The influence of dynamic strain aging on fatigue and creep-fatigue characterization of nickel-base solid solution strengthened alloys

Abstract

The nickel-base solid solution alloys, Alloy 617 and Alloy 230, have been observed to exhibit serrated yielding or dynamic strain aging (DSA) in a temperatureystrain rate regime of interest for intermediate heat exchangers (IHX) of high temperature nuclear reactors. At 800 C, these nickel-base alloys are prone to large serrated yielding events at relatively low strains. The presence of DSA introduces challenges in characterizing the creep-fatigue and low cycle fatigue behaviour. These challenges include inability to control the target strains as a result of DSA induced strain excursions and distorted hysteresis loops. Methods to eliminate or reduce the influence of DSA on creep-fatigue testing have been investigated, including varying the strain rate, stepping to the target strain, and adjusting servo-hydraulic tuning parameters. It has not been possible to eliminate the impact of serrated flow in the temperature range of interest for these alloys without compromising the desired test protocols.

Life Estimation of Pressurized-Air Solar-Thermal Receiver Tubes

“…particularly for small strain amplitudes like those in the solarthermal receiver. As a check, we compared the predictions of correlations based on the data of Carroll et al [17], Lu et al [18], and more recent data [19]. At low strain amplitude the agreement between low cycle fatigue data and creep-fatigue data are close; all of the correlations that we compared agreed to within a factor of two for strain ranges smaller than 0.1%.…”

“…Dðe 1 À e 2 Þ j ¼ ðe total;z À e total;h Þ j À max ðe total;z À e total;h Þ j h i (15) Dðe 1 À e 3 Þ j ¼ ðe total;z À e total;r Þ j À max ðe total;z À e total;r Þ j h i (16) Dðe 2 À e 3 Þ j ¼ ðe total;h À e total;r Þ j À max ðe total;h À e total;r Þ j h i (17) and v, the Poisson ratio for elastic strain, is equal to 0.31. When choosing N in Eq.…”

“…Creep-Fatigue Data. Carroll et al [17] have measured the creepfatigue interaction for high temperature nickel alloys, including alloy 617 and Haynes 230. These measurements include creephold times of up to 30 min during the fatigue strain cycle; this is analogous to the long periods of creep following diurnal or cloud driven thermal cycles.…”

A New 3D Creep-Fatigue-Elasticity Damage Interaction Diagram Based on the Total Tensile Strain Energy Density Model

“…The creep failure energy density ∆W c calculated by Equation (12) and applied stress amplitude σ a is plotted in Figure 8, and a good linear relation was obtained between ∆W c and σ a within a certain stress range. Hence, the ∆W c in this paper was assumed as a linear function of σ a for calculation simplification.…”

“…Date et al [11] investigated the environmental effect on the fatigue and creep-fatigue behavior of 316 fire-resistant steel, longer fatigue lives were obtained in sodium than in air, and the hold position also affected the fracture behavior. In addition to environment and hold position effects, the influences of dynamic strain aging [12], strain rate [13], strain amplitude [14], and microstructural changes due to long-term service [15,16] were also pronounced in many cases. Since the material degradation under high-temperature fatigue loading possesses a very complex interaction process, modeling a reliable lifetime is still a challenging issue.…”