In the case of a rear-wheel drive vehicle, a propeller shaft is installed to transmit the driving force of the engine. At this time, the propeller shaft is divided into 2 or 3 pipes, and the bearing is mounted on the vehicle body. And the end of the propeller shaft is connected to the rear differential and connected to the body through the chassis. Due to this complex structure, the propeller shaft must be highly balanced and the mounting angle must be well maintained. However, depending on the driving conditions of the car, various noise and vibration problems occur due to the aging of the parts and the propeller shaft. Hyundai Motor Company's maintenance center uses 'Noise Observer' to resolve various noise and vibration customer complaints. This paper describes the mechanism of vibration problems caused by unbalance of the propeller shaft and the diagnosis process using a 'Noise Observer'.

A comparison and validation between the analysis and vibration test data of a nuclear fuel assembly were conducted. During the comparison and validation process, various parameters that govern the vibration behavior of the fuel assembly were determined, including nuclear fuel rod’s stiffness, spring constants of the dimple and spring of support structures, and damping coefficients. The calibration of the vibration analysis model aimed to find analysis parameters that can accurately simulate the vibration behavior of the test data. For calibration, power spectral density (PSD) diagrams were generated for both the measured signals from the test and the calculated signals from the analysis. The correlation coefficient between these two PSD plots was calculated. To find the analysis parameters, each parameter was defined as a variable with an appropriate range. Latin hypercube sampling was used to generate multiple sample points in the variable space. Analysis was performed for the generated sample points, and PSD plot correlation coefficients were calculated. Using the generated sample points and their corresponding results, a Gaussian Process Regression model was implemented for PSD plot correlation coefficients and the maximum PSD value. Based on the constructed surrogate model, the optimal analysis parameters were easily found without additional computations. Through this method, it was confirmed that the analysis model using the optimal parametes appropriately simulates the vibration behavior of the test.

이 논문에서는 이동하는 질량체의 연직 방향에 대한 관성 효과를 고려하여 보의 진동을 해석할 수 있는 유한요소해석 방법을 제안 한다. 제안하는 방법은 정밀한 상호작용 해석을 요하지 않는 경우에 계산의 효율성을 높이는 방법으로서, 이동하는 질량체의 관성 효 과를 운동방정식에 연계시키고 질량체와 보의 상호작용력은 외부 하중으로만 고려한다. 범용 유한요소해석 소프트웨어인 Abaqus를 이용하여 시간 영역 해석을 수행하고 보의 절점과 이동하는 강체 질량의 절점 변위를 다지점 구속조건으로 연계하여 해석하는 방법 을 제시하였다. 기존 해석적 방법에 의한 해와 비교하여 제안하는 방법을 검증하고 보행하중 모델을 이용한 이동 보행 하중해석에서 보행자의 질량 효과를 살펴보기 위한 간단한 연속 보 모델에 대한 해석 결과를 제시하였다.

최근 회전 회전기계의 건전성 관련 연구가 활발하게 진행중이며, 조선업의 대표적인 회전기계인 갠트리 크레인에도 이를 적용하고자 하는 연구가 활발하게 진행되고 있다. 하지만 조선업의 갠트리 크레인의 경우 상대적으로 낮은 RPM으로 구동되고 잦은 운 전과 정지가 이루어지며 충격, 소음 등의 외부환경 인자가 측정 데이터에 영향을 크게 미쳐 오차를 발생시킬 수 있다. 본 연구에서는 조선업의 내업공정에서 사용되는 갠트리 크레인의 Hoist 모사장비를 제작하여, 운전조건(RPM) 변화와 데이터 획득 센서의 위치 차이가 획득 데이터에 미치는 오차를 통계적으로 분석하였다. 연구결과 상대적으로 낮은 운전조건에서는 센서 위치 차이에 따른 획득 데이터 의 오차는 크게 발생하지 않았으나, 상대적으로 높은 운전조건에서는 획득 데이터의 오차가 크게 발생하는 것으로 확인하였으며, 회전 기계의 데이터 획득 시 운전조건과 획득 센서위치가 획득 데이터에 영향을 미치는 것으로 확인하였다.

