• Structural Engineering and Mechanics
• /
• v.91 no.2
• /
• pp.197-209
• /
• 2024

The vibration of elastically supported bidirectional functionally graded (BDFG) sandwich beams on an elastic foundation is investigated. The sandwich structure is composed of upper and lower layers of BDFG material and the core layer of isotropic material. Material properties of upper and lower layers are assumed to vary continuously along the length and thickness of the beam with a power-law function. Hamilton's principle is used to deduce the vibration equations of motion of the sandwich Timoshenko beam. Then, the partial differential equation of motion is spatially discretized into a time-varying ordinary differential equation in terms of Chebyshev differential matrices. The eigenvalue equation associated with the free vibration is formulated to study the influence of various slenderness ratios, material gradient indexes, thickness ratios, foundation and support spring constants on the vibration frequency of BDFG sandwich beams. The present method can provide researchers with deep insight into the impact of various geometric, material, foundation and support parameters on the vibration behavior of BDFG sandwich beam structures.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.15 no.3
• /
• pp.91-96
• /
• 2006

The aim of this paper is to clarify the structural compliance of the constrained spatial flexible manipulator and to develop the force control by using the compliance of the links. Using the dependency of elastic deflections of links on contact force, vibrations for constrained vertical motion have been suppressed successfully by controlling the position of end-effector. However, for constrained horizontal motion, the vibrations cannot be suppressed by only controlling position of end-effector. We present the experimental results for constrained vertical motion, and constrained horizontal motion. Finally, a comparison between these results is presented to show the validity of link compliance.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.6
• /
• pp.583-593
• /
• 2003

The effect of liquid confined in a pipe on elastic waves propagating in the pipe wall was studied theoretically and experimentally. The axisymmetric motion of the wave was modeled with the cylindrical membrane shell theory. The liquid pressure satisfying the axisymmetric wave equation was included in the governing equation as a radial load. The phase speed of the wave propagating in the axial direction was calculated, accounting for the apparent mass of the liquid. Experiments were performed in a pipe equipped with ring-shaped, piezoelectric transducers that were used for transmitting and receiving axisymmetric elastic waves in the pipe wall. The measured wave speeds were compared with the analytical ones. This work demonstrates the feasibility of using pipe waves for the determination of the density and, eventually, the flow rate of the liquid in a pipe.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.8
• /
• pp.763-770
• /
• 2012

The free vibration characteristics of fluid-filled cylindrical shells on partial elastic foundations are investigated by an analytical method. The cylindrical shell is fully or partially surrounded by the elastic foundations, these are represented by the Winkler or Pasternak model. The motion of shell is represented by the first order shear deformation theory to account for rotary inertia and transverse shear strains. The steady flow of fluid is described by the classical potential flow theory. The fluid-structure interaction is considered in the analysis. The effect of internal fluid can be considered by imposing a relation between the fluid pressure and the radial displacement of the structure at the interface. To validate the present method, the numerical example is presented and compared with the available existing results.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.17 no.4
• /
• pp.63-71
• /
• 2009

The elastic effects of the valve train components are analyzed by using the finite element models of the rocker arm and valve. The whole equations of motion of the valvetrain of an internal combustion engine formulated by finite element techniques are solved by imposing the contact conditions with the augmented Lagrange multiplier method. The velocity and acceleration constraints as well as the displacement constraints are imposed on the contact points. The numerical simulations show that, even if the magnitude of the elastic deformation of the components is very small, it may have large effects on the valvetrain dynamics of a high-speed engine.

• Journal of Korean Association for Spatial Structures
• /
• v.1 no.2 s.2
• /
• pp.101-110
• /
• 2001

A large floating structure is attracting great attention in recent years from the view of ocean space utilization. Its huge scale in the horizontal directions compared with the wavelength and relatively shallow depth make this type of floating structure flexible and its wave-induced motion be characterized by the elastic deformation. In this paper, a boundary integral equation method is proposed to predict the wave-induced dynamic response mat-like floating offshore structure. The structure is modeled as an elastic plate and its elastic deformation is expressed as a superposition of free-vibration modes in air. This makes it straightforward to expand the well-established boundary integral technique for rigid floating bodies to include the hydroelastic effects. In order to validate the theoretical analysis, we compare with the experimental result of reduced model test. Satisfactory agreement is found between theory and experiment.

• Journal of Institute of Control, Robotics and Systems
• /
• v.16 no.8
• /
• pp.794-798
• /
• 2010

This paper presents a new obstacle-avoidance method for mobile robots. This approach, called the FEB (Fast Elastic Band) method, has been developed and successfully tested on the experimental mobile robot PHOPE-1S. The FEB method eliminates the shortcomings of the elastic band method previously introduced, yet retains all the advantages of its predecessor. The FEB algorithm is computationally efficient, and it allows continuous and fast motion of the mobile robot without stopping for obstacles. The FEB-controlled mobile robot traverses very densely cluttered obstacle courses and is able to pass through narrow openings or narrow corridors without oscillations. The results of the simulation and experiment have verified the validity of the proposed method.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.5
• /
• pp.33-40
• /
• 2007

This paper proposes the Elastic force application on the obstacle avoidance of Silvermate robots. The method deals with the problem associated with a Silvermate robot driving to a goal configuration as avoiding obstacles. The initial trajectory of a robot is determined by a motion planner, and the trajectory modification is accomplished by adjusting the control points. The control points are obtained based on the elastic force approach. Consequently the trajectory of a robot is incrementally modified to maintain a smooth and adaptive trajectory in an environment with obstacles. The suggested algorithm drives the robot to avoid obstacle in real-time. Finally, The simulation studies are carried out to illustrate the effectiveness of the proposed approach.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.3 s.246
• /
• pp.279-286
• /
• 2006

The main purpose of this paper is to apply differential transformation method(DTM) and generalized differential quadrature method(GDQM) to vibration analysis of Euler-Bernoulli beam with open cracks on elastic foundation. In this paper the concepts of DTM and GDQM were briefly introduced. The governing equation of motion of the beam with open cracks on elastic foundation is derived. The cracks are modeled by massless substitute spring. The effects of the crack location, size and the foundation constants, on the natural frequencies of the beam, are investigated. Numerical calculations are carried out and compared with previous published results.

• Journal of Mechanical Science and Technology
• /
• v.18 no.12
• /
• pp.2148-2157
• /
• 2004

The paper deals with the vibration and dynamic stability of cantilevered pipes conveying fluid on elastic foundations. The relationship between the eigenvalue branches and corresponding unstable modes associated with the flutter of the pipe is thoroughly investigated. Governing equations of motion are derived from the extended Hamilton's principle, and a numerical scheme using finite element methods is applied to obtain the discretized equations. The critical flow velocity and stability maps of the pipe are obtained for various elastic foundation parameters, mass ratios of the pipe, and structural damping coefficients. Especially critical mass ratios, at which the transference of the eigenvalue branches related to flutter takes place, are precisely determined. Finally, the flutter configuration of the pipe at the critical flow velocities is drawn graphically at every twelfth period to define the order of the quasi-mode of flutter configuration.