The Loss of Plasticity Stability

Abstract

The real values of plastic properties of steel sheets are basic input parameters for objectification of deep drawing technological processes. The loss of stability of plastic properties is the criterion of evaluation of plastic properties of steel sheets in most cases. The loss of stability of plastic properties depends on stress-strain scheme in real conditions of deep drawing of sheets. In the contribution will be evaluated the loss of plastic properties stability of thin double reduced packaging sheets made from low carbon steels. For evaluation of strength and plastic properties of thin packaging sheets is the tensile test most used at present. The material is stressed by uniaxial tension during this test. In the conditions of technological processes of drawing, which thin packaging sheets are mostly treating, is this way of stress not very objective. In most cases it deals about multiaxial stress of sheet by deformation of sheet to require draw cup. At the present, the biggest problem of thin steel sheets by uniaxial tension test evaluation is the loss of plastic deformation stability (localization of plastic deformation). Therefore, obtained results of plastic deformation during this test do not correspond with real plastic properties of thin steel sheets. In the contribution, will be compared the evaluation of plastic properties of these sheets by uniaxial and biaxial load. Biaxial load is unfavourable from stress point, but less sensitive on loss stability of plastic deformation from conditions test influence point.