Evaluation of crack tip constraint using photoelasticity

Computational and experimental identification of coefficients of the Williams series expansion by considering higher order terms in the cracked specimens through digital image analysis

In this article, the interaction of arbitrary multiple cracks in an infinite plate is examined by means of a boundary element method consisting of the non-singular displacement discontinuity element presented by Crouch and Starfied and the crack tip displacement discontinuity elements proposed by the present author. In the boundary element implementation, the left or the right crack tip element is placed locally at the corresponding left or right crack tip on top of the constant displacement discontinuity elements that cover the entire crack surface and the other boundaries. The present numerical results of stress intensity factors (SIFs) for some typical multiple crack problems show that the numerical approach is simple yet very accurate for analysing the interaction of arbitrary multiple cracks in an infinite plate.

Stress intensity factors for cracks emanating from a triangular or square hole in an infinite plate by boundary elements

Thermal shock fracture of a cylinder with a penny-shaped crack based on hyperbolic heat conduction

Effect of T-stress on the fracture of a four point bend specimen

Determination of dynamic fracture toughness for PMMA

Adaptive Delaunay triangulation with object-oriented programming for crack propagation analysis

The effect of T-stress on the brittle fracture under mixed mode loading

The optical methods of photoelasticity and caustics have extensively been used for the determination of stress intensity factors (SIFs) in static and dynamic crack problems. Both methods present their potentialities and limitations. In crack problems the state of stress in the neighborhood of the crack tip changes from plane strain near the tip to plane stress away from the tip through an intermediate three-dimensional region. This affects the determination of SIFs using experimental methods. In the present work the methods of photoelasticity and caustics applied to crack problems are briefly presented and compared regarding the following criteria: the optical set-up, the efficiency in the determination of stress intensity factors, the effect of crack tip radius, the effect of plate boundaries, the location of the crack tip and the changing state of stress near the crack tip.KeywordsPhotoelasticityCausticsCracksStress intensity factorsPlane-stress-Strain

Investigation on fracture toughness and micro-deformation field of SCB sandstone including different inclination angles cracks

Analysis of subsurface crack propagation and implications for wear of elastically deforming materials

Aging aircraft may contain many cracks resulting from their long service. Therefore, it is necessary to repair the cracked aircraft structural components to extend the service life of the aircraft. Adhesively bonded composite repair is an efficient method to extend the fatigue life of cracked components in advanced aerospace structures. In this study, a 2-D finite element model of an aluminum panel with a crack perpendicular to the load direction has been developed which is also used to model and analyze the repaired thick panel.. The panel is reinforced with singlesided composite patch made of Carbon/Epoxy composite material. Different lay-ups of 0°, +45°, and 90° have been used to achieve the minimum stress intensity factor at the crack tip. At +45°, due to generation of maximum in-plane shear stress in composite patch and adhesive the effect of patch on crack suppression is minimized. The configuration consists of aluminum panel, composite patch and adhesive layer denoted here as PCA. The uniqueness of this configuration is due to its stacking and lay-up of the adhesive layer. Instead of spring elements commonly used in previous studies, this analysis modeled the adhesive layer as an elastic continuum. The stress intensity factor is calculated using both the displacement and the JIntegral methods. The importance of using J-Integral method here is the selection of path around the crack tip, where, one path is chosen in the plastic zone at crack tip and the other is selected in the elastic region. For patched cracked aluminum panel it has been found that both counters have resulted in close values of stress intensity factors due to effectiveness of the PCA configuration. Finally, methods to measure the stress intensity factor and the fiber angle for achieving the minimum stress intensity at crack tip have been discussed.

The dynamic stress field near a propagating crack tip is usually characterized in terms of one parameter, namely, the dynamic stress intensity factor. While analytically this is an exact representation at the crack tip itself, under transient conditions, the domain of dominance of the stress intensity factor varies as discussed by Ma and Freund (1986). In this paper, we present experimental results which show that while the stress intensity factor may dominate the near tip stress field under transient conditions as long as the crack velocity is small, it may not be dominant over an appreciable region under other transient conditions of crack tip motion, thus making it difficult to determine this quantity experimentally.

About the effect of plastic dissipation in heat at the crack tip on the stress intensity factor under cyclic loading

The use of quarter point element in dynamic crack analysis