Takanori Arima

Fundamental Study on the Nondestructive Testing for Evaluating the Strength of Adhesive Wood Joints. Propagation Time of Sound Waves.

In order to develop a nondestructive testing method applicable to manufacture more reliable adhesive wood components, fundamental experiments were performed. The strength of adhesive wood joints was evaluated by measuring the time of sound waves (stress waves, ultrasonics) propagating the part involving adhesive joints to guarantee the bonding strength more directly. The three types of experiments employed were as follows:(1) Measuring the propagation time of stress waves for the end joint and lap joint specimens in the curing process.(2) Measuring the propagation time of sound waves for the end joint specimens before and after gluing.(3) Mesuring the propagation time of ultrasonics in both thickness and width directions and the adhesive shear strength for the two-layer specimens.The results are summarized as follows:(1) Curing of adhesive joints could be evaluated by the propagation time of stress waves.(2) The change of propagation time before and after gluing indicates the difference in the state of adhesive joints.(3) The propagation time of ultrasonics in the thickness direction was effective for evaluating the shear strength of adhesive joints, but that in the width direction was not so effective.However, the shear strength can be evaluated more effective by combining the propagation time in these two directions.

Nail driving force and withdrawal resistance of wood.

木 材 の釘 圧 入 力 と釘 引 抜 き抵 抗 † 有 馬 孝 禮* 早 村 俊 二** 丸 山 則 義** Nail Driving Force and Withdrawal Resistance of Wood by Takanori ARIMA*, Syunji HAYAMURA** and Noriyoshi MARUYAMA** The force in driving a nail into wood by pressing and the withdrawal resistance were measured. Among the factors affecting the force and resistance against nail of wood at various specific gravities (Hem-Fir) were the diameter of nail, nail point and type of shank. (1) A curve for driving force and moving distance of a nail could be separated into two regions: the I-region as affected by the nail point inserted into wood and separating fibers and the II-region as affected by the friction between shank and fibers. (2) The maximum driving force and withdrawal resistance had a linear relationship to the diameter of nail and the specific gravity of wood. The slope of nail driving force into wood in the II-region was reasonably equal to the slope of withdrawal resistance as affected by friction. (3) The effect of screw-or ringshank, when compared to that of common smooth-shank was recognized in the shape of curve near the maximum point and the change in residual strength with moisture conditions.