MI: .1. MI IK <>\ TIII-: i:i-:n>\ I-.I;N <>K II;M\ 



HVKKSTBAIN 



It 



iif tin- same I J-inch n>d, but after the rod had U-eii overstrained largely in tension 1\- 

 a |..; t (l of :V.\ tons |,,.| square inch. The compression specimen was cut from the 

 strained \x\r immediately after the large stretching load wan removed, care lx-in 

 taken t. piv\ . -m uarming during the cutting and mechanical manipulation necessary 

 to the making \' the small compression block. To test the eti'e< ( of such mechanical 

 treatment on the elastic condition of the material, a tension specimen was overstrained, 

 tested, immediately turned down to n smaller diameter and tested again. As has 

 already been recorded on page 39, considerable, though by no means perfect, 

 recovery of elasticity was found to have been produced. Owing to the precautions 

 taken in making the compression specimen used for this second series of readings, the 

 mechanical manipulation may be assumed to have produced no effect on the elastic 

 properties of the material. 



SKI CM > Series of '( '.impression Readings. (Material freshly overstrained, 



Curve 2, Diagram XIII.) 



\ oiu|>ari*oii of' the difference column of the present series of readings with that of 

 the \;>^ \ei-y clearly shows tlie change in the elastic condition of the material, pro- 

 duced by tensile overstrain. There is now not even approximate conformity with 

 HOOKK'S law at the lowest load-. 



The recovery of elasticity, which is brought about either by prolonged rest at 



o 2 



