A NEW GENERALISED FORMULATION TO EVALUATE PLASTIC J-INTEGRAL FROM EXPERIMENTAL DATA

摘要

Experimental evaluation of J-integral requires 'η_(pl)' and 'γ' functions for the specific geometry. The 'η_(pl)' and 'γ' functions are available for very limited geometry under specified loading conditions. In the present paper, limit load based general expressions of 'η_(pl)' and 'γ' functions are proposed. These expressions are validated by deriving the known 'η_(pl)' and 'γ' functions of pipe with throughwall circumferential crack under four point bending load. The general expressions are then used to derive the 'η_(pl)' and 'γ' functions of elbow with throughwall circumferential crack configurations under in-plane bending moment, for which no solutions are available in the literature. Finally, experiments have been carried out on 200mm NB (Nominal Bore) elbows with throughwall circumferential crack under in-plane bending moment. The proposed new expressions of 'η_(pl)' and 'γ' functions for this geometry are used to obtain the J-R curve from the experimental load vs. load-line-displacement and load vs. crack growth data.