Stress-strain curves for hot-rolled steels

Abstract

The use of advanced analytical and numerical modelling in structural engineering has increased rapidly in recent years. A key feature of these models is an accurate description of the material stress-strain behaviour. Development of standardised constitutive equations for the full engineering stress-strain response of hot-rolled carbon steels is the subject of the present paper.The proposed models, which offer different options for the representation of the strain hardening region, feature an elastic response up to the yield point, followed by a yield plateau and strain hardening up to the ultimate tensile stress. The Young's modulus E, the yield stress fy and the ultimate stress fu are generally readily available to the engineer, but other key parameters, including the strains at the onset of strain hardening and at the ultimate stress, are not, and hence require predictive expressions. These expressions have been developed herein and calibrated against material stress-strain data collected from the literature. Unlike the widely used ECCS model, which has a constant length of yield plateau and constant strain hardening slope, the proposed models, reflecting the collected test data, have a yield plateau length and strain hardening characteristics which vary with the ratio of yield to ultimate stress (i.e. with material grade). The proposed models require three basic input parameters (E, fy and fu), are simple to implement in analytical or numerical models, and are shown herein to be more accurate than the widely employed ECCS model. The proposed models are based on and hence representative of modern hot-rolled steels from around the world.

The generalised slenderness‐based resistance method for the design of CHS and EHS

“…Parametric studies were conducted to produce additional cross-section resistance data on CHS and EHS over a wide range of cross-section aspect ratios (1, 1.5, 2 and 3), cross-section slendernesses (D e /tε 2 = 20 to 240), production routes (hot-rolled and cold-formed), material grades (S355, S460, S550, S690/S700 and S900) and load combinations. The stress-strain relationships were generated using the predictive models developed by [11] and [12] for hot-rolled and cold-formed steels respectively, with the required input parameters, including the Young's modulus E, yield strength f y and ultimate strength f u , taken from prEN 1993-1-1:2018 [1]. A range of initial loading eccentricities and combinations of major and minor axis bending were considered to capture the cross-sectional behaviour under various combined loading scenarios.…”

Preliminary study on the impact of initial imperfections on the post‐buckling rotation of square hollow sections in uniform bending

“…The material model for hot-rolled carbon steel is based on a bilinear plus non-linear hardening description (18). The material model for hot-rolled carbon steel is based on a bilinear plus non-linear hardening description (18).…”

Deformation based design of steel and composite structural elements

“…However, this bi-linear material model is unsuitable for hotrolled carbon steels due to the presence of the characteristic yield plateau, with strain hardening not commencing until the attainment of strain hardening strain εsh. Thus, the quadlinear material model proposed in [6], as illustrated in Fig. 2 and described in Eq.…”

“…The strain hardening strain εsh for hot-rolled carbon steels may be determined from Eq. (6). Note that the quadlinear material adopts the same definitions for the material coefficients as used in the previous CSM elastic, linear hardening material model, and can indeed be seen as a superset of the previous model, with the principal difference being that the strain hardening strain εsh is equal to the yield strain εy in the CSM elastic, linear and cold-formed steels (…”