13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- fracture resistance test results for the SE(B) specimens made of aluminum alloy (Al-alloy) 5083 H-112 reported by the authors [5]. The Al-alloy has a Young’s modulus E of 69 GPa, with a Poisson’s ratio of υ = 0.3, the yield stress of σy = 243 MPa and the ultimate stress of σu = 347 MPa. Figure 2a presents the uniaxial stress-strain curves for the aluminum alloy material obtained from the axial tension test. Figure 2a sketches the geometry of the SE(B) specimen. The total thickness of all the SE(B) specimen equals B = 18 mm, with the net-thickness after side-grooving equal to 80% of the total thickness, or BN = 0.8B. The width of the specimen, W, equals to 36 mm, while the span over width, S/W, has a constant ratio of 4 for all SE(B) specimens. The CMOD or Δ is measured by the crack opening displacement gauge mounted at the mouth of the crack. The initial crack depth over the width ratios, a0/W, equal 0.222 and 0.513 for the Al-alloy SE(B) specimens. The SE(B) specimen with a relatively shallow crack depth (a0/W ≈ 0.2) represents a fracture specimen with low crack-front constraints, while the deep crack (a0/W ≈ 0.5) corresponds to a high crack-front constraint condition complying with the ASTM E-1820 requirement [1]. (a) (b) (c) Figure 2. (a) Uniaxial stress-strain curves for the aluminum alloy material; (b) geometric configuration of the SE(B) specimen; and (c) the typical FE mesh for the SE(B) specimen. Figure 2c shows a typical, half FE model for the Mode I SE(B) specimens, built from 3D 8-node brick elements. The FE model consists of one-layer of elements in the thickness direction, with all nodes in the FE model constrained against the out-of-plane displacement to represent the
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