MEASUREMENT OF THE FRACTURE ENERGY USING 3-POINT BEND TESTS .3. INFLUENCE OF CUTTING THE P-DELTA TAIL

Available measures of the fracture energy G(F) obtained with the procedure proposed by RILEM TC-50 provide values that appear to change with sample size, calling into question the possibility of considering G(F) as a material parameter. In previous papers several sources of energy dissipation were analysed and it was concluded that, although important, they were not enough to account for the measured size effect. Here, the dissipated energy at the very end of the test is analysed. It is shown that this energy cannot be neglected for small specimens if the tests are interrupted at a reasonably low rotation. When this energy is taken into account, the final values of G(F) appear to be almost size-independent. This result supports G(F) as a material parameter and provides further confidence in the RILEM proposal. Moreover, it furnishes a physical explanation for the perturbed ligament model previously developed by the authors.