Experimental investigation of void coalescence in metallic sheets containing laser drilled holes

Although important, ductility remains difficult to predict and there is a tremendous need for more precise modelling. Progress in this field is hampered by a lack of quantitative experimental results to assess the validity of these models due to the stochastic nature of ductile fracture. In this paper, tensile tests have been carried out in a scanning electron microscope on model materials made of thin metallic sheets containing laser drilled holes. Depending on the material and hole configuration, different failure modes and strains are observed. The results show the importance of void spacing and orientation, constraining effects, materials yield stress and work hardening rate, and the competition between ductile fracture and shear localization. Finally, it is shown that the Thomason model for void coalescence is not appropriate for predicting fracture of the model material. However, the McClintock model for void growth, and the Brown and Embury and the McClintock models for void coalescence provide relatively good predictions.