Mil. .1. MI'Ii; ON THK UKCOVKKY OF IKON FK<M oVKl;M l;.UN. 

 The Mftlu,<l ./ 



The general procedure adopted in experimenting will now be described. First, the 

 iliameter < >t' the specimen WHS determined from the mean of ten micrometer readings, 

 taken at five equidistant places along the 8-inch length to which the extens.. meter 

 \\.i.s to l applied. For example, the following readings were obtained tor a certain 

 unturned specimen : 



{r-0069 71 65 64 61 1 

 J. = 1"-0066. 

 70 71 71 59 54 J 



Not only was this done for virgin specimens, but whenever a yield-point had U-eu 

 jMissecl, the diameter was re-determined by means of fresh readings. For example, the 

 specimen already instanced was subjected to a pull gradually increasing to 35 tons to 

 the square inch of original section, the yield-point occurring at 23 tons per square 

 inch. After the removal of this large stretching load the new diameter was deter- 

 mined from the following readings : 



(V-9918 21 18 20 25 1 

 Diameter = 4 > = 0'9920 of an inch. 



14 *?? Oji 1 *\ *? * 

 ,4 * ' *' - 



After the determination of the diameter of a specimen at each stage of an experi- 

 ment, a table was formulated, from which the total load applied could be translated 

 into tons per square inch of section, the stress being in every case measured with 

 reference to the section at the beginning of each separate test. 



These preliminaries having been completed, the specimen was put into the testing 

 machine, the extensometer was attached, and the load was gradually applied. Extenso- 

 meter readings were token sometimes only after the addition of every four tons of 

 .stress, sometimes after each ton, sometimes after each half or quarter ton, according to 

 judgment. 



The l'"ll' >\v'mg two series of readings aire given for a typical experiment; they will 

 -. i ve to explain the usual procedure. The first series shows the elastic properties <>!' 

 a certain virgin specimen; the second shows the plastic nature of the same 

 immediately after the overstrain produced by the primary loading. 



