• 소음진동
• /
• 제11권1호
• /
• pp.118-124
• /
• 2001

The effect of a concentrated mass on the regions of dynamic instability of an axially oscillating cantilever beam is investigated in this paper. The equations of motion are derived using Kane's method and the assumed mode method. It is found that the bending stiffness is harmonically varied by axial inertia forces due to oscillating motion. Under the certain conditions between oscillating frequency and the natural frequencies, dynamic instability may occur and the magnitude of the bending vibration increase without bound. By using the multiple time scales method, the regions of dynamic instability are obtained. The regions of dynamic instability are found to be depend on the magnitude of a concentrated mass or its location.

• 한국소음진동공학회논문집
• /
• 제21권3호
• /
• pp.264-270
• /
• 2011

This paper deals with dynamic response of a beam structure with discrete spring-damper supports under a moving mass. Governing equations of motion taking into account of all inertia effects of the moving mass were derived by Galerkin's mode summation method, and Runge-Kutta integration method was applied to solve the differential equations. The effects of the speed of the moving mass, spring stiffness, damping coefficient, span number of a beam structure, mass ratio of the moving mass on the dynamic response of the beam structure have been studied. Some numerical results provide design engineers for the beam structure design with discrete supports under a moving mass.

• 한국소음진동공학회논문집
• /
• 제21권3호
• /
• pp.271-279
• /
• 2011

In this study, the dynamic analysis of a beam is analyzed by using the finite element method when the beam has moving mass and axial load. To consider the contact force between the moving mass and beam, coupled nonlinear equations of contact dynamics are derived, and then the weak form for the finite element method is established. The finite element computer programs based on the Lagrange multiplier method are developed to compute the contact force. Furthermore, a variety of simulations are performed for various design parameters such as moving mass velocity, compressive axial load and tension load. Finally, relations between the dynamic response and contact force are also discussed.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.868-873
• /
• 2003

This paper deals with the linear dynamic response of an elastically restrained beam under a moving mass, where the elastic support was modelled by translational springs of variable stiffness. Governing equations of motion taking into account of all inertia effects of the moving mass were derived by Galerkin's mode summation method, and Runge-Kutta integration method was applied to solve the differential equations. The effects of the speed, the magnitude of the moving mass, stiffness and the position of the support springs on the response of the beam have been studied. A variety of numerical results allows us to draw important conclusions for structural design purposes.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 추계학술대회 논문집
• /
• pp.127-131
• /
• 2000

The paper presents both theoretical and experimental study for dynamic instabilities of a vertical cantilevered pipe with two attached lumped masses conveying fluid. The two attached lumped masses can be considered as valves or some mechanical parts in real pipe system. Eigenvalue behaviors depending on the flow velocity are investigated for the change of positions and magnitudes of an attached lumped mass and a tip mass. In order to verify appropriaty of numerical solutions, experiments were accomplished. Theoretical predictions have a good agreement with experimental ones.

• 한국정밀공학회지
• /
• 제12권8호
• /
• pp.5-18
• /
• 1995

공작기계의 정밀도는 정적, 동족 그리고 열적 특성에 좌우된다는 사실은 4장 Fig. 4-3의 예를 들어 충분히 설명한 바 있다. 4장에서는 주로 정적특성(Static behavior)에 대해서 설명한 바 있으나 이번에는 동적특성에 대해서 논술하고자 한다. 진동문제의 해소는 가공기술의 향상, 공작기계의 진보에 절대적으로 중요한 과제이다. 절삭, 연삭 및 미세가공에서 진동이 발생하여 가공을 계속할 수 없게 되거나 가공을 했다해도 가공표면에 Chatter mark를 남기게 되어 요구 품질을 만족할 수 없는 경우가 있다. 공작기계는 많은 부품을 조립하여 만든 것이기 때문에 동적현상은 다질량(Mult-mass)으로 고려해서 진동을 생각해야 겠지만 대부준의 경우 단위 질량(Single-mass) 으로 생각하여 Fig. 5-1과 같이 그 진동이론을 종합하고 있다.

• 한국정밀공학회지
• /
• 제8권4호
• /
• pp.107-117
• /
• 1991

The dynamic stability problem of nonconservative system is one of the important problems. In this study, flexible missile with mass variation is regarded as a free Timoshenko beam subjected to a controlled follower force. The stability was studied numerically through the finite element method. Through the study, the obtained results are as follows: [1] Without force direction control (1) In the case of no mass reduction, the existence of concentrated mass increases critical follower force. (2) Mass reduction rate of the beam slightly effects on the change of critical follower force. [2] With force direction control (1) Shear deformation parameter S contributes insignificantly to the force at instability when $S{\geq}10^4$. (2) With mass variation, increase of concentrated mass increases critical follower force at instbility. (3) The type of promary instability is determined by the sensor location.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 춘계학술대회논문집
• /
• pp.320-325
• /
• 2004

The paper deals with the dynamic response of a cantilevered beam under a travelling mass with constant acceleration. Governing equations of motion taking into account all inertia effects of the travelling mass are derived by Galerkin's mode summation method, and Runge-Kutta integration method is applied to solve the differential equations. The effects of the speed, acceleration and the magnitude of the travelling mass on the response of the beam are fully investigated. A variety of numerical results allows us to draw important conclusions for structural design purposes.

• 소음진동
• /
• 제10권6호
• /
• pp.1017-1021
• /
• 2000

This paper addresses experimental results carried out to investigate the characteristics of dynamic mass for Korean. Vertical seat vibration in the frequency range of 0.5-30 Hz was applied to a seated Korean male subject. To examine the intra-variable effects on dynamic mass, five different postures and three different vibration excitation levels were considered. The applied acceleration and transmitted force to the hip of the seated subject were measured simultaneously. Detailed experimental results of measured dynamic mass are illustrated for each posture and/or vibration excitation level. Maximum peaks of around 5 Hz were observed for most experimental cases. They are found to allow the identification of dynamic characteristics of Korean seated body for various real vibration environments. Furthermore, they are expected to be very useful in designing new seats for automotive and railway vehicles and in improving their vibration ride duality.

• 한국정밀공학회지
• /
• 제22권10호
• /
• pp.65-71
• /
• 2005

This paper presents the dynamic stability of a cantilevered Timoshenko beam on partial elastic foundations subjected to a follower force. The beam with a tip concentrated mass is assumed to be a Timoshenko beam taking into account its rotary inertia and shear deformation. Governing equations are derived by extended Hamilton's principle, and finite element method is applied to solve the discretized equation. Critical follower force depending on the attachment ratios of partial elastic foundations, rotary inertia of the beam and magnitude and rotary inertia of the tip mass is fully investigated.