Creep-rupture prediction for steels and alloys by parametric methods and the base diagram method. Part 2. Extrapolation analysis of experimental data

Abstract

Results of extrapolation analysis of over 250 creep-rupture diagrams by the Larson-Miller, Manson-Haferd, Orr-Sherby-Dorn methods and the base diagram method are presented. It is established that the use of extrapolation calculations instead of interpolation ones may lead to a two-fourfold increase in prediction errors. The reasons for a considerable increase in prediction errors and possibilities of their elimination are analyzed.

Methodological aspects of creep prediction for heat-resistant steels and alloys. Part 2. Prediction over wide ranges of temperatures and loading times

“…This monotonicity is in agreement with the concepts predominant in creep-rupture prediction. At the same time, NIMS* data analysis results point to a considerable disturbance of monotonicity [12]. For example, for 12Kh2M1 steel at 500, 550, 600, and 650°C and 10 4 -10 5 -h loadings, Δβ 2 values, characterizing changes in slopes of corresponding creep-rupture diagram portions, were 0.2, 0.2, 0.7, and −0.2, for 25Kh1M1F steel at 500, 550, and 600°C, those values were 0.2, 0.7, and 0.5, respectively, which is the evidence of monotonicity disturbance.…”

Studies on the chemical composition–creep-rupture strength relation for heat-resistant nickel alloys

“…However, most investigations were carried out by BDM-2 [16,17], which is used for two-three log-time prediction cycle, i.e., at q = 1-3 or more. At the same β β − e difference, prediction accuracy can show a decrease due to an increase in the number of log-time prediction cycles, as well as due to stress-dependent β values.…”

“…From formula (16), such an increase in the C value for hardened alloys is controlled by the value of log( ), σ σ 1 2 and, thus, is attributed to different slopes of the two diagrams at two temperatures. Analysis [16,17] points to a low sensitivity of the constants of parametric methods to strain-softening of examined metals and alloys.…”