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Recent Woek in Wood Physics. 



By William Kendeick Hatt. 



(Abstract.) 1 



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 small, perfect specimens with uniform moisture content, represent- 

 ing material collected from the forest, in which tbe 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 2 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 : 



Large beans 0007 



Small beams 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. 



2 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. 



