FRACTURE TOUGHNESS DETERMINED FROM FULL-SCALE PIPE

摘要

Fracture toughness for full scale steel pipe of API 5L grade X65 PSL1 (ASTM A694F65) medium strength grade pipeline steel has been measured by a new test specimen utilizing the same procedure of the standard test methods ASTM E 399 -90 and E 1820-01. Full scale pipe with circumferentially machined notch is pulled axially by tensile load up to fracture. An external circumferential sharp notch has been machined in the wall of the pipe to simulate the crack. To insure a plane strain condition around the crack a well lubricated and axially free loaded plug has been mounted, symmetrically around the circumferential notch, inside the pipe. Evidences of cleavage fracture have been observed on the fracture surface. The measured value of the fracture toughness has been found to be very close to the values measured according to the standard test for steel plates of similar grade .The new proposed testing method for full scale pipe can be used regardless its dimensions since it appears to provide plane strain condition around the crack.