• Title/Summary/Keyword: Isochromatics

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A Study on the Development of Photoelastic Experimental Hybrid Method for Color Isochromatics (칼라 등색선무늬용 광탄성실험 하이브릿법 개발에 관한연구)

  • Kwon, O-Sung;Hawong, Jai-Sug;Nam, Jeong-Hwan;Han, Song-Ling;Kwon, Gun;Liu, Yi
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.66-71
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    • 2007
  • Isochromatics obtained from photoelastic experiment shows the stress distributions of full field of a structure under a load. Therefore stress distributions of the structure can be read at a glace through isochromatics. Many experimental data are obtained from isochromatics. And then, the various photoelastic experimental hybrid methods have been developed. Until now, monochromatic light has been used for photoelastic experimental hybrid method. Therefore the photoelastic experimental hybrid method used until now is called the photoelastic experimental hybrid method for black and white isochromatics. When stresses are analyed by photoelastic experimental hybrid method, many experimental data are needed. Therefore some fringe orders of isochromatics are needed for the photoelastic experimental hybrid method for white and black isochromatics. Therefore in this paper, the photoelastic experimental hybrid method for color isochromatics is developed. In this case, two fringe orders are enough for the experimental data of photoelastic experimental hybrid method for color isochromatics. Applying the method to stress concentration problems, its validity is confirmed. In the precision, the photoelastic experimental hybrid method for color isochromatics is better than the photoelastic experimental hybrid method for white and black isochromatics when fringe orders of isochromatics are few. When fringe orders are few, the photoelastic experimental hybrid method for color isochromatics can be used to analyze stress through few fringe orders of isochromatics.

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Separation of Isochromatics and Isoclinics from Photoelastic Fringes in a Circular Disk by Phase Measuring Technique

  • Baek, Tae-Hyun;Kim, Myung-Soo;Yoshihau Morimoto;Motoharu Fujigaki
    • Journal of Mechanical Science and Technology
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    • v.16 no.2
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    • pp.175-181
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    • 2002
  • A new polariscope system involving two rotating optical elements and a digital camera for whole field fringe analysis allows automated data to be acquired quickly and efficiently. The developed phase measuring technique that uses eight images through a circular polariscope is presented for the digital measurement of isochromatics and isoclinics, respectively, from photoelastic fringes in a circular disk under diametric compression. Isochromatics can directly be obtained using wrapped isoclinic phases calculated by the arc tangent operator which is the four-quadrant operator from -$\pi$ to $\pi$. It is not required to unwrap isoclinic phases for the calculations of isochromatics. Unwrapped isoclinics are directly determined from isochromatic parameters. Distributions of digitally determined isoclinics are in close agreement to manual measurements. The errors which would appear in unwrapping process of isoclinics can be avoided in the determination of isochromatics.

The Maximum Shear Stress Distribution in a Stiffener attached to a Plate (평판(平板)에 붙은 Stiffener 속에서의 전단응력(剪斷應力)의 분포(分布))

  • Sahng-Jun,Yim
    • Bulletin of the Society of Naval Architects of Korea
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    • v.3 no.1
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    • pp.19-24
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    • 1966
  • The maximum shear stress distribution in a stiffening flat attached to a plat undergoing a single tensile force has been investigated by photoelastic method. In the experiments a photoelastic model, as shown in Fig. 1, has been studied in the fields of a polariscope, as shown in Fig. 2. Fig. 3 shows the isoclinics and Fig. 4 and 5 are stress trajectories of the principal stresses and maximum shear stresses, respectively. Fig. 6 is the isochromatics in light field. The maximum shear stress at each point in the stiffener were determined from the isochromatics in both of light field of light field and dark field. Then the maximum shear stresses were divided by the average shear stress in the model, to obtain the ratio ${\tau}max/{\tau}av$ at each point. Finaly the variations of the ratio ${\tau}max/{\tau}av$ along the horizontal and vertical lines in the stiffener have been plotted, as shown in Fig. 7 and 8. The conclusions reached in this investigation are as follows: (1) The shear stresses transmitted to the stiffener through the juncture are concentrated on the end portions. (2) The maximum shear stress at the ends of the stiffener reaches to about 4 times of average shear stress. (3) The irregularities in the stress distribution are restricted in the end portions of the stiffener.

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Stress Intensity Factor Measurement of Inclined Crack in Tensile Plates by Use of Photoelasticity (광탄성법을 이용한 인장판의 경사균열 응력확대계수 측정)

  • Baek, Tae-Hyun;Lee, Chun-Tae;Kim, Young-Chul
    • Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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    • v.5 no.2
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    • pp.215-222
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    • 2015
  • This paper presents the measurement of stress intensity factors of inclined cracks by use of photoelasticity. The distributions of isochromatics near a crack tip of the specimen loaded by uniaxially tensile load are used for analysis. Accuracy and reliability is enhanced by twice multiplying and sharpening the measured isochromatics using digital image processing. Photoelastic results are compared with those obtained by finite element method. Good agreement between them shows that the photoelastic analysis is reliable.

