13th International Conference on Fracture June 16–21, 2013, Beijing, China -3- in Eq. (6) denotes the total crack-front length. Equating Eqs. (4) and (6) allows the determination of the value of the dimensionless parameter η. 3. Experimental Validation 3.1. Specimen Configuration and Set-up The experimental program includes four specimens made of high-strength steels extracted from a large-scale circular hollow section joint [6]. Figure 1 illustrates the geometric configuration of the steel plate specimens with a machined surface notch. The shape of the surface notch follows a semi-elliptical configuration with the crack aspect ratio (a/c) equal to 0.5, i.e., the machined crack depth equals 10 mm. Figure 1. Configuration of the surface cracked plate specimens. Figure 2 shows the uniaxial true stress-true strain curve obtained from the axial tension test following the ASTM E-8M [7]. The steel material has a specified grade of S690, with a measured yield strength equal to 810 MPa, and a tensile strength of 866 MPa. The Young’s modulus of the material equals 206 GPa, with a Poisson’s ratio of 0.3. Figure 2. True stress-true strain curve of the S690 steel.
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