The stress distribution in the vicinity of circular perforations has been studied by Kirsch over a century ago [1]. Inglis extended the analysis of circular openings to elliptical holes [4] which subsequently led to the development of linear elastic and…
The stress distribution in the vicinity of circular perforations has been studied by Kirsch over a century ago [1]. Inglis extended the analysis of circular openings to elliptical holes [4] which subsequently led to the development of linear elastic and nonlinear inelastic fracture mechanics. This paper revisits the fundamentals of elastic stress concentrations in the proximity of circular perforations of different diameters and presents results of an experimental series on ferrous flat bars made of high strength steel, mild steel and cast iron. Focus is the issue whether strain hardening and localized yielding emanating from the stress concentrations at the circular perforation explain the puzzling effect described by Kirsch that the ultimate load capacity of the perforated bars increase rather than decrease and definitely not by by a factor of three as expected for brittle materials when compared to the non-perforated bars. Anewly acquired digital image correlation system sheds additional light on the development of plastic zones and shear bands beyond the original area reduction measurements by Kirsch. Elasto- plastic finite element simulations complement the digital image analysis with field data from com- putational simulations of plasticity models for brittle an ductile fracture. The paper concludes with remarks on the effect of ductility on the mode of failure, the reduction of strength due to the opening, and the load ratio of perforated over non-perforated specimens.