Treesearch

A direct-reading strain gage has been developed at the U.S. Forest Products Laboratory that provides rapid and accurate measurement of the stress - strain properties of paper. The gage, which employs a differential transformer, is particularly suited to servo-operated x-y recorders.

In 1959, a new technique was devised at the Forest Products Laboratory that provided a means of examining, evaluating, and recording the show- through pattern (often called telegraphing) of panels made with particle board cores. Although the technique was devised as a working tool to evaluate show-through characteristics of particle board cores, it can be used equally well on anyfurniture panel, regardless of color, pattern, or type of core, provided the surface is finished with a satin (or brighter) finish. This means that the technique has potential applications far beyond the original...

Douglas-fir is one of the largest, most abundant and widely distributed species of trees native to North America, and next to the southern yellow pines, it is cut in the greatest quantities of any wood of commercial importance. It belongs to the coniferous family and is, therefore, a softwood. Other names for Douglas -fir are red fir, yellow fir, Oregon pine, Puget Sound pine, red pine, red spruce, and Douglas spruce. Its botanical name is Pseudotsuga menziesii (Mirb.) Franco.

Common methods of measuring the moisture content of wood are described briefly, and a short historical account of the development of electric moisture meters is given. Electrical properties of wood are discussed briefly, and the basic operation of the resistance type and the radio- frequency types of moisture meter is outlined. Data relating the electrical resistance and moisture content of various species of wood are also presented. A list of manufacturers and suppliers of electrical moisture meters is included.

Wood is a fairly complex material, whether you think of it in terms of boards or timbers or string along with what the chemist says it is. For ages wood has been vital to an ever-mounting scale of living. If it is to continue to serve in more ways and in new forms, most of the means for these changes will have to be found by looking into the physical and chemical maze that lies below the surface.

There are three commercially important tupelo species: Water tupelo (Nyssa aquatica), black tupelo (N. sylvatica), and swamp tupelo (N. sylvatica var. biflora). Water tupelo and swamp tupelo, as the names indicate, are water-loving trees and grow principally in the fresh-water swamps and along the edges of streams and ponds in southeastern United States. Black tupelo, which has a much larger range, grows throughout most of the eastern half of the United States.

A theory of the strength of orthotropic materials subjected to combined stresses, based on the Henky-von Mises theory of energy due to change of shape, is presented. When this theory is applied to macroscopically isotropic materials, it yields the diagram currently used in design with metals. Equations relating the strength of orthotropic materials subjected to a single stress at angles to the natural axes of the material are deduced from the theory. These equations are shown to agree with available test values.