• 한국소음진동공학회논문집
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• 제16권6호
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• pp.602-608
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• 2006

In order to evaluate performance of anti-vibration gloves, it is necessary to measure the transmitted vibration to the hand and the applied forces at the same time while gripping the vibrating handle. In the study a system was developed to measure both the vibration and the forces. The system consists of a measurement handle with eight strain gauges and two accelerometers and a PC-based system with a software for signal processing and evaluation of the hand-transmitted vibration and for control of applied forces in the pre-determined range. The handle was installed on the vibration shaker which is strong enough so as not to be affected by dynamic coupling with the hand-arm system. Whole procedure of ISO 10819 to determine the vibration transmissibility of anti-vibration gloves was programmed into the system. As an example of the application, three subjects joined the test to get vibration transmissibilities of anti-vibration gloves where each glove was tested twice a subject. Average and standard deviation of vibration transmissibility were also calculated.

• Structural Engineering and Mechanics
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• 제53권3호
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• pp.537-573
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• 2015

Multiple-step beams carrying intermediate lumped masses with/without rotary inertias are widely used in engineering applications, but in the literature for free vibration analysis of such structural systems; Bernoulli-Euler Beam Theory (BEBT) without axial force effect is used. The literature regarding the free vibration analysis of Bernoulli-Euler single-span beams carrying a number of spring-mass systems, Bernoulli-Euler multiple-step and multi-span beams carrying multiple spring-mass systems and multiple point masses are plenty, but that of Timoshenko multiple-step beams carrying intermediate lumped masses and/or rotary inertias with axial force effect is fewer. The purpose of this paper is to utilize Numerical Assembly Technique (NAT) and Differential Transform Method (DTM) to determine the exact natural frequencies and mode shapes of the axial-loaded Timoshenko multiple-step beam carrying a number of intermediate lumped masses and/or rotary inertias. The model allows analyzing the influence of the shear and axial force effects, intermediate lumped masses and rotary inertias on the free vibration analysis of the multiple-step beams by using Timoshenko Beam Theory (TBT). At first, the coefficient matrices for the intermediate lumped mass with rotary inertia, the step change in cross-section, left-end support and right-end support of the multiple-step Timoshenko beam are derived from the analytical solution. After the derivation of the coefficient matrices, NAT is used to establish the overall coefficient matrix for the whole vibrating system. Finally, equating the overall coefficient matrix to zero one determines the natural frequencies of the vibrating system and substituting the corresponding values of integration constants into the related eigenfunctions one determines the associated mode shapes. After the analytical solution, an efficient and easy mathematical technique called DTM is used to solve the differential equations of the motion. The calculated natural frequencies of Timoshenko multiple-step beam carrying intermediate lumped masses and/or rotary inertias for the different values of axial force are given in tables. The first five mode shapes are presented in graphs. The effects of axial force, intermediate lumped masses and rotary inertias on the free vibration analysis of Timoshenko multiple-step beam are investigated.

• Smart Structures and Systems
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• 제23권6호
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• pp.565-577
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• 2019

One of the most effective countermeasures for mitigating cable vibration is to install mechanical dampers near the anchorage of the cable. Most of the dampers used in the field are so-called passive dampers where their parameters cannot be changed once designed. The parameters of passive dampers are usually determined based on the optimal damper force obtained from the universal design curve for linear dampers, which will provide a maximum additional damping for the cable. As the optimal damper force is chosen based on a predetermined principal vibration mode, passive dampers will be most effective if cable undergoes single-mode vibration where the vibration mode is the same as the principal mode used in the design. However, in the actual engineering practice, multi-mode vibrations are often observed for cables. Therefore, it is desirable to have dampers that can suppress different modes of cable vibrations simultaneously. In this paper, MR dampers are proposed for controlling multi-mode cable vibrations, because of its ability to change parameters and its adaptability of active control without inquiring large power resources. Although the highly nonlinear feature of the MR material leads to a relatively complex representation of its mathematical model, effective control strategies can still be derived for suppressing multi-mode cable vibrations based on nonlinear modelling, as proposed in this paper. Firstly, the nonlinear Bouc-wen model is employed to accurately portray the salient characteristics of the MR damper. Then, the desired optimal damper force is determined from the universal design curve of friction dampers. Finally, the input voltage (current) of MR damper corresponding to the desired optimal damper force is calculated from the nonlinear Bouc-wen model of the damper using a piecewise linear interpolation scheme. Numerical simulations are carried out to validate the effectiveness of the proposed control algorithm for mitigating multi-mode cable vibrations induced by different external excitations.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.265-268
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• 2004

Impact sounds, such as those created by footsteps, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. Running and jumping impact sound by child are one of the most irritating noises in an apartment buildings. It's necessary to know that the impact force characteristics of real impact source in an apartment buildings. This study aims to investigate the impact force characteristics and impact force time of running and jumping by child. This study cud out investigation through the 155 children in school. The results of this study is that jumping impact force is greater than running impact force but impact force time is lower than that.

