Tensile test of a specimen from different-thickness sheet material

Abstract

A technique for tensile testing of a sample cut from a sheet blank of different thicknesses is proposed. Gage interference sheet blanks are obtained by rolling or welding sheet materials of different thicknesses and are used in the manufacture of various shells by metal forming in the automotive, electrical, and aerospace industries. Currently existing test methods provide for the tension of samples having the same thickness and width. Therefore, an urgent task is to develop a technique for tensile testing of a sample of different thicknesses. The proposed technique uses a sample cut from a sheet material of different thicknesses joined by welding, having different widths, in which the cross-sectional area along the estimated length is constant, which creates the same conditions for its deformation throughout the volume. In contrast to existing tensile test methods, in which the averaged values of mechanical and plastic properties are determined, the proposed method obtains mechanical and plastic properties in several cross sections of the sample located along the estimated length. The sample is subjected to tension with a uniform rate of deformation until the onset of the neck formation with the recording of the load-displacement diagram. By changing the dimensions of the cross sections when using the load-displacement diagram, at the considered moment of tension, the intensity of stresses and strains, parameters of hardening curves, anisotropy coefficients, and the non-uniformity of plastic deformation in each cross section of the sample are determined. For example, tests of a different thickness sample made of NHX260YD steel with a weld in the transverse direction are given.