Luders Deformation Mechanisms on Yield Point in X80 Grade Pipeline with Ultrafine Structure

Strain ageing in X80 grade pipeline with ultrafine ferrite-bainite structure by Digital Image Correlation (DIC) technique at tensile test has been studied. Three types of Luders deformation mechanisms on yield point were observed using DIC fields analysis. It was determined that mechanical behavior of the material on uniform parabolic stage of deformation strongly depends on Luders deformation mechanism type.     Keywords: X80 grade pipeline steel, stress-strain curve, discontinuous yielding, Luders deformation, Digital Image Correlation analysis, strain ageing