EFFECTS OF GRAIN AND RING ANGLES ON ULTRA SONIC VELOCITY IN WOOD

The effects of grain and annual ring angles on ultrasonic velocity wer e examined with cubic and multi-faced specimens. The ultrasonic veloci ties in LT (longitudinal-tangential) and LR (longitudinal-radial) plan es decreased rapidly from L (longitudinal) to T (tangential) or to R ( radial) directions as grain angles changed. Its tendencies with grain angles were similar to those of Young's modulus and strength in both s oftwoods and hardwoods. However, in the RT (radial-tangential) planes, ultrasonic velocities with annual ring angles in softewoods had diffe rent tendencies from those of hardwoods. In softwoods, the ultrasonic velocities had minimum values, when the annual ring angles were about 50 degrees, and their overall tendencies were similar to those of Youn g's modulus and strength, but in hardwoods, they had tendencies to dec rease rapidly as the annual ring angles changed from the radial to the tangential directions. In the RT planes in softwoods, the ultrasonic velocities in 16-faced specimens were greater than those in 8-faced an d cubic specimens for all annual ring angles except for those in the r adial directions.