International Journal of Mechanics and Materials in Design最新文献

Frequency optimization of stiffened piezolaminated composite plates has not been investigated so far. Therefore, this study focuses on optimizing the fundamental frequency of stiffened piezolaminated composite plates using a novel special relativity search based on hill climbing (SRSHC) algorithm. The optimization process maximizes the fundamental frequency by adjusting the fibre orientations within the composite layers. The mathematical models, based on classical laminated plate theory (CLPT) with von Karman nonlinearity, are solved using MATLAB. The impact of various parameters, including boundary conditions, grid shapes, angles of diagonal ribs, and plate aspect ratios, on the optimized frequency results is thoroughly examined. The results demonstrate that the SRSHC algorithm outperforms the Special Relativity Search (SRS) algorithm, confirming its effectiveness in complex optimization problems with large search spaces. This research contributes to advancing the design of smart structures with enhanced dynamic performance.

This work presents a methodology for automatic detection of internal defects in parts manufactured from 3D printing with two of the most common materials for these purposes. Active Thermography has been used, specifically the Lock-in technique. To ensure reliable detection, the varying frequencies of the stimulation source have been compared to determine the optimal configuration. Results have been analysed to identify the parameters that most affect the identification of defects. Results show that the frequency and the type of material used are the most critical parameters that condition the detection though the influence of this latter was less clear, so it was necessary apply a novel analysis based on Machine Learning. Most effective algorithm was an ensemble model, which achieved an accuracy rate of 88.9%. A variation of Maximum Stable External Regions is presented to automatised detection.

In this present, the finite element approach is employed to analyze the free oscillation, static and dynamic buckling of skew-nanoplate made of piezoelectric materials with variable thickness resting on variable Pasternak medium in a hygro-temperature environment. This study is a wonderful combination of Kirchhoff plate theory, nonlocal strain gradient hypothesis, and surface effect and Hamilton’s principle to derive the general equilibrium equation of the plate. A four-node quadrilateral plate element with six degrees of freedom per node is developed using a Hermit C²-level non-conforming shape function. This element offers high accuracy and fast convergence for a variety of shapes and boundary conditions, outperforming lower-order elements. Bolotin’s method is applied to determine the dynamic instability region of the non-uniform piezoelectric skew nanoplate. The accuracy of the present approach is validated through numerical comparisons with established data. Furthermore, the effects of parameters such as residual surface stress, applied voltage, temperature gradient, moisture, elastic foundation stiffness, thickness variation, skew angle, geometric factors, and boundary conditions on free oscillation and stability of skew nanoplate are thoroughly assessed. The present study will offer the physical insights required to model size-dependent multifunctional systems for active control of mechanical characteristics and electromechanical energy harvesting, given the recent developments in nanoscale manufacturing.

This study develops a comprehensive mathematical model for vibration-based energy harvesting in laminated bimorph cylindrical microshells with hexagonal honeycomb cores, subjected to nonlinear thermal gradients and moisture environments, and supported by a viscoelastic foundation. It is assumed that the sandwich microshell is subjected to various boundary conditions. The external layers use piezoelectric materials to improve energy conversion. First-order shear deformation theory (FSDT) and modified strain gradient theory (MSGT) are utilized to formulate size-dependent dynamic equations that incorporate microscale effects. The modified Gibson’s equation is used to estimate the material characteristics of the honeycomb core, which is considered a homogeneous orthotropic medium. Employing Hamilton’s principle and Gauss’s law, coupled electromechanical equations are derived to characterize the system’s dynamic behavior. Frequency response functions are found using analytical methods that correlate electrical power production with resistance to external loads. An extensive parametric study examines how energy harvesting efficiency is affected by geometric dimensions, length scale parameters, fluctuation of the temperature, variation of moisture, viscoelastic medium, parallel and series piezoelectric setups, boundary conditions, and honeycomb characteristics. The results provide important information for improving the design of nanoscale energy harvesters and their performance in viscoelastic and thermally dynamic environments.

This study utilizes the nonlocal strain gradient elasticity theory to investigate the dimensionless frequency shift caused by adsorption in a dynamic resonator system. The system consists of double functionally graded porous sandwich microbeams with a two-dimensional periodic square holes network, connected through an elastic medium and influenced by a magnetic field, compressive loading, and distributed water molecules. The double functional microbeams follow a power-law distribution for thickness-dependent properties, considering two porosity patterns. The impact of the applied magnetic field is analyzed using Maxwell’s equations. Nonlocal strain gradient elasticity theory is employed to capture small-scale effects. Both Euler–Bernoulli and Rayleigh beam theories are utilized to account for bending and rotary inertia effects. Interatomic interaction energies are modeled using Lennard–Jones (6–12), Morse, and Buckingham potentials, while perforation effects are incorporated into the equivalent bending stiffness. Analytical solutions are derived using the Navier-type method, and numerical solutions via the differential quadrature method. Results indicate that the dimensionless frequency shift is strongly influenced by porosity volume fraction and hole configuration. Water molecule adsorption reduces the frequency shift, while increases in magnetic field intensity and length-to-width ratio improve structural sensitivity. Additionally, both dimensionless compressive force and spring parameter introduce a softening effect, lowering system stiffness and amplifying the drop in dimensionless nonlocal frequency. A clear discrepancy between Euler–Bernoulli and Rayleigh model predictions highlights the role of rotary inertia. This model offers a comprehensive framework for designing advanced microresonators for nano/microscale sensing applications, such as mass detection and virus-induced frequency modulation.

