NONDESTRUCTIVE EVALUATION OF A TROPICAL HARDWOOD: INTERRELATIONSHIP BETWEEN METHODS AND PHYSICAL-ACOUSTICAL VARIABLES

The paper aimed at evaluating the interrelationship between three nondestructive methods to predict the stiffness of a tropical hardwood (Sextonia rubra). Lumber material from Sextonia rubra was collected, ripped and planned and boards were then nondestructively tested using three methods: stress wave, transverse vibration and static bending. Stress wave (Edsw) and transverse vibration (Edtv) testing were done using commercial equipment while the static bending testing (Esb) was conducted according to the ASTM D4761. According to the results, linear regression models could be fitted to explain the interrelationship between the nondestructive properties. The best model was observed for the relationship between Esb and Edtv (R2=0.946), followed by Esb/Edsw (R2=0.834) and Edtv/Edsw (R2=0.817). The values of dynamic modulus of elasticity were frequently higher (Edsw=4.19 %; Edtv= 9.44 %) than the Esb values (15314 N/mm2). On the other hand, Edtv values were higher (5.35%) than Edsw values. It can be concluded that the three nondestructive testing methods studied are suitable to estimate the stiffness of this tropical hardwood. However, corrected models must be employed to improve the reliability of the predicted values.