]G 



SHEARING. 



the ratio of the former to the latter 



e 



. =m . . . 

 9 



This has a value for 

 4 ; for the metals it is 



(V.) 



solid 



Y.-ry 



is called Poisson's Ratio, 

 bodies varying from 3 to 

 nearly 4. 



In the case of indiarubber, so long as the strains are 

 small, the value is about 2. 



10. Tangential or Shearing Strain. When a shearing 

 stress acts on a prism, it is not axially, and upon a section 

 perpendicular to the axis, but transversely in a direction 

 parallel to the section considered. 



prism or bar subjected 

 to a shearing stress, 

 brought upon a section 

 at right angles to the 

 axis of the bar. The 

 stress need not 

 necessarily be on such a 

 section, in fact, it may 

 act upon any plane 

 within the material, but 

 the case exhibited here 

 is the one which most 

 commonly occurs in 

 practice, in rivets, 

 knuckle-joints and eye- 

 joints generally. 

 The prism A B is supposed to be so constrained that the 

 left-hand portion tends to move bodily upwards, while the 

 tendency of the right-hand portion is to move downwards. 



If the figure of a square a, b. c. d, 

 be drawn upon the bar, so as to be 

 intersected by the section under 

 stress, when the shearing load F is 

 brought to bear upon the bar, this 

 square will be distorted, so as to 

 assume the form of a rhombus, as 

 shown in the figure. A clear 

 understanding of what actually 

 takes place in the case of a shear- 

 ing stress will be obtained by a 

 consideration of the case exhibited 

 on Fig. 6 ; here A B C D is a prism 



B 



