276 



TKSTS KOI! II. \KD\KSS. 



an inch. A careful determination of the compression of 

 the apparatus itself under different loads makes it possible 

 to take the relative movement of the plunger and the 

 block, minus this compression, as the amount of linear 

 indentation or penetration of the tool into the test-piece. 

 From a series of preliminary tests Professor Unwin found 



FIG. 138. Uxwix's GEAI: FOB HARMLESS TESTS. 



that the relation existing between the indentation and the 

 load producing it is expressed by an equation of the 

 following form : 



Ci=p rz 



where i is the depth of the indentation in inches, p is the 

 pressure per inch width of the knife edge producing the 

 indentation, and C is a constant depending upon the 





