International Journal of Mechanics and Materials in Design最新文献

Carbon fiber-reinforced polymer (CFRP) has garnered extensive scholarly attention owing to its remarkable mechanical properties and inherent lightweight nature. However, there remains a need for a straightforward and effective optimization approach for designing CFRP automotive components. Hence, this study introduces the CFRP multilevel optimization strategy, which is applied to the optimization design of the CFRP seatback and seat pan. Firstly, the accuracy of the two selected finite element models is validated through physical experiments. On this basis, CFRP is employed as a substitute for the original steel seatback and seat pan. Secondly, two typical dynamic working conditions are transformed into static ones, enabling the application of the ply optimization. The ply angle, shape, thickness, and stacking sequence are determined through the process of free size optimization, size optimization, and ply stacking sequence optimization. Subsequently, a reliability optimization method is established, incorporating Optimal Latin Hypercube Sampling, adaptive Kriging surrogate model, Monte Carlo Simulation, Non-dominated Sorting Genetic Algorithm-II, Entropy Weighting Method, and Modified Visekriterijumsko KOmpromisno Rangiranje. This method is applied to the reliability design of both the seatback and seat pan. Lastly, a comprehensive comparative analysis of various optimization schemes shows that, despite a slight increase in mass, reliability optimization significantly improves the reliability indices compared to ply optimization. Additionally, compared to the original steel seat frame, the reliability-optimized CFRP seatback and seat pan achieve a 31.59% reduction in mass while preserving reliability, dummy injury, and comfort measures. Hence, the CFRP multilevel optimization strategy proposed in this paper performs well in terms of both accuracy and effectiveness, providing a dependable point of reference for related CFRP optimization.

This study explores the free vibration and controlled dynamic behaviour of smart auxetic sandwich panel consisting a tetrachiral auxetic core affixed with dual-functionally graded (FG) nanocomposite skins, using a microscale-focus on chiral unit cell size through representative volume element homogenization-assisted finite element (FE) approach. A piezoelectric sensor-actuator pair, coupled with a constant velocity feedback controller, effectively attenuates vibrations produced in the mechanical meta structure. Controlled dynamic motion equations based on the first order shear deformation theory are obtained via energy-based variational principle and solved under FE framework, considering quadratic interpolation functions. Key findings highlight that, the design parameters of the auxetic core’s unit cell (i.e. ligament arm length and thickness of the cell walls) can significantly alter the ease of flexibility of the chiral core layer, which in turn drastically affects the free vibration and controlled dynamic responses of the sandwich meta structure. Also, carbon nanotube reinforcement into the FG matrix-blend (Al-ZrO₂) of the skin layers substantially improves the structural responses of the sandwich panel. The study validates its numerical approach against existing literature and addresses the impact of several influencing parameters on the micro and macro-mechanical performances of the proposed auxetic structure.

Significant advances have been made in material synthesis in the last two decades, with a focus on polymers, ceramics, metals, and smart materials. Piezoelectric-based smart materials generate an electric voltage in response to loads, enabling distributed monitoring in critical structural parts. Friction stir processing (FSP) is a versatile approach that can enhance material performance in various engineering fields. The primary objective of the current research is to examine the sensorial properties of heat-treated AA7075-T651 aluminium plates that have been included with Lead Zirconate Titanate (PZT) and Barium Titanate (BT) particles via FSP. This study includes a comparative analysis of sensitivities with AA5083-H111 self-sensing material, metallographic and physicochemical characterization, and an assessment of the mechanical properties impacted by the incorporation of piezoelectric particles. The sensitivity of AA7075-PZT was found to be significantly higher than that of AA7075-BT. AA7075-PZT achieved a maximum sensitivity of 15.27 × 10⁻⁴ μV/MPa while AA7075-BT had a sensitivity of only 7.28 × 10⁻⁴ μV/MPa, which is 52% lower. Microhardness and uniaxial tensile tests demonstrated that the presence of particles has an influence on both mechanical strength and electrical conductivity of aluminium components, as opposed to those that do not have particles. The complete investigation intends to give significant insights into the performance and prospective uses of these innovative smart materials, therefore advancing materials science and engineering.

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The nonlinear characterization of the response of a multi-stable electromagnetic vibration energy harvester is performed. By applying an initial compression to the harvester’s supporting springs, a geometrical nonlinearity develops and can transition the system through mono-stable, bi-stable, and tri-stable configurations based on the geometrical parameters. Considering a low frequency design criterion for the multi-stable energy harvester, the dynamics and effectiveness of the mono-, bi-, and tri-stable harvester is studied individually for up- and down-swept excitations considering the influence of the damping ratio and excitation amplitude on the system’s dynamics. Furthermore, this study introduces a novel methodology for configuring the harvester to specifically capture a predetermined range of frequencies, determined by the selection of the linearized frequency of the nonlinear system. A comparative study is carried out among the three harvesters’ configurations as well. It is demonstrated that the effectiveness and dynamics of bi-stable and tri-stable energy harvesting systems are strongly dependent on the input excitation and damping. This is due to the existence of intra-well and inter-well motions and hence the overall system’s dynamics change. The results of the comparisons demonstrate that the tri-stable harvester has great advantage in ultra-low frequencies due to the chaotic inter-well motion of the system. However, this tri-stable design is strongly dependent on several factors that may result in low performance due to the intra-well motion.

