A tensile stress criterion for cleavage in precracked, notched and smooth bars

Abstract

Using a statistical model derived for cleavage induced by hard particles, an analysis has been carried out of a newly defined critical tensile stress for cleavage, i.e. the statistical mean stress with respect to cleavage fracture probability. The results of the analysis show that the critical tensile stress (cleavage stress) is highest for a precracked bar, intermediate for a notched bar and lowest for a smooth bar, owing to the fact that small particles are possible to trigger cleavage when stress distribution in a bar is uneven. The cleavage stress for the precracked bar is found to decrease rapidly with increasing temperature while those for the notched and smooth bars remain almost constant. The cleavage stresses for the precracked, notched and smooth bars can be correlated through a definite formula. For a pure-bending notched bar, the conventional cleavage stress (maximum stress in the bar) is found to be a good approximation of the new cleavage stress. The difference between the two will increase when stress gradient becomes steeper.