Free vibration analysis of beams with non-ideal clamped boundary conditions

이진희 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.2

A non-ideal boundary condition is modeled as a linear combination of the ideal simply supported and the ideal clamped boundary conditions with the weighting factors k and 1-k, respectively. The proposed non-ideal boundary model is applied to the free vibration analyses of Euler-Bernoulli beam and Timoshenko beam. The free vibration analysis of the Euler-Bernoulli beam is carried out analyti-cally, and the pseudospectral method is employed to accommodate the non-ideal boundary conditions in the analysis of the free vibration of Timoshenko beam. For the free vibration with the non-ideal boundary condition at one end and the free boundary condition at the other end, the natural frequencies of the beam decrease as k increases. The free vibration where both the ends of a beam are restrained by the non-ideal boundary conditions is also considered. It is found that when the non-ideal boundary conditions are close to the ideal clamped boundary conditions the natural frequencies are reduced noticeably as k increases. When the non-ideal boundary conditions are close to the ideal simply supported boundary conditions, however, the natural frequencies hardly change as k varies, which indicate that the proposed boundary condition model is more suitable to the non-ideal boundary condition close to the ideal clamped boundary condition.

Characteristics of Vibration Condition Indicator with Gear Tooth Damage

이동형(Dong-Hyung Lee),이웅용(Woong-Yong Lee),문경호(Kyung-Ho Moon) Korean Society for Precision Engineering 2015 한국정밀공학회지 Vol.32 No.7

In the development of a vibration-based condition monitoring system in gearbox, one of the most important research topics is a quantitative analysis and test of the effect of gear damage on vibration of gearbox. This paper presents the evaluation result of vibration condition indicator according to the gear tooth damage through the vibration test of gearbox. The dynamic load test was performed with high speed railway (KTX)’s gearbox. The vibration of gearbox was measured according to a rotational speed change with the common gear fault modes, such as pitting and tooth breakage. The characteristics and the possibility of applying of vibration condition indicator on condition monitoring system were analyzed. As a result, the value of most condition indicator is gradually increased with the severity of gear faults. The NA6 indicator shows a low variation with the rotational speed change and high sensitivity in accordance with the gear fault.

Vibration analysis of laminated plates with various boundary conditions using extended Kantorovich method

Pairod Singhatanadgid,Thanawut Wetchayanon 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.1

In this study, an extended Kantorovich method, employing multi-term displacement functions, is applied to analyze the vibration problem of symmetrically laminated plates with arbitrary boundary conditions. The vibration behaviors of laminated plates are determined based on the variational principle of total energy minimization and the iterative Kantorovich method. The out-of-plane displacement is represented in the form of a series of a sum of products of functions in x and y directions. With a known function in the x or y directions, the formulation for the variation of total potential energy is transformed to a set of governing equations and a set of boundary conditions. The equations and boundary conditions are then numerically solved for the natural frequency and vibration mode shape. The solutions are verified with available solutions from the literature and solutions from the Ritz and finite element analysis. In most cases, the natural frequencies compare very well with the reference solutions. The vibration mode shapes are also very well modeled using the multi-term assumed displacement function in the terms of a power series. With the method used in this study, it is possible to solve the angle-ply plate problem, where the Kantorovich method with single-term displacement function is ineffective.

Development of Condition Monitoring System for Reduction Unit of High-speed Rail

Dong-Hyong Lee(이동형),Seok Jin Kwon(권석진),Byoung-Su Park(박병수),Duk-Young Cho(조덕영),Jin-Woo Kim(김진우) Korean Society for Precision Engineering 2013 한국정밀공학회지 Vol.30 No.7

This paper presents the development of a condition monitoring system that monitors the operating conditions of a reduction unit, such as the bearing temperature, gearbox vibration, and gear oil deterioration, and notifies the operator of potential problems or abnormal conditions. A series of field tests on high-speed rail and conventional lines was performed to identify the characteristics of temperature rise and vibration levels on the reduction unit during operation. The monitoring system was designed based on the proper sensor selection, measurement method, and signal analysis to optimize the interface with the operating system of high-speed trains. Application of this monitoring system to high-speed trains will play an important role in their proper maintenance and safe operation.

Vibration analysis of laminated plates with various boundary conditions using extended Kantorovich method

Singhatanadgid, Pairod,Wetchayanon, Thanawut Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.1

In this study, an extended Kantorovich method, employing multi-term displacement functions, is applied to analyze the vibration problem of symmetrically laminated plates with arbitrary boundary conditions. The vibration behaviors of laminated plates are determined based on the variational principle of total energy minimization and the iterative Kantorovich method. The out-of-plane displacement is represented in the form of a series of a sum of products of functions in x and y directions. With a known function in the x or y directions, the formulation for the variation of total potential energy is transformed to a set of governing equations and a set of boundary conditions. The equations and boundary conditions are then numerically solved for the natural frequency and vibration mode shape. The solutions are verified with available solutions from the literature and solutions from the Ritz and finite element analysis. In most cases, the natural frequencies compare very well with the reference solutions. The vibration mode shapes are also very well modeled using the multi-term assumed displacement function in the terms of a power series. With the method used in this study, it is possible to solve the angle-ply plate problem, where the Kantorovich method with single-term displacement function is ineffective.

