60 



DISPLACEMENT INTERFEROMETRY BY 



TABLE 3. Hard rubber. Thinner rod. 2L=4.go cm.; 2^ = 0.353 cm.; .4=0.098 cm. 2 ,- 

 other data as above. Load kg. permanent. R/R' = 10.3/7.0 = 1.47. 



* Loads 4, 5, 4 kg. ** Loads 5, 4, 5 kg. 



The values of the modulus E were then computed from the triplets in suc- 

 cession. One may note that the succession 5, 4, 5 kg. gives a much larger value 

 of E than the contrasting succession of loads 4, 5, 4, kg. One can not, there- 



fore, expect a smooth march of values unless this difference is systematically 

 included, while it would be exceedingly difficult to even conjecture a rational 

 method of quantitative interpretation. With this conceded, the mean values 



Were Load= 15 25 35 is l<g-/cm. 2 



io- 10 = i. 60 2.15 2.53 3.32 



These data are shown in figure 4 1 . From them the mean rate R = AE/A (P/A ) 

 = 0.053 ma Y be deduced. This is in fact less than one-half the preceding 

 ratio R, so that the suspicion that the rigid sheath containing the rod loosely 

 contributes to the high E values at high loads is not removed. It is neces- 

 sary to reduce the thickness of rods further. 



In figures 42 and 43 cyclic data are given for the same rod turned down 

 further to the following dimensions: 



= 4.gocm. 2^ = 0.33 cm. A = 0.085 cm. 2 



