TESTING MACHINE FOR EQUAL ALTERNATING STRESSES. CXXXI. 



it will be observed that in the illustration (Fig. 1) one of the test 

 pieces is considerably shorter than the other two. The extreme 

 lengths between the shoulders of the piece are 18 inches and 3 

 inches respectively. The specimen to be tested is screwed at 

 each end into the overhanging spindles, and these rotate in 

 bearings supported on knife edges. In this way the bending 

 moment is constant over the span from knife-edge to knife-edge, 

 and the test piece in breaking will therefore select the plane of 

 greatest weakness throughout its length. 



The machine will be used in the first place for determining the 

 vibrating strength of materials, and the effect of alternating stress 

 upon the position of the elastic limit. 



