SHKAKIM; TKSTS. 



ivquired dimension will be the diameter at the bottom of 

 the grooves where failure may be expected to take place. 

 When the bar has been placed in the machine it is only 

 necessary to increase the load until failure takes place. 

 This applies to both kinds of holding apparatus. Only in 

 very few cases has an attempt been made to measure the 

 strains in a bar under direct shear. Mr. Andrew Kirkaldy 

 has measured the amount the dies have moved relatively to 

 one another before actual shear had taken place, which strain 

 he has called the "detrusion." This he found to be a 

 sensibly constant quantity for the same metal. 



The following are two examples of shearing tests, one 

 of a bar of mild steel and the other of cast-iron. The data 

 obtained from the test and the calculated results are both 

 given ; it will also be seen that the tensile strength of the 

 same material is given, and the ratio which the shearing 

 strength, in tons per square inch of total section, bears to 

 the tensile strength is calculated also. 



SHEARING TESTS. 



These figures hardly require any explanation. In both 

 cases the bars were tested in double shear, and the total 

 area is taken as the sum of the two individual areas 

 through which shearing has taken place. The shearing 

 load is the actual load required to cause the bar to be 

 completely severed in three pieces. The ratio of the 

 shearing to the tensile stress should always be ascertained 

 where possible. This value is found to vary somewhat in the 

 different metals. Generally speaking this ratio is higher 

 the lower the tensile strength. In the following table are 

 quoted a few typical examples of the results of shearing 

 tests, as given by different authorities. 



