168 



REPORTS ON THE STATE OF SCIENCE. — 1915. 



where 



and 



fmai is the maximum permissible combined stress 

 tg being the steady component of stress and 

 A being the range of variation. 

 f is the ultimate strength of the metal 

 n the ratio between f and A (= approximately unity for this 

 metal), the stresses being in tons per sq. in. 



On the left hand side of the diagram, Fig. 4, representing the 

 results obtained with combinations of alternating and compressive 

 stresses, the curve deviates noticeably from the parabolic form. The 



Fig. 6. 



