Papers by Keyword: General Singular Stress Concentrator

Abstract: General Singular Stress Concentrators (GSSCs) which exhibit singular stress concentration are often responsible for crack initiation and thus failure of the component. The GSSC of the type of bonded bi-material junction occurs in a variety of technical applications including but not limited to sharp material inclusions, silicate based composites and electronic components. The GSSC cannot be assessed by means of standard fracture mechanics. Approaches of generalized fracture mechanics require precise description of stress distribution near the stress concentration points. In order to determine the stress field accurately, the paper incorporates the multi-parameter based description.

Abstract: The paper focuses on the geometrical proportions of cube-shaped quasi-brittle specimens subjected to a wedge-splitting test (WST). The minimal/optimal initial crack/notch length for successful performance of WST on these specimens is studied numerically (ANSYS). This second part of the paper treats the problem asymptotically, i.e. from the point of view of a very fine grained silicate composite material with negligible characteristic length which describes the level of the material brittleness (i.e. brittle). The problem of competition of the crack initiation point between the notch tip and the groove corner in the load-imposing area of the specimen is solved using theories of both linear elastic fracture mechanics and fracture mechanics of generalized singular stress concentrators. The numerically obtained crack/notch length is compared to results of numerical simulations using cohesive crack model reported in the first part of the paper. The minimal notch length is recommended.

Abstract: Composite materials or generally materials with interfaces are nowadays used in many varied engineering applications. In comparison with classical engineering materials the existence of material interface causes locally different stress distribution, which can strongly influence behaviour of whole structure and can have an important influence on failure mechanisms of such materials. The paper presented is devoted to the investigation of stress singularity exponents of a crack growing in a bimaterial body perpendicularly to the interface and touching the material interface. Discrepancies between value of stress singularity exponent in the centre of bimaterial body and on the free surface were found. The assumptions of linear elastic fracture mechanics (LEFM) and small scale yielding (SSY) are considered. For numerical calculations finite element analysis was used. Results obtained can contribute to a better understanding of failure of materials with interfaces.

Abstract: The influence of corner singularity on the distribution of the stresses around the crack front for a three-dimensional structure is described in this paper. The distribution of stress singularity through the thickness of the middle tension specimen provides us an indication of crack behaviour close to a free surface. An estimation of the region where the change of singularity exponent plays an important role in fatigue crack propagation rate was carried out. A decrease in fatigue crack propagation rate close to the free surface was found. The lower fatigue crack propagation rate in the boundary layer in comparison with the interior of the specimen leads to a change of intersecting angle between crack and free surface and depends on Poisson’s ratio.