Hybrid determination of mixed-mode stress intensity factors on discontinuous finite-width plate by finite element and photoelasticity

Journal of Mechanical Science and Technology (Impact Factor: 0.7). 10/2011; 25(10):2535-2543. DOI: 10.1007/s12206-011-0740-1

ABSTRACT For isotropic material structure, the stress in the vicinity of crack tip is generally much higher than the stress far away
from it. This phenomenon usually leads to stress concentration and fracture of structure. Previous researches and studies
show that the stress intensity factor is one of most important parameter for crack growth and propagation. This paper provides
a convenient numerical method, which is called hybrid photoelasticity method, to accurately determine the stress field distribution
in the vicinity of crack tip and mixed-mode stress intensity factors. The model was simulated by finite element method and
isochromatic data along straight lines far away from the crack tip were calculated. By using the isochromatic data obtained
from finite element method and a conformal mapping procedure, stress components and photoelastic fringes in the hybrid region
were calculated. To easily compare calculated photoelastic fringes with experiment results, the fringe patterns were reconstructed,
doubled and sharpened. Good agreement shows that the method presented in this paper is reliable and convenient. This method
can then directly be applied to obtain mixed mode stress intensity factors from the experimentally measured isochromatic data
along the straight lines.

KeywordsPhotoelasticity–Polariscope–Stress intensity factor–Isochromatics–Isoclinics–Inclined crack–Mixed-mode stress intensity factor–Photoelastic fringe doubling–Fringe sharpening

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Available from: Tae Hyun Baek, May 05, 2015
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    ABSTRACT: In this research, a study on stress shape functions was conducted to analyze the contact stress problem by using a hybrid photoelasticity. Because the contact stress problem is generally solved as a half-plane problem, the relationship between two analytical stress functions, which are compositions of the Airy stress function, was similar to one of the crack problem. However, this relationship in itself could not be used to solve the contact stress problem (especially one with singular points). Therefore, to analyze the contact stress problem more correctly, stress shape functions based on the condition of two contact end points had to be considered in the form of these two analytical stress functions. The four types of stress shape functions were related to the stress singularities at the two contact end points. Among them, the primary two types used for the analysis of an O-ring were selected, and their validities were verified in this work.
    Transactions of the Korean Society of Mechanical Engineers A 03/2013; 37(3). DOI:10.3795/KSME-A.2013.37.3.345