Search

The study focuses on harnessing recycled materials to create sustainable and efficient composites, addressing both environmental issues related to waste management and industrial requirements for materials with improved vibration damping properties. The research involves the analysis of the physico-mechanical properties of the obtained composites and the evaluation of their performance in practical applications. Composite materials were tested in terms of their tensile strength and vibration damping capabilities, considering stress–strain diagrams, vibration amplitudes, frequency response functions (FRFs) and vibration modes. The research results have shown that by adding PVC and FA to the rubber-based matrix composition, the stiffness decreases and elasticity increases. The use of FA in the structure of composite materials causes an increase in the vibration damping possibilities due to the fact that it contributes to the chemical properties of the analyzed composite materials. Additionally, the use of PVC results in increased material elasticity, as evidenced by the higher damping factor compared to materials containing only rubber. Simultaneously, the addition of FA and PVC in specific proportions (60 phr) can lead to a decrease in stiffness and a greater increase in the damping factor. The incorporation of PVC and fly ash (FA) particles into rubber-based matrix composites reduces their stiffness and increases their elasticity. These effects are due to the fact that FA particles behave as extensions of chemical bonds during traction, which contributes to the increase in yield elongation. In addition, the use of flexible PVC increases the elasticity of the material, which is evidenced by the increase in the damping factor. [ABSTRACT FROM AUTHOR]

Although research on incremental forming process began a few decades ago, it is still a process in development phase. Single point incremental forming is a simple process and the deformation of the sheet blank is done with the help of a punch that follows a known toolpath. In the case of this process, one important aspect is the prediction of material failure. To achieve this with the help of a finite element analysis, a series of experiments were performed to determine the forming limit diagram. In this paper, an attempt has been made to determine the forming limit diagram for the AA1050 aluminum alloy. The experiments were performed with the help of an industrial robot, KUKA KR 210-2, thus the part can be measured with an optical measuring instrument obtaining the major and minor strain from forming limit diagram.

A series of researches related to aluminium-steel plating by press welding are presented in the paper. In this sense, the influence of the roughness of the aluminium and steel test samples was taken into account, but also of the post-welding heat treatment on the characteristics of the joints made. S355 steel specimens and AlMgSi0.7 F27 aluminium specimens were analyzed. The samples were processed and roughness Ra = 2.51-51.09 µm were obtained. Also, after making the joints, a postwelding heat treatment was applied which consisted of a heating at a temperature of 425 °C with a duration of 6.5 hours and a slow cooling to room temperature. Six distinct samples were made in terms of surface roughness in the joint area. After making the joints and applying the heat treatment, the samples were analyzed in terms of metallographic structure, the thickness of the interface layer and the hardness of the material in it. Thus, it was found that both the roughness of the test tube surfaces and the post-weld heat treatment have a substantial influence on the metallographic structure and the hardness of the material in the interface layer. The highest hardness of the material in the interface layer and its lowest thickness were obtained for the samples with the lowest roughness of the joint surfaces.

Most of the technological equipment has welded metal structures in its composition, which are strongly affected by the corrosion phenomenon. In order to achieve a reduction of the corrosion phenomenon it is very important that the welded joints are made using optimal parameters of the welding regime. In the research were made 6 different welded specimens, respectively 3 for the welded T-shaped joint and 3 for the cross-welded joint. The welded joints were made of 10 mm thick using S 355JR steel by the MAG welding process and using welding wire G4 Si 1 as an additive. For the 6 specimens were made analyzes of the metallographic structure thus observing what are parameters of the welding regime that allows to obtain the welded joints with high corrosion resistance.

Thus, at present, a large amount of rubber waste cannot be higher harnessed due to recovery technologies used. Also, the requirements for new products of rubber worldwide are greater than the production capacity and the availability of raw materials. To offset this balance is necessary to improve technologies for recycling waste rubber so to can get regenerated rubber with the best mechanical physical characteristics. The main technology for obtaining the regenerated rubber is based on the rubber waste shredding and making the powder, so that it can be carried out de-vulcanization in autoclave. All the time it was monitored as the de-vulcanization process to be as economical and less polluting, and this requires that the sizes of the crumb rubber to be optimal. Thus, in the conducted researches was aimed to establish the particle size of crumb rubber from waste rubber so as to obtain an economical de-vulcanization, but also a reclaimed rubber with superior physical and mechanical characteristics. The organization of researches was made so that crumb of rubber waste was divided into 5 groups, bowing from crumb rubber with particle’s size of 1000 μm (RPS1), and reaching up to crumb rubber with particle’s size of 200 μm (RPS 5).

Artificial roughness on the absorber of the solar air heater (SAH) is considered to be the best passive technology for performance improvement. The roughened SAHs perform better in comparison to conventional SAHs under the same operational conditions, with some penalty of higher pumping power requirements. Thermo-hydraulic performance, based on effective efficiency, is much more appropriate to design roughened SAH, as it considers both the requirement of pumping power and useful heat gain. The shape, size, and arrangement of artificial roughness are the most important factors for the performance optimization of SAHs. The parameters of artificial roughness and operating parameters, such as the Reynolds number (Re), temperature rise parameter (ΔT/I) and insolation (I) show a combined effect on the performance of SAH. In this case study, various performance parameters of SAH have been evaluated to show the effect of distinct artificial roughness, investigated previously. Therefore, thermal efficiency, thermal efficiency improvement factor (TEIF) and the effective efficiency of various roughened absorbers of SAH have been predicted. As a result, thermal and effective efficiencies strongly depend on the roughness parameter, Re and ΔT/I. Staggered, broken arc hybrid-rib roughness shows a higher value of TEIF, thermal and effective efficiencies consistently among all other distinct roughness geometries for the ascending values of ΔT/I. This roughness shows the maximum value of effective efficiency equals 74.63% at a ΔT/I = 0.01 K·m2/W. The unique combination of parameters p/e = 10, e/Dh = 0.043 and α = 60° are observed for best performance at a ΔT/I higher than 0.00789 K·m2/W. [ABSTRACT FROM AUTHOR]