Fracture Studies of Straight Pipes Subjected to Internal Pressure and Bending Moment

Total three straight pipes have been studied which are used in the Primary Heat Transport system of Indian PHWRs (Pressurized Heavy Water Reactor). The pipes have been fabricated with either circumferential throughwall crack or surface crack. Fracture tests have been performed on these pipes subjected to constant internal pressure and monotonically increasing four point bending load. Different experimental and finite element results like load vs. load line displacement, load vs. CMOD (Crack Mouth Opening Displacement), crack initiation loads are compared and found in good agreement. The experimental results have been used for calculation of fracture toughness i.e J-R curves for all three pipes. The differences in these J-R curves have been investigated in the light of prevalent crack tip constraints. Higher J-R curve of surface cracked pipe is attributed to prevalent lower crack tip constraint and vice versa is true for throughwall cracked pipes.