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For a reactor pressure vessel steel 15Kh2MFA(III) experiments and calculations have been carried out to study the factors that have an influence on the increase of the lower-shelf fracture toughness in the temperature dependence diagrams upon warm prestressing. Stereoscopic fractography and numerical investigation have demonstrated that after the warm prestressing the crack tip remains blunt. This reduces the stress singularity during subsequent loading and raises the material fracture toughness. The paper gives the calculated data on residual stresses and crack-tip opening displacement during warm prestressing and upon relief. The calculated results are shown to agree well with the known analytical relations and experimental data. [ABSTRACT FROM AUTHOR]

The paper addresses the use of small-sized specimens of various types, including those with deep (50%) side grooves, for the purpose of fracture toughness prediction. The experimental data for numerous (more than 500) small-sized specimens prepared from materials of various degrees of embrittlement are compared to the test results for full-sized specimens of C(T) type. The concepts of Master Curve and Unified Curve are applied for the processing of experimental data. To handle the test results for small-sized deep-grooved specimens a calculation procedure has been elaborated, which adjusts the calculation method specified in the ASTM Standard E 1921. We provide recommendations of how to use precracked Charpy type deep-grooved (50%) specimens for prediction of a representative temperature dependence of fracture toughness. [ABSTRACT FROM AUTHOR]

Using the Unified Curve method as proposed by the authors earlier and a probabilistic model based on the local approach and physical background of the influence of impurities and carbide size on the local strength of material, a method has been elaborated for predicting a variation of the temperature dependence of fracture toughness with neutron fluence. The results calculated by this method are compared to the available experimental data. [ABSTRACT FROM AUTHOR]

We have studied the effect of residual stresses on fracture resistance and crack arrest behavior of asymmetric ceramic laminated Si3N4/Si3N4-TiN structures. Using the compliance method, we assessed the technique of R-curve construction for laminar composites. For laminar structures with layers varying by their elastic characteristics we developed an analytical method for calculation of "fracture resistance - crack length" dependence. The method applicability is verified by calculation of stress intensity factors for laminar specimens with an edge crack The calculated results are compared to the experimental data. [ABSTRACT FROM AUTHOR]