Qin Yin

In today’s data-driven age, the thermal properties of computer transistors play an important role. In this research, finite element simulation is employed to construct the structural model of the primary components within a computer chassis, and the thermal performance is evaluated based on ambient temperature, thermal conductivity, and heat dissipation rate. By combining the particle swarm optimization algorithm with numerical simulation for joint simulation and structural optimization, the component layout was optimized to reduce the working temperature. The results show that when the background temperature, that is, the ambient temperature, rises from −20 °C to 60 °C, the maximum operating temperature of the computer is approximately 88 °C. The maximum temperature is mainly in the transistor core and the minimum temperature is in the intake grille, and the operating temperature of the optimized structure decreases by approximately 10 °C. The research shows that the operating temperature is most sensitive to the change of background temperature, and the transistor core is the main heating source. The maximum temperature can be reduced by rationally adjusting the position of the components. This study provides a reference for analyzing the thermal performance of computers and optimizing structures.

Rubber is widely applied in the field of electrical engineering due to its high elasticity. However, its poor thermal conductivity can cause localized overheating and eventual failure. This issue can be addressed through adding fillers with high thermal conductivity. In this study, natural rubber is selected as the matrix, while braided carbon fiber (B-CF), known for its excellent thermal conductivity, serves as the reinforcing phase. This research defines cubic Bessel curves, establishes a curvilinear coordinate system, and examines the orthogonal anisotropic thermal conductivity of B-CF bundles. It has been verified that eight cycles of fiber accurately represent the finite element simulation model. Based on this, the impact of the cross-sectional shape and area of the fiber bundle on heat dissipation was studied. The results show that the cross-sectional shape has minimal impact on heat dissipation, with temperature differences between the heat source center and the end of the cross-section line remaining within 1 °C. In contrast, the cross-sectional area significantly affects the reduction of the temperature, achieving reductions of up to 32.6% at the heat source center and 40.4% at the opposite side, respectively. This study provides valuable guidance for improving the thermal performance of braided fiber-reinforced rubber products.

Due to the viscoelasticity of rubber materials, hysteresis loss due to deformation is the main reason for the rolling resistance of high-speed rubber tracks. Since the structure and material of high-speed rubber track assemblies are different from traditional tires and metal tracks, the rolling resistance theory of traditional wheeled and tracked vehicles is not applicable. Therefore, in order to determine the rolling resistance scientifically and accurately, the mechanism research of the rolling resistance of high-speed rubber track assembly is the key to the design of high-speed rubber crawler vehicles. In this paper, the stress–strain characteristics of rubber track under the action of compression, tension, bending, and driving were studied. The strain load spectrum of rubber tracks was established, and the strain cyclic load was extracted by the rainflow method. The temperature model of the rubber track was developed based on its dynamic characteristics. On the basis of energy conservation, the hysteresis loss of rubber is equivalent to the energy consumption of rolling resistance, and the theoretical model of rolling resistance of high-speed rubber track assembly is established. In accordance with the model above, the key influencing factors and changing trends of rolling resistance are analyzed, which provides a theoretical basis for the performance optimization of high-speed rubber track assembly.

Polyisoprene, with a high degree of polymerization, is the main component of natural rubber. In the industrial production process, it is necessary to adjust the length of the macromolecule of polyisoprene to improve its plasticity. It is thus of vital importance to explore the effect of the degree of polymerization of polyisoprene on its properties, e.g., mechanical property and thermal property. Molecular dynamics simulations link microstructure to macroscopic properties. In this paper, Moltemplate was used to establish polyisoprene models with different degrees of polymerization, and the mechanical properties of polyisoprene under uniaxial tension were analyzed under an OPLS all-atom force field. The results showed that the strength and elastic modulus of the material increased with the increase in the degree of polymerization of the molecular chain. In the process of tensile loading, the non-bonded potential energy played a dominant role in the change of the total system potential energy. Then, the thermal conductivity of polyisoprene with different degrees of polymerization was calculated by the non-equilibrium molecular dynamics method (NEMD). The thermal conductivity of PI was predicted to converge to 0.179 W/(m·K). The mechanism of thermal conductivity of the polymer containing branched chains was also discussed and analyzed. The research content of this paper aims to provide theoretical support for improving the mechanical and thermal properties of natural rubber base materials.

In order to solve the problem of poor interfacial adhesion between aramid fibers and a rubber matrix, an efficient and mild modification method was proposed via polydopamine and mercapto functionalized graphene oxide (GO) and carbon nanotube (CNTs) hybrids synergistically modifying aramid fibers. GO and CNTs were firstly stacked and assembled into unique 3D GO-CNTs hybrids through π-π conjugation. Then, the mercapto functionalization of the assembled 3D GO-CNTs hybrids was realized via the dehydration condensation reaction between the hydroxyls of GO and the silanol groups of coupling agent. Finally, the mercapto functionalized 3D GO-CNTs hybrids were grafted onto the aramid fibers, which were pre-modified by polydopamine through the Michael addition reaction mechanism. The surface morphology and chemical structures of GO-CNTs hybrids and fibers and the interfacial adhesion strength between fibers and rubber matrix were investigated. The results showed that the modification method had brought about great changes in the surface structure of fibers but not generated any damage traces. More importantly, this modification method could improve the interfacial strength by 110.95%, and the reason was not only the reactivity of functional groups but also that the 3D GO-CNTs hybrids with excellent mechanical properties could effectively share interfacial stress. The method proposed in this paper was universal and had the potential to be applied to other high-performance fiber-reinforced composites.

