Quantification of Crack-Tip Constraint Effect on Master Curve Reference Temperature Based on Two-Parameter Approach

摘要

The master curve has evolved into a mature technology for characterizing the fracture toughness transition of ferritic steels. However, it is well known that the master curve reference temperature (T_o) values estimated from small laboratory specimen may be biased low due to loss of crack-tip constraint. To quantify such variations of T_o resulting from differences of crack-tip constraint of testing specimen, two-parameter fracture mechanics approaches are employed in the present study. In this context, fracture toughness test and 3-dimensional finite element (FE) analysis for several standard and nonstandard test specimens are performed to quantify relationship between variations of T_o and constraint parameters and to find best constraint parameter representing effect of crack-tip constraint on T_o values evidently. Based on testing and present FE results, T_o and constraint parameter loci are constructed and engineering T_o correlation models considering crack-tip constraint are suggested.