• 한국소음진동공학회논문집
• /
• 제17권10호
• /
• pp.946-949
• /
• 2007

This paper discusses the lateral vibration of a beam with boundary condition of one end fixed and the other end free. The uniform beam has a solution by summation of some simple exponential functions. But if its shape is not uniform, its solution could be by Bessel's function or mathematical solution could not exist. Even if the solution of Bessel's function exists, as Bessel function is a series function, we must get the solution by numerical method. Author had proposed the solution of the matrix method by Ritz's method and a new mode shape function, and had earned the good results for a wedge beam. Hereby a vibration analysis for the tapered beam with circle cross section was executed, and so good results were showed.

• Composites Research
• /
• 제14권3호
• /
• pp.69-76
• /
• 2001

본 연구에서는 고무의 동탄성계수와 손실계수에 대한 주파수 의존성을 평가하기 위한 새로운 양팔 샌드위치보 시험법을 제안하였다. 고무층이 삽입되어 접착된 양팔샌드위치보 시험편의 횡진동 거동에 대해 유한요소 모달변형률 에너지법을 조합한 사인스위프 시험을 이용하여 분석하고 동적 점 탄성해석시험 및 단순공진시험 결과와 비교 검토하였다. 양팔 샌드위치보의 횡진동 모드에 따라 고무층의 주파수별 동탄성계수와 재료감쇠계수를 측정하고, 이들을 최소자승오차법에 의거하여 주파수의 이차함수로 회귀시켜 평가할 수 있었다.

• 전산구조공학
• /
• 제15권2호
• /
• pp.67-72
• /
• 2002

• 기계저널
• /
• 제25권5호
• /
• pp.406-412
• /
• 1985

연소 동안에 크랭크 축은 오일 필름을 통하여 연소압력이 실린더 블록으로 전달된다. 점화 전에 관성력에 의한 크랭크 축의 굽힘 변형은 크랭크 축으로부터 메인 베어링까지의 연소하중 전달에 큰 영향을 미친다. 메인 베어링에 베어링 보를 부착시키거나 크랭크 축의 굽힘 강성을 변화시켜 실린더 블록의 스커어트 진동을 감소시키는 효과를 얻었다. 크랭크 축의 비틂 진 동을 일으키는 회전력과 관성력 변동의 합력은 크랭크 저어널의 횡진동을 일으킨다. 크랭크 축의 횡 강제진동은 베어링 1에서 최대값이기 때문에 실린더 블록의 굽힘, 비듦 진동에 대하여 기진력이 된다. 실린더 블록의 진동 진폭은 관성력 변동의 주파수가 실린더 블록의 공진진 동수에 가까워지는 정도와 크랭크 축 비듦 진동의 진폭에 의존한다. 크랭크 풀리의 극관성 모우멘트와 크랭크 축 비듦 진동을 감소시키는데 효과를 준다.

• 대한기계학회논문집A
• /
• 제26권2호
• /
• pp.225-233
• /
• 2002

The flexural vibration characteristics of a sandwich beam system with a partially inserted viscoelastic layer have been quantitatively studied using a finite element analysis in combination with a sine-sweep test. Antisymmetric mode shapes of the flexural vibration were visualized by the holographic interferometry and agreed with those calculated by the finite element simulation. Effects of the beam thickness as well as the length and thickness of partial viscoelastic layers on the system loss factor(η$\_$s/) and resonant frequency($\omega$$\_$r/) were significantly large fur the symmetric and antisymmetric modes of the beam system.

• 한국기계가공학회지
• /
• 제10권4호
• /
• pp.8-15
• /
• 2011

In this paper, the influence of a crack on the natural frequency of cracked cantilever L-shaped beam with coupled bending and torsional vibrations by analytically and experimentally is analyzed. The L-shaped beam with a crack is modeled by Hamilton's principle with consideration of bending and torsional energy. The two coupled governing differential equations are reduced to one sixth-order ordinary differential equation in terms of the flexural displacement. The crack is assumed to be in the first, second and third mode of fracture and to be always opened during the vibrations. The theoretical results are validated by a comparison with experimental measurements. The maximal difference between the theoretical results and experimental measurements of the natural frequency is less than 7.5% in the second vibration mode.

• 한국정밀공학회지
• /
• 제28권8호
• /
• pp.959-965
• /
• 2011

This paper presents the dynamic modeling and vibration suppression methods for axially deploying beams subjected to gravity. A modal modeling method is employed to develop the lateral vibration model for axially deploying beams. Simulation is made to validate the proposed model as well as to investigate the dynamics of axially deploying beams. This paper rigorously investigates the gravity effect as a source of vibration for axially deploying beams. In order to suppress lateral vibration for deploying beams, the moving speed command is modified by using the input shaping method, Experiments are also performed to prove the proposed vibration suppression method. The simulations and experiments show that the proposed modeling and input shaping methods are effective for the dynamic analysis and vibration suppression of axially deploying beams subjected to gravity.

• 한국소음진동공학회논문집
• /
• 제12권5호
• /
• pp.330-337
• /
• 2002

A frequency equation of beam subjected to the axial load and having ηthrough-the-width-splits is developed. The beam comprises of beam elements that are split into the upper and the lower part, and non-split beam elements. Equations of motion of each beam element are non-dimensionalized with respect to length. The frequency equation of beam is derived from that of each beam element, which satisfies the displacement of the longitudinal and transverse vibration and the boundary conditions between the beam elements. Numerical simulation and experimental work for the beam having several split beam elements are carried out to demonstrate the analytical development and its validity. The experimental results are in good agreement with those of the present frequency equation. The relationships between the split beam width and natural frequencies, and also the relationships between number of split and natural frequencies, in case that the total beam split length is same. are discussed.

• 한국음향학회지
• /
• 제31권8호
• /
• pp.514-522
• /
• 2012

횡진동 모드 압전진동자의 우주-항공산업에의 적극적인 활용을 위하여 우주환경을 모사한 열진공 챔버를 사용하여 $-100^{\circ}C{\sim}90^{\circ}C$의 범위에서 PZT-5계열의 압전세라믹 진동자의 온도변화에 따른 특성변화를 조사하였다. 그 결과 공진 및 반공진주파수는 상온일 때를 중심으로 온도의 변화에 따라 증가하였고 유전상수의 경우 주어진 온도 범위에서 2500~7500의 범위에서 선형적으로 증가하였다. 기계적 손실은 0.08~0.03의 범위에서 선형적으로 감소하는 경향을 보였다. 이들에 대한 회귀분석을 통하여 1차원 및 2차원 회귀함수를 이용하여 압전진동자의 각 특성에 대한 온도의존함수들을 도출하였다. 이들 함수를 적용하여 구한 횡모드 압전 진동자의 입력어드미턴스의 계산결과는 측정결과와 좋은 일치를 보이고 있었으며 우주환경에서의 온도에 따른 특성변화 예측에 유효함을 확인할 수 있었다.

• 소음진동
• /
• 제9권1호
• /
• pp.174-183
• /
• 1999

An analytical model for the lateral vibration of beams with a bonded lap joint and partial layered dampers has been proposed in this paper. Both shear and normal forces acting along the interface between the elastic and viscoelastic layers were considered in the vibration analysis. Analytical results were compared with those obtained by a finite element method. Effects of the size and location of layers in partial dampers on system loss factor($\eta_s$) and resonant frequency($\omega_r$) were studied. which showed that partial dampers adhered to the site exhibiting the maximum amplitude of vibration were most influential in the increase of $\eta_s$ and the decrease of $\omega_r$. Specific system loss factor( $\eta_s$ divided by total mass of system) was also evaluated in the analysis.