Issue 41

V.Shlyannikov et alii, Frattura ed Integrità Strutturale, 41 (2017) 285-292; DOI: 10.3221/IGF-ESIS.41.38 Focused on Crack Tip Fields 285 The effect of creep damage formulation on crack tip fields, creep stress intensity factor and crack growth assessments V. Shlyannikov Kazan Scientific Center of the Russian Academy of Sciences, Russia shlyannikov@mail.ru , http://orcid.org/0000-0001-2345-6789 A. Tumanov Kazan Scientific Center of the Russian Academy of Sciences, Russia tumanoff@rambler.ru , http://orcid.org/0000-0002-2345-6790 A BSTRACT . Fields of stress, strain rate and process zone of a mode I creep crack growth are analyzed by employing damage evolution equations. Damage models for fracture of process zone represented by stress based formulation. Two expressions are presented to describe the stress-sensitive nature of multi- axial rupture behavior. Both damage free and defective creeping solids have been studied. The variation of creep stress and the crack-tip governing parameter in the form of creep I n -integral with time and the evolution of creep damage were analyzed by using the FE-model. The effect of the introduced creep stress intensity factor as a function of creep time through the continuum damage mechanics of the creep crack growth are discussed in detail. K EYWORDS . Creep damage; Creep SIF; Multi-axial stress function. Citation: Shlyannikov, V., Tumanov, A., The effect of creep damage formulation on crack tip fields, creep stress intensity factor and crack growth assessments, Frattura ed Integrità Strutturale, 41 (2017) 285-292. Received: 28.02.2017 Accepted: 03.05.2017 Published: 01.07.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he high temperature damage accumulation and growth that occurs under creep conditions unites of changes in material microstructure, void nucleation, interaction and growth on grain boundaries leading to creep rupture. A number of approaches have been proposed in the literature for the damage analysis and the estimation of stress- strain rate variation at the crack tip in creeping solids [1-8]. Some of them take into account the effect of multi-axial states of stress in the form of stress and ductility based models [1,2,8]. The authors analyzed the influence of creep damage on crack tip fields under small-scale and extensive creep conditions by the use of an asymptotic analyses [5,6] and finite element method [7]. In this paper, attention is directed on defective solids behavior in which stress-strain state changed as a result of the damage accumulation at the crack tip for steady state secondary creep conditions. The multi-axial stress function and continuum damage model are discussed and developed in order to assess the creep crack growth on the basis of a creep stress intensity factor. T