Papers by Keyword: Damping Capacity

Abstract: Magnetron sputtering with a chromium-containing Fe-19at.%Cr alloy is used to improve the corrosion resistance of Fe-20at.%Ga alloy. The structure of the 2 μm coated layer and distribution of the elements (Fe, Cr, and Ga) are investigated. The bcc phase (A2 structure) is observed in the sputtered sample by XRD analysis. The corrosion resistance in 3.5%NaCl solution increases 14 times in the sample with 2 μm Fe-Cr coated layer. At the same time, the magnetron sputtering leads to a 10% decrease in magnetostriction and a 20% decrease in damping. This difference is explained by schemes of loading during magnetostriction and damping tests.

Abstract: Special features of the high-damping state formation in bimetallic materials produced by explosion welding have been studied. High-damping Mn-Cu alloy was used for the damping base of the bimetallic composite and high–strength steel (grade: 30HGSA) was used to form the coating layer. The effect of planar tensile stresses (observed in the damping component of the bimetal and caused by valuable difference between coefficients of thermal expansion of components of the bimetal) is discussed. Damping properties of bimetallic materials were found to be comparable with damping characteristics of monolithic high damping alloys. High-strength steel provides high-strength characteristics of the surface layer of the bimetal, where the strength level reaches 1100MPa and the hardness is equal to 50 HRC. Obtained combination of high damping and high strength in developed bimetallic materials provides real chance for practical application of these materials in industry.

Abstract: Copper-based shape memory alloys (SMAs) gaining attention due to their high damping properties during martensitic transformation and effective in energy dissipation which is applicable to damping application. However, copper-based SMAs such as the ternary Cu-Al-Ni are not easily deformed in the lower temperature martensitic phase which can be attributed to brittleness induced by coarse grain size, high degree of order and elastic anisotropy. Hence, this study aims to improve the properties of Cu-Al-Ni SMAs by addition of fourth alloying element. In this research, Cu-Al-Ni alloys with the addition of the fourth additional element, cobalt were prepared by casting. Microstructure characteristics of Cu-Al-Ni SMAs with and without Co addition were investigated via scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Damping capacity was determined by dynamic mechanical analysis (DMA). It was found that the alloy with 0.7wt% of Co addition showed the best improvement on the damping properties.

Abstract: In a previous study, the damping capacity gradually increased with increasing annealing time and temperature in AZ31. Also, at damping capacity test under similar conditions, AZ61 with a higher solute content showed a more rapid microstructure change than AZ31. In this study, it was investigated damping capacity on various aluminum concentration conditions in order to damping capacity that was influenced by microstructure and solute content. Three types such as pure Mg, AZ31 and AZ61 alloy of specimens were rolled at 673K with a rolling reduction of 30%, respectively. The annealing were conducted at various temperature and time. In this study, static recrystallization was occurred under all annealing conditions. The hardness gradually decreased until 60 minutes after the heat treatment. All annealing conditions, the damping capacity gradually increased with increasing annealing time and temperature. Especially, damping capacity and C₁ value were increased with a decreasing of solute content.

Abstract: The effect of crystal orientation on damping capacity is studied on hot rolled AZ31 magnesium alloy. AZ31 magnesium alloys which was machined out parallel to rolled direction and perpendicular to rolled direction were investigated about the relationship between the initial texture and damping capacity. The specimens are annealed at 623 K and time ranging from 30 to 180 minutes. After heat treatment recrystallization is occurred. Then, average grain size and damping capacity are increased with increasing annealing time. Two types of specimens show different main component of texture and damping capacity respectively. It is found that initial texture was affected on damping capacity.

Abstract: Mechanical, damping and specific properties of new structural high-damping steel have been studied in the present research. Studied high-damping steel was specially produced by the JSC Severstal in order to obtain metallic material with specified level of damping and mechanical properties. Experiments show that the damping properties of industrial high-damping steel are comparable with damping properties of high-purity damping alloys, produced using laboratory equipment. Mechanical properties of the industrial high-damping steel were found to be comparable with the level of properties of well-known structural steels, widely used in the modern industry. Analysis of the combination of mechanical and specific properties of the new steel indicates that this material can be used for the construction of rigid structures requiring high damping. Specific features of practical application of high-damping steels are also discussed.

Abstract: In this paper, the influence from fraction of coverage to the damping capacity of partial constrained layer damping structure was studied by single point hammer test with two sides simply supported constraints and finite element simulation based on the theory of modal strain energy. Combining with time domain and vibration acceleration with the composite loss factors from finite element analysis, vibration reduction effect was remarkable with the fraction of coverage from 40% to 80%. The combined result showed that partial constrained layer damping structure with 80% damping layer coverage had better damping capacity.

Abstract: The change about molecular chain of viscoelastic material in salt fog environment was tested by FTIR. The effects of salt fog aging on material and damping capacity of the damping layer in the constrained damping structure were researched by macro-mechanical properties and micro-molecular chain movement. The results showed that salt fog could reduce the mechanical properties of the viscoelastic material, the chemical bonds of molecular which were mainly hydrogen bonds had varying degrees of breaking, the composite loss factor of constrained damping structure decreased over time, and the vibration acceleration level increased gradually. The composite loss factors of the viscoelastic material after 90 days salt fog aging were 0.2047 and respectively, which illustrated that the material still had strong energy dissipation capacity.

Abstract: New requests from the automotive industry suppose to apply new materials with mechanical resistance to heat and vibrations and also with low weight. In order to replace plastic materials with high damping capacity a viable solution can be the metallic materials with sufficient internal friction to transform the external mechanical energy in thermal energy without affecting the microstructure or the mechanical properties of the metallic materials. In automotive applications an important role, especially in low velocity impacts, are the bumper elements. In this article possibility of copper-based shape memory alloys to fulfill the damping necessity of metallic materials is analyzed. Dynamic - mechanical analyze of few copper based shape memory alloys is realized and the results compared to proposed a better solution of Cu-based shape memory alloy for damping materials applications. The damping capacity difference between martensite and austenite like phases is also analyzed.

Abstract: The AlN particles reinforced magnesium-aluminum matrix composites were fabricated by powder metallurgy and the damping mechanism was discussed. The results showed that the best damping capacity of composite reached with the addition of 6wt% AlN reinforcement, while the AlN particles were uniformly dispersed in the matrix. The damping capacity of composites decreases with the increasing of the reinforcement content and the experimental frequency. The internal friction peak related to dislocation appearance in the temperature ranges of 100-150°C. In addition, another internal friction peak of composites between 200 and 250°C arose, which was related to interface sliding.