Special Features of Creep-Crack Propagation in Refractory Nickel Alloys under Static Loading

We study creep-crack growth rate in standard specimens of alloys ÉP742 and ÉP962 at a temperature of 973 K under static loading. It is demonstrated that the alloys, which are close in chemical composition and mechanical properties, differ in creep-crack growth resistance.     

A calculation-experimental study of crack-tip opening displacement and residual stresses upon warm prestressing

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.     

Prediction of the temperature dependence of fracture toughness of 12Cr–2Ni–Mo refractory steel

We study the influence of temperature and the size of the specimens on the characteristics of static crack resistance of 12Cr–2Ni–Mo refractory steel. It is shown that, in the temperature range 20–450°C, the increase in the thickness of specimens leads to an insignificant increase in fracture toughness obtained along a 5% secant line according to the standards of evaluation of the characteristics of crack resistance. The evaluation of the characteristics of crack resistance of 12Cr–2Ni–Mo steel with regard for the scale effect according to an earlier developed numerical-experimental model reveals the existence of satisfactory agreement with the experimental data in the entire investigated temperature range. Translated from Problemy Prochnosti, No. 4, pp. 78–88, July–August, 2009.     

Theoretical-experimental model for predicting crack growth rate in structural alloys under combined action of fatigue and creep

Holding periods of 300 and 3600 s in a trapezoidal load cycle are shown to increase the crack growth rate dozens of times for alloy éP962 and several-fold for alloy éP742 at a temperature of 973 K. It is demonstrated that in the presence of the first portion on the creep crack growth diagram, whereon the crack growth rate decreases, the crack growth kinetics for a trapezoidal load cycle can be predicted using the hypothesis of the linear summation of fatigue and creep crack growth rates provided that the peculiarities of the first portion of the creep crack growth diagram are taken into account. Empirical approaches are proposed for determining the mean crack velocity in the first portion of the creep crack growth diagram. __________ Translated from Problemy Prochnosti, No. 1, pp. 105–112, January–February, 2009.     

On Experimental Procedure Development for Evaluating the Effect of Biaxial Loading on the Static Crack Resistance Characteristics of Reactor Vessel Steels

Strength of Materials - According to modern normative documents, the loading of postulated cracks in reactor vessels and standard specimens during crack resistance tests has a number of...