Comparison of Collision Behaviors of Several Wood-Species Using Image Analysis

Abstract

The collision between a free-falling ball and wood was observed with a digital camera, and the collision parameters (e.g., the coefficient of restitution, COR) were evaluated. A charge-coupled device (CCD) camera (600 fps) was used to obtain the COR, and a high-speed camera (54000 fps) was used to measure the contact time of the ball. In addition, an indentation test using steel balls was performed to evaluate the surface properties and the corresponding results were compared with the results of the collision test. Consequently, with respect to the collisions between the ball and wood, it was observed that the COR depends on the density of the wood, and either elastic or inelastic collisions may occur. In inelastic collisions, there was a correlation between the contact time of the ball and the COR. For some tree species, such as Melia azedarach, the contact time deviated from the relationship observed among other species. In addition to the density, the tissue structure of the wood, such as the annual ring or radial tissue, may influence the contact time. Permanent dents were observed on the wood surface during the inelastic collisions. Furthermore, the surface density and COR slightly increased owing to the plastic deformation of the dents.