• Journal of Power System Engineering
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• v.18 no.4
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• pp.66-71
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• 2014

In this study, effect of heat treatment on the microstructure and damping capacity of hot rolled magnesium alloys was investigated. The microstructure of hot rolled magnesium consisted of dendrite structure and $Mg_{17}Al_{12}$ compounds precipitated along the grain boundry. The dendrite structure was dissipated and $Mg_{17}Al_{12}$ compounds was decomposed by annealing treatment, and then they dissolved in ${\alpha}-Mg$. With an increasing the annealing temperature and time, damping capacity was slowly increased by the growth of grain size and decreasing of defects induced by hot rolling. Two kinds of magnesium alloys AZ 31 and AZ 61 after annealing showed no difference in damping capacity.

• Journal of Korea Foundry Society
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• v.25 no.2
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• pp.73-79
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• 2005

Effects of Cr and Ni addition on damping capacity, mechanical property, and corrosion resistance of Fe-17%Mn martensitic alloy have been studied. Martensite start temperature($M_{S}$) of the alloy decreases linearly with increasing Cr and Ni contents up to 15%. The damping capacity decreases gradually from 27 to 22% in specific damping capacity(SDC) with increasing Cr and Ni contents from zero to 10%, and decreases rapidly with further Cr and Ni content in Fe-17%Mn alloy. The tensile strength of the alloy maintains a level of 60 $kgf/mm^{2}$ regardless of Cr content with an elongation of 20 to 25%. But, in case of Fe-17%Mn-x%Ni alloy, the tensile strength decreased rapidly with the Ni content of above 10% because of austenite morphology. Immersion test in 5% NaCl solution leads to the result that the corrosion resistance of the alloy becomes excellent above 10% Cr. From the above results, it is concluded that the optimum Cr content to improve the mechanical property and corrosion resistance of the alloy in 5%NaCl solution with a lesser decrease in damping capacity is about 10%. In the case of 5% $H_{2}SO_{4}$ condition, the Fe-17%Mn-10%Ni is an optimum alloy.

• Journal of Power System Engineering
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• v.16 no.4
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• pp.60-65
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• 2012

This study was carried out to investigate the effect of reverse transformation on the damping capacity in high manganese austenitic stainless steel. ${\alpha}^{\prime}$-martensite was formed with the specific direction and surface relief by deformation. Over 95% of the austenite phase was transformed to deformation-induced ${\alpha}^{\prime}$-martensite by 70% cold rolling. Reverse transformation became rapid above an annealing temperature of $550^{\circ}C$, but there was no significant transformation above $700^{\circ}C$. In addition, with increasing annealing time at $700^{\circ}C$, reverse transformation was induced rapidly, but the transformation was almost completed at 10 min. Damping capacity was increased up to $700^{\circ}C$, and than unchanged with the increasing annealing temperature. Damping capacity increased steeply with an increasing reverse treatment time up to 10min, whereas there were no significant change with a treatment time of more than 10 min. Damping capacity increased with an increasing the reversed austenite and was strongly affected by reversed austenite.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.6
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• pp.295-301
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• 2014

In this study, the relationship between strength and damping capacity of annealed magnesium alloys after hot rolling was investigated. The microstructure of hot rolled magnesium consisted of dendrite structure and $Mg_{17}Al_{12}$ compounds precipitated along the grain boundary. The dendrite structure was dissipated, $Mg_{17}Al_{12}$ compounds was decomposed by annealing, and then its dissolved in ${\alpha}$-Mg. With an increasing the annealing temperature and time, strength was slowly decreased and damping capacity was slowly increased by the growth of grain size and decreasing of defects induced by hot rolling. In annealing treatmented magnesium alloys after hot rolling, damping capacity was decreased rapidly with an increase of strength. There was on proportional relationship between tensile strength, and damping capacity.

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.502-509
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• 1994

New damping measurement equipment was designed using the dynamic strain gage and high speed analog to digital signal 12 bit converter and compared it with existing equipment. The damping properties of general material and high damping material were also studied by this machine. The SDC (specific damping capacity) was measured with various heat treatment condition, initial vibration amplitude and internal stress. The vibration amplitude of high damping material is decreased within nearly less than 0.4 second after applying the initial forced vibration. But that of general material is still vibrating at the same time. After furnace-cooling heat treatment, SDCmax of Fe-lGwt.%Cr system was more than 40% and that of Fe-5.5wt.%Al alloy was more than 30% after air-cooling heat treatment. Upon increasing of initial vibration amplitude, it is detected the migration of SDCmax into the region of small vibraton amplitude. Damping capacity is decreased rapidly as the internal stress Increases. Damping measurement equipment in the present study was ahln to give the more accurate results of damping properties in the small vibration amplitude region.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2123-2138
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• 1994

