CRACK INITIATION AND GROWTH UNDER CREEP AND CREEP-FATIGUE LOADINGS OF 1Cr-1Mo-0.25V STEEL

R. Piques  E. Moline  A. Pineau      

Anales de la Mecánica de la Fractura, nº 9 . 1992 . Pág. 176 -182
Ver (.pdf): Anales09-031

Resumen: The present study deals with crack initiation and growth, under creep and creep-fatigue conditions, in 1Cr-1Mo-0.25V steel. In this creep ductile material, most studies have focussed on the creep crack growth (CCG) rates, da/dt, and load-geometry parameter C* correlations. Here the creep crack initiation (CCI) time is defined as the time, T¡, necessary for a defect to grow by a small critical distance, Xc. This initiation stage may represent a large part of the rupture life of a cracked component. The importance of such studies is discussed in the first part. In the second part, an attempt is made to present a simplified method based on the fracture mechanics of creeping solids (FMCS) to define the relevant load-geometry parameters for crack initiation and crack growth under creep-fatigue loadings. In particular, it is shown that da/dN-L1K correlations apply only when the hold time, th is lower than the transition time, ttr between small-scale and large-scale yielding conditions. Converse! y, for long hold times, it is suggested to use the T¡- C * correlatíon to predict the fatigue life.

LocalizaciónAiguablava, Gerona

Centre des Matériaux - Ecole des Mines. B.P.87- 91003 EVRY CEDEX- France