• 한국생산제조학회지
• /
• 제8권1호
• /
• pp.21-27
• /
• 1999

In this study, stress intensity factors KI, KII, KIII are existing at the same time to a hollow cylindrical bar of three dimension inclination crack. In order to investigate by experimentally the effect of the inclination angle $\psi$ of crack, artificial inclination cracks in the circumferential direction are put in the surface of a hollow cylindrical bar made by the epoxy-resin. Experimentally, stress analysis methods of stress intensity factors were proposed. But, suitable method are the caustic method and the photoelastic stress freezing method. The mixed mode of KI, and KII, were determined by the photoelastic method of the classical approach method and the FORTRAN language program of the used smallest square method.

• 비파괴검사학회지
• /
• 제25권1호
• /
• pp.1-8
• /
• 2005

본 연구에서는 TV 유리패널의 등색프린지 분포를 광탄성 4단계 위상이동법에 의하여 측정한 실험결과를 제시하였다. 재래식 광탄성법에서는 등색 프린지 차수를 각각의 점에 대해서 수작업으로 측정한다. 4단계 위상이동법을 이용하기 위하여, 원형편광기 요소들은 등색프린지분포가 측정되는 지점 혹은 선상을 따라 등경각 방향에 일치시켜야 한다. 4단계 위상이동법은 원형편광기의 검광판을 $0^{\circ},\;45^{\circ},\;90^{\circ}$ 및 $135^{\circ}$ 회전시켜 얻은 4개의 영상을 이용한다. 4단계 위상이동법을 적용하기 위해서는 등경각이 측정하고자 하는 지점이나 선상에 일치하도록 편광기 요소를 정렬시켜야 한다. 4단계 위상이동법으로부터 얻은 실험결과는 세나르몽보간법에 의해 측정한 값과 비교한 결과 서로 잘 일치하였다. 또한, TV 유리패널의 열처리 전 후에 등색프린지 분포를 비교하였다. 측정 결과, TV 유리패널의 열처리 전 후의 등색프린지 차수는 약 2배정도 차이가 나타났다.

• 비파괴검사학회지
• /
• 제29권6호
• /
• pp.557-562
• /
• 2009

Abrupt change of cross-section in mechanical parts is one of significant causes of structural fracture. In this paper, a hybrid method is employed to analyze the stress distribution of a discontinuous plate. The plate with an inclined crack is utilized in our experiment and the stress field in the vicinity of crack tip is calculated through isochromatic fringe order of given points. This calculation can be made handy through least-squares method integrated with complex power series representation(Laurent series) implemented on a computer program for high-speed processing. In order to accurately compare calculated results with experimental ones, both of actual and regenerated photoelastic fringe patterns are doubled and sharpened by digital image processing. The experiment results show that regenerated patterns obtained by hybrid method are quite comparable to actual patterns.

• 한국안전학회지
• /
• 제7권1호
• /
• pp.5-12
• /
• 1992

Disc specimen with the center crack and edge crack simulated by two-dimensional static method is used to analyze the stress field around the crack tip in terms of the stress intensity factor, K. A simple and convenient method of testing to realize the mifed mode stress intensity factor of the cracked body is used, The conclusions obtatined in this photoelastlc analysis are as follows ; 1. According to this experiment, cracked disc specimen can be used to demonstrate the mixed mode stress intensity factor analysis by simply changing the crack angle from the loading line. 2. Despite the simplicity and continuous data reading, the photoelastic method shows the slightly lower strain reading comparing to the FEM analysis method. 3. In this photoelastic analysis, $K_{I}$ of center cracked disc specimen under a pair of compressive load shows negative value as the crack angle increases over 30$^{\circ}$.

