Impact fatigue resistance of structural Steels

A study has been made of the impact fatigue properties of some structural steels using transverse impact stressing on rotating un-notched test pieces. In steels tested curves showing the kinetic energy/number of impacts exhibit the characteristic of S.N. curves based on conventional fatigue tests, indicating a limiting value of K.E. i.e., a definite endurance limit under impact. Using an ingenious electronic set up of electrical resistance strain gangue and measurements it has been possible for the first time to find the stress criterion for failure under repeated transverse impact data of fundamental value for designs based on impact stresses. It is further shown that endurance fatigue limit in transverse impact is slightly less than endurance limit under alternate bonding; probable reasons for this slight difference have been discussed.