Article

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: 1.09). 01/2011; 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

0 Bookmarks
 · 
121 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Fracture coefficients, together with the exact origin of the crack, were extracted from data sets produced an overdeterministic system solved by an iterative least squares method. Power series type williams equations were used in the analyses. The accuracy evaluation indicated that the first four terms of williams equations are sufficient to describe the stress field in the vicinity of the crack tip for both mode I and mixed mode cases. Experimental study showed that the first two terms of williams equations, which are the same as the modified westergaard equations, cannot be used to extract mixed mode fracture parameters accurately within the data collection region of 0.07 <r/a <0.30, where r and a are radial coordinate and crack length for an edge crack, respectively.
    Journal of Mechanical Science and Technology 02/1991; 5(1):22-27. · 1.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Photoelasticity is one of the most widely used whole-field optical methods for stress analysis. The technique of birefringent coatings, also called the method of photoelastic coatings, extends the classical procedures of model photoelasticity to the measurement of surface strains in opaque models made of any structural material. Photoelastic phase-shifting method can be used for the determination of the phase values of isochromatics and isoclinics. In this paper, photoelastic phase-shifting technique and conventional Babinet-Soleil compensation method were utilized to analyze a specimen with a triangular hole and a circular hole under bending. Photoelastic phase-shifting technique is whole-field measurement. On the other hand, conventional compensation method is point measurement. Three groups of results were obtained by phase-shifting method with reflective polariscope arrangement, conventional compensation method and FEM simulation, respectively. The results from the first two methods agree with each other relatively well considering experiment error. The advantage of photoelastic phase-shifting method is that it is possible to measure the stress distribution accurately close to the edge of holes.
    Journal of Solid Mechanics and Materials Engineering 01/2008; 2:549-556.
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, the linear and nonlinear leastsquares methods are developed in matrix notation as solution schemes to determine key parameters from whole-field fringe patterns. Examples of the proposed methods to the determination of the photoelastic-fringe constant from a disk in diametral compression and the opening-mode geometric stress-intensity factor from the photoelastic-fringe loops in the neighborhood of a crack tip are presented. In the latter example, the location of the crack tip is treated as an unknown to be determined from the analysis.
    Experimental Mechanics 05/1980; 20(6):192-197. · 1.55 Impact Factor

Full-text

View
2 Downloads
Available from