J-RESISTANCE RESULTS FROM MULTI-SPECIMEN AND SINGLE-SPECIMEN SURFACE NOTCHED SEN(T) GEOMETRY

摘要

In a collaborative program, J-R results were compared from multi-specimen and single-specimen procedures for toughness testing with single-edge notched tensile loaded SEN(T) specimens. Grade 483 MPa (X70) grade pipeline steel was used to prepare surface notched axially loaded specimens. Test procedures followed the multi-specimen method and a single-specimen recommended practice recently developed at the CANMET Materials Technology Laboratory (recently name-changed to CanmetMATERIALS) in a program jointly funded by PERD, PRCI, and DOT. The multi-specimen method adopted side grooves with the objective of comparison with results from the single-specimen method. The specimen geometry was B x B for both test procedures. The target a_o/W was about 0.5. The multi-specimen testing was performed at BMT Fleet Technology. The single-specimen testing was performed at the CANMET laboratory, formerly located in Ottawa. The paper describes experimental and analysis details, and compares results from the two techniques, using J expressions developed at CANMET. The results showed similar J-resistance curves at small crack extensions for both techniques, and higher J-resistance values at larger crack extensions for the multi-specimen method. The results are discussed in terms of initial crack length and the analysis methods adopted for the two techniques. Validity criteria according to ASTM El820 were applied and the results are presented.