진동은 농업용 트랙터 운전자의 쾌적한 작업 환경 조성을 방해하고, 건강을 위협하는 요소이다. 본 연구에서는 국제 표준안(ISO 2631-1)에 따라 트랙터 운전자의 전신 진동을 평가하였다. 진동 시험은 재현성과 반복성이 뛰어난 four-post road simulator 상에서 6가지 노면 조건을 적용하여 수행하였다. 취득한 진동 신호의 파고율, 최대 진동 진폭, 피폭 진동 누적량, 실효치 등을 이용하여 진동 특성을 분석하였다. 최종적으로 건강 지도 위험 수준과 안락도에 대한 반응도를 평가 방법에 따른 실효치와 피폭 진동 누적량에 적용하여 농업용 트랙터의 운전자 전신 진동을 정량적으로 평가하였다.

Among the various causes of the vibration problem of the radial sluice gate used in Saemangeum, the effect of flow-induced vibration was studied by the method of computational fluid analysis. In this study, the effect on the flow-induced vibration of the Saemangeum radial sluice gate was evaluated by 2D unsteady flow numerical analysis using ANSYS Fluent. Gate opening cases of 0.2m, 0.3m, 0.4m, 0.5m, and 1.0m were analyzed. As a result, the flow-induced vibration characteristics due to the instability of turbulent flow were observed through FFT analysis. As the gate opening increases, the frequency of the maximum amplitude moves gradually to a lower frequency region with the reduction of the magnitude. Therefore the flow-induced vibration effects can be considered as small with the gate opening increase.

Many piping systems installed in the power plant are directly related to the safety and operation of the plant. Various dampers have been applied to the piping system to reduce the damage caused by earthquakes. In order to reduce the vibration of the piping system, this study developed a steel coil damper (SCD) with a straightforward structure but excellent damping performance. SCD reduces the vibration of the objective structure by hysteretic damping. The new SCD damper can be applied to high-temperature environments since it consists of steel members. The paper introduces a design method for the elastoplastic coil spring, which is the critical element of SCD. The practical applicability of the design procedure was validated by comparing the nonlinear force-displacement curves calculated by design equations with the results obtained from nonlinear finite element analysis and repeated loading test. It was found that the designed SCD’s have a damping ratio higher than 25%. In addition, this study performed a set of seismic tests using a shaking table with an existing piping system to verify the vibration control capacity on the piping system by SCD. Test results prove that the SCD can effectively control the displacement vibration of the piping system up to 80%.

최근 유기농산물에 대한 선호가 증가하고 있다. 유기농산물 생산에 있어 물리적 제초는 필수적이다. 하지만, 국내 밭 제초작업 기계화율은 60% 미만으로 낮으며, 농촌 인구의 고령화·여성화로 소형 제초기의 개발이 필요하다. 또한, 제초기의 경우 사용자가 반복적 진동에 노출되기 때문에 이를 절감할 수 있는 노력이 필요하나, 이에 대한 연구는 미흡한 실정이다. 따라서, 본 연구에서는 여성·고령 농업인도 사용하기 편리한 전동 배부식 중경제초기를 개발하는 데 있어 수평 회전식 원판에 부착된 제초날의 형상(원형, 삼각형, 일자형) 및 폭(15, 20, 25mm)에 따른 제초성능 및 ISO5349-1에 따라 손에 전달되는 진동을 분석하였다. 제초율은 원형 제초날에서 90.4~96.4%로 가장 높게 나타났으며, 진동 또한 원형 제초날을 사용하였을 때 사용자의 10%가 수지백증이 발병하는데 걸리는 시간이 20년 내외로 삼각형 및 일자형 제초날을 사용했을 때 보다 200% 가량 증가하는 것으로 나타났다. 따라서, 원형 제초날을 사용하였을 때 진동을 감소시킬 수 있으며, 불필요한 반력을 줄여 높은 제초효과를 볼 수 있을 것으로 판단된다.

