J - Resistance curve of X60 steel using SE(T) specimens by elastic compliance and potential drop methods André LM Carvalho  1 , Juliana P Martins 2 , Roberto R. Piovatto 3 and Waldek W Bose Filho 3 1 Department of Materials Engineering, Ponta Grossa State University, 84030-900, PR, Brazil 2 Chemical Engineering, UTFPR, 84016-210, Ponta Grossa, PR, Brazil 3 Department of Materials, Aeronautics and Automotive Engineering, EESC-USP, 13566-590, São Carlos, SP, Brazil  ’andrelmc@uepg.br Keywords: J-R curve, SE(T) specimen, unloading compliance, potential drop, API 5L X60 steel Abstract. In this article investigate J-R curves behavior through standard single-specimen technique using both the unloading compliance and potential drop method for measuring crack extension performed in shallow and deep cracked nonstandard specimens. Analysis from Electron Backscattered Diffraction (EBSD) was performed in the fracture regions where took place the delamination phenomena to obtain crystallography orientation all cleavage fracture zone. The results show in the delamination where predominates cleavage fracture has displayed crystallography orientation of {3 3 5}      with maxim intensity of 3.715. Potential drop method has showed the best performed in predict initiate crack length in comparison to unloading compliance. Introduction Large–diameter, high-pressure gas transmission pipelines have been used more and more widely all over the world. With the development of the pipeline network, safety and maintenance become an important task. The accurate prediction of fracture for oil and gas pipelines with crack-like flaws is essential for fitness-for-service (FFS) methodology, for instance, repair decisions and life-extension procedures and to ensure fail-safe operations which avoid costly leaks and rupture. As defects of various sizes are detected and thinning of pipe walls by aggressive gas gradients is inevitable with time, a better understanding of the fracture toughness and cracking resistance of the pipe materials is required [1]. Structural pipeline steels generally exhibit a significant increase in fracture toughness, characterized by the J-integral, over the first few millimeters of stable crack extension [2]. The J- integral values have been used extensively as indexes of material toughness for alloy design, material processing, material selection and specification, as well as quality assurance [3]. The fracture toughness J IC and J-integral resistance curves, namely, J-R curves have been also used in the integrity assessment of engineering structures with ductile crack tearing or growth. High pipeline steel press, it shows low-constraint because thin wall structure did not supply the strain plane stress. Whereas, the fracture toughness test standard ASTM E1820 was developed only for high constraint specimens, like deep cracked single-edge notched bend SE(B) and compact tension C(T) specimens with the expectation that the results represent lower bound toughness. Accordingly, the application of fracture toughness from high-constraint specimens to low-constraint geometries introduces a degree of conservatism into design [4]. While most of nonstandard specimens (SE(T) or real cracked structures (pipelines) have low crack-tip constraint. As results, the test data of J IC and J-R curves are strongly depend on the crack size or crack-tip constraint level [5]. Application of the measured