QUALITIES OF IVORY 229 



in pounds per inch of length and the compression or elongation 

 per unit of length, a quantity results which is termed the 

 modulus of elasticity — the ratio of stress to strain. The ratio 

 above referred to is constant up to a certain applied load, after 

 which it gradually decreases in value. The point on the curve 

 at which this ratio ceases to remain constant is called the 

 elastic limit, the limit of deformation beyond which the 

 body will fail to resume its previous state when the strain 



S^,'vss - Strain ^iavrrrtnts Stress - Str^t'n- Sta^ram/ 



of ./ 



y^Jisroit T&^^s Comh^essiorv Test 



on on* 



fjo.t Hard Iiiory 

 Ma. Z Se^t Ivory 



Tension and Compbession Tests 



is removed. In the same table will be found what is termed 

 the ultimate resistance, which is defined as the highest load 

 a material will carry in pounds per square inch. 



The specimen tested in compression was a one and one 

 half inch cube. Compressive stress results from the appli- 

 cation to a body of two forces acting in directions toward 

 each other. The definitions, as given above apply to the terms 

 in the tabled results of the compression test. The curve 

 plotted on Figure II shows the unit compressive strains or 

 deformations resulting from applied loads in pounds per 



