Yoshihiko Nishino

Colorimetry of wood specimens from French Guiana

The color of 97 species of wood specimens from French Guiana was measured on their radial and tangential surfaces with a colorimeter. We obtained the tristimulus values of X, Y, and Z of the 10° standard observer under the illuminant of D65, and the values of the CIELAB color system, L*, a*, b*, C*, and h. When the lightness index (L*) was <54, b*, C*, and h showed positive correlations against L*. When L* was >54, a* and C* showed negative correlations against L*. These results imply that wood color should be discussed by separating wood specimens into the high and low-lightness groups. A good positive correlation was found between the L* and h throughout the whole range of L*. It is thought that the value of h can be an important index, as can L*, for comparing of wood color because h shows a simple relation with L*.

Relations between the colorimetric values and densities of sapwood

Color measurements were made for sapwood specimens of 26 hardwood species. The densities of the specimens ranged from 258.5 to 945.6kg/m3. The colorimetric values and densities were compared among the species. The tristimulus values ofX, Y, andZ were poorly correlated with the densities. The chromaticity coordinatex had a good linear correlation with the densities of the wood specimens, especially in the transverse planes. The transverse plane of wood fibers is thought to emphasize the relative values in the long wavelength region of the visible ray.

Effects of helical angle of router bit on acoustic emission

The purpose of this study was to investigate the effects of changes in the helical angle of the router bit on the acoustic emission (AE) signal for various workpiece grain angles. The helical angle varied from 0° to 50° at 10° increments. The workpiece grains were oriented from 0 degrees (cutting parallel to the grain), through 90° (cutting end of the grain), to 165° at 15° increments. The AE signals and machined surface roughness were measured in an attempt to clarify the relations between them. The results were summarized as follows: (1) The AE signals were lowest in the “with the grain” cutting zones and slightly increased in the “against the grain” cutting zones; they rapidly reached the highest values at the 135°–165° grain angles. The greater the helical angle of the router bit, the smaller were the AE count rates for each grain angle investigated. There was no significant change in AE generation for helical angles of 0° and 10°. Moreover, the greater the feed rate, the greater was the AE count rate for every cutting condition investigated. (2) The surface roughness, similar to the AE count rate, had the lowest values in the “with the grain” cutting zones, slightly increased until the 120° grain angle, and then rapidly become extremely rough, reaching a maximum at the grain angles of 135°–150°. There was no remarkable change in the machined surface roughness while routing “with the grain” using the router bit of greater helical angle. However, when routing “against the grain,” the greater the helical angle the smoother was the machined surface. (3) There were correlations between the AE count rate and the machined surface roughness for each helical angle investigated. Therefore, acoustic emission has shown promise for monitoring and controlling the routing operation, including various grain angles and helical angles of the router bit.