Correlation of the Master curve reference temperature T0 with unified constraint parameter

The Master Curve (MC) reference temperature T0 is affected by specimen or component geometry, crack size and loading condition, i.e, affected by the crack-tip constraint. In order to apply the MC method in fracture assessment more accurately, it is necessary to consider the constraint effect and establish a quantitative correlation between T0 and constraint parameter. In this work, the correlation between the T0 and a new unified constraint parameter Ad*, which can characterize both in-plane and out-of-plane constraints, has been investigated. A large number of experimental fracture toughness and T0 data of different materials and specimen geometries in the literature were collected and used in the study. The parameter Ad* value of each specimen was calculated using finite element analysis. A linear T0-Ad* correlation equation has been established and validated by experimental data. The equation has good capability to predict the MC T0 for any cracked structures, and it is applicable to a wide range of materials, structural geometries, crack sizes, loading levels and temperatures.