International Journal of Mechanics and Materials in Design最新文献

This study concentrates on developing an analytical mode-matching method, combined with the Galerkin approach, to investigate the scattering of radiation through a flexible shell within a finite, coaxial lined chamber connected by membrane discs at the interfaces. The modeled problem involves dynamical boundary and interface conditions, as well as various ring conditions. Eigenfunction expansions are derived in different regions with homogeneous media and boundary conditions, incorporating unknown coefficients. The associated eigenfunctions are non-orthogonal, forming non-Sturm-Liouville systems. The dynamical behavior of the membrane discs is formulated using the Galerkin approach. By applying field matching at the interfaces and utilizing generalized orthogonal properties, the differential systems are transformed into linear algebraic systems. Numerical solutions of these systems, after truncation, yield the unknown amplitudes. The validation of the matching conditions at the interfaces and the convergence of the computed powers strongly support the accuracy of the truncated solution and the algebraic procedures. The interaction between the flexible shell and the compressible fluid within it significantly influences the system’s vibration characteristics. Results on scattering powers and transmission loss across various parametric settings provide insights for optimizing the attenuation of fluid–structure coupled modes within the guiding channel.

In this paper, the nonlinear free vibration and static bending of functionally graded porous graphene platelets-reinforced (FGP-GPLs) composite plates with discretized piezoelectric patches integrated on the upper and lower surfaces are numerically studied. For the first time, this research examines how the flexoelectric effect affects the stiffness of functionally graded graphene plates with piezoelectric laminates, and it explores the influence of porosity coefficient and graphene weight fraction on the strength of the flexoelectric effect. The material model of the composite layer comprises various porosity and GPLs distributions. Both porosity types and graphene patterns in the thickness direction are categorized into three distinct groups: uniform, symmetric, and asymmetric. The Halpin–Tsai micromechanical model, the rule of mixture, and the closed-cell Gaussian random field (GRF) scheme are used to determine the effective material properties of the composite layer. The computational model for piezoelectric smart structures is developed by considering the material characteristics, piezoelectric effect, flexoelectric effect, and von Kármán nonlinearity assumption. The nonlinear governing equations for the structures are derived by Hamilton principle combined with the first-order shear deformation theory (FSDT). The numerical model is discretized via the isogeometric analysis (IGA) technique and solved using a direct iterative method. The solution approach is validated against existing literature to confirm its accuracy and effectiveness. Finally, this paper thoroughly examines the effects of various parameters on the nonlinear static bending and free vibration of piezoelectric smart structures. These parameters include porosity and GPLs distribution patterns, porosity coefficients, GPLs weight fractions, load parameters, and the flexoelectric effect. Results indicate that the numerical model exhibits a stiffness-hardening mechanism under the flexoelectric effect.

Within active vibration control (AVC) Lead Zirconate Titanate (PZT) elements are a very popular choice as both sensors and actuators. Notably they have a smaller influence on the stiffness and mass of the host structure and have a high force output to weight/size ratio compared to alternatives. This research envisions their use with a flexible robot manipulator link within an AVC application. For systems using PZT sensors it has been previously found that their characteristics provide unconventional responses when part of a control system. Thus, this research aims to investigate this further through the employment of a proportional-integral-derivative (PID) control scheme in addition to combinations of the constituent gains. Additionally, the dynamics of a system including PZT sensors and/or actuators subsequently lead to issues with employing popular PID tuning methods. Thus, two alternative methods are employed to obtain the gains for the system, parametric sweeps of the gains, and an optimisation of them based on the minimisation of the integral of the time-weighted absolute error (ITAE).

Since the mass of wind turbine blades (WTBs) is increasing with the demand for wind energy, more attention is being paid to the topology optimization of WTBs to obtain an optimal structure which can reduce mass while retaining shape. An innovative level set method based on conformal geometry theory is proposed in this paper for the topology optimization of the leading edge of WTBs. The leading edge is transformed to a Euclidean 2D domain using conformal mapping. This allows the topology optimization problem of the leading edge to be treated as a 2D problem, and the optimization is conducted within this 2D domain. From the optimized result in the 2D domain, the optimal design of the leading edge is obtained. The proposed level set method significantly simplifies the computational complexity of the optimization process while preserving the advantages of traditional level set methods and offers a promising research approach for topology optimization of WTBs.

In today’s advanced engineering applications, fast and high-accuracy estimation of the mechanical performance of composite materials is of vital importance. This study aims to estimate the force and deformation values of hybrid structures containing hexagonal boron nitride (h-BN) nanoadditives in certain proportions of carbon and basalt fiber-reinforced composite materials. The research problem is to question the ability of artificial neural networks (ANNs) to model these complex force–deformation relationships and to provide reliable results using the data obtained from experimental three-point bending tests. The developed model was trained with the Levenberg–Marquardt backpropagation algorithm, and overlearning was prevented by the early stopping method. The obtained results showed that the model produced high accuracy estimations with the R² value of 0.987, the mean error of 0.0021, and the maximum error of 0.015; the error value decreased from 0.08 to 0.0012 during the training process. These findings reveal that the proposed ANN-based approach provides a faster, cost-effective, and reliable estimation alternative compared to traditional experimental methods.

