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직교이방성 재료의 구멍주위에 관한 하이브리드 응력해석시 요소크기의 효과
백태현,Baek, Tae-Hyun 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.10
A numerical study for the number of terms of a power series stress function and the effect of hybrid element size on stress analysis around a hole in loaded orthotropic composites is presented. The hybrid method coupling experimental and/or theoretical inputs and complex variable formulations involving conformal mappings and analytical continuity is used to calculate tangential stress on the boundary of the hole in uniaxially loaded, finite width glass epoxy tensile plate. The tests are done by rarying the number of terms, element size and nodal locations on the external boundary of the hybrid region. The numerical results indicate that the hybrid method is accurate and powerful in both experimental and numerical stress analysis.
정수압을 받는 축대칭 절두체 원추형 압력용기의 응력해석
백태현,정태진,Baek, Tae-Hyun,Chung, Tae-Jin 한국정밀공학회 1992 한국정밀공학회지 Vol. No.
Theoretical equations for hoop stress, longitudinal or meridian stress and Von Mises stress of an axismmetric conical pressure vessel and a frustum of conical pressure velle, both of which are pressuized by hydrostatic loading, are derived from equilibrium equations. The membrane stresses conputed by theoretical equations for a conical pressure vessel and a frustum of conical pressure vessel are compared with the values obtained from finite elelment method. Based on the fact that the computational values by theoretical equations are well agreed with the finite element results, derived equations are proved to be valid and it is possible for those equations to be conveniently used for structural analysis or design of frustum of conical pressure vessel which is a part of silo body.
백태현,Baek, Tae-Hyun 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.5
Risidual stress of cylindrical glass rods are measured by photoelasticity to study the variation of stresses with respect to heat treatment temperatures. In order to measure the stresses accurately, fringe sharpening and multiplication techniques are applied to the determination of photoelastic fringe orders. Filon's separationmethod is used to resolve circumferential and redial stress ocmponents from isochromatic fringes which are the same as in-plane maximum shearing stresses. According to the photoelastic measurements, residual stress is increased as the heat treatment temperature of the rods is raised from $560^{\circ}C$ to $650^{\circ}C$ All the circumferential stress components are changed from tensile stresses to compressive ones at approximate $R_m$/$R_o$ = 0.6, where $R_o$/ is outer radius and $R_m$any measured radius. This analysis shows that residual stresses of the glass rods approach zero if the rods are heat-treated near the strain point.
등각사상 맵핑 및 광탄성 실험법에 의한 원형구명 주위의 하이브리드 응력장 해석
백태현,김명수,이주훈,Baek, Tae-Hyun,Kim, Myung-Soo,Rhee, Ju-Hun 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.6
An experimental study is presented for the effect of number of terms of a pewee series type stress function on stress analysis around a hole in tensile loaded plate. The hybrid method coupling photoelastsic data inputs and complex variable formulations involving conformal mappings and analytical continuity is used to calculate tangential stress on the boundary of the hole in uniaxially loaded, finite width tensile plate. In order to measure isochromatic data accurately, actual photoelastic fringe patterns are two times multiplied and sharpened by digital image processing. For qualitative comparison, actual fringes are compared with calculated ones. For quantitative comparison, percentage errors and standard deviations with respect to percentage errors are caculated for all measured points by changing the number of terms of stress function. The experimental results indicate that stress concentration factors analyzed by the hybrid method are accurate within three percent compared with ones obtained by theoretical and finite element analysis.
유한요소 변위값을 이용한 인장하중 판재 균열선단 주위의 응력분포 해석
백태현(Tae Hyun Baek) Korean Society for Precision Engineering 2008 한국정밀공학회지 Vol.25 No.10
Due to the complexity of the engineering problems, it is difficult to obtain directly the stress field around the crack tip by theoretical derivation. In this paper, the hybrid method is employed to calculate full-field stress around the crack tip in uni-axially loaded finite width tensile plate, using the displacement data of given points calculated by finite element method as input data. The method uses complex variable formulations involving conformal mappings and analytical continuity. In order to accurately compare calculated fringes with experimental ones, both actual and reconstructed photoelastic fringe patterns are two times multiplied and sharpened by digital image processing. Reconstructed fringes by hybrid method are quite comparable to actual fringes. The experimental results indicate that Mode I stress intensity factor analyzed by the hybrid method are accurate within a few percent compared with ones obtained by empirical equation and finite element analysis.
