• 열처리공학회지
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• 제15권6호
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• pp.272-278
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• 2002

The changes in damping capacity with volume fractions of thermal and deformation-induced ${\varepsilon}$ martensites were compared and analyzed in an Fe-23%-Mn alloy. The volume fraction of thermal ${\varepsilon}$ martensite increased with decreasing cooling temperature, whereas that of deformation-induced ${\varepsilon}$ martensite increased steeply up to 10%- of cold rolling and nearly saturated in further cold rolling. In the case of thermal ${\varepsilon}$ martensite, the damping capacity increased linearly with the increase in ${\varepsilon}$ martensite content. For the deformation-induced ${\varepsilon}$ martensite, however, the damping capacity increased continuously up to 70%- of ${\varepsilon}$ martensite, over which it decreased suddenly. TEM microstructures showed that the deterioration of damping capacity above 70%- of deformation-induced ${\varepsilon}$ martensite is ascribed to the introduction of perfect dislocations, which play a important role in inhibiting the movement of damping sources such as stacking fault boundaries inside ${\varepsilon}$ martensite, ${\varepsilon}$ martensite variant boundaries and ${\gamma}/{\varepsilon}$ interfaces.

• 동력기계공학회지
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• 제11권1호
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• pp.115-120
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• 2007

The effect of grain size on the damping capacity of Fe-26Mn-2Al alloy studied in this paper has been investigated after changing the microstructure by cold rolling and changing grain size. Micro structures in Fe-26Mn-2Al at room temperature consist of a large quantity of austenite and a small quantity of ${\varepsilon}\;and\;{\alpha}'$ martensite. And ${\varepsilon}\;and\;{\alpha}'$ martensite was increased by increasing the degree of cold rolling. The content of deformation induced martensite was increased with increasing the degree of cold rolling. Damping capacity was linearly increased with increasing ${\varepsilon}$ martensite content, which suggests that stacking faults and ${\varepsilon}$ martensite variant boundaries are the principle damping sources. With increasing the grain size in Fe-26Mn-2Al alloy, the damping capacity was increased due to increasing the volume fraction of ${\varepsilon}$ martensite by decrement in stability of austenite phase. With decreasing the grain size, the content of deformation induced martensite was decreased and the damping capacity was decreased.

• 한국재료학회지
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• 제28권10호
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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 ${\alpha}^{\prime}-martensite$.

• 한국해양공학회지
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• 제20권1호
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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.

• Steel and Composite Structures
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• 제19권5호
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• pp.1321-1331
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• 2015

A square steel sandwich plate with lattice corrugated core is explored for damping improvement. A range of damping materials are filled inside the openings provided by the corrugated core, or are applied on the surfaces of the facesheets. The dynamic properties such as natural frequency and damping factor are experimentally measured for the sandwich plate with each filling solution. The relative performance of each insertion is compared in terms of damping capacity and added mass.

• Structural Engineering and Mechanics
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• 제20권6호
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• pp.631-653
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• 2005

In this work, the mechanism of damping and its theoretical evaluation for layered aluminium cantilever structures jointed with a number of equispaced connecting bolts under an equal tightening torque have been considered. Extensive experiments have been conducted on a number of specimens for comparison with numerical results. Intensity of interface pressure, its distribution pattern, dynamic slip ratio and kinematic coefficient of friction at the interfaces, relative spacing of the connecting bolts, frequency and amplitude of excitation are found to play a major role on the damping capacity of such structures. It is established that the damping capacity of structures jointed with connecting bolts can be improved largely with an increase in number of layers maintaining uniform intensity of pressure distribution at the interfaces. Thus the above principle can be utilized in practice for construction of aircraft and aerospace structures effectively in order to improve their damping capacity which is one of the prime considerations for their design.

• 열처리공학회지
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• 제30권6호
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• pp.258-263
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• 2017

The effect of cooling rate on the damping capacity of pure Mg was studied. Two Mg samples with different cooling rates were prepared by heat treatment at 873 K for 24 h, followed by water quenching and by furnace cooling to room temperature, respectively. The average grain sizes of the Mg samples were almost identical regardless of the cooling rate, but more twins were observed in the sample with faster cooling rate. The calculated vacancy fraction was higher in the fast cooling sample than the slow cooling one. It is noted that the fast cooling sample exhibited lower damping capacity both in the strain-amplitude independent and strain-amplitude dependent regions. Higher values of vacancy concentration and number density of twins in the fast cooling sample are considered to be responsible for the deteriorated damping capacity in the strain-amplitude independent and strain-amplitude dependent regions, respectively.

• 동력기계공학회지
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• 제14권2호
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• pp.78-83
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• 2010

This study was carried out to investigate the effect of microstructure on the damping capacity of 12Cr martensite heat-resisting steels, in case of the specimen with martensite phase contained the volume faction of ferrite phases, under 5%. The damping capacity was decreased with the increase of solution treatment temperature and time. While it was increased with the increase of tempering temperature and time. The damping capacity was higher in case of specimen with martensite single phase structure than the specimen with martensite phase contained of ferrite phases.

• 한국주조공학회지
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• 제17권1호
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• pp.51-57
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• 1997

Effects of the amount of flake type graphite, morphology and (V,Mo)carbides on the specific damping capacity of austenitic low thermal expansion cast irons were investigated. Specific damping capacity(SDC) of low thermal expansion cast irons increased with the increased amount of graphite. Specific damping capacity of low thermal expansion cast iron decreased with the increased Young's modulus. In the case of V and Mo addition, SDC decreased with the increased amount of carbides. Specific damping capacity increased about 2% by the movement of magenetic domains which appeared in ferromagnetic materials.

• 동력기계공학회지
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• 제18권4호
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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.