomechanical measurement platforms have become effective tools for detecting myocardial contractility due to their high sensitivity, compact size, and ease of integration. In this paper, a piezoelectric curved micro-beam model is proposed based on the extended dielectric theory and Hamilton's principle to predict the contractile force of cardiomyocytes. The governing Eqs. and boundary conditions are derived, and the differential quadrature method (DQM) is employed for numerical solutions. The electromechanical coupling response is analyzed to indirectly measure cardiomyocyte contractility. Considering the structural complexity, adhesion patterns, and mechanical properties of cardiomyocytes, we introduce an equivalent modeling approach: ideal elastic bodies with similar physical properties are used as substitutes for real cells. Periodic thermal excitation induces thermal expansion and contraction in these bodies, thereby simulating the cyclic contraction-relaxation behavior of cardiomyocytes. This method streamlines the modeling process, improves system controllability and computational feasibility, and lays a practical foundation for subsequent experimental validation.
The wear of the barrel mainly occurred at the forcing cone, which greatly changed the projectile engraving characteristics and the gun's inner ballistic characteristics. To further reveal the projectile-engraving dynamic characteristics of the large caliber wear gun, a parametric structural model of the worn barrel was proposed and regular meshed. A finite element model of the projectile dynamic engraving process was established under different barrel wear amounts, which considering the change of internal ballistic parameters caused by wear. The numerical calculation results were in good agreement with the experimental results and the projectile dynamic engraving characteristics under different barrel wear amounts were analyzed. The results indicated that with the wear intensified, the chamber pressure-boosting rates and projectile engraving resistance decreased, the projectile velocity and angular velocity at the end of the engraving process increased due to the projectile's total engraving displacement increasing. As the barrel wear increased, the average stress on the belt element gradually decreased and the stress on the inner barrel liner reduced, the belt unit proportion sheared by the forcing cone was reduced. When the barrel wear was greater than 2.4 mm, the front belt showed a flattening phenomenon, which changed the groove shape and stress-strain state of the copper belt.
Five-axis milling of free-form surfaces requires simultaneous optimization of toolpaths and continuously varying tool orientations. However, most commercial CAM workflows focus only on geometric simulation and neglect critical physical quantities such as cutting forces, leading to force spikes, tool deflection and surface inaccuracies. This study proposes an integrated optimization framework that combines automatic toolpath generation from STEP/B-Rep models with solid-model-based extraction of cutter-workpiece engagement (CWE). The CWE data are transformed into entry and exit immersion parameters and undeformed chip thickness to enable mechanistic cutting-force prediction. Tool orientations are then optimized using a curvature-aware parameterization method and a particle swarm optimization (PSO) algorithm. Numerical validation on representative free-form surfaces demonstrated that the proposed method reduced the maximum cutting force from 214 N to 170 N (a 20.6% reduction) compared with the original path. A secondary optimization stage incorporating polynomial-fitted force smoothing decreased force fluctuation amplitude by over 40%, resulting in both smoother tool-axis trajectories and improved machining stability. By integrating geometric modeling, physical simulation and metaheuristic optimization, the proposed PSO-based framework provides a quantitatively verified improvement in force-aware toolpath planning. The approach can be readily incorporated into existing CAD/CAM environments for efficient and reliable five-axis machining of complex free-form surfaces.
To address the challenges associated with conducting large-scale and complex acoustic vibration experiments on dual-layer cylindrical shells, which are both difficult and costly, this paper proposes a method that predicts the vibrational response of a full-scale dual-layer cylindrical shell using the vibrational response of a single-layer scaled-down model. Finite element models of both the full-scale dual-layer cylindrical shell and its scaled-down counterpart were developed using Virtual.Lab Acoustic software. The vibrational responses of these models were analyzed within the 100–500 Hz frequency range, and a comparative analysis was conducted to validate the accuracy of the scaling method and the similarity of vibrational responses. The results indicate that the displacement ratio between the scaled-down model and the original model aligns closely with the geometric scaling factor. Furthermore, the similarity coefficients of the vibrational responses for both the inner and outer shells of the scaled-down model exceed 0.9, confirming the effectiveness of the proposed approach.
This study presents a thorough investigation of the Au10In3 intermetallic compound using density functional theory, to clarify its fundamental properties and potential applications in microelectronic packaging and high-reliability bonding. As a significant yet underexplored phase in the Au–In system, Au10In3 is systematically analyzed through first-principles calculations within a generalized gradient approximation framework, focusing on its structural stability, anisotropic elastic response and thermophysical properties. Optimized structural calculations confirm the thermodynamic stability of Au10In3, with a negative formation enthalpy of −0.138 eV/atom. Elastic constants satisfy mechanical stability criteria, establishing the compound's stability under mechanical stress. Further mechanical analysis implies ductile behavior, indicated by a high Pugh's ratio of 4.94, positive Cauchy pressures and a Poisson's ratio of 0.405. The material demonstrates Vickers hardness of 1.40 GPa and fracture toughness of 0.897 MPa·m1/2, reflecting resistance to both deformation and fracture. Elastic anisotropy of Au10In3 is estimated with several indices: symmetry-invariant universal anisotropy index (AU) is 1.21, Zener-based equivalent anisotropy parameter (Aeq) is 2.63 and logarithmic Euclidean metric (AL) is 0.48. Directional dependence of elastic moduli is illustrated through three-dimensional mappings of Young's modulus, shear modulus and Poisson's ratio, providing insight into its anisotropic behavior. In thermophysical characteristics, Au10In3 presents a Debye temperature of 151.5 K, thermal expansion coefficient of 24.3 ppm/K and lattice thermal conductivity of 0.291 W/mK, indicative of low phonon transport efficiency. Comparative analyses with related phases, Au3In and Au3In2, highlight that Au10In3 possesses intermediate mechanical strength and thermal conductivity within the Au–In system.
A three-dimensional infinite element method (IEM) for modeling a multihole plate is presented. Additionally, a new concept based on cylindrical coordinates to create a similar mesh layer is proposed. A specific element, embedded with a through-hole of various radii, is formulated using the conventional finite element method (FEM) based on the similarity stiffness of isoparametric eight-node hexagonal elements and matrix condensation operations. An IEM-FEM coupling scheme is developed and implemented in the commercial software MATLAB to conduct the bending analysis of perforated plate. Four numerical examples involving complicated geometries and multiple holes are considered to examine the applicability of the proposed approach. The available solutions computed using the commercial FEM software ABAQUS are used for comparison. The proposed approach demonstrates higher accuracy and efficiency compared with conventional FEM approaches.
