jmc-xavier

The direct identification of the cohesive law in pure mode I of Pinus pinaster is addressed. The approach couples the double cantilever beam (DCB) test with digital image correlation (DIC). Wooden beam specimens loaded in the radial-longitudinal (RL) fracture propagation system are used. The strain energy release rate in mode I (GI ) is uniquely determined from the load-displacement ( P ?? ) curve by means of the compliance-based beam method (CBBM). This method relies on the concept of equivalent elastic crack length ( eq a ) and therefore does not require the monitoring of crack propagation during test. The crack tip opening displacement in mode I ? ? I w is determined from the displacement field at the initial crack tip. The cohesive law in mode I I I (? ? w ) is then identified by numerical differentiation of the I I G ? w relationship. Moreover, the proposed procedure is validated by finite element analyses including cohesive zone modelling. It is concluded that the proposed data reduction scheme is adequate for assessing the cohesive law in pure mode I of P. pinaster.

The non-linear shear behaviour of bovine cortical bone is measured by coupling the Arcan test with digital image correlation. The experimental study is carried out on specimens taken from bovine femur and oriented along the longitudinal-tangential material plane. An ad hoc Arcan fixture is built to transfer the cross-head displacement of the testing machine into a shear loading at the centre of the V-notched section. A validation of predominant shear behaviour at the gauge section is shown from full-field deformation measurements. Moreover, direct evaluation of the shear modulus is obtained by integrating the shear strain component along the V-notches, avoiding numerical correction factors required in the classical data reduction scheme. The shear modulus of bovine cortical bone is found in good agreement with references from literature. Moreover, the shear stress at maximum load is understood as a suitable estimation of the shear strength. Furthermore, the Ramberg�Osgood model is found to provide an accurate description of the non-linear shear behaviour of bone tissue.