Fitted Equation of Specimen Thickness versus Critical Value of CTOD

A mathematical expression of the relation between crack tip opening displacement (CTOD) critical value (δ) and material thickness (t) was obtained by Barenblatt′s theory to study the effect of material thickness on CTOD critical value. A theoretical equation of δ and t was fitted by the least square method, and was verified by comparing with test results of 16MnNbp steel in a CTOD experiment. Results show that the fitted equation could be described as δ=0.05te－0.03t0.125+0.16(1－e－0.03t0.125). The calculated results could fitted well with test results.