• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 춘계학술대회논문집
• /
• pp.499-504
• /
• 2004

The purpose of this study is to investigate a investigating of a floor-impact isolation system using damping materials in apartment buildings. The stiffness elastic modulus(k) by puls impact forces were calculated loss factor by Hilbert transforms. It is absolved that natural frequency was moved floor shock-absorbing materials and the impact force was reduced by floor panel. The slab was constructed by damping materials. As towards a result, the system showed inverse A 45dB by heavy weight-impact noise and inverse A 52dB by light-impact noise. High frequencies impact-noise can be reduced by upgrading naturial frequency of vibration and noise in the system.

• 한국소음진동공학회논문집
• /
• 제26권3호
• /
• pp.235-241
• /
• 2016

Underwater weapon system is required to structurally strong material, since as it is directly exposed to external shock. It should also be using the lightweight material in order to take advantage of buoyancy. Composite materials meet these requirements simultaneously. Particularly in the case of submarine, composite materials are widely used. It is important to have a high strength enough to be able to withstand external shock, but it is also important to attenuate it. In a method for the shock damping, viscoelastic damping materials are inserted between the high strength composite material as a sandwich structure. Shock attenuation can be evaluated in the loss factor. In ASTM(American Society of Testing Materials), evaluation method of the loss factor of cantilever specimens is specified. In this paper, mode tests of the cantilever are performed by the ASTM standard, in order to calculate the loss factor of the viscoelastic damping material by the specified expression. Further, for verifying of the calculated loss factor, mode test of compound beams is carried out. In addition, the characteristics of the material were analyzed the effect on the loss factor.

• 한국소음진동공학회논문집
• /
• 제11권4호
• /
• pp.13-21
• /
• 2001

Electrorheological(ER) fluid is a kind of smart material with variable shear stress and dynamic viscosity under various electric field intensity. Electric field can control the damping characteristics of ER damper. The objective of this study is the analysis of the performance of ER damper and its application to shock absorber. Idealized nonlinear Bingham plastic shear flow model is used to predict the velocity profile between electrodes. Cylindrical dashpot ER damper with moving electrode is constructed and tested under various electric fields. The analytic and experimental results for damping force are compared and discussed. Drop test system using ER damper is prepared to identify transient vibration characteristics. The rebound is eased as the applied electric field increases. When semi-active control algorithm is applied, rebound phenomenon disappears and vibration energy level decays faster than the case of zero electric field.

• 소음진동
• /
• 제9권4호
• /
• pp.720-729
• /
• 1999

Coventional methods for reducing vibration in engineering designs (i.e. by stifferning or detuning) may be undesirable in conditions where size or weight must be minimized, or where complex vibration spectra exist. Some alloys with a combination of high damping capacity and good mechanical properties can provide attractive techanical and economical solutions to problems involving seismic, shock and vibration isolation. Although several non ferrous damping alloys have been developed, none of those materials are applied in any industrial factor due largely to high production cost. To meet these requirement, we have developed a new Fe-Mn high damping alloy. In previous studies, we have reported that an Fe-17%Mn alloy exhibits the highest damping capacity(Specific Damping Capacity:SDC, 30%) among Fe-Mn binary system, and proposed that the boundaries of various types such as $\varepsilon$-martensite variant boundaries, stacking faults in $\varepsilon$-martensite, stacking faults in austenitic and ${\gamma}$$\gamma /\varepsilon$ interfaces give rise to a high damping capacity. The Fe-17%Mn alloy also has advantages of good mechanical properties(T.S. 70 kg/nm$^2$ and low cost over other damping alloys(1/4 times the cost of non-ferrous damping alloy). Thus, the Fe-17%Mn high damping alloy can be widely applied to household appliances, automobiles, industrial facilities and power plant components. In this paper, the overall properties of the Fe-17%Mn high damping alloy is introduced, and its applicability to containment spray pump in the power plant is discussed.

