Crack Path Prediction by the Mvcci-Method and Experimental Verification for Specimens Under Proportional Bending and Shear Loading

Abstract

The Modified Virtual Crack Closure Integral (MVCCI)-method has proved to be a highly effective and versatile numerical procedure for the fracture analysis of various crack problems in linear elasticity. In the present paper it is shown that the MVCCI-Method also can readily be utilised for the computer aided prediction of curved crack growth paths under proportional loading conditions. Further it will be shown, that the common computer aided crack path prediction can be improved in accuracy in combination with the MVCCI-Method. The proposed numerical crack path prediction is still based on a step-by-step technique but using a new predictor-corrector procedure that results in a piece by piece curved approximation of the simulated crack path. By this powerful method both, the new locus of the crack tip and the slope of the crack path can be computed simultaneously by one virtual tangential crack extension with respect to the previous step.
In order to evaluate the validity and the efficiency of the proposed crack path simulation method in relation to the basic
strategies, experiments of non-coplanar fatigue crack growth are carried out with two special specimens under combined
proportional bending and shear loading. The specimens have been designed in order to produce non-homogeneous stress
fields. Crack initiations from different positions along the edges of these two types of specimens are investigated for
different interactions with the produced asymmetrical stress states.
In all cases considered the computationally predicted crack trajectories show an excellent agreement with the different
types of curved cracks that are obtained in the experiments as a function of the position of crack initiation.
The present 2D investigation shows that the MVCCI-method in conjunction with the proposed predictor-corrector procedure provides a powerful numerical tool for a general computational approach to the fracture analysis of complex
crack configurations under proportional loading conditions.