Plastic deformation at short edge cracks under fatigue loading

The mechanical behaviour of short surface cracks is investigated and analys ed with respect to its importance for fatigue crack growth. The elastic str ess field and the plastic deformation are computed by means of the Boundary Element Method. The influence of material parameters, crack length and loa ding conditions on the crack tip deformation are investigated. The results are compared to the usual long crack equations based on Linear Elastic Frac ture Mechanics (LEFM) and conditions are identified when LEFM becomes non-c onservative. A yield stress reduction method is proposed to modify the LEFM equations for such cases in order to obtain reasonable and always conserva tive predictions for the crack tip deformation. (C) 2000 Elsevier Science L td. All rights reserved.