Objective comparison of the Unified Curve and Master Curve methods

Kim Wallin

    Research output: Contribution to journalArticleScientificpeer-review

    4 Citations (Scopus)


    The Unified Curve and the Master Curve are two popular cleavage fracture toughness assessment engineering methods. The methods are very similar. They basically differ only in the assumed fracture toughness temperature dependence. The standard Master Curve approximates the temperature dependence as being fixed, whereas the Unified Curve assumes that the shape changes as a function of transition temperature. The shape difference becomes significant only for highly brittle steels. Previous comparisons of the two methods have applied a procedure that may cause a bias on the comparison when assessing censored data sets. Here, a fully objective comparison using the censored likelihood, have been made for 50 large data sets with transition temperatures in the range +8 °C ... +179 °C. The standard Master Curve shows overall a trend of higher likelihood than the Unified Curve. It is also shown that, because of shortages connected to the use of the Prometey probabilistic cleavage fracture model, the Unified Curve cannot be considered universally applicable.
    Original languageEnglish
    Pages (from-to)31-40
    JournalInternational Journal of Pressure Vessels and Piping
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed


    • master curve method
    • unified curve method
    • brittle fractures
    • WST model
    • Prometey model


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