Papers by Keyword: Work Hardening Exponent

Abstract: This research work analyses the effect of cold working level produced by drawing, on the work hardening exponent of 0.18 and 0.43 % C ferrite-pearlite steels. Such analysis is carried out by means of true stress-true strain curves derived from uniaxial tension tests. The work hardening exponent behaviour was determined by using Hollomon and differential Crussard-Jaoul models. It is found that the work hardening exponent decreases as a function of the applied cold-drawing level, and negative values were obtained when differential analysis is used. The results indicate that the Hollomon analysis shows some deviations from the experimentally determined true stress - true strain curves while the differential Crussard-Jaoul analysis fits better when two work hardening exponents are considered. This analysis establishes two exponents for different stages of plastic deformation which are determined by the sharp slope change in the plot of ln (d σ/d ε) - ln ε.

Abstract: The yield ratio of various HSLA steels has been correlated with the materials constants of Swift equation. It has been shown that the materials constants, b and N, of Swift equation can be related to microstructural features such as the dislocation density and volume fraction of constituent phases. In particular, the constant b can be expressed as a function of volume fraction of constituent phases. It has also been shown that the yield ratio has a linear relationship with ln(b/N2). Since the microstructural features often have opposing effects on the values of b and N, careful control of microstructure is necessary to optimize the yield ratio and other properties. The possible way of decreasing the yield ratio without sacrificing other properties of HSLA steels is suggested based on the relationship between yield ratio and the materials constants of Swift equations.