In general, data regarding the mechanical properties of wood is still incomplete, mainly owing to the difficulties involved in preparing well-made standard testing samples, as well as the time-consuming evaluation tests. Therefore, the elastic constants for Pinus radiata in this paper were determined using ultrasound technology. In parallel, typical compression mechanical testing was carried out to compare the effectiveness of the nondestructive test using the ultrasound. The longitudinal elastic constant values were similar to the mechanical testing (ultrasound was 12,8 % higher than mechanical testing), showing that ultrasound technique is a reliable and valid tool. The values for radial and tangential moduli obtained by the ultrasound versus mechanical testing showed statistically significant differences. This may be due to the difficulty in obtaining adequate samples for mechanical testing. The symmetry of the shear modulus was revealed by the ultrasound technique (G_ij = G_ji). Poisson’s ratios were not comparable using either method; however, values obtained were more consistent with the existing literature for Pinus species. Additionally, the elastic anisotropy of the analyzed wood samples was demonstrated through the ultrasound velocity propagation in the material. It was thus possible to obtain the twelve engineering constants that characterize the mechanical behavior of wood employing of the proposed ultrasound technique. The results proved that this technique could be a useful tool for such characterization.

La utilización de técnicas no destructivas juega un papel importante y complementario en los procesos de caracterización de la madera. En este trabajo el objetivo fue evaluar algunas propiedades físicomecánicas de maderas nativas chilenas por medio de ultrasonido y compararlas con ensayos mecánicos tradicionales de flexión. Las maderas seleccionadas fueron cuatro latifoliadas: tepa (Laureliopsis philipiana), olivillo (Aextoxicon punctatum), laurel (Laurelia sempervirens) y lenga (Nothofagus pumilio), y dos coníferas: alerce (Fitzroya cupressoides) y mañío (Podocarpus nubigena). Para ésto, se utilizaron los equipos de ultrasonido Steinkamp BP5 y Panametric Epoch XT. Los resultados mostraron mayor anisotropía elástica para las latifoliadas que para las coníferas y una relativa simetría en las velocidades de propagación transversal y los módulos de corte a lo largo de las tres principales direcciones del árbol. También los valores medios de los módulos de elasticidad calculados por ultrasonido resultaron entre 25 y 47 % más altos que los medidos por ensayos mecánicos. AbstractThe non-destructive techniques are a very important tool in the process of wood characterization and evaluation. In this work, the objective is the evaluation of physical and mechanical properties of some native Chilean wood species by using the ultrasound techniques and their comparision with the results of typical mechanical tests. The selected woods were four hardwoods: tepa (Laureliopsis philipiana), olivillo (Aextoxicon punctatum), laurel (Laurelia sempervirens) and lenga (Nothofagus pumilio) and two softwoods: alerce (Fitzroya cupressoides) and mañío (Podocarpus nubigena). The equipment used were two types of ultrasound generators: Steinkamp BP5 and Panametric Epoch XT. The results shown a higher anisotropy for hardwoods than for softwoods, and a relatively symmetry for transversal wave propagation velocities and for shear modulus of elasticity, along the principal directions of the tree. At the same time the mean values of Young modulus of elasticity (MOE) obtained by using the ultrasound equipments were a 25-47 % higher than the same modulus measured by mechanical tests.

This work aimed to quantify axial deformations of a human premolar during occlusion with its antagonist and to compare them with the same premolar restored with a ceramic crown. The deformations were put under stress using a mechanical press with a force ranging from 1 to 100 Newtons. These deformations were quantified using the optical interferometry technique with a laser source (633 nm, 0.95 mW). Using a CMOS camera, interference fringes were obtained, stored, and subsequently processed. The premolars were restored with Cerasmart GC ceramic, using the CAD-CAM system. The average deformations of healthy premolars were found to be in a range of 0.69 to 1.74 µm, while the restored ones were deformed in a range of 0.53 to 1.10 µm. The results of this work showed that the Cerasmart ceramic material had similar properties to those of the natural tooth for small forces. However, for higher forces, the ceramics increased the coronal stiffness of the tooth. This modified the optimal combination of stiffness, strength, and resilience between the enamel and dentin, causing a decrease in the tooth’s ability to dissipate energy; therefore, the tooth could receive more stress. The observed mechanical properties lead to the conclusion that the Cerasmart material can be indicated for the restoration of anterior and premolar teeth in most cases where a fixed prosthesis is required.