An experimental investigation of large-strain tensile behavior of a metal sheet

A method for determining the stress–strain curve of a larger strain is proposed when plastic instability occurs in standard tension tests. A thin tested sheet of clod-rolled steel is subjected to tension loading until a fracture occurs. The deformation process is captured with a digital camera and using a mesh-free point interpolation method (PIM) method, a displacement field and strain field of material deformation can be calculated. In order to verify that the local measuring stress–strain curve by the PIM method near the center of the specimen can describe a full stress–strain curve, a tensile experiment with different gauge lengths (25 mm, 35 mm and 50 mm) and numerical simulation at different locations along the specimen axial have been presented that different parts of specimen have a different deformation distribution in tensile and the center fracture part of the tensile specimen is the only region which can experience a full strain. The true stress–strain curves based on the estimated parameters are validated in all strain regions by comparison with curves from standard tension tests. The measured curves by the PIM method are very stable. Compared with several material constitutive equations, Ludwik’s and Swift’s equation is very close to the experimental curve at plastic deformation.