A theoretical model has been studied to describe the sound radiation analysis for structure vibration noise of tire under the action of random moving line forces. When a tire is analyzed, it had been modeled as curved beams with distributed springs and dashpots that represent the radial, tangential stiffness and damping of tire, respectively. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y=0 and to be axially infinite. The curved beam material and elastic foundation are assumed to be lossless Bernoulli-Euler beam theory including a tension force(T), damping coefficient (C) and stiffness of foundation(κ2) will be employed. The expression for sound power is integrated numerically and the results examined as a function of Mach number(M), wave-number ratio(γ) and stiffness factor(ψ). The experimental investigation for structure vibration noise of vehicle tire under the action of random moving line forces has been made. Based on the STSF(Spatial Transformation of Sound Field) techniques, the sound power and sound radiation are measured. Results strongly suggest that operation condition in the tire material properties and design factors of the tire govern the sound power and sound radiation characteristics.

선박 및 해양구조물과 같은 대형 유한요소모델의 진동 특성을 평가하기 위해 고유치 해석 및 가진 주파수에 따른 응답 계산을 필수적으로 수행해야 한다. 하지만 이러한 해석들은 과도한 전산 장비와 계산 시간이 요구되어 고성능 해석 프로그램의 개발이 필요하다. 특히 선형연립방정식에서 발생하는 역행렬 계산 및 고유치 해석 시에는 상당한 전산 해석 시간이 발생하기 때문에 최신 고성능 라이브러리를 적용함으로써 이를 개선할 수 있다. 본 연구에서는 병렬식 선형연립방정식 계산 라이브러리인 PARDISO와 고성능 고유치 해석 라이 브러리인 ARPACK을 적용하여 빠르고 정확한 해석이 가능한 진동해석 프로그램을 개발하였다. 끝으로 개발된 해석 프로그램의 정확도와 효율성을 검증하기 위해 여러 선박해양공학 수치 예제를 사용하였고, 상용 유한요소 프로그램인 ABAQUS와의 결과 비교 검토를 통해 개발된 진동해석 프로그램의 신뢰성을 검증, 제시하였다.

A new lighting support structure composing of two-way wires and pulley, a pulley-type wireway system, was developed to improve the seismic performance of a ceiling type lighting equipment. This study verifies the seismic performance of the pulley-type wireway system using a numerical approach. A theoretical model fitted to the physical features of the newly-developed system was proposed, and it was utilized to compute a frictional coefficient between the wire and pulley sections under tension forces. The frictional coefficient was implemented to a finite element model representing the pulley-type wireway system. Using the numerical model, the seismic responses of the pulley-type wireway system were compared to those of the existing lighting support structure, a one-way wire system. The addition of the pulley component resulted in the increasement of energy absorption capacity as well as friction effect and showed in significant reduction in maximum displacement and oscillation after the peak responses. Thus, the newly-developed wireway system can minimize earthquake-induced vibration and damage on electric equipment.

In this study, the structural stability of an align unit was studied to investigate the deformation and vibration characteristics of the upper and lower modules of the align unit during LCD panel transfer. The align unit consists of upper module and lower module. SolidWorks Simulation was used to analyze the structure, fatigue, and modes, to understand the deformation and vibration of the stiffness of the align unit. Because of the upper eccentric structure of the align unit, the main strain was large at the contact of the upper and lower modules and at the bottom of the support, and more pronounced at it’s front. The stress was large in the front support of the upper and lower modules, and the displacement was observed in the front of the upper module. The minimum life cycle that indicates the structural integrity of the align unit has exceeded its usable number. Also, the increase in natural frequency of the align unit gradually slowed down, as the vibration mode increased.

The study conducted finite element analysis in advance to understand the natural frequency, con-ducted static structural analysis and analyzed stress behavior occurring on the boundary of wheel and rail when passing the straight line and curve line. According to the FEA, the wheel had natural frequency of 1st mode 238.4Hz to 10th mode 1,320Hz, and the rail had natural frequency of 457.4Hz to 619.7Hz. When looking at the correlated frequency range, the natural frequency of 4th~6th mode of wheel and 3rd~9th mode of rail track were correlated. As for the result of stress behavior translation occurring on the boundary of wheel and track, it was 53.4MPa when passing the curve line, which was 16MPa higher than when passing the straight line.