Papers by Keyword: High Damping

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Authors: Qian Feng Fang, T. Liu, Chun Li, X.P. Wang, G.G. Zhang
Abstract: In this paper, we review the damping mechanisms in oxide materials, such as the short-range jump of oxygen vacancies and cation vacancies, movement of domain walls, and grain boundary sliding. Some examples in doped ZrO2, La2CuO4+δ, La2Mo2O9 and other oxide materials are briefly discussed, in which the damping capacity can reach as high as 30%. These oxides could be possibly applied as high damping materials either in the form of bulk components, or as additives in composites, or as hard damping coatings. In the last two potential applications, the high hardness and strength as well as high damping capacity of the oxides are simultaneously exploited, which cannot be realized by the usual high-damping metals and alloys.
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Authors: Wei Guo Wang, Gang Ling Hao, Xin Cheng Ren, Lei Lv
Abstract: The higher damping capacity and hardness Li6La2SrBi2O12ceramic particles at room temperature were added into the cement to form the composite materials. The maximum damping capacity of the 25 wt% Li6La2SrBi2O12ceramic/cement composites is as high as 0.015 at 310 K and 9 Hz, corresponding to a vibration energy dissipation of about 10% in each vibration cycle. The flexural strength of the the 10 wt% Li6La2SrBi2O12ceramic/cement composite is about 50% higher than that of the pure cement sample
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Authors: I. Yoshida, Kazuhiro Otsuka
Abstract: Low frequency internal friction of Ti49Ni51 binary and Ti50Ni40Cu10 ternary shape memory alloys has been measured. The effect of solution and aging heat treatments on the damping property was examined. The temperature spectrum of internal friction for TiNi binary alloy consists, in general, of two peaks; one is a transition peak which is associated with the parent-martensite transformation and is rather unstable in a sense that it strongly depends on the frequency and decreases considerably when held at a constant temperature. The other one is a very high peak of the order of 10-2, which appears at around 200K. It appears both on cooling and on heating with no temperature hysteresis, and is very stable. The behavior of the peak is strongly influenced by the heat treatments. The trial of two-stage aging with a purpose of improving the damping capacity has been proved unsatisfactory. TiNiCu has a very high damping, the highest internal friction reaching 0.2, but by quenching from very high temperature, say 1373K, the damping is remarkably lowered. For the realization of high damping the quenching from a certain temperature range around 1173K seems the most preferable condition.
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Authors: Andre Rivière, Veronique Pelosin, Michel Gerland
Abstract: sothermal mechanical spectroscopy measurements were performed in an Al-51 at % Zn alloy at various temperatures below and above the eutectoid transition temperature: during a heating the α-β eutectoid mixture changes into α solid solution at 550 K. Damping experiments were performed in a very large frequency range (10-5– 50 Hz) between room temperature and 673 K. Internal friction spectra performed between 200 K and 540 K, exhibit two thermally activated relaxation peaks (P1 and P2). P1 decreases and disappears with the increase of measurement temperature while P2 appears and increases. P2 totally disappears above the eutectoid transition temperature. Above 550 K, a new peak (P3) is evidenced at very low frequency. The relaxation parameters of P3 (limit relaxation time τ0 = 9×10-7 and activation energy H = 105 kJ/mole (1.1 eV)) allow to associate this peak with the motion of sub grain boundaries. P1 and P2 (τ0 ≈ 10-7 and H ≈ 70 kJ/mole (0.75 eV) for both peaks) are associated with a thermally induced atom diffusion across the α-β interface.
167
Authors: Andre Rivière, Veronique Pelosin, G. Covarel, Michel Gerland
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Authors: Terlize Cristina Niemeyer, Carlos Roberto Grandini, Sandra G. Schneider
Abstract: Recent studies have been done to achieve biomedical alloys containing non-toxic elements and presenting low elastic moduli. It has been reported that Ti-Nb-Zr alloys rich in beta phase, especially Ti-13Nb-13Zr, have potential characteristics for substituting conventional materials such as Ti-6Al-4V, stainless steel and Co alloys. The aim of this work is to study the internal friction (IF) of Ti-13Nb-13Zr (TNZ) alloy due to the importance of the absorption impacts in orthopedic applications. The internal friction of this alloy produced by arc melting was measured using an inverted torsion pendulum with the free decay method. The measurements were performed from 77 to 700 K with heating rate of 1 K/min, in a vacuum better than 10-5 mBar. The results show a relaxation structure at high temperature strongly dependent on microstructure of the material. Qualitative discussions are presented for the experimental results, and the possibility of using the TNZ as a high damping material is briefly mentioned.
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Authors: Xian Lan Liu, Chu Ming Liu, Wen Yu Zhang, Jian Hua Luo, Su Min Zeng
Abstract: The dynamic mechanical analyzer (DMA) was applied to investigate the damping properties of Mg-6Zn-0.6Zr alloys. The results show that the as-cast Mg-6Zn-0.6Zr alloy exhibits higher strain amplitude independent damping performance than that of as-homogenized. The strain amplitude dependent damping of the as-homogenized has the best damping performance with the strain amplitude from 3×10-5 to 6×10-4, and the as-extruded is the lowest. When the strain amplitude exceeded 6×10-4, the as-extruded has the best damping capacity all the time within the experimental strain amplitude, and all the alloys reach the high damping capacity. Two critical strain amplitude points were detected in the alloy as-extruded and as-homogenized. The damping peak value is 0.0192 with the strain amplitude of 1.5×10-3 presented in the alloy as-extruded.
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Authors: Rolf Gotthardt
Abstract: The shape memory effect and the high damping in shape memory alloys are based on the martensitic phase transformation, which takes place essentially without diffusion and any change of order have an influence on its side effects: the memory effect, the superelasticity and the high damping capacity of the martensitic phase. A new method to control the performance of shape memory alloys is presented, which is based on selective modification of specified parts of working components. In this research, ion irradiation has been used to introduce locally disorder into a crystal or even amorphise it. A pre-deformed Ni-Ti, 6μm thin film in its martensitic state has been irradiated with Ni-ions of energy of 5 MeV up to a dose of 1016 ions/cm2. By this treatment, a 2μm thin surface layer has been finally transformed into an amorphous state, in which the martensitic transformation is suppressed. During heating the underlying non-modified layer is contracting and an out-of-plane movement is observed. The amorphous layer is elastically deformed and its energy is used during cooling to bring the film in its original shape. In this way, a reversible movement of the film is created. This new technique not only allows us to design new types of micro-actuators, but also to influence locally the high damping, which can be of great importance for micro-engineering applications.
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