Papers by Keyword: Damping Capacity

Abstract: The damping capacity, which was characterized by dissipating of mechanical energy, was examined in magnesium alloys (AZ31, AZ61 and AZ91). Internal damping is usually divided into three regions, namely the regions in which the internal damping is strain independent, weakly dependent and strongly dependent. The article is focused on the critical amplitudes of deformation which separate the strain independent, weakly dependent and strongly dependent regions. In experimental measurements resonance method was used, which is based on continuous excitation of oscillations of the specimen and the entire apparatus vibrates at a frequency which is near to the resonance.

Abstract: In previous study, it was investigated damping capacity on various deformation and heat treatment conditions in order to study damping capacity that was influenced by grain size and dislocation motion in detail. Magnesium alloy AZ31 was rolled at 673K with different rolling reduction, respectively. Specimens were machined out parallel to the rolled direction and annealed on various temperature and time. Then, damping capacity, microstructure and hardness was measured at room temperature. Factors affected on damping capacity are grain size, crystal orientation, dislocation motion, and so on. It was found that damping capacity has been affected by grain size and crystal orientation. Grain size and hardness is not examined obvious difference after annealing. In large prior strain, however, low damping capacity is appeared and damping capacity increases with increasing of heat treatment temperature. The reason is that resolved shear stress factor is influenced by damping capacity.

Abstract: Mg/Al alloy multilayered composites were produced by accumulative roll bonding (ARB) technique. The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy, and damping capacity of the composite was tested by dynamic mechanical analyzer.It can be found that the diffusion layers were produced in Al and Mg alloy layers, and the diffusion layers increased with increasing of the ARB pass. With the increasing of ARB pass, the room temperature damping value of Mg/A1 multilayered composite presented a downward trend. The temperature damping spectrum of the composite had two internal friction peaks, with the increasing of the ARB pass, the peak height of P1 peak increased gradually and P2 peak moved to low temperature gradually.

Abstract: Annealing treatment is an important step of rolling deformation that contributes to microstructural evolution and leads to the significant changes in damping capacity. Damping capacities were analyzed in the parallel to rolling direction at 1 and 10 Hz respectively. It was found that severe plastic deformation at 40 percent reduction has lower damping capacity compared to that of 30 percent and 20 percent reductions respectively. The microstructural results show that the grains of as rolled alloys were changed to almost equiaxed structures after a rolling reduction at 40 percent reduction.

Abstract: ZK60 alloy strip with 3.5mm thickness which produced by Twin Roll Casting (designated as TRC in short) was used in this paper. The effect of sequential annealing on microstructure and damping capacity of TRC ZK60 alloy was studied by using optical microscope (OM) and dynamic mechanical analyzer (DMA). The dendrite structure was present in TRC ZK60 alloy strip before and after annealing heat treatment. A few of recrystallized grains were present after annealed at 400°C for 1hr. The damping capacity of the strip as annealed at 400°C was better than that of annealed at the lower temperature. The room temperature (25°C) damping values (Q^-1) of ZK60 strip which was annealed at 300°C, 350°C and 400°C were 0.0079, 0.0085 and 0.0096, respectively. The damping peak P1 is a relaxation process, but the damping peak P2 is not a relaxation process. The activation energy H for P1 of TRC ZK60 strip after annealed at 400°C for 1hr was 114KJ/mol. The damping peak P1 was attributed to boundary slip controlled by grain boundary diffusion and lattice self-diffusion.

Abstract: Considering that, in Accordance with the Laws of Physics, the Sound Travels only through Elastic Bodies, the Main Characteristic of an Acoustic Material is the Elasticity. Classifying the Metallic Materials in this Regard is Quite Difficult, as the Elasticity is Characterized by more than One Component (static Elastic Modulus, Dynamic Elastic Modulus, Static Elastic Limit, Elastic Limit, Elastic Deformation Linearity, Damping Capacity). Best Acoustic Properties of some Metallic Materials are Widely Used in the Construction of Transducers, Musical Instruments, Bells Etc. for this Purpose, a Study on Three Metallic Materials was Conducted: a Cusn Alloy for Bells, a Cast Aluminum Alloy and a Martensitic Cast Iron. this Study Highlights both the Chemical Composition, Structure, Mechanical Properties and Damping Capacity of Sounds.

Abstract: There is the opinion, imprinted by tradition, that only bronze alloyed with tin may be used to build bells, musical instruments or sound transmitters, without the need to bring a scientific explanation. Starting from the physical theory and experimental determination that sound travels only through bodies with elastic proprieties, a study over acoustic white cast iron was proposed. After convincing experiments, it results that white cast irons have good properties for producing and transmitting sound waves. The measurements focused two fundamental aspects, the elastic energy available for producing and transmitting sounds and amortization, resulting that white cast irons can substitute with success bronze with tin or even better properties.

Abstract: 2219 aluminum alloy reinforced with 10wt. % TiB₂ particulate was fabricated through mixed-salts method. The damping capacity and dynamic Yongs modulus was investigated. The damping capacity and dynamic Yongs modulus of 10wt. % TiB₂/2219 is higher than that of the matrix alloy.The improved damping capacity is due to dislocation damping at low temperature, and grain boundary damping and interface damping at high temperature.

Abstract: The paper analyzes the length variety of the crystal gain and sub-crystal gain of magnesium alloy materials during the strain amplitude augmentation in the linearity stage of the material deformation, and then based on G-L model derives the mathematical model of the damping variety durign the strain amplitude augmentation in the linearity strain stage of the magnesium alloys. Consequently, magnesium alloy damping mechanism is studied theoretically. It is proved that the magnesium alloy material has the advantages of high damping capacities. In addition, a comparison test in terms of damping performance is made between magnesium alloy and other alloys, which further confirms the high damping of magnesium alloy and the rightness of the theoretical deduced conclusion.

Abstract: Microstructure of as-cast AZ91D alloy doped with 0.7wt% silicon was investigated, the damping capacity of the alloy was measured by cantilever beam technique, and the damping mechanism was also analyzed. The results show that after addition 0.7%Si into AZ91D alloy, the dendritic grains are refined, and Chinese script Mg2Si phase forms in the interdendritic areas. The damping capacities of the alloy are improved by Si addition, and increase with increasing of strain amplitude. The damping behavior of the alloy is mainly resulted from dislocation movement, and can be explained by the theory of Granato and Lücke.