13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- The value of r in Eq. (8) equals 0.44 for SE(B) specimens, as outlined in standard material testing procedures [1]. This value of r, however, requires re-evaluation for the plate specimens subjected to the four-point bending shown in Figure 3. This study determines the r value through a detailed, large-deformation finite element analyses for plate specimens with a stationary crack. Figure 6 compares the deformed crack plane computed from the finite element analyses (represented by the discrete symbols) with the deformed shape calculated from a regressed rotation center with r = 0.18. The displacement uY in Figure 6 refers to the displacement in a direction perpendicular to the crack plane (see Figure 1 for the coordinate system X-Y-Z), while the Z value defines the crack-front position corresponding to which the displacements on the crack plane are measured. The results in Figure 6 indicates that the deformed crack plane aligns along a rotated plane with the rotation center calculated using r = 0.18. Figure 6. The r value for the plate specimens subjected to four-point bending. Figure 7. Evolution of the strain energy U for the four plate specimens. Using an r value of 0.18, the strain energy U for the plate specimen can now derive from Eqs. (7)
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