Creep crack growth behavior in 316 stainless steel at 594�C (1100�F)

A~traet. The time-dependent deformation and cracking behavior of the quenched and tempered steel 15 NiCuMoNb 5 was investigated in the temperature range 20°C to 400°C. Fracture mechanics tests were carried out under various loading conditions including load-hold times of up to three weeks. The time-dependent crack growth can be described by the crack resistance (JR-) curve. Only above 300°C, the JR-curves obtained from constant-load tests start to deviate substantially from constant-displacement-rate tests. In this temperature range, the C,-parameter, which has been developed for creep crack growth testing, can be used to describe crack growth rates. For practical purposes, it is important to note that hold-time effects reduce the load-bearing capacity of cracked specimens by less than 10 percent for the present material and testing conditions.

Section: An Attempt To Relate Crack Growth Rate To Jmentioning

confidence: 94%

Time-dependent deformation and fracture of steel between 20�C and 400�C

Kuhnle

Riedel

1987

“…F is the K-calibration factor, F = ( K / P ) B W 1/2. F t = dF/d(a/W), r 1 are geometric functions given in [15,16].…”

Section: Estimation Of (Ct)avg and (Da/dt)avgmentioning

confidence: 99%

Characterization of creep-fatigue crack growth behavior in 2.25 Cr-1 Mo steel using (C t)avg

Grover

Saxena

1995

Time-dependent creep-fatigue crack growth (CFCG) is an important consideration in the design and remaining life estimation of high temperature components. CFCG tests were carried out on compact type (CT) specimens of 2.25 Cr-1.0 Mo steel and its behavior, for hold times ranging from 10 seconds to 50 seconds, at 594°C (1100°F) was characterized using the average value of the Gt-parameter, (Ct)avg. The trends in the creep-crack growth (CCG) data for this material are also compared with the CFCG data. The analytically estimated values of (Ct)avg are compared with the experimental values of (Ct)avg obtained from the measured values of load-line deflection rates. It is also shown that even in the absence of accurate creep deformation constants, accurate estimates of the measured values of (Ct)avg can be obtained in CT specimens.

“…A number of authors have found a rather good correlation with C* in experiments for carbon steel, chromium-molybdenum steel and various stainless steels (see Taira et al [1], Ohtani [2], Jansson [3], and Riedel [4]). In experiments for stainless steel Maas and Pineau [5] also find a reasonable correlation with an experimentally measured C* at relatively high crack growth rates; but these authors as well as Saxena et al [6] caution against the use of the experimentally measured C* value, proportional to the load displacement rate, since this experimental value is not always representative of the contour integral.…”

Section: Introductionmentioning

confidence: 87%

Analysis of creep crack growth by grain boundary cavitation

Tvergaard

1986

Intergranular creep crack growth in metals at high temperatures is analysed by assuming that the crack advances when cavities coalesce on grain boundary facets approximately normal to the maximum principal tensile stress. The analyses are based on a material model that describes the nucleation and growth of grain boundary cavities, accounting for diffusive growth as well as growth by dislocation creep of the surrounding grains, and also incorporating the effect of grain boundary sliding. Plane strain center cracked panels are analysed by a numerical method that fully accounts for the development of damage in every point of the specimen, and the solutions are compared with crack growth rates predicted by a simple model based on the singular stress fields around the tip of a sharp crack. The development of crack growth rates and the general crack growth patterns predicted by this material model are determined for a range of material parameters, including cases where failure occurs at small strains as well as cases where failure occurs at large strains.