Plastic Strain Concentrations in Ligaments

The sheet perforated with a uniform array of circular holes arranged in a square pattern is investigated. The plastic strains are derived for progressive in-plane loading which eventually results in gross yielding. The finite element method is used to obtain numerical solutions. Plane stress conditions and elastic perfectly plastic solid material properties are assumed. Thus the results provide conservative values of plastic strain concentrations for a considerable range of perforated materials. The plastic strain multipliers for equibiaxial and pure shear loading are given for three ligament efficiencies of the penetration pattern. The tendency of forming highly localized plastic strains with progressive yielding is observed, and the implications of the results in plastic design are discussed.