Evaluation of the Pinus taeda quality using ultrasound

The pinus is a type of wood that is widely used as feedstock for the production of softwood pulp and higher quality paper, boards, MDF (Medium Density Fiberboard), OSB (Oriented Standard Board), plywood, furniture and others. The main problem for the pinus is the attack by the wood wasps (Sirex noctilio F., 1793) (Hymenoptera; Siricidae) that damages the wood due to galleries built by the wasps larvae. The use of nondestructive techniques to assess the quality and to evaluate mechanically the wood has been the focus of many studies and is certainly an essential tool to decrease the production costs. This work aimed to evaluate the damage due to the infestation of S. noctilio in Pinus taeda L. using ultrasound. The tests have been carried out in the through transmission mode, using a pulser-receiver, two pairs of ultrasound transducers (50 kHz and 100 kHz of central frequencies for each), a digital oscilloscope and a portable microcomputer for data storage. The initial tests have been done using seven logs of pinus samples (lengths in the range 0.70 - 0.94 m and diameters 0.09 - 0.18 m). The transducers were positioned in the samples to measure the ultrasound propagation velocity and the attenuation in the axial, radial (lower, middle and upper parts of the logs), longitudinal (middle and upper parts), inclined at approximately 45 degrees (middle and upper parts), longitudinal/transversal (middle and upper parts) and inclined/transversal (middle and upper parts) modes. The initial results of the 960 tests (430 with each pair of transducers) that have been done with the pinus samples have shown that the infested samples presented a decrease in the propagation velocity and an increase in the attenuation when compared to the control sample results. The initial results showed that the ultrasound technique can help the quality evaluation of P. taeda and to detect the infestation of wood wasps. Further tests should be made with a larger number of samples to evaluate the e- astic modulus and other ultrasound parameters. The results will be used to define a novel test protocol to be used for material characterization in the agronomical area.