• 전산구조공학
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• 제3권4호
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• pp.123-132
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• 1990

일반적으로 구조물의 내진설계에 있어서는 등가정적해석법이 주로 사용되고 있다. 현재 사용되고 있는 등가정적해석법은 구조물의 거동이 주로 기본진동 모드에 의해 지배된다는 가정하에 유도되었으므로 기본진동 주기가 긴 구조물에 대해서는 구조물의 동적특성을 정확하게 예측하기가 어렵다. 본 연구에서는 구조물의 설계시 직접적인 영향을 미치게 되는 층전단력의 분포를 주요 관점으로하여 구조물의 동적특성에 미치는 고차모드의 영향을 정확히 고려할 수 있는 층지진하중에 대하여 연구했다. 층지진하중의 분포를 개선하기 위해 현행 내진설계 기준의 등가정적해석법에서 쓰이는 층지진하중과 모드해석을 이용하여 얻은 층지진하중의 차이를 파악하고 이로부터 고차모드의 영향이 고려된 층지진하중의 분포를 제안했다.

• 전기학회논문지
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• 제62권11호
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• pp.1535-1540
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• 2013

In this paper, the Radial Magnetic Force(RMF) and cogging torque which cause vibration and noise in IPM type BLDC motor were analyzed. The cogging torque and RMF cause electromagnetic vibration. So, a notch was installed for the equilibrium of RMF and cogging torque reduction. The notch was analyzed by using a Fourier Series for the energy distribution of the air-gap. The equilibrium of RMF and the reduction of cogging torque were performed by a Design Of Experiment(DOE) with the notch. Also, operating characteristics and efficiency were analyzed and compared.

• 한국기계가공학회지
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• 제14권6호
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• pp.27-34
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• 2015

Dynamic vibration absorbers are widely used in machinery, buildings, and structures, including bridges. Two cases of their usage are considered in this paper. One is a simply supported beam subjected to either a moving force or a sequence of moving forces, which simulates a train-bridge interaction problem. The other is a case where a primary system is mounted on a base that is not grounded and is excited by an external force. The conditions that the dynamic vibration absorbers must meet in these cases are found and compared to those for usual cases where bases of primary systems are grounded.

• 한국소음진동공학회논문집
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• 제14권1호
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• pp.24-31
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• 2004

Recently, as the marine compressor power is increased, vibration problems on the marine vessel with V/W type reciprocating compressor have been occurred. A research on the balancing of marine V/W type reciprocating compressor has hardly been reported though a number of researches on the balancing of rotating machinery have been conducted. As a V/W type compressor has high capacity with long stroke, compact size and high center of gravity, It is easy to have a vibration problem by a little bit unbalanced force and moment. In this study, calculation methods for balance weight of the V/W type reciprocating compressors, which have different piston weight and asymmetry structure, are formulated. And their reliability were verified by comparing calculated balance weight with the experimental results of the real marine V/W type reciprocating compressors.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.879_880
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• 2009

this paper studies the influence of permanent magnet on the vibration of synchronous motor two PM motors with NdFeB and Ferrite magents which have same Back-EMF and output power have been desined. First, the dynamic simulation is performed with these two motors' parameters. The current waveforms can be evaluated. And then based on the equivalent magnetization current principle, the magnetic force density and force including the tangential and radial direction components can be calculated. According to the relationship between the vibration and radial force, the vibration of these two motors can be predicted. This result will give meaningful advice to the motor design.

• 한국소음진동공학회논문집
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• 제16권12호
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• pp.1244-1251
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• 2006

The objective of this paper is to get excitation forces of the engine at each of the brackets for the prediction of the vehicle interior noise by the powertrain. A powertrain geometry model is produced by CATIA and its FE model is made by MSC/Patran. A vibration mode analysis and a running mode analysis are experimentally implemented. After getting a satisfied MAC value by doing a correlation about a measured mode analysis value and analyzed value through MSC/Nastran software, all components are assembled through MSC/ADAMS software which is a dynamic analysis tool. We can predict the vibration of brackets which is the last points to occur the force of the engine combustion by analyzing the combustion force produced by engine mechanism.