UBC Theses and Dissertations
Fracture toughness of pipe line steels Maiti, Ranen
The fracture toughness of two acicular ferrite, HSLA pipeline steels was investigated utilising the linear elastic fracture mechanics analysis (K[sub Ic] testing according to ASTM Standard E399-74) as well as the elastic-plastic fracture mechanics analysis (J-Integral and crack opening displacement COD methods). The tests were conducted at a static strain rate of 10⁻⁵/sec, K = 10 ksi√in/sec with H inch thick compact tension specimens. A resistance curve test technique developed by Landes and Begley was employed to obtain the J[sub Ic] fracture toughness; whereas the British Standard for COD testing was followed for measuring the δ[sub c] fracture toughness. The anisotropy in fracture toughness and the tensile properties of the two x-70 steels were measured and explained in terms of sulphur content and rare earth additions. An attempt was made to correlate the linear elastic fracture toughness K[sub Ic] or K[sub Q] values with the elastic-plastic fracture toughness, J[sub Ic],and COD data for both steels for tests in each of three notch orientations i.e. parallel to the rolling direction (T-L); parallel to the pipe axis; transverse to the rolling direction (L-T). Tests were performed at temperatures throughout the transition range i.e. from RT down to - 196°C. Finally the static fracture toughness data as generated in this study, was compared with the dynamic fracture toughness as obtained from IIT test for both steels.
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