Diameter effect on stress-wave evaluation of modulus of elasticity of logs

Abstract

Recent studies on nondestructive evaluation (NDE) of logs have shown that a longitudinal stress-wave method can be used to nondestructively evaluate the modulus of elasticity (MOE) of logs. A strong relationship has been found between stress-wave MOE and static MOE of logs, but a significant deviation was observed between stress-wave and static values. The objective of this study was to investigate the effect of log diameter on stress-wave evaluation of MOE of logs and to develop a new stress-wave model by relating stress wave MOE to log diameter for static MOE prediction. A total of 201 small-diameter logs, including jack pine (Pinus banksiana), red pine ( Pinus resinosa Ait.), Douglas-fir (Pseudotsuga menziesii ), and ponderosa pine (Pinus ponderosa), were nondestructively evaluated. The results of this study indicate that the longitudinal stress-wave technique is sensitive to the size and geometrical imperfections of logs. As log diameter increases, the deviation between stress-wave MOE and static MOE increases. It was also found that log diameter has an interactive effect that contributed significantly when used in conjunction with the fundamental wave equation. The newly developed multi-variable prediction model relating static MOE to stress-wave speed, log density, and log diameter was found to be a better predictor for static MOE of logs than the fundamental wave equation. This could allow for the prediction of static bending properties of logs using longitudinal stress-wave technique at levels of accuracy previously considered unattainable.

Citation

Wang, Xiping; Ross, Robert J.; Brashaw, Brian K.; Erickson, John R.; Forsman, John W.; Pellerin, Roy. 2003. Diameter effect on stress-wave evaluation of modulus of elasticity of logs. Proceedings of the 13th International Symposium on Nondestructive Testing of Wood : August 19-21, 2002, University of California, Berkeley Campus California, USA. Madison, WI : Forest Products Society, 2003: Pages 149-156