A study on the dynamic mechanical properties of the high strength carbon fiber epoxy composite beam was carried out. The macromechanical model was used for the theoretical analysis of the symmetric laminated composite beam. The anisotropic plate theory and Bernoulli-Euler beam theory were used to predict the effective flexural elastic modulus and the specific damping capacity of laminated composite beam. The free flexural vibration and torsional vibration tests were carried out to determine the specific damping capacities of the unidirectional laminated composite beam. The vibration tests were performed in a vacuum chamber with laser vibrometer system and electromagnetic hammer to obtain accurate experimental data. From the computational and experimental results, it was found that the theoretical values with the macromechanical analysis and the experimental data of symmetric laminated composite beam were in good agreement.

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.583-589
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• 2018

This study investigates the effect of fatigue stress on the damping capacity in a damaged Fe-22Mn-12Cr-3Ni-2Si-4Co damping alloy under fatigue stress. ${\alpha}^{\prime}$ and ${\varepsilon}-martensite$ forms by fatigue stress in the damaged Fe-22Mn-12Cr-3Ni-2Si4-Co damping alloy under fatigue stress. The ${\alpha}^{\prime}$ and ${\varepsilon}-martensite$ forms with the specific direction and surface relief, or they cross each other. With an increasing fatigue stress, the volume fraction of ${\alpha}^{\prime}-martensite$ and ${\varepsilon}-martensite$ increases. With an increasing fatigue stress, the damping capacity increases with an increase in the volume fraction of ${\varepsilon}-martensite$. The increase in the damping capacity in the damaged Fe-22Mn-12Cr-3Ni-2Si-4Co alloy under fatigue stress strongly affects the increase of ${\varepsilon}-martensite$ formed by fatigue stress, but the damping capacity of the damaged Fe-22Mn-12Cr-3Ni-2Si-4Co damping alloy under fatigue stress is strongly controlled by a large amount of ${\alpha}^{\prime}-martensite$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.565-569
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• 2004

Conventional methods for reducing vibration in engineering designs (i.e. by stiffening or detuning) may be undesirable or inadequate in conditions where size or weight must be minimized or where complex vibration spectra exist. Alloys which combine high damping capacity with good mechanical properties can provide attractive technical and economic solutions to problems involving seismic, shock and vibration isolation. To meet these trends, we have developed a new high damping Fe-17%Mn alloys. Also, the alloy has advantages of good mechanical properties and more economical than any other known damping alloys(1/4 times as cost of non-ferrous damping alloy). Thus, the high damping Fe-17%6Mn alloy can be widely applied to household appliances, automobiles, industrial facilities and power plant components with its excellent damping capacity(SDC, 30%) and mechanical property(T.S 700MPa). It is the purpose of this paper to introduce the characterization of the high damping Fe-17%Mn alloy and the results of retrofit several such applications.

• Smart Structures and Systems
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• v.4 no.2
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• pp.123-135
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• 2008

Damping capacity of SMA damping devices is simulated numerically under distinct geometry and loading conditions. Two-dimensional numerical simulations are performed on the basis of a phenomenological model of dynamics of martensite-austenite phase boundaries. Results of the simulations predict the time delay and the value of the stress transferred to other parts of a construction by a damper device.

• Journal of Ocean Engineering and Technology
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• v.20 no.1 s.68
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• pp.1-6
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• 2006

The effects of microstructure on the damping capacity and tensile properties of 316L stainless steel were investigated. Increasing the degree of cold working, the volume fraction of $\varepsilon-martensite$ decreased after rising to maximum value at specific level of cold working, the volume fraction of d-martensite slowly increased and then dramatically increased from the point of decreasing $\varepsilon-martensite$ volume fraction. Increasing the degree of cold working, the behnvior of damping capacity is similar to that of the $\varepsilon-martensite$. After the damping capacity showing the maximum value at about $20\%$ of cold rolling, damping capacity was decreased with the volume fraction of $\varepsilon-martensite$. Tensile strength was proportional to the volume fraction of d-martensite, and elongation steeply decreased in the range low volume fraction of a'-martensite, then slowly decreased in range the above $10\%$ volume fraction of d-martensite. The damping capacity and elongation is strongly controlled by the volume fraction of $\varepsilon$ martensite with liner relationship. However, the effect of the volume fraction of d-martensite and austenite phase on the damping capacity was not observed. Tensile strength was governed by the volume fraction of d-martensite.