Cite as: Heerens, J.; Schwalbe, K.; Cornec, A.: Modifications of ASTM E 813-81 standard test method for an improved definition of Jic using new blunting-line equation. In: Read, D.; Reed, R. (Ed.): Fracture Mechanics: Eighteenth Symposium - ASTM STP. Philadelphia: ASTM. 1988. 374-389.