Application of the Photoelastic Experimental Hybrid Method with New Numerical Method to the High Stress Distribution (고응력 분포에 새로운 광탄성실험 하이브릿법 적용)

  • Hawong, Jai-Sug;Tche, Konstantin;Lee, Dong-Hun;Lee, Dong-Ha
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.73-78
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    • 2004
  • In this research, the photoelastic experimental hybrid method with Hook-Jeeves numerical method has been developed: This method is more precise and stable than the photoelastic experimental hybrid method with Newton-Rapson numerical method with Gaussian elimination method. Using the photoelastic experimental hybrid method with Hook-Jeeves numerical method, we can separate stress components from isochromatics only and stress intensity factors and stress concentration factors can be determined. The photoelastic experimental hybrid method with Hook-Jeeves had better be used in the full field experiment than the photoelastic experimental hybrid method with Newton-Rapson with Gaussian elimination method.

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Test and Evaluation of a Newly Built Multi-purpose Transmission Type Polariscope (다목적 투과형 편광기 시험 및 평가)

  • Baek Tae Hyun;Kim Myung Soo;Lee Choon Tae;Kim Whan;Park Tae Guen
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.1
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    • pp.73-81
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    • 2005
  • A multi-purpose polariscope is developed by applying an electro-mechanical control system to a diffused transmission-type circular polariscope. A conventional polariscope is only good for manual control of optical elements. The new polariscope system is devised to be controlled through two stepping motors and two magnetic clutches. The developed system has both functions of a conventional linear- and circular-polariscope. The new polariscope can be used not only for the point-wise measurement using Tardy compensation technique but also for the full-field fringe analysis using conventional and/or phase measuring techniques, if applicable.

Development of Dynamic Photoelastic Experimental Hybrid method for Propagating Cracks in Orthotropic Material (직교이방성체내의 진전 균열에 대한 동적 광탄성 실험의 Hybrid 법 개발)

  • Shin, Dong-Chul;Hawong, Jai-Sug
    • Proceedings of the KSME Conference
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    • 2000.04a
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    • pp.236-241
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    • 2000
  • In this paper, transparent dynamic photoelastic experimental hybrid method for propagating cracks in orthotropic material is developed. Using transparent dynamic photoelastic experimental hybrid method, we can obtain stress intensity factor and separate the stress components from only isochromatic fringe patterns without using isoclinics. It is certified that the dynamic photoelastic experimental hybrid method is very useful for the problems of the dynamic tincture mechanics.

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Development of Dynamic Photoelastic Experimental Hybrid Method for Propagating Cracks in Orthotropic Material (직교이방성체내의 진전 균열에 대한 동적 광탄성 실험 Hybrid 법 개발)

  • Shin, Dong-Chul;Hawong, Jai-Sug;Sung, Jong-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.8
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    • pp.1273-1280
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    • 2003
  • In this paper, transparent dynamic photoelastic experimental hybrid method for propagating cracks in orthotropic material was developed. Using transparent dynamic photoelastic experimental hybrid method, we can obtain stress intensity factor and separate the stress components from only isochromatic fringe patterns without using isoclinics. When crack is propagated with constant velocity, the contours of stress components in the vicinity of crack tip in orthotropic material are similar to those of isotropic material or orthotropic material with stationary crack under the static load. Dynamic stress intensity factors are decreased as crack growths. It was certified that the dynamic photoelastic experimental hybrid method was very useful for the analysis of the dynamic fracture mechanics.

Stress Measurement of a Squarely Perforated Plate by Photoelastic Phase Shifting Method (광탄성 위상이동법에 의한 사각형 구멍주위의 응력해석)

  • Lee C.T.;Park T.G.;Jung J.;Panganiban H.;Chung T.J.;Baek T.H.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2006.05a
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    • pp.49-50
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    • 2006
  • Photoelasticity is widely and conveniently used methods for whole field stress analysis. In this paper, 8-step photoelastic phase shifting method was performed by using a multi-purpose polariscope to measure the fringe orders along a specified line on the specimen containing a square hole. The material of the specimen is made of Polycarbonate. The measurement results by 8-step phase shifting method were compared with the those calculated by ABAQUS.

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Simulation of Separating Isoclinics and Isochromatics from Photoelastic Fringes of a Disk using 8-step Phase Shifting Methodology (광탄성 프린지 위상이동법을 적용한 디스크의 등경 및 등색프린지 분리법에 관한 시뮬레이션)

  • Baek, Tae-Hyun;Kim, Myung-Soo;Cho, Sung-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.2
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    • pp.189-196
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    • 2001
  • Photoelasticity is one of the most widely used methods for whole field stress analysis. In photoelasticity, the difference and the directions of the principal stresses we given isochromatic and isoclinic fringe patterns. Conventionally, principal stress directions are measured manually by relating the polarizer and analyzer of a plane polariscope at the same time. This is known to be the Tardy compensation method. This measurement can be very tedious and time consuming in whole field analysis. It is not possible to separate isoclincs from photoelastic fringes by conventional photoelastic technique. In this study, photoelastic theory is represented by Jones matrices and 4-steps and 8-steps phase shifting methods are described A feasibility study using computer simulation is done to separate isoclincs and isochomatics from photoelastic fringes of a circular disk under diametrical compression. Fringe patterns of the disk are generated using stress optic law. The magnitudes of isoclincs and isochromatics obtained from 8-step phase shifting method are compared with those of theories. From computer simulation, it is verified to separate isoclincs and isochomatics from photoelastic fringes.

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