ON STRESS DISTRIBUTIONS IN ENGINEERING MATERIALS. 



291 



Results of the Tests. 

 The results obtained up to the present are given in the following 

 table : — 



Table V. 



Limiting Fatigue Range of Stress for British Association Mild Steel 

 Specimens prepared from the 1-5/16 in. round bar and not heat-treated. 



EeMABKS on THE TeSTS. 



It will be seen in the first place that the results under alternations of 

 bending in one plane are in agreement with those obtained under alternate 

 bending in rotating planes as in the Wohler test, so that results obtained 

 in the two types of machines are comparable. 



Further, the limiting shear stresses in the pure bending and in the pure 

 torsion tests are seen to be in close agreement. 



Finally, although in the tour cases of combined stress the limiting 

 maximum shear stresses seem to be appreciably below the values for 

 pure bending and pure torsion, the general agreement is so close that 

 further investigation is required before it can be stated definitely that 

 the result indicated is a real one. This investigation is now in hand. 



General Conclusions. 

 Although the number of tests carried out up to the present does not 

 justify any general conclusion as to the nature of the criterion for ultimate 

 failure, the general results of the investigation appear to demonstrate 

 that, as a first approximation, Mr. Guest's hypothesis that failure is due 

 to a particular value of the maximum shear stress may be applied to this 

 particular steel. 



V 2 



