• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.7
• /
• pp.639-647
• /
• 2004

This paper concerns the analytical modeling and dynamic analysis of advanced rotating blade structure implemented by a dual approach based on structural tailoring and viscoelastic material technology. Whereas structural tailoring uses the directionality properties of advanced composite materials, the passive material technology exploits the damping capabilities of viscoelastic material (VEM) embedded into the host structure. The main structure is modeled as a composite thin-walled beam Incorporating a number of nonclassical features such as transverse shear. anisotropy of constituent materials, and rotary inertia etc. The VEM layer damping treatment is modeled by using the Golla-Hughes-McTavish (GHM) method, which is employed to account for the frequency-dependent characteristics of the VEM. The displayed numerical results provide a comprehensive picture of the synergistic implications of both techniques, namely, the tailoring and damping technology on dynamic response of a thin-walled beam structure exposed to external time-dependent excitation.

• International Journal of Highway Engineering
• /
• v.16 no.6
• /
• pp.121-128
• /
• 2014

PURPOSES : The objective of this study is to evaluate the tack-coating material's properties using the bitumen bond strength(BBS) test and damping test as function of changed curing times. In this study, bonding strength tests were performed according to the curing time of tack coating materials. METHODS : In order to investigate bonding characteristic of tack coating materials, the Pneumatic Adhesion tensile Testing Instrument(PATTI) device is used to measure the bond strength between the tack coating materials and aggregate substrate based on the AASHTO TP-91. Also, damping test as in situ test was used to determine an appropriate traffic openting time for construction vehicle. Four different tack-coating materials were used in this study. The BBS tests were performed a one hour curing and testing temperatures of $5^{\circ}C$, $15^{\circ}C$, and $25^{\circ}C$. Damping test was conducted at 30min, 60min, 90min, and 120 min of curing times with temperatures of $20^{\circ}C$ and $30^{\circ}C$. RESULTS and CONCLUSIONS : The BBS test results show various bond strength as function of tack coat materials. At the same testing condition, A tack coat material shows almost two times higher than D tack coat materials although both materials are satisfied the criteria of material's physical properties. Also, Dampting test results shows similar trend with BBS test result. The damping test result was significantly changed as function of tack coat materials. Based on this study, the tack coating material's curing time is very important. Therefore, both curing time and the bond strength's characteristic has to be considered in standard specification.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.11 no.7
• /
• pp.261-266
• /
• 2001

The flexural vibration of laminated composite beams with active and passive constrained layer damping has been investigated to design a structure with maximum possible damping capacity. The equations of motion are derived fro flexural vibrations of symmetrical,. multi-layer laminated beams. The damping ratio and model damping of the first bending mode are calculated by means of iterative complex eigensolution method. The direct negative velocity feedback control is used for the active constrained layer damping. It is shown that the flexible laminated beam is more effective in the vibration control for both active and passive constrained layer damping. and this paper addresses a design strategy of laminated composite under flexural vibrations with constrained layer damping.

• Steel and Composite Structures
• /
• v.17 no.6
• /
• pp.803-824
• /
• 2014

The dynamic characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of the tower with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as can mass and stiffness. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping, such as steel/concrete mixed structure - supporting soil coupled system. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. An analytical approach capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to define and investigate dynamic characteristics of hybrid tower of cable-stayed bridges: The first approach makes use of a simplified approximation of two lumped masses to investigate the structure irregularity effects including damping of different material, mass ratio, frequency ratio on dynamic characteristics and modal damping; the second approach employs a detailed numerical step-by step integration procedure in which the damping matrices of the upper and the lower substructures are modeled with the Rayleigh damping formulation.

• Journal of Korea Foundry Society
• /
• v.21 no.2
• /
• pp.119-126
• /
• 2001

Al/15%Gr. composite have been manufactured by mixing, compacting, and extruding aluminium powder and graphite powder. Then, Al-6%Si/x%Gr., Al-12%Si/x%Gr., and Al-18%Si/x%Gr.(x: 0, 2, 4, 6, 8) composites have been manufactured by remelting the extruded materials(Al/15%Gr.), Al-33.3%Si alloy, and Al ingot, etc. We conducted experiments to chracterize the microstructure, and damping properties and hardness. The result of microstructure experiment on Al-x%Si/y%Gr. composites reveals the good dispersion of graphite. As to Al-Si/y%Gr. composites, the more the graphite contents, the less the tensile strength. And the tensile strength varied according to contents of Si: with its highest value in Al-18%Si/y%Gr. composites and lowest in Al-6%Si/y%Gr. composites. As to Al-x%Si/y%Gr. composites, the more the contents of graphite, the more the vibration damping properties. And we can get the highest vibration damping rate in Al-12%Si/y%Gr. composites which matrix structure is an eutectic component.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.13 no.8
• /
• pp.651-657
• /
• 2003

A new mechanical-electrical hybrid passive damping treatment is proposed to improve the performance of structural vibration control. The proposed hybrid passive damping system consists of a constrained layer damping treatment and a shunt circuit. In a passive mechanical constrained layer damping, a viscoelastic material damping layer is used to control the structural vibration modes in high frequency range. The passive electrical damping is designed for targeting the nitration amplitude in the low frequency range. The governing equations of motion are derived through the Hamilton's principle. The obtained mathematical model Is validated experimentally. The presented theoretical and experimental techniques provide invaluable tools for controlling the multiple modes of a vibrating structure over a wide frequency band.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.79-82
• /
• 2005

This study aims to propose fundamental data for development of noise reduction system that is applied to classification for light-weight impact sound. For this reason, eight types of damping materials were constructed in new construction field. Comparison and analysis among the reduction materials were carried out on the acoustical characteristics through test. In the end, the suitability as a damping material was evaluated by the analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.10
• /
• pp.766-772
• /
• 2002

In this investigation, experimental attempts were made to observe and determine the variations in elastic and damping properties of the PVC depending on the amounts of MBS added to the mixture, PVC/MBS, and also on the thicknesses of the specimens. An acoustic resonance technique was used for the tests In this investigation. It serves as a method to characterize properties of materials set in vibrational motions, which is initiated by low level stresses generated by externally supplied acoustic energy. Substantial variations were observed in the test results with the addition of the MBS to the PVC. It was found that the magnitudes of elastic constants decrease while the damping capacity improve when MBS rubber was added in the range up to 9 phr.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2004.10a
• /
• pp.290-293
• /
• 2004

In this paper a new sandwich composite is developed by injection silicone rubber into the honeycomb core. This composite material is designed to have a improved damping performance. For verification damping tests were conducted to the specimens with different stacked USNl25 carbon/epoxy prepreg laminate facesheets, $[0/90]_{4s},\;[0/45-45/90]_{2s},\;[45/-45]_{4s}$. Frequency response, displacement response and damping ratio were checked and compared for the both groups of specimens, with and without rubber fillings. The experimental results provided a good agreement with our original material design concept.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.05a
• /
• pp.133-137
• /
• 2001

Active control of flexural vibrations of smart laminated composite beams has been carried out using piezoceramic sensor/actuator and viscoelastic material. The beams with passive constrained-layer damping have been analyzed by formulating the equations of motion through the use of extended Hamilton's principle. The dynamic characteristics such as damping ratio and modal damping of the beam are calculated for various fiber orientations by means of iterative complex eigensolution method, This paper addresses a design strategy of laminated composite under flexural vibrations to design structure with maximum possible damping capacity.