MECHANICAL PROPERTIES OF WOODS GROWN IN UNITED STATES. 45 



Table 3.— Approximate figures for change of properties with change of moisture con- 

 tent; variation of properties with specific gravity; reliability of averages, and probable 

 deviations from averages of individual trees and specimens. For use with Tables 1 

 and 2. 



Property. 



Average 

 increase 

 (or de- 

 crease) in 

 value ef- 

 fected by 

 raising (or 

 lowering) 

 the mois- 

 ture con- 

 tent 1 per 

 cent when 

 at about 

 12 per cent. 

 (Seep. 18.) 



Approxi- 

 mate 

 power of 

 specific 

 gravity 

 according 

 to which 

 property 



varies. 

 (Seep. 18.) 



Probable 



variation 



of present 



average 



(when 



from 5 



trees) 



from true 



species 



average. 



(Seep. 19.) 



Probable 

 variation 



of random 



tree from 



average 



for species. 



(See p. 19..) 



Specific gravity based on volume when green 



Weight per cubic foot • 



Shrinkage 2 



Static bending: 



Fiber stress at elastic limit 



Modulus of rupture 



Modulus of elasticity 



Work to elastic limit 



Work to maximum load 



Impact bending: 



Fiber stress at elastic limit 



Work to elastic limit 



Height of drop 



Compression parallel to grain: 



Fiber stress at elastic limit 



Crushing strength 



Compression perpendicular to grain — fiber stress at 



elastic limit 



Hardness, end 



Hardness, side 



Shearing strength parallel to grain 



Tension perpendicular to grain 



Per cent. 



Per cent. 

 1.7 



Per cent. 

 3. 



5 



12 



4 



9 



5 



11 



7 



16 



6 



14 



4 



8 



5 



12 



7 



15 



5 



12 



4 



9 



6 



14 



4 



9 



5 



10 



3 



7 



5 



12 



1 See explanation, p. 11. 



2 See explanation, p. 12. 



3 The minus sign indicates decrease. 



