Influence of the Inclusion Particles Present in the Immediate Vicinity of a Crack on Stress Variation

Fracture toughness occurring in a material that has micro-cracks originating in its manufacture process may be improved by particle addition, these particles having different properties than the basic material [1]. This paper includes the outcome of a research on the influence of softer or harder particles added to the basic material, on the stresses occurring in the immediate vicinity of micro-cracks. Our research is designed to determine to what extent this process may result into preventing a crack from advancing into the material subject to unfavorable loads, depending on the direction of that crack. The outcome we achieved using finite element analysis supports the assumption that, by adding a certain amount of particles, which have specific characteristics, to the basic material, fracture toughness may increase significantly, [2]

Aspects of the determination of residual stresses in ceramics by ultrasounds hole-drilling

The paper presents a method of drilling in ceramics materials, applied for the determination of macroscopic residual stresses. To this end, high frequency vibrations of the ultrasound waves exercised on a drilling device are utilized. The shape and dimensions of the resulting hole depend on the shape and dimensions of the drilling device. The advantages of this method are: no additional stresses result from the application of this drilling procedure, the resulting hole has a satisfactory precision and the experiment may be repeated, macrostresses' variation in the studied material's depth may be determined