Papers by Keyword: Anelasticity

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.

Abstract: The chemical diffusion coefficient (Dc) of hydrogen in the Ni30Ti50Cu20 shape memory alloy has been determined in the temperature range 700 - 1150 K by investigating the kinetics of H2 absorption. The mobility of H has also been deduced between 250 K and 280 K from a Snoek-type internal friction peak. The values of the Einstein diffusion coefficient (DE) derived from the relaxation time of this peak were in keeping with those of Dc obtained at low H contents (nH = H/Me < 0.01 ). The combined Arrhenius plot of DE and Dc gave the following values for the diffusion parameters: W = 0.52 ± 0.02 eV, D0 = (5±2)x10-4 cm2/s.

Abstract: A list of monographs on internal friction, anelasticity, ultrasonic attenuation, relaxation phenomena in solids, and mechanical spectroscopy published in Soviet Union, Russia, and Ukraine is provided. A complete list of proceedings from international and Russian conferences is also given. This work is a valuable supplement to the Mechanical Spectroscopy - Suggested Reading Series.

Abstract: Al is well known to serve as a metallic matrix in a composite due to its enhanced ductility and toughness. In the present study, pure Al (AA1050) is reinforced with two different reinforcements viz., an interconnected, axisymmetrical, galvanized iron wire perform and SiC particulates and were tested in a free-free type suspended beam arrangement, coupled with circle-fit approach to determine damping characteristics. The results show the effect of individual and combined presence of two different reinforcements in terms of damping loss factor. Addition of ~ 2 vol. % of interconnected reinforcement increases the overall damping capacity of the aluminium matrix by ~ 15 % which is equivalent to the presence of ~ 4.8 vol. % of SiCp. But combined presence of ~2 vol. % of interconnected wire reinforcement along with ~0.5 vol. % of SiCp increases the damping capacity to 24 % which forms a new breed of hybrid composites. This increase in damping can be rationalized in terms of the induced plastic zone and reinforcement’s aspect ratio.

Abstract: Mechanical spectroscopy was employed to investigate the microstructure evolution of a Zr-modified 6082 Al-Mg-Si alloy and the same alloy with Sc addition after ageing and following severe plastic deformation through equal channel angular pressing. Measurements of the internal friction and dynamic young modulus have been performed in isothermal and isochronal runs in the frequency range 0.1 - 104 Hz. The anelasticity spectra reveal in the temperature range 470-870 K both structural and anelastic relaxation processes. Two structural damping maxima connected with inverse temperature trend of the modulus occur in the alloys submitted to equal channel angular pressing, the first one is strongly suppresed by Sc and Zr addition. An anelastic relaxation peak whose strength depends on the nature and morphology of precipitates and dispersoids and on the deformation and ageing condition was observed in all samples investigated. The high background damping occurring before the first structural damping maximum is analyzed with reference to a superplastic behavior of the equal channel angular pressing processed alloys.

Abstract: Low temperature dislocation- and point defect-related anelasticity in high pressure torsion (HPT) deformed metallic materials bcc Fe-26Al, fcc Fe-36Ni, hcp Ti is studied by mechanical spectroscopy. Internal friction (IF) peaks, which correspond to these phenomena, have different stability against heating. Up to five IF peaks are recorded, at least some of these peaks can be classify as Hasiguti peaks. Mechanical spectroscopy gives a useful tool to study early stages of severely plastic deformed alloys study.

Abstract: In the present study, elemental Ni powder was mechanically milled (MMed) for 10 hours to reduce the grain (crystalline) size in the nano-range (<100nm). The mechanically milled powder (10h-MMed) was consolidated by die-cold compaction and was further hot extruded at high temperatures to maintain a crystallite size within the nano range. Further, the specimen was tested by a novel free-free type suspended beam arrangement, coupled with circle-fit approach to determine damping characteristics. To vary the resonant frequency of the suspended beam, end masses with different weights were added. The characterization results revealed that the nano-size grains exhibit increased damping compared to a coarse-grained sample, under similar vibration frequency. Results also show that the damping capacity of both nano and coarse grained samples decreases with an increase in frequency of vibration. Particular emphasis was placed to correlate the damping capacity with the process induced residual stresses present in the samples.