To achieve the broadband sound absorption at low frequencies within a limited space, an optimal design of joint simulation method incorporating the finite element simulation and cuckoo search algorithm was proposed. An acoustic metamaterial of multiple parallel hexagonal Helmholtz resonators with sub-wavelength dimensions was designed and optimized in this research. First, the initial geometric parameters of the investigated acoustic metamaterials were confirmed according to the actual noise reduction requirements to reduce the optimization burden and improve the optimization efficiency. Then, the acoustic metamaterial with the various depths of the necks was optimized by the joint simulation method, which combined the finite element simulation and the cuckoo search algorithm. The experimental sample was prepared using the 3D printer according to the obtained optimal parameters. The simulation results and experimental results exhibited excellent consistency. Compared with the derived sound absorption coefficients by theoretical modeling, those achieved in the finite element simulation were closer to the experimental results, which also verified the accuracy of this optimal design method. The results proved that the optimal design method was applicable to the achievement of broadband sound absorption with different low frequency ranges, which provided a novel method for the development and application of acoustic metamaterials.

The binding amount of rubber and reinforcing filler directly affects the quality of rubber products. The effect of aromatic solvent oil (S-150) on the binding amount of rubber and reinforcing filler was studied. In order to determine the suitability of rubber after adding S-150, the curing characteristics, physical performance and tensile properties of rubber samples were tested and analyzed. Meanwhile, the microstructure of the composite was analyzed by scanning electron microscopy (SEM). The test results showed that the binding amount of rubber and reinforcing filler was increased after adding S-150. The density and Shore A hardness were decreased. When carbon black was 80 phr, after adding 40 phr of S-150, the rebound resilience of rubber increased by 13% on average, and the elongation at break increased by 88% on average. When white carbon black was between 10-70 phr, after adding 65 phr of S-150, the rebound resilience of rubber increased by 9% on average, and the elongation at break increased by 51% on average. Modulus at 100% and tensile strength were decreased. Meanwhile, it could be judged from the microstructure results that the reticulation space inside the rubber was increased, the agglomerate particles were relatively uniform, and no bubbles or holes were observed. The mechanism that S-150 could increase the binding amount of rubber was analyzed according to the like-dissolves-like principle. This research achievement could lead to improvements in the quality of rubber products and promote their practical application.

Acoustic metamaterials based on Helmholtz resonance have perfect sound absorption characteristics with the subwavelength size, but the absorption bandwidth is narrow, which limits the practical applications for noise control with broadband. On the basis of the Fabry–Perot resonance principle, a novel sound absorber of the acoustic metamaterial by parallel connection of the multiple spiral chambers (abbreviated as MSC-AM) is proposed and investigated in this research. Through the theoretical modeling, finite element simulation, sample preparation and experimental validation, the effectiveness and practicability of the MSC-AM are verified. Actual sound absorption coefficients of the MSC-AM in the frequency range of 360–680 Hz (with the bandwidth Δf₁ = 320 Hz) are larger than 0.8, which exhibit the extraordinarily low-frequency sound absorption performance. Moreover, actual sound absorption coefficients are above 0.5 in the 350–1600 Hz range (with a bandwidth Δf₂ = 1250 Hz), which achieve broadband sound absorption in the low–middle frequency range. According to various actual demands, the structural parameters can be adjusted flexibly to realize the customization of sound absorption bandwidth, which provides a novel way to design and improve acoustic metamaterials to reduce the noise with various frequency bands and has promising prospects of application in low-frequency sound absorption.

An acoustic metamaterial absorber of parallel–connection square Helmholtz resonators is proposed in this study, and its sound absorption coefficients are optimized to reduce the noise for the given conditions in the factory. A two–dimensional equivalent simulation model is built to obtain the initial value of parameters and a three–dimensional finite element model is constructed to simulate the sound absorption performance of the metamaterial cell, which aims to improve the research efficiency. The optimal parameters of metamaterial cells are obtained through the particle swarm optimization algorithm, and its effectiveness and accuracy are validated through preparing the experimental sample using 3D printing and measuring the sound absorption coefficient by the standing wave tube detection. The consistency between the experimental data and simulation data verifies feasibility of the proposed optimization method and usefulness of the developed acoustic metamaterial absorber, and the desired sound absorption performances for given conditions are achieved. The experimental results prove that parallel–connection square Helmholtz resonators can achieve an adjustable frequency spectrum for the low frequency noise control by parameter optimization, which is propitious to promote its application in reducing the noise in the factory.