THE MECHANICAL PROPERTIES OF WOOD
Frontispiece.
Photomicrograph of a small block of western hemlock. At the topis the cross section showing to the right the late wood of oneseason's growth, to the left the early wood of the next season.The other two sections are longitudinal and show the fibrouscharacter of the wood. To the left is the radial section withthree rays crossing it. To the right is the tangential sectionupon which the rays appear as vertical rows of beads. × 35.Photo by the author.
THE MECHANICAL PROPERTIES OF WOOD
Including a Discussion
of the Factors Affecting the MechanicalProperties,
and Methods of Timber Testing
BY
SAMUEL J. RECORD, M.A., M.F.
ASSISTANT PROFESSOR OF FOREST PRODUCTS, YALE UNIVERSITY
FIRST EDITION
FIRST THOUSAND
1914
BY THE SAME AUTHOR
Identification of the Economic Woods of the United States.
8vo, vi + 117 pages, 15 figures. Cloth, $1.25 net.
TO THE STAFF OF THE
FOREST PRODUCTS LABORATORY, AT MADISON, WISCONSIN
IN APPRECIATION OF THE MANY OPPORTUNITIES
AFFORDED AND COURTESIES EXTENDED
THE AUTHOR
PREFACE
This book was written primarily for students of forestry to whoma knowledge of the technical properties of wood is essential.The mechanics involved is reduced to the simplest terms andwithout reference to higher mathematics, with which the studentsrarely are familiar. The intention throughout has been to avoidall unnecessarily technical language and descriptions, therebymaking the subject-matter readily available to every oneinterested in wood.
Part I is devoted to a discussion of the mechanical propertiesof wood—the relation of wood material to stresses and strains.Much of the subject-matter is merely elementary mechanics ofmaterials in general, though written with reference to wood inparticular. Numerous tables are included, showing the variousstrength values of many of the more important American woods.
Part II deals with the factors affecting the mechanicalproperties of wood. This is a subject of interest to all who areconcerned in the rational use of wood, and to the forester italso, by retrospection, suggests ways and means of regulatinghis forest product through control of the conditions ofproduction. Attempt has been made, in the light of all data athand, to answer many moot questions, such as the effect on thequality of wood of rate of growth, season of cutting, heartwoodand sapwood, locality of growth, weight, water content,steaming, and defects.
Part III describes methods of timber testing. They are for themost part those followed by the U.S. Forest Service. In schoolsequipped with the necessary machinery the instructions willserve to direct the tests; in others a study of the text withreference to the illustrations should give an adequateconception of the methods employed in this most important lineof research.
The appendix contains a copy of the working plan followed by theU.S. Forest Service in the extensive investigations covering themechanical properties of the woods grown in the United States.It contains many valuable suggestions for the independentinvestigator. In addition four tables of strength values forstructural timbers, both green and air-seasoned, are included.The relation of the stresses developed in different structuralforms to those developed in the small clear specimens is given.
In the bibliography att