Assessment of the formability of a low-carbon steel sheet

The objectives of this study were: 1) to measure and analyse work-hardening characters for low-carbon steel sheets 2) to calculate the forming limit strain and forming limit diagram (left hand) 3) to evaluate limit drawing ratio. In this study, experiments on the plastic properties of several low-carbon steel sheets were performed under the uniaxial tension and plane-strain tension. The specimens were painted grid pattern and pulled in a tensile testing machine while precision photographs were .taken of the grid pattern. The yield behaviour and strain hardening characters depend primarily on the temper designation. The stress-strain curves show that an evidently yield strain exists in the T-4CA steel sheets and not in the others. The forming limit strains of these steel sheets were experimentally determined for the uniaxial tension and plane-strain tension. It is clarified that sheet breaks generally due to localised necking (localised-type instability). In the plane-strain tension, the crack was initiated at the centre of the specimen by shear deformation and then propagated. The left-hand sides of the forming limit diagrams (FLD) for each kind of the specimens were calculated by applying Wagoner's method. The limit strains for T-3 or T-4CA steel sheets are greater than that for DR-8CA steel sheets. The limit drawing ratio (LDR) of these steel sheets were examined and calculated. The value of LDR for T-3 steel sheet is greater. than that of the others.