• 비파괴검사학회지
• /
• 제32권1호
• /
• pp.27-33
• /
• 2012

광탄성법은 실험역학에서 응력 또는 변형률을 해석하기 위한 여러 실험방법 중의 하나이며, 다양한 종류의 구조물의 응력 분포를 실험적으로 결정하는 기법이다. 광탄성법은 광탄성 영상의 등색 프린지와 등경 프린지로부터 광탄성 시편에 나타나는 전체의 응력장 분포를 정밀하게 측정할 수 있다. 본 논문에서는 여러 가지 광탄성 기법중 8단계 위상이동법(8-step phase-shifting method)에 관한 이론을 살펴보고, 경사균열이 있는 평판 시편에 인장을 가하여 나타난 광탄성 프린지로부터 경사균열 선단주위의 응력분포를 8단계 위상이동법으로 결정한 후, 이들 결과를 유한요소법(FEM)에 의한 결과와 비교하였다. 8단계 위상이동법을 이용한 실험에 의해 측정된 프린지 차수는 유한요소법에 의한 계산된 프린지 차수값에 근접하였다.

• 대한기계학회논문집A
• /
• 제20권5호
• /
• pp.1524-1533
• /
• 1996

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.

• 한국해양공학회지
• /
• 제2권2호
• /
• pp.96-103
• /
• 1988

The stress distribution in the vicinity of the crack tip in the fracture mechanics is ordenarily indicated by the stress intensity factor. In the analysis of stress intensity factors, there are many theoretical and experimental methods. The stress analysis in photoelastic technique is usually made by using the difference of the principal stress of isochromatic fringe patterns. In this paper, the teflon molding technique is adopted to make a test specimen with a circular arc-crack, and that upgraded the accuracy of experiment. As the result, the experimental values of the stress intensity factors for the circular disk with a straight crack are coincided with the theoretical values. But, there is quite a difference between this expermental results on the finite plate for circular arc-crack and its theoretical values on the infinite one. Therefore, a boundary condition with regard to the loading condition on finite disk must be considered.

• Journal of Biosystems Engineering
• /
• 제8권2호
• /
• pp.11-17
• /
• 1983

Stress distribution under a driving lugged wheel was obtained by photoelastic method. The distribution showed two distinct parts, one part is due to sinkage and other due to compression. Results of the study are summarized as follows. 1. The tangential reactions of sinkage as well as compressing parts were directly proportional to tangential load to the driving wheel, that's appeared to be thrust of the driving wheel. The normal reactions of both sinkage and compressing parts were directly proportional to the vertical load to the driving wheel, that's appeared to be resistance against wheel motion. 2. When the tangential load was constant, changing the vertical load did not show any significant thrust variation of the driving wheel. 3. Under the condition of this experiment, the ratio of vertical load to tangential load (T.L/V.L) must be greater than 1.0 in order for the wheel to roll.

• 대한기계학회논문집A
• /
• 제28권12호
• /
• pp.1897-1905
• /
• 2004

In many part of machines or structures that made of bimaterial bonded with two dissimilar materials, most failures occur at their interface. Therefore, the accurate analysis of fracture characteristics and the evaluation of mechanical strength for interfacial crack are essential when we design those structures. In this research, stress and displacement components in the vicinity of stationary interfacial crack tip in the two dissimilar isotropic bimaterials are established. Hereafter, the stress components established in this research can be applied to the photoelastic hybrid method which can be used to analyze the fracture behavior of the two dissimilar isotropic bimaterials.

• 대한기계학회논문집A
• /
• 제32권7호
• /
• pp.576-582
• /
• 2008

This paper describes a synthesized photoelastic method developed for the visualization and evaluation of sound pressure distribution of elastic wave in a solid. The visualization of wave stress field is achieved by synthesizing two photoelastic pictures, in which the direction of the principal axis of linear polariscopes differs by $45^{\circ}$. From the analysis of the wave stress distribution using this method, it is possible to evaluate the characteristics of elastic waves in a solid, such as the intensity of stress, directivity and resolution characteristics of the wave emitted from a commercial probe, and characteristics of scattering from various types of defects.