Treesearch

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.

This paper deals with the relationships between the machining properties of ponderosa pine and Douglas fir and their density and growth rate.