On the identification of earlywood and latewood radial elastic modulus of Pinus pinaster by digital image correlation: a parametric analysis

This work addresses the reconstruction of strain gradient fields at the wood growth ring scale from full-field deformation measurements provided by digital image correlation. Moreover, the spatial distribution of the earlywood and latewood radial modulus of elasticity is assessed. Meso-scale tensile tests are carried out on Pinus pinaster Ait. Wooden specimens oriented in the radial–tangential plane under quasi-static loading conditions. A parametric analysis of the twodimensional digital image correlation extrinsic and intrinsic setting parameters is performed, in a balance between spatial resolution and resolution. It is shown that the parametric module is an effective way to quantitatively support the choice of digital image correlation parameters in the presence of the high deformation gradient fields generated by the structure–property relationships at the scale of observation. Under the assumption of a uniaxial tensile stress state, the spatial distribution of the radial elastic modulus across the growth rings is obtained. It is observed that the ratio of the radial modulus of elasticity between latewood and earlywood tissues can vary significantly as a function of the digital image correlation parameters. It is pointed out, however, that a convergence value can be systematically established. Effectively, earlywood and latewood stress–strain curves are obtained and elastic properties are determined assuming the converged digital image correlation setting parameters

Single cube apparatus - Shear properties determination and shear strain variation in natural density gradient materials

Transversal shear of softwoods was studied with the single cube apparatus (SCA). Fullfield strain data and FEA were used to validate the device. Once a close to pure shear strainregion was confirmed, the relationship between shear strain and radial density gradient wasobtained; finally an improved FE model was created.</p

Basis set effects on Cu(I) coordination in Cu-ZSM-5: a computational study

DFT calculations on the coordination of Cu+ to the framework oxygen atoms of Al-substituted ZSM-5 were performed by using combinations of different basis sets in order to investigate the dependence of the results on the adopted computational level. With low-end basis sets, a large basis set superposition error (BSSE) favors the coordination of Cu+ to three to four oxygen atoms of the framework, only two of which belong to the AlO4 tetrahedron corresponding to the investigated T-site. More extended basis sets considerably lower the BSSE and favor the coordination of Cu+ to only two oxygen atoms of the AlO4 tetrahedron. Upon interaction with NO, the Cu+ ion is always coordinated by two oxygen atoms of the AlO4 tetrahedron, independently of the basis set adopted and of the coordination number before NO adsorption. The shift from three-to twofold coordination caused by the Cu+-NO interaction requires a deformation energy that lowers the final adsorption energy. Such an effect is relevant with low-end basis sets, whereas it is substantially absent with more extended basis sets, which favor the twofold coordination of Cu+ even before NO adsorption. As a result, high-end basis sets increase the NO interaction energy with respect to that calculated by low-end basis sets, in agreement with experiments and suggesting a possible re-interpretation of the catalytic properties of the investigated sites. Provided suitable scale factors are employed, the N-O stretching frequencies of adsorbed nitrogen oxide calculated by sufficiently extended basis sets turned out in fair agreement with experimental findings