CTODi MEASURED BY MEANS OF A MODIFIED CHARPY-V-SPECIMEN

Abstract— Measurements of CTOD_i on Charpy-V-specitnens of mild steel St 37 and pressure-vessel steel 22NiMoCr37 have been carried out. Slotted and precracked specimens have been used besides the original V-notched ones. A definition of CTOD = 2(R – R_o) has been proposed which corresponds to δ₄₅, defining the CTOD of fatigue cracks. The symbols R_o and R represent the original and the actual crack tip radii respectively. Additionally, this definition presents the opportunity to measure CTOD and CTOD_i by a direct metallographic method. It is demonstrated that COD testing, based on the hinge model, can also be applied to slotted bars, delivering CTOD and CTOD_i values which are equal to those evaluated by direct metallographic measurements.
The results obtained on four different tip radii, R_o, show a linear increase of CTOD_i as a function of R_o, which is steeper for the softer material St 37. The extrapolation to the tip radius R_o=0 gives a CTOD_i, which is equal to those determined from precracked specimens.