Abstract
A unified criterion is proposed that allows one to predict the effects of phase difference and mean stress on the fatigue strength of components containing small holes under combined loading. Combined axial and torsional fatigue tests were conducted using annealed JIS S35C steel and quenched/tempered JIS SCM435 steel specimens containing a small hole of either 100 μm or 500 μm in diameter. The phase differences between axial and torsional loads were 0° and 90°. Non-propagating small cracks were observed to emanate in the radial direction from the holes at the fatigue limit. Moreover, these cracks were always in the plane of maximum principal stress. This indicates that a crack on this specific plane plays an important role in the determination of fatigue strength. A criterion was proposed on the basis of the assumption that at the threshold level, the time-variation in the Mode I stress intensity factor of a crack under multiaxial cyclic loading is equal to that under uniaxial cyclic loading. A predictive method for the determination of fatigue strength under combined loading conditions was also presented making use of this criterion. This method is useful in practice since no fatigue tests are necessary in making predictions. Good agreement between experimental results and predictions was obtained.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call