• Journal of the Korean Society for Nondestructive Testing
• /
• v.13 no.2
• /
• pp.20-30
• /
• 1993

Electric Speckle Pattern Interferometry (ESPI) using a CW-laser, a video system and an image processor was applied to the thermal coefficient measurements on free thermal expansions at high temperatures : ESPI provides the distribution of in-plane displacement resolved in a preselected direction. ESPI retains the merits of little or no surface preparation, no contact with the surface and the real-time presentation of interference fringes. Appling ESPI at high temperatures, several problem which caused the reduction of fringe visibility were encountered. The problem on the turbulence in the hot air surrounding high temperature objects will be solved by using a vacuum chamber. The background radiations from the objects were suppressed considerably by an interference filter. The problem on the oxidation of the object surface could't be solved. The interference fringe, whose spacings were calculated by FFT to avoid human error, were observable up to $800^{\circ}C$. The results measured by ESPI were nearly equal to the data which have already been published, up to about $800^{\circ}C$.

• Journal of the Society of Naval Architects of Korea
• /
• v.51 no.4
• /
• pp.265-273
• /
• 2014

Wave-body interaction is simulated using a developed code based on the flux-difference splitting scheme for immiscible and incompressible fluids and the hybrid Cartesian/immersed boundary method. A free surface is captured as a moving contact discontinuity within a fluid domain and an approximated Riemann solver is used to estimate the inviscid flux across the discontinuity. Immersed boundary nodes are identified inside an instantaneous fluid domain near a moving body, then dependent variables are reconstructed at those immersed boundary nodes based on interpolation along local normal lines to the boundary. Free surface flows around an oscillating cylinder are simulated and the computed wave elevations are compared with other reported results. The generation of a solitary wave by a moving wave-maker is simulated and the time histories of wave elevations at two different points are compared with other results. The developed code is applied to simulate body motion of an elastically mounted circular cylinder as a solitary wave passes the body. The force acting on an elastically mounted cylinder is compared with the force acting on a fixed cylinder. Grid independency of the computed body motion is established based on a comparison of results using three different-size grids.

• The Journal of the Acoustical Society of Korea
• /
• v.16 no.5
• /
• pp.26-35
• /
• 1997

This paper deals with establishing correspondent points of feature pints and sampling period when we estimate object motion parameters from image information of freely moving objects in space of gravity-free state. Replacing the inertial coordinate system with the camera coordinate system which is equipped within a space robot, it is investigated to be able to analyze a problem of correspond points from image information, and to obtain sequence of angular velocity $\omega$ which determine a motion of object by means of computer simulation. And if a sampling period ${\Delta}t$ is shortened, the relative errors of angular velocity are increased because the relative errors against moving distance of feature points are increased by quantization. In reverse, if a sampling period ${\Delta}t$ is lengthened too much, the relative error are likewise increased because a sampling period is long for angular velocity to be approximated, and we confirmed the precision that grows according to ascending of resolution.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.2
• /
• pp.156-165
• /
• 2015

A survivability-analysis program has been developed to analyze the ground collision risk of atmospheric reentry objects, such the upper stages of a launch vehicle or satellites, which move at or near the orbital velocity. The aero-thermodynamic load during the free fall, the temperature variation due to thermal load, and the phase shift after reaching the melting point are integrated into the 3 degree-of-freedom trajectory simulation of the reentry objects to analyze the size and weight of its debris impacting the ground. The analysis results of the present method for simple-shaped objects are compared with the data predicted by similar codes developed by NASA and ESA. Also, the analysis for actual reentry orbital objects has been performed, of which results are compared with the measurement data.