• 대한치과보철학회지
• /
• 제35권1호
• /
• pp.118-129
• /
• 1997

The purpose of this study was to evaluate the shock absorbing effect of 4 restorative materials and intramobile connector. The damping effect of four restorative materials used to veneer test crown rigidly connected to IMZ implant and subjected to an impact force was measured. These materials included a gold alloy(stabilor G) : a noble metal ceramic alloy(Degudent H) : porcelain(Duceram) : composite resin(Dentacolor). In addition, this study compared damping effect of same restoretive materials after using polyoxymethylene intramobile connector(POM IMC). The result of this study suggest that : In case of using metal IMC 1. Veneered composite resin(group IV) reduced the impact force by 75%, when compared to an equivalent thickness of porcelain(group III). Group IV reduced the impact force by 87% and 89%, respectively, when compared to Stabilor G(group I) and Degudent H(group II). 2. The impact force recorded was higher for the alloy with the higher elastic modulus.(Stabilor G, group I, Young's modulus 107 Gpa, versus Degudent H, Group II, Young's modulus 95 Gpa) 3. It took the longest time for composite resin veneered group(IV) to reach to peak force when compared group I, II, III. In case of using POM IMC 4. The mean impact force recorded were reduced by 79%(group I), 78%(group II), 69%(group III), 84%(group IV), respectively, when compared to using metal IMC. 5. The time required to reach the peak force were increased by 78%(group I, II) 87%(group III), 34%(group IV), respectively, when compared to using metal IMC>.

• Composites Research
• /
• 제37권1호
• /
• pp.21-31
• /
• 2024

이 리뷰 논문은 복합재에 함유되어 충격파를 감쇠하는 물질에 대한 탐구를 통해 폭발로 인한 외상성 뇌손상(bTBI)에 대비하여 인적자원을 보호하는 방법을 살펴보고자 한다. 이에 더하여 복합재의 충격파 감소의 정량화를 위한 충격파의 생성과 측정에 관련된 실험적인 방법들을 알아보고자 한다. 충격파는 고에너지 폭발물, 충격관, 레이저 및 레이저-플라이어 기술과 같은 다양한 접근법을 통해 생성이 가능하다. 충격파 전파 및 감쇠의 평가는 압전, 간섭계, 전자기 유도 및 스트릭 카메라 방법을 비롯한 첨단 기술을 활용하여 진행된다. 또한 충격파 압력감쇠 특성이 알려진 폴리우레아, 이온액체를 포함한 상분리 물질을 조사하였고 복합재 구조의 구성을 통해서 충격파를 감소시킬 수 있는 방법을 제시한다. 본 리뷰에서는 충격파 감쇠 물질 개발에 관한 연구를 종합하고 분석함으로써 폭발로 인한 외상성 뇌 손상에 대한 위험을 낮출 수 있는 재료적인 관점을 제시하고자 한다.

• 연구논문집
• /
• 통권28호
• /
• pp.73-87
• /
• 1998

A pneumatic control system of compressed air as a working fluid has a variety of advantages such as low price, high respondence, non-explosion and good control performance and thus has many applications in the field of automobile, electronic and semiconductor industry. However, it has a difficulty in contolling a precise position due to quick response of system and compressibility of working fluid and. in particular, shock stress may occur due to an external load, resulting in fracture of a cylinder cap unless cushion device is equipped in the linear actuator. To avoid this, a cushion device should be installed for damping effect of the external load and the supply pressure as well as for decreasing shock stress and vibration caused by high speed rotation. Previous studies include dimensionless analyses and computer simulations of cushion capability and experiments of horizontally-mounted cylinder performances. A new attempt is experimentally made in this study using a vertically-mounted cylinder under an operation condition of 4, 5 and 6 (bar) as supply pressure and 40, 70 and 100 (kgf) as external load. It turns out that the cushion pressure is mainly a function of the external load rather than the supply pressure. The cushion characteristics was also revealed in the meter-in circuit.

