Tearing modulus based on J and COD was investigated on SNCM 8 alloy steel using three point bend specimen. Crack Growth were measured by the single specimen unloading compliance technique. The material tearing moduli $T_J$, mat and Tδ, mat were found nearly constant within the initial crack ratios studied in this work.
The empirical relationship between plastic component of J, Jp and plastic component of δ(CTOD), δp was estimated to calculate the applied tearing modulus based on J-integral($T_J$, appl) and the condition of unstable fracture was investigated.
It was concluded that the tearing theories based on J-R curve and COD-R curve could be almost equally applied to predict instability.