This paper focuses on the linear dynamic responses of a piezoelectric semiconductor (PS) sandwich cylindrical shell covered with functionally graded piezoelectric semiconductor (FGPS) layers. The PS sandwich cylindrical shell is composed of a PS core layer and two FGPS surface layers. The FGPS surface layer consists of the metal material (i.e., aluminum) and piezoelectric semiconductor material (i.e., zinc oxide). According to the virtual work, strain energy as well as kinetic energy of the FGPS sandwich cylindrical shell, the vibration governing differential equations are achieved on the basis of Hamilton’s principle. Then the theoretical solutions of the vibration responses are obtained by solving the governing equations with Navier method. Through numerical examples, the effect of the functionally graded index, thickness ratio, initial electron concentration and excitation frequency on the dynamic responses of the FGPS sandwich cylindrical shell is analyzed. The main novelty of the manuscript is that the induced electric potential, perturbation of electron concentration and radial displacement of the FGPS sandwich cylindrical shell may be regulated effectively by designing a proper initial electron concentration and applying an appropriate excitation frequency. The multi-field coupling mechanism among carrier, polarization as well as deformation is demonstrated. The current outcomes also show that the geometric parameter, circumference wave number and functionally graded index have a significant effect on the vibration frequency and damping characteristic of the FGPS sandwich cylindrical shell.

Recent developments in stacking of weakly bonded van der Waals of atomically thin layers has the potential of fabricating nano-systems with desired properties. In this effort, we carried out comprehensive molecular dynamics simulations to study the mechanical behaviour of boron nitride layer, graphene layer, and their stacked configurations using modified Tersoff and Lennard–Jones force fields under varied conditions. We evaluated their mechanical properties for distinct chirality angles ranging from (0^{^circ }) to (30^{^circ }) directions. We found that the (i) armchair configuration of the nano-structure possesses higher elastic modulus, irrespective of the stacking sequence and the applied strain rate, and (ii) elastic moduli of boron nitride AB-stacked configurations are higher than boron nitride monolayer. The effect of chirality angle was largely observed at higher strains. At lower strains, the effect of chirality angle is negligible for boron nitride/graphene heterogeneous structures. In this effort, we provide a comprehensive understanding of the mechanical properties of stacked configurations of boron nitride and graphene layers, accounting for the effect of chirality angle and strain rate for the design and development of the staking configurations of 2D nano-devices.

Contact mechanics models need to be developed for a comprehensive contact analysis in ball-on-socket joints. These models can be used consequently predict wear for non-linear, nearly conformal contacts in hard-on-hard hip implants. At present, some theoretical models are used to estimate the contact conditions in hip implants. The prediction of contact conditions in these nearly conformal contacts using analytical models may not be accurate due to their theoretical assumptions, and their accuracy must be verified. This study has comprehensively analysed the capability of existing popular Hertz and Fang theoretical models under various system parameters, particularly for hard-on-hard hip implants, and verified the results with finite element method (FEM). The models are analysed under different system parameters such as gait load, femoral head size, thickness of the acetabular cup, radial clearance and equivalent modulus of the tribo-pair. The contact parameters, such as the maximum contact pressure, contact radius and maximum deformation, are considered for the validation with FEM. Both analytical models fail to predict the contact conditions throughout a gait cycle. The limitations and discrepancies to be addressed in the existing analytical models are discussed, which will pave the way for developing a futuristic model for accurate contact analysis. Until now, FEM stands out as a precise method to analyse contact conditions in nearly conformal contacts.

Designing structures often relies on the experience of engineers, involving an iterative process to achieve a balance between cost-effectiveness, durability, reliability, and to fulfill the required specifications. In this context, this paper introduces a novel multi-material topology optimization approach for reinforced concrete structures with D regions, considering multiple load cases during the optimization process. The methodology adopts a two-loop approach. The first loop minimizes the structure's compliance to reduce weight within a given material volume constraint. The second loop iteratively replaces concrete exceeding the Ottosen four-parameter failure surface by steel, ensuring a safe stress level under a stress constraint. The required steel area is determined based on the equivalent principal forces in finite elements classified as steel in the resulting topology from the multiple load cases. Finally, a nonlinear comparative analysis considering both material and geometric nonlinearity of the optimized and reference structures is performed using Simulia Abaqus. This analysis evaluates the crack pattern, stress distribution, and the yielding of the reinforcement up to the ultimate load of the structure. The outcomes demonstrate lightweight designs meeting the required structural performance standards.