44] 
Recent Work 1n Woop Puysics. 
3y WILLIAM KENDRICK HATT. 
(Abstract. )* 
The new series timber tests of the Forest Service, which constitutes 
the most important recent series of experiments, was begun in 1902 under 
the direction of Mr. Gifford Pinchot, Forester, Forest Service, United 
States Department of Agriculture. About 44,000 test pieces have been 
tested. 
These timber tests are divided into two parts: Class (a). Tests on 
market products of actual size, in which characteristic defects occur, such 
as stringers, vehicle parts, railroad ties, of interest and value to engineers 
and manufacturers. These correspond to tests on riveted joints or built- 
up structures in metal testing. Class (b) includes so-called “scientific” 
tests of smal!, perfect specimens with uniform moisture content, represent- 
ing material collected from the forest, in which the strength is related to 
the physical structure and position in the tree. These tests are of espe- 
cial value to the botanists and foresters and aid the solution of silvicultural 
problems. 
A summary of results obtained to date will be presented. 
INFLUENCE OF CONDITIONS OF TESTS UPON RESULTS. 
(In these studies small, perfect specimens are used). 
1. Speed of Test—The strength of wood varies significantly with 
the speed at which stress is applied. increasing more rapidly as the 
speed increases. Tests are standardized for speed*® on the basis of fiber 
strain per unit of time; and experimental factors obtained to adjust 
strength values from one speed to another. The adopted standards of 
fiber strain are as follows, expressed in inches per inch per minute: 
AMS SCAMS tear oie Urea rarecenee ers a Secs) cise sishd quguel el aiens 0007 
Small beamse ce Sean eee Se Sree Beale Sieh as 0015 
Compression parallel to grain, small pieces ......  .003 
Compression parallel to grain, large pieces ...... 0015 
1 Abstracted from paper by the author, read before the Copenhagen Congress of 
the International Society for Testing Materials. 
*See Proceedings American Society for Testing Materials, Vol. 8, 1908, page 
541. “The Effect of the Speed of Testing upon the Strength of Wood and the 
Standardization of Tests for Speed,” by H. D. Tiemann. 