• 한국지반신소재학회논문집
• /
• 제21권2호
• /
• pp.57-65
• /
• 2022

본 연구에서는 폭약과 발파공 사이의 충전매질을 통한 충격파 전파 효과를 수치적으로 시뮬레이션하고 검증하였다. 고체(Lagrangian)와 유체(Eulerian)를 혼합 모델링하기 위해 Arbitrary Lagrangian-Eulerian(ALE) 방법을 선택하였다. 시간의존적 해석은 발파공정 시간 동안 수행되었다. 폭약과 매질(공기 또는 물)을 유한 요소망으로 모델링하였고, 발파공은 시작점(폭약)에서 발파공벽에 도달하는 전파 속도와 충격력을 결정할 수 있는 강체로 가정하였다. 해석결과에 따르면 물의 전파속도와 충격력은 공기의 경우보다 컸다. 추가로 발파 작업의 실제 현장을 모델링하고 시뮬레이션하였다. 암석은 탄소성체로 가정하였다. 해석결과에 따르면 충전매질이 물인 경우 순간 충격력이 더 크고, 파쇄블록 크기는 더 작은 것으로 나타났다. 반면 발파공배면에서의 충격량은 물인 경우에 더 작았는데, 이는 파쇄에 충격에너지가 상당부분 사용되고, 파쇄로 인한 감쇠 효과에 의해 주변의 고체를 통한 압력 전파는 공기보다 작아지기 때문이다. 이로써 충전매질로서 물이 공기보다 경제성이 더 높다는 것이 입증되었다.

• 박물관보존과학
• /
• 제31권
• /
• pp.39-54
• /
• 2024

솜포 포장재를 이용해 수작업으로 이루어지는 도자기 포장 기술을 3차원 디지털 기술로의 대체 가능성을 확인해 보고자 하였다. TPU 소재를 이용해 출력한 3D 포장재의 충격 흡수성과 내진동성, 압축 저항성 확인을 위해 복합진동, 포장압축, 포장낙하 시험을 진행하였다. 시험 결과 3D 포장재가 복합진동시험 감쇠비 기준 약 10~20% 증진된 내진동성을 가지고, 약 5배 이상의 압축 저항 성능을 보여주었으며, 6면의 낙하 시험에서 파손되지 않아 충격 흡수 성능도 향상된 것을 확인하였다. 이러한 결과 도자기 포장재의 재사용성을 확보하고 포장 기법을 간소화할 수 있으며, 포장재 및 포장 기술의 다양성을 제시할 수 있을 것으로 판단된다.

• Steel and Composite Structures
• /
• 제35권1호
• /
• pp.77-92
• /
• 2020

The present paper outlined a procedure for geometrically nonlinear dynamic analysis of functionally graded graphene platelets-reinforced (GPLR-FG) nanocomposite cylinder subjected to mechanical shock loading. The governing equation of motion for large deformation problems is derived using meshless local Petrov-Galerkin (MLPG) method based on total lagrangian approach. In the MLPG method, the radial point interpolation technique is employed to construct the shape functions. A micromechanical model based on the Halpin-Tsai model and rule of mixture is used for formulation the nonlinear functionally graded distribution of GPLs in polymer matrix of composites. Energy dissipation in analyses of the structure responding to dynamic loads is considered using the Rayleigh damping. The Newmark-Newton/Raphson method which is an incremental-iterative approach is implemented to solve the nonlinear dynamic equations. The results of the proposed method for homogenous material are compared with the finite element ones. A very good agreement is achieved between the MLPG and FEM with very fine meshing. In addition, the results have demonstrated that the MLPG method is more effective method compared with the FEM for very large deformation problems due to avoiding mesh distortion issues. Finally, the effect of GPLs distribution on strength, stiffness and dynamic characteristics of the cylinder are discussed in details. The obtained results show that the distribution of GPLs changed the mechanical properties, so a classification of different types and volume fraction exponent is established. Indeed by comparing the obtained results, the best compromise of nanocomposite cylinder is determined in terms of mechanical and dynamic properties for different load patterns. All these applications have shown that the present MLPG method is very effective for geometrically nonlinear analyses of GPLR-FG nanocomposite cylinder because of vanishing mesh distortion issue in large deformation problems. In addition, since in proposed method the distributed nodes are used for discretization the problem domain (rather than the meshing), modeling the functionally graded media yields to more accurate results.