Exact derivation of the geometric correction factor of the center notched test specimen, based on small cracks merging as explanation of softening

The exact derivation of the mode I geometric correction factor is given, based on the small crack merging mechanism to show that this always is the real fracture mechanism in wood. This mechanism dominates at late softening and explains fully the apparent decrease of the energy release rate of macrocrack extension as already known for mode I and...