Papers by Keyword: Isochromatic Fringe

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Authors: Tae Hyun Baek, Seung Kee Koh, Tae Geun Park
Abstract: hybrid experimental-numerical method is presented for determining the stresses around a circular hole in a finite-width, tensile loaded plate. Calculated fringes obtained by FEA provided the information about the external boundary of the hybrid element, and those fringes on straight lines were used for hybrid analysis. In order to see the effects of varying stress field, different numbers of terms in a power-series representation of the complex type stress function were tested. Actual and reconstructed fringes were compared. The hybrid results were highly comparable with those predicted by FEA. The result showed that this approach is effective and promising because isochromatic data along the straight lines in photoelasticity can be conveniently measured by use of phase shifting photoelasticity.
Authors: Mario Guagliano, Majid R. Ayatollahi, Mahnaz Zakeri, Chiara Colombo
Abstract: According to classical definition of crack deformation modes, the constant stress term (Tstress) exists only in presence of mode I. However, some studies show that this term can exist in mode II problems as well; and significantly affect the elastic stress field around the crack tip. Based on the previous analytical results, T-stress changes the photoelastic fringe patterns from symmetric closed shapes to asymmetric and discontinuous loops. In this research, the effects of T-stress on the fringe patterns in mode II cracks is investigated experimentally. Test specimens are Brazilian disks made of polycarbonate, and thermal treatment is performed to remove the residual stresses after generation of the cracks. Observed isochromatic fringes are in good agreement with theoretical predictions. Also, experimental results indicate that this specimen contains a negative T-stress in pure mode II condition.
Authors: Jia Quan Wu, Hong Yan Li, Fei Ye, Xing Yu Zhang, Kun Ma
Abstract: How to truncate stress wave is an important problem that must be considered in design of engineering structure. As an effective detection method of stress distribution, the dynamic photoelasticity has been wide used in stress analysis, such as detection of mechanical structure, civil engineering and water conservancy etc. In this paper, the stress wave isochromatic fringe at different interface structure has been obtained through vertical shooting experiment. The structural stress wave propagation rule of three kinds of case is studied by comparison fringe pattern. The experimental research results show that the stress wave propagation can be effectively guided to a fixed direction through installed connecting parts in structural connection position and the method can avoid integrity damage of structure caused by local large stress changes. Finally, the dynamic photoelasticity is an intuitive and effective way to study stress wave truncation problem.
Authors: Tae Hyun Baek, Myung Soo Kim
Abstract: A multi-purpose polariscope was 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 was devised to be controlled through two stepping motors and two magnetic clutches. 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. The distributions of digitally determined unwrapped isoclinics and isochromatics using the digitized images obtained from the developed polariscope were in close agreement to manual measurements.
Authors: Peter Frankovský, František Trebuňa, Oskar Ostertag, Patrik Šarga, Ingrid Delyová, Ján Kostka
Abstract: The presented paper demonstrates the determination of residual stresses by means of PhotoStress® method. The identification was performed on a drilled and subsequently loaded sample of a split ring. Through drilling and subsequent loading of the sample we were able to simulate residual stresses throughout the surface of the split ring. Using the values of residual stresses, a gradient of residual stresses was specified. The 3 mm thick split ring was laser-cut from a non-alloyed fine-grained structural steel sheet suitable for welding, i.e. steel 11 523. It was coated with 3.125 mm thick photoelastic coating PS-1A with fringe constant.
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