Experimental Investigation of Internal Friction in Rubber Concrete and Fiber-Reinforced Rubber Concrete

Постановка задачи. Работа посвящена экспериментальному определению внутреннего трения в таких материалах, как каучуковые бетоны (каутоны) на основе низкомолекулярного полибутадиенового каучука смешанной микроструктуры марки ПБН и цис-полибутадиенового низкомолекулярного каучука марки СКДН-Н, с помощью метода импульсного воздействия. Результаты. Установлено, что каутон на основе каучука марки ПБН обладает более выраженными вязкоупругими свойствами по сравнению с аналогичным материалом на основе каучука марки СКДН-Н. Введение стальной фибры снижает внутреннее трение в материале, в то время как полимерная фибра дает обратный эффект. Это связано с тем, что волокнистая пропиленовая фибра служит дополнительным демпфирующим материалом, усиливающим диссипацию энергии при динамическом нагружении. Выводы. Впервые измерено внутреннее трение для каутона и фиброкаутона. Полученные данные являются дополнительными микроструктурными характеристиками материалов, описывающими их вязкость. Определены реальные значения исследуемых величин, которые позволяют применять модели с дробными производными при расчете строительных конструкций из каутона и фиброкаутона на динамические воздействия с учетом явления вязкоупругости. Statement of the problem. The paper is devoted to the experimental identification of damping for such materials as butadiene rubber (BR) and cis-butadiene low-molecular weight rubber (SKDN-N) based concrete and fiber-reinforced rubber concrete by means of the Impulse Excitation Technique (IET). Results. It was found that BR based concrete with or without fiber-reinforcement shows more obvious viscoelastic properties than the corresponding materials based on SKDN-N rubber. The addition of steel fiber reduces internal friction in the material, while propylene fiber has the opposite effect. This is due to the fact that the fibrous propylene acts as an additional damping material, which enhances energy dissipation under dynamic loading. Conclusion. The internal friction in the rubber concrete and fiber-reinforced rubber concrete has been measured for the first time. The obtained data are the additional microstructural characteristics of polymer concrete, which describes its viscosity. The actual values of the investigated quantities have been determined, which makes it possible to use the models with fractional derivatives in the calculations of building structures made of rubber concrete and fiber-reinforced rubber concrete for dynamic loads taking into account the phenomenon of viscoelasticity.

Compressive mechanical behavior and model of composite elastic-porous metal materials

This work presents the experimental characterization and theoretical modeling of composite elastic-porous metal materials (C-EPMM). C-EPMM is a novel porous metallic damping material made of wire mesh and wire helix. A series of quasi-static compressive experiments were carried out to investigate the stiffness and energy absorption ability of the C-EPMM with different mass ratios. The experimental results show that the mass ratios can significantly affect the stiffness and loss factor of C-EPMM. To efficiently predict the nonlinear mechanical properties of the C-EPMM a theoretical model of C-EPMM was proposed for the first time, the model was based on the manufacturing process. A comparison between the predicted data and the experimental data was conducted. The results show that the theoretical model can accurately predict the mechanical performance of C-EPMM. The conclusions derived from this work can provide a new method for adjusting the mechanical performance of EPMM in applications.

EXPERIMENTAL INVESTIGATION OF INTERNAL FRICTION IN RUBBER CONCRETE AND FIBER-REINFORCED RUBBER CONCRETE

Statement of the problem. The paper is devoted to the experimental identification of damping for such materials as butadiene rubber (BR) and cis-butadiene low-molecular weight rubber (SKDN-N) based concrete and fiber-reinforced rubber concrete by means of the Impulse Excitation Technique (IET). Results. It was found that BR based concrete with or without fiber-reinforcement shows more obvious viscoelastic properties than the corresponding materials based on SKDN-N rubber. The addition of steel fiber reduces internal friction in the material, while propylene fiber has the opposite effect. This is due to the fact that the fibrous propylene acts as an additional damping material, which enhances energy dissipation under dynamic loading.Conclusion. The internal friction in the rubber concrete and fiber-reinforced rubber concrete was measured for the first time. The obtained data are the additional microstructural characteristics of polymer concrete, which describes its viscosity. The real values of the investigated quantities have been determined, which makes it possible to use the models with fractional derivatives in the calculations of building structures made of rubber concrete and fiber-reinforced rubber concrete for dynamic loads, taking into account the phenomenon of viscoelasticity.

Impact damping and vibration attenuation in nematic liquid crystal elastomers

Nematic liquid crystal elastomers (LCE) exhibit unique mechanical properties, placing them in a category distinct from other viscoelastic systems. One of their most celebrated properties is the ‘soft elasticity’, leading to a wide plateau of low, nearly-constant stress upon stretching, a characteristically slow stress relaxation, enhanced surface adhesion, and other remarkable effects. The dynamic soft response of LCE to shear deformations leads to the extremely large loss behaviour with the loss factor tanδ approaching unity over a wide temperature and frequency ranges, with clear implications for damping applications. Here we investigate this effect of anomalous damping, optimising the impact and vibration geometries to reach the greatest benefits in vibration isolation and impact damping by accessing internal shear deformation modes. We compare impact energy dissipation in shaped samples and projectiles, with elastic wave transmission and resonance, finding a good correlation between the results of such diverse tests. By comparing with ordinary elastomers used for industrial damping, we demonstrate that the nematic LCE is an exceptional damping material and propose directions that should be explored for further improvements in practical damping applications.

Damping Properties and Microstructure Analysis of Microbial Consolidated Rubber Sand

Up to now, there are few reports on the application of microbial-induced calcium carbonate precipitation (MICP) consolidated rubber sand. By means of uniaxial or cyclic loading test and SEM test, the consolidation effect of rubber sand samples with different rubber particle content after MICP consolidation is tested and analyzed. The results show that MICP is not affected by the amount of rubber particles; rubber particles improve the compressive strength and deformation ability of consolidated rubber sand samples and significantly enhance the damping ratio, resistance to deformation, and energy dissipation ability of consolidated rubber sand samples. Rubber sand after MICP consolidation is a good shock damping material. The conclusion of this paper provides reference data for the application of microbial-induced calcium carbonate precipitation consolidated rubber sand.

Optimization of Damping Configurations in a Plate Embedded with ABH Array

Owing to its broadband and lightweight features, the Acoustic Black Hole (ABH) effect has attracted increasing interests in the structural dynamics and vibration-acoustic communities in recent years. And damping material is essential to achieve effective ABH phenomena. To explore effective vibration and noise control in thin-walled structures such as vehicle body panel using ABH effect, aiming at the plate embedded with two-dimensional ABH array, this paper investigates the coupling between ABH structure and damping material. First, the energy dissipation mechanism of viscoelastic damping material is analyzed to obtain the deformation characteristic that leads to effective energy dissipation. Next, the bending deflection of a plate with a single ABH under harmonic excitation is investigated, and the damping material configuration is optimized to obtain an optimal vibration suppression. Finally, the above-mentioned configuration is applied to a plate embedded with the ABH array and compared with the conventional damping arranging method. And the advantages of this damping material configuration scheme in vibration and noise control are investigated and summarized. This paper provides a reference for the damping material configuration and optimization of the thin plates embedded with ABHs.