Kh. Kloos et al., DIRECT CREEP CURVE ASSESSMENT AND OPTIMIZATION OF CREEP EQUATIONS FORHIGH-TEMPERATURE ALLOYS, Steel research, 67(4), 1996, pp. 156-162
The conventional use of a time temperature parameter method for the ba
sic assessment of a multi-heat creep data set facilitates the establis
hment of a creep equation for a material type. However, the parameter
can introduce some distortion to the creep data and hence the creep eq
uation. To avoid this disadvantage, a new method for the direct creep
curve assessment of multi-heat data was developed. Systematic deviatio
ns in creep behaviour of individual test materials in respect to the m
ean behaviour of the multi-heat data set are reduced and the creep cur
ves for individual stresses are transformed to mid creep curves of a l
imited number of stress classes. With this method large multi-heat cre
ep data sets of Alloy 100 and Alloy 738 LC could be reduced to mean cr
eep curves. On this basis, existing parameter based creep equations we
re examined and optimized, if necessary. Further, the confidence limit
s of these equations were determined. With a stress modification the c
reep behaviour of a material similar in structure can be described. In
finite element analyses some verification experiments which simulate
typical loading conditions of components could be successfully recalcu
lated with the optimized creep equations.