탄소성 이론과 유한요소법에 의한 강판재의 프레스 성형성 해석
백태현(Tae Hyun Baek),고승기(Seung Kee Koh),박태근(Tae-Geun Park),정걸(Girl Jung),황한영(Han Young Han) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.8
This paper presents the results obtained from the analysis for centralized stress distributions on the steel sheet metal sheet of vehicle's front bumper developed in press-forming and bending process. After calculating the stress distribution by finite element analysis, the point where the maximum stress comes into being can be determined. In order to avoid the crack which might be occurred in material when bending process, the product's material, shape and the minimum bending radius are proposed to be calculated by the simple elasto-plastic and empirical equation.
인장하중을 받는 쐐기형 판을 이용한 재료 응력프린지 값 측정
백태현(Tae-Hyun Baek),김명수(Myung-Soo Kim),김은총(Eun-Chong Kim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.춘계 No.-
In a photoelastic experiment, it is necessary to know the material stress fringe constant of the photoelastic specimen to determine the stresses from the measured isochromatic fringe orders. The radial state of stress developed in a wedge can be utilized to make a simplified compensator. This type of compensator was proposed by the previous researchers. The stress in the tapered shank of this strip may be treated as approximately radial. The material stress fringe constant is determined using the distributions of isochromatic fringes in the wedge shaped plate under tensile load The stress fringe constant measured with this method is applied to obtain the stress distribution along the central line on the tapered shank of the sedge-shaped plate. Photoelastic results using the measured material fringe constant are compared with FEM analysis. Two results are comparable, so it can be seen for the measured material fringe constant to be valid.
태권도 숙련성과 시간차단 수준에 따른 예측능력과 시각탐색 전략의 차이
백태현(Baek, Tae-hyun),이승민(Lee, Seung-Min),안종성(An, Jong-seong),권택용(Kwon, Taeg-yong) 한국웰니스학회 2016 한국웰니스학회지 Vol.11 No.4
본 연구는 태권도 숙련성과 시간차단 수준에 따른 예측 능력의 차이를 살펴보는 것을 목적으로 하고 있다. 이러한 목적을 달성하기 위해 총 16명(expert 8, novice 8)의 피험자가 참여 하였으며, 태권도 예측 능력 평가 프로그램, 동영상, 빔 프로젝트 등이 사용되었다. 실험 과제는, 시간차단 기법을 활용하여 다섯 구간으로 구성된 태권도 공격 동영상을 보고 가능한 빠르고 정확하게 발차기 형태와 공격 방향을 예측하는 것이다. 본 연구를 통해 도출된 결과는 다음과 같다. 첫째, 숙련성에 따라 시간차단 T1~T4에서 유의한 차이가 있는 것으로 나타났다. 둘째, 숙련자는 초보자보다 예측에 대한 확신 정도가 더 높은 것으로 나타났다. 셋째, 숙련성에 따라 활용하는 사전 시각 단서에 있어서 차이가 있는데, 초보자는 발, 무릎, 숙련자는 발등, 허리, 어깨, 무릎 등 다양한 정보에 초점을 맞출 수 있다. The aim of this study is to examine the anticipation skill level of different expertise and temporal occlusion in variety Taekwondo kick tasks. 8 experts group(M=12.5 years) and 8 novice group(M=career none) were participated in the research, and Teakwondo anticipation program, Video Clip, beam project were used for the apparatus. The experiment task was to anticipate the attack direction and different kick type as quick as possible, from watching the video clips using temporal occlusion technique. The result of this study is as follow: First, there was significant difference between expertise level in T1-T4. Second, expert showed higher confidence of anticipation skill than novice group. Third, there was difference in ability of using previous visual ques. Novice groups were focusing on foot, knee, and experts were more focused on variety information(Foot, hip, shoulder, knee).