A two-step approach to non-destructive testing of mechanical structures is proposed in this study. The first step involves the identification of holes/inclusions with different physical properties and arbitrary geometry in 3D structures based on temperature field, method of moving asymptotes and finite element methods. Results demonstrating the detection of inclusions with different geometric shapes (cube, sphere, ellipsoid, torus and complex inclusions) in steel, copper and aluminium are presented. In the second step of the approach, an iterative procedure for the determination of elastic-plastic deformations of structures with inclusions identified in the first step in the 3D formulation is constructed. According to the deformation theory of plasticity, the procedure is based on finite element methods and Birger's method of variable elasticity parameters. As an example, the stress-strain state of a square steel plate clamped along the contour under the action of a transversely distributed load is studied for two types of aluminium inclusions: a central rectangular inclusion and a displaced spherical inclusion, identified in the first step of the proposed approach. The developed approach is essentially a generalised methodology for 3D identification of inclusions/holes. The study of the elastic-plastic 3D problem with inclusions has both scientific significance and great practical interest for engineers working in the field of non-destructive testing.

Vibration can damage sensitive components and mountings on printed circuit boards (PCBs) within active electronically scanned array radar transmit/receive modules, which can result in reduced system performance and system failure. To solve this issue, a novel vibration reduction measure by incorporating particle dampers within the PCB enclosure is proposed. To install particle dampers, finite element-based modal analysis was performed to identify vibration-sensitive areas inside the structure. The dominant modal frequency was validated with a sinusoidal sweep test performed on a vibration shaker. Based on these results and spatial constraints, two cavities were created for particle damper installation: one near the sensitive area (damper A) and another farther away (damper B). Steel particles of varying sizes, i.e. 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, and 3.5 mm, were used to fill these cavities. Experimental investigations were conducted to evaluate the effect of particle size and filling ratio on peak vibration response under different acceleration loads. Both dampers achieved the best response reductions with a 2.5 mm particle size, though their critical filling ratios differed: 92% for damper A and 96% for damper B. The findings indicate an 89% and 64% reduction in acceleration response with dampers A and B, respectively. This novel method of integrating particle dampers within the housing enhances its vibration suppression capabilities and provides superior response reductions compared to the previous approach of mounting them on the periphery. Furthermore, the method is reliable even in elevated temperature environments due to the use of metallic particles.

The present study focuses on the numerical and experimental investigation of a hat-stiffened composite inverted conical structure to identify its strength and stability under axial compressive loading conditions. A new design for the 3rd stage adapter with few changes in the present polar satellite launch vehicles launch vehicle is considered. An inverted conical structure with a hat-stiffened type of construction is used to obtain the higher bending stiffness. Both high-modulus and low-modulus uni-directional carbon prepreg are considered for the inverted conical structure. The experimental and numerical study is carried out on a hat-stiffened panel with a low-modulus carbon fiber prepreg material. Using the commercial software CATIA^®, the geometry of the inverted conical structure and hat-stiffened panel is generated. The structural analysis is carried out using MSC NASTRAN/PATRAN^® to determine the maximum load-carrying capacity, maximum stress and displacement values. It was observed that the strain obtained experimentally on the surface of the stiffened panel at twenty-six points using the 26-strain gauges shows good correlations with those obtained numerically.

We study the design of a neutral spheroidal piezoelectric inhomogeneity that does not disturb the prescribed uniform axisymmetric electromechanical loading in a piezoelectric matrix. Both the inhomogeneity and the matrix are transversely isotropic. Our design methodology is based on an imperfect interface model with infinitesimal thickness that is spring-type in elasticity and weakly conducting in dielectricity, and is characterized by two non-negative imperfect interface functions which are determined for given material properties of the composite and given geometry of the spheroid. The inhomogeneity is neutral to either a hydrostatic or non-hydrostatic stress field through the interface design. Of particular note is that for the first time, we have achieved the neutrality of a three-dimensional anisotropic piezoelectric inhomogeneity through interface design.

Thermal protection system (TPS) of spacecraft requires enhanced impact resistance and thermal insulation capability while pursuing higher stiffness. Considering this, a topology optimization method of periodic microstructures with negative Poisson’s ratio and insulation performance is proposed for the filling material design of the core layer in TPS, in which homogenization approach is adopted in calculating properties of microstructures and multi-objective optimization is used for balancing the mechanical and thermal properties of the optimized microstructures. Considering the optimization design of impact-resistant structures with negative Poisson’s ratio, a novel objective function is proposed to reduce the influence of iteration steps on the optimization results. For the topology optimization of insulation structures, a suitable objective function is selected by comparing the optimization results of two existing objectives. Based on the weighted linear combination, a multi-objective microstructural topology optimization method is proposed, simultaneously incorporating negative Poisson’s ratio and insulation performance. By adjusting the weighting coefficient of the objective functions, the microstructure of the materials can be designed according to different performance requirements. Several 2D and 3D optimized microstructures with both better impact resistance and insulation performance of TPS are successfully designed. In addition, the 2D optimized microstructures under different weights are assembled into sandwich structures, and the compression and heat conduction are simulated to further illustrates the validity and flexibility of the proposed method considering requirements of both impact-resistant and thermal insulation performances of sandwich structures.