This study presents exact analytical solutions for the local and nonlocal transverse vibration of Euler–Bernoulli nanobeams resting on Winkler–Pasternak elastic foundations. Incorporating Eringen’s nonlocal elasticity theory, the model captures small-scale effects, while rotational and translational springs represent general boundary conditions. For the first time, exact and general frequency equations are derived for nanobeams with arbitrary boundary conditions, elastic foundations, and tip masses. These equations are numerically solved to obtain precise natural frequencies, showcasing the accuracy and versatility of the proposed framework. The influence of key parameters such as nonlocal effects, boundary flexibility, foundation stiffness, tip masses, and slenderness ratio on the first three natural frequencies and mode shapes is systematically analyzed. Results reveal the significant role these factors play in shaping vibrational behavior, providing critical insights into the dynamic response of nanostructures. Presented in graphical and tabular formats, the findings offer benchmark solutions for validating future models. This work advances the understanding of nanobeam dynamics and supports the design and optimization of advanced nanoscale systems embedded in elastic media with flexible supports and tip masses.

The growing demand for energy has led to significant attention being given to the energy harvesting process from vibrations using piezoelectric materials. Given the limited energy available for conversion, robust designs that minimize sensitivity to parameter uncertainties or external variations are essential. To ensure project quality, multi-objective optimizations are necessary to maximize the mean and minimize the standard deviation of the response, but the computational cost increases with the number of uncertain parameters, requiring more efficient approaches. In this way, with metamodels, which are computational tools, it is possible to provide a faster and less costly evaluation of such computationally expensive models. This study proposes the use of a Kriging metamodel to design robust cantilever beam energy harvesting devices, combined with Monte Carlo Simulation to estimate the mean and standard deviation of the Frequency Response Function of power output. Multi-objective optimization and sensitivity analysis are applied. Results indicate that using more design variables leads to a metamodel with higher computational cost due to the larger number of experimental samples required. Nevertheless, this cost remains low compared to direct model optimization, with a satisfactory time reduction in the optimization process.

The detonation of landmines poses a significant threat to armored vehicles and their crews on battlefield. To enhance the resistance of vehicles to shallow-buried explosives, sandwich structures are commonly employed. This paper employs an uncertain design approach with the optimization objective of rear panel displacement to conduct reliability optimization of sandwich anti-explosion structures and perform parameter sensitivity analysis. In order to improve the computational efficiency and the robustness of the algorithm, the single-objective optimization problem of minimizing the weight of the structure under the reliability constraints is transformed into a bi-objective optimization problem in terms of the structural areal density and the probability of failure, and is solved using the NSGA-II optimization algorithm. In local sensitivity analysis, the thickness of the front and rear panels, as well as the core thickness, exhibits a substantial influence on rear panel displacement. Regarding global reliability sensitivity analysis, the displacement of the front and rear panels exerts a more significant impact on the failure probability of rear panel displacement. The reliability optimization method proposed in this paper holds considerable engineering significance for optimizing sandwich panels under explosive loads. This offers a valuable framework for researchers and engineers involved in the design of sandwich structures for efficient energy absorption in the context of shallow-buried landmine scenarios.

This paper presents a numerical simulation using ANSYS Fluent to investigate the performance of two water desalination systems under identical conditions. Realistic environmental conditions such as ambient pressure, temperature, fluid inlet velocity, and temperature of the fluid entering the tank and the heat source (both being water) were considered. Both models were tested under the same conditions: a pressure of 1 atm, an ambient temperature of 27 °C, an inlet fluid velocity in the tank of 0.08 m/s, an inlet fluid temperature to the tank of 27 °C, an inlet fluid velocity to the heat source of 0.01 m/s, and an inlet fluid temperature to the heat source of 67 °C. The tank and heat source were made of aluminum and copper, respectively. The obtained results showed significant differences and will be discussed in detail in the following sections.

Magnetic gears show important potential applications in the field of wind power generation equipment due to their low maintenance cost, low noise, no lubrication, and overload protection. However, the existing dual-modulated magnetic ring double modulated axial magnetic gears suffer from weak modulation effect, susceptibility to magnetic saturation, and magnetic leakage. In response to these problems, a single modulator modulated axial field flux focusing magnetic gear is proposed in this paper. This axial field flux focusing magnetic gear (AFFMG) combines an H-type modulated stator and an array of Halbach permanent magnets (PMs) and is designed to replace mechanical gearboxes in wind power generation systems. By introducing an H-type modulated stator in the middle of the high and low-speed rotor of the AFFMG, the magnetic field of the PMs is double modulated in the axial and transverse directions, and the hybrid double modulated utilization is realized. This design effectively suppresses the magnetic leakage and magnetic saturation effect of the PMs and improves the torque density and utilization rate of the PMs. In addition, the high-speed rotor PMs are magnetized with Halbach arrays, which significantly improves the magnetic flux density of the air gap and reduces the non-operating harmonics, thereby effectively improving the torque density. In this study, the topology and working principle of the proposed AFFMG are introduced in detail, and the proposed AFFMG finite element model is established. Based on the results of the comprehensive sensitivity analysis, the response surface method and the multi-objective whale optimization algorithm were used to optimize the design, and the optimal structure size parameters were determined. The performance comparison analysis verifies the effectiveness of the optimized design method. The results show that the proposed AFFMG can effectively reduce the magnetic flux leakage at the end, suppress the magnetic saturation effect, increase the torque density by 140.67%, and significantly enhance the magnetic field modulation effect. By observing the starting torque and starting speed curves, it is found that the proposed AFFMG can provide stable torque output during the start-up phase. At the same time, the torque ripple of the high-speed rotor and the external rotor is reduced by 12.31 and 16.16% respectively, and the transmission reliability is significantly improved. This study provides a useful reference for the design of high-performance new double modulated flux focusing axial magnetic gear.