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

Measurements of CTODi on Charpy-V-specimens of mild steel St 37 and pr essure-vessel steel 22NiMoCr37 have been carried out. Slotted and prec racked specimens have been used besides the original V-notched ones. A definition of CTOD=2(R - R(o)) has been proposed which corresponds to delta(45), 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 CTODi 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 CTODi values which are equal to those evalua ted by direct metallographic measurements. The results obtained on fou r different tip radii, R(o), show a linear increase of CTODi as a func tion of R(o), which is steeper for the softer material St 37. The extr apolation to the tip radius R(o)=0 gives a CTODi, which is equal to th ose determined from precracked specimens.