Characteristics of Piezoceramics Sensors for Vibration Detection

Tan, A.C.C.,Dunbabin, M. The Korean Society of Marine Engineering 2004 한국마린엔지니어링학회지 Vol.28 No.2

Early detection of an internal malfunction of machinery plays a very important part in all condition monitoring programs. Sensors to detect amplitude. velocity and acceleration are widely used in vibration detection and control. Piezoceramic materials are largely used in sensors and actuators for vibration monitoring and control due to their relatively large output from an induced strain and their arguable self powering characteristics. In this paper a cheap and yet reliable sensors/actuators were developed to detect vibration. The results show that low cost PZT can be designed for optimum detection of bearing vibration. This paper presents the experimental results of a number of piezoceramics characteristics in terms of resonant frequencies and variation of PZT constants with temperature.

Vibration characteristics of caisson breakwater for various waves, sea levels, and foundations

So-Young Lee,Thanh-Canh Huynh,Ngoc-Loi Dang,Jeong-Tae Kim 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.24 No.4

In this study, vibration characteristics of a gravity-based caisson-foundation breakwater system are investigated for ambient and geometric parameters such as various waves, sea levels, and foundation conditions. To achieve the objective, following approaches are implemented. Firstly, operational modal analysis methods are selected to identify vibration modes from output-only dynamic responses. Secondly, a finite element model of an existing caisson-foundation breakwater system is established by using a structural analysis program, ANSYS. Thirdly, forced vibration analyses are performed on the caisson-foundation system for two types of external forces such as controlled impacts and wave-induced dynamic pressures. For the ideal impact, the wave force is converted to a triangular impulse function. For the wave flow, the wave pressure acting on the system is obtained from wave field analysis. Fourthly, vibration modes of the caisson-foundation system are identified from the forced vibration responses by combined use of the operational modal analysis methods. Finally, vibration characteristics of the caisson-foundation system are investigated under various waves, sea levels, and foundations. Relative effects of foundation conditions on vibration characteristics are distinguished from that induced by waves and sea levels.

볼 베어링의 마멸 상태에 따른 진동 특성의 변화

조상경(SangKyung Cho),박정우(JoungWoo Park),조연상(YonSang Cho) 한국트라이볼로지학회 2017 한국윤활학회지(윤활학회지) Vol.33 No.4

The vibration data of bearings are very useful for monitoring and determining the condition of the bearings. The defect frequencies of ball bearings have been used for monitoring there condition. However, it is not easy to verify the defect frequencies as the wear progress. Therefore there is a need for an easy method to monitor the damages of bearings in real-time and to observe the variations in vibration characteristics as the wear progress. In this study, a bearing test equipment is constructed to diagnose the damage of bearings. The friction coefficient and vibration data are measured by using a torque sensor and an acceleration sensor, and the correlation between the measured data is analyzed to diagnose the condition of the bearing. We reached the following conclusions from the results. When the ball surface, inner and outer rings of a ball bearing are damaged, the friction coefficient increases to over 0.02 with an adhesion on the surface. Moreover this damage occurs more quickly with an increase in the number of revolutions. In the vibration characteristics, the amplitude of vibration wave appears high with an increase in the friction coefficient. In the high frequency range between 1000 and 2000 Hz, a wide range of frequency components with high amplitude occurs continuously irrespective of the number of revolutions.

Investigation of Vibration Damping Characteristics of Automotive Air Conditioning Pipeline Systems

한성렬,조진래 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.2

The pipeline system that is composed of fiber reinforced rubber hoses is subject to various severe dynamic excitations once an air conditioning system is mounted on vehicle, and the prolonged exposure of air conditioner to the severe vibration environments may cause micro cracks and leakage of rubber hoses. Therefore, rubber hoses are desired to have high damping performance to suppress the excessive structural vibration. Meanwhile, the fixing bracket is usually manufactured with aluminum to reduce the total weight, but it is also desired to be replaced with other material for the sake of production cost down. In this context, the natural frequencies, frequency responses and the vibration acceleration levels (VALs) of the pipeline system are analyzed by the finite element analysis and the vibration experiment was performed. As well, the vibration damping characteristics of the five-layered reinforced rubber hoses of automotive air conditioner are parametrically investigated with respect to the rubber hose hardness and the material type of fixing bracket. It is found that the soft rubber hoses provide the best damping performance, which is also verified through the actual vibration experiment. In addition, the possibility of changing the bracket material to reduce the production cost is also confirmed.

안테나 야외 구동 시 풍력에 의한 진동 응답 저감 방법론

이창균(Chang-Kyun Lee),이은호(EunHo Lee),이상정(SangJeong Lee),김상현(Sang-Hyun Kim),전종익(Jong-Ik Jeon),박노철(No-Cheol Park) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11

In vehicles with antenna, since the antenna is used for communication with satellites, it is important to have vibration characteristics that do not affect the communication quality due to vibration. The antenna mounted on the vehicle should be able to be used outdoors, but in the outdoors, various environmental variables cause deterioration of communication quality. The purpose of this study is to reduce the vibration of the antenna to enable the vehicle equipped with the satellite antenna to communicate smoothly under the wind conditions that have a major influence on the antenna communication quality when used outdoors. Artificial wind experiments were conducted for this study, and the Ansys FEM Model was used to select the frequency bands affecting the communication quality and to investigate the design optimization method using peak response frequency avoidance and response amplitude reduction. As a result, we can achieve method for vibration reduction and avoidance. Based on this research, it is expected to be used in the design of vibration reduction by artificial wind as it is reflected in the design process of the antenna mounted on the vehicle.