APPARATUS FOP MEASURING STRAIN AND APPLYING STRESS. 



275 



a torque of 75 inch pounds. A time-recovery curve, fig. 17, has been plotted, the 

 ordinates of which correspond to the reading under a torque of 375 inch pounds and 

 the abscissae are times ; this curve shows in a marked manner how rapid is the recovery 

 at first. 



As a means of comparison with, the last bar, a steel bar was now tested, the speci- 

 men being classed as machinery steel, i.e., semi- mild. Length under test 4 "00 ; dia- 

 meter 0*425 ; calibratioD 1 min. = 12*85 divisions. 



The following results were obtained : — 



Torque in inch lbs. 



Reading. 



Difference. 











385 



75 



385 



385 



150 



770 



387 



225 



1157 



386 



300 



1543 



387 



375 



1930 



393 



450 



2323 



387 



525 



2710 



393 



600 



3103 



400 



675 



3503 



420 



750 



3920 



311 



780 



4231 



444 



810 



4675 



254 



825 



4929 



380 



840 



5309 



700 



855 



6009 





870 



Went off scale 





The load was then removed, and again applied by increments of 75 inch pounds 

 until a limit of 750 inch pounds was reached, the load being afterwards reduced by 75 

 inch pounds to nothing. Tests were made at intervals of time, as recorded in Table 

 IV., which latter shows that the recovery is much slower in the former case ; and even 

 at the end of nineteen days the specimen showed signs of the initial overstrain. 



The curves, fig. 18, showing the results of the experiments were plotted by the 

 indirect method previously described, 350 units being subtracted for an increment of 



