Papers by Keyword: Pre-Strain Effect

Abstract: This paper investigates the dynamic tensile characteristics of TRIP600, TRIP800, DP600 and DP800 at the range of strain rate from 0.003 to 200/s. The tensile test acquires stress−strain curves and the strain rate sensitivity of each material. Experimental results show two important aspects for TRIP-type and DP-type sheets quantitatively: the flow stress increases as the strain rate increases; the elongation is not a monotonic function of the strain rate and increases at the same level of the strain rate even when the strain rate increases. In order to investigate the pre-strain effect for two types of metals at the high strain rate, TRIP600 and DP600 were elongated with the pre-strain of 5 and 10% at the strain rate of 0.003/s. Then, dynamic tensile tests were carried out at the strain rate of 0.003, 1, 10 and 100/s. The results demonstrate that the material properties of TRIP600 and DP600 are noticeably influenced by the pre-strain when the strain rate was over 1/s. The ultimate tensile strength as well as the yield stress increases due to the pre-strain effect.

Abstract: This paper presents a micro-mechanical model of ductile fracture for the API X65 steel, using the Gurson-Tvergaard-Needleman (GTN) model. Experimental tests and FE damage simulations using the GTN model are performed for smooth and notched tensile bars with three different notch radii, from which micromechanical parameters in the GTN model are calibrated. The calibrated micro-mechanical model is applied to quantify pre-strain effects on plastic deformation and fracture of the API X65 steel. Good agreements of the FE damage results with experimental data suggest confidence in the use of the proposed micro-mechanical model to simulate ductile failure of pipelines made of API X65 steels.