• 대한공업교육학회지
• /
• v.34 no.2
• /
• pp.363-378
• /
• 2009

The objective of the paper is to design and produce a walking robot such as humanoid robot under the given design requirements and constraints. An approach to design and produce walking robot with 2 legs was suggested. It is walking robot of 5 joints which have both of ankles, both of knee joint, and pelvis. It has 5 degrees of freedom and moves by only rotations. We review the key points before the design of the walking robot. The walking robot is consisted of 2 portions : motor and frame, control board. Final goal is to walk stably and if it detects and cognizes a special object, the walking robot avoids it and moves in other direction. The walking robot was made according to design procedures and tested by proposed algorithms. The running test was successful under given 4 modes. The findings of this research could think kinds of technologies concurrently and approach synthetically through process of design and production.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.2
• /
• pp.95-101
• /
• 2017

In this study, we derived theoretical equations for the zigzag movement of a leading vehicle, which is the most frequent behavior in train accidents, by using a simplified spring-mass model for the rolling stock. In order to solve the equations of motion, we applied the Runge-Kutta method, which is the typical numerical analysis method used for differential equations. Furthermore, the lateral displacement of the wheel-set at the wheel-rail interface was estimated using kinetic energy. In order to verify the derived equations, we compared the theoretical and simulated results under various collision conditions. The maximum relative deviations of the lateral displacements were 0.8 [%] ~ 4.7 [%] in light collisions and 0.6 [%] ~ 5.1 [%] under derailment conditions. When an accident is simulated, these theoretical equations can be used to predict the overall behavior and obtain the offset of the body-to-body link as the initial perturbation.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.4
• /
• pp.12-20
• /
• 1997

A potential-based panel method has been developed to investigate the resistance characteristics of a high speed catamaran advancing on the free surface. Normal dipoles and sources are distributed on the body surface while sources are distributed on the free surface. Linearised free surface conditions are used in the present analysis. To avoid the instabilities due to the velocity difference between inner and outer flow of a high speed catamaran, Kutta condition has been applied at the stern. Model test has been carried out not only to validate the numerical results but to confirm the capabilities of a CWC(Circulating Water Channel). It is believed that we can obtain the qualitatively reasonable results in the CWC. Computed results are compared with those of experiments and Insel's experimental values. Since the Kutta condition is applied at the stern, stable solutions are obtained at the high speed range. The present method, using linearised free surface conditions at the high speed range, seems to be a useful tool in the hull form design of a high speed catamaran.

• Korean Journal of Computational Design and Engineering
• /
• v.15 no.2
• /
• pp.106-114
• /
• 2010

The swept volume, the region of a moving object, is applied in many fields such as valid paths for motions of tools, visualization in robot paths and interference tests for parts assembling or disjointing. The shape of a swept volume depends on an generators computed with normal vectors of an object and velocity vectors of a motion. Although free-from surfaces are widely used to represent geometric models in CAD, computing the generators for a free-form object is a formidable task. Previous approaches exploit the closed form expressions of generators but limited to planer or quadric faces. In this paper, we propose the algorithm to compute swept volumes generated by free-form objects in screw motions. For the algorithm a tracing method is applied to the computation of generators. It considers curvatures of surfaces of an object to increase the computational accuracy. We implemented our algorithm in the CATIA V.5 environment to test the validity of our algorithm and to generate examples.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.98-106
• /
• 1991

Future generation of robots will be considerably more autonomous than present robotic systems. The main objective of research on theoretical problems in robotics is to endow robotics system with basic capabilities they will need to operate in an intelligent and autonomous manner. This paper discusses the problem of collision free movement of robot manipulator. It is formulated in path planning with obstacle avoidance expressed in the term of the distance between convex shapes in the three dimensional space. The examples are given to illustrate the main feature of the method.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.223-228
• /
• 2001

This study was obtained the pressure distribution of a falling body that is deadrise angle $0^{\circ}$ and deadrise angle $5^{\circ}$ upon a water surface by the experiment with the impact machine. The theoretical equation was obtained the air region and the interface and the water region which devide 3 parties between the body and the water surface for an investigation of the complete phenomena. Pressure distributions and histories compare favorably with available experimental data. The numerical results are similar to the experimental results for the impact force type with $Fo(1+cos{\pi}t/tc)$.