Abstract In order to enable accurate analysis and prediction on structural behaviour of high strength S690 steel member at large deformations, an integrated experimental, theoretical and numerical investigation to formulate a full range constitutive model is reported in this paper. It is well known that standard tensile tests are effective means to obtain key mechanical properties of coupons for deformations up to on-set of necking. However, owing to non-uniform cross-sectional distributions in both stresses and strains within the necking regions of the coupons, it is important to allow for these effects when analysing measured forces and extensions to give true stresses and strains of the coupons. The proposed instantaneous area method has been developed and calibrated against test results of a total of 30 standard tensile tests on S690 cylindrical coupons, and it is formulated with key mechanical properties of engineering stress-strain curves readily obtained from these tests. High resolution digital images of the deformed coupons are captured and analysed to obtain instantaneous dimensions of the necking areas. Through theoretical formulation, true stress-strain curves of the coupons after on-set of necking are derived, and modified with numerical correction factors through successive approximations. After normalization on all the corrected true stress-strain curves, a set of formulae to describe the full-range constitutive model for the high strength S690 steels is proposed. Consequently, the proposed model is readily applicable to both analytical and numerical analyses of the high strength S690 steels and their structural members undergoing both small and large deformations up to fracture.

中文翻译：

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确定高强度 S690 钢的全范围本构模型

摘要 为了准确分析和预测高强度S690钢构件在大变形下的结构行为，本文通过实验、理论和数值研究相结合的方法建立全范围本构模型。众所周知，标准拉伸试验是获得试样关键机械性能的有效手段，用于变形直至颈缩开始。然而，由于试样颈缩区域内应力和应变的横截面分布不均匀，因此在分析测量的力和延伸以给出试样的真实应力和应变时考虑这些影响是很重要的。所提出的瞬时面积法是针对 S690 圆柱试样总共 30 次标准拉伸试验的试验结果开发和校准的，并且它是用从这些试验中容易获得的工程应力-应变曲线的关键机械性能来制定的。捕获并分析变形试样的高分辨率数字图像以获得颈缩区域的瞬时尺寸。通过理论公式，推导出颈缩开始后试样的真实应力-应变曲线，并通过逐次逼近用数值修正因子进行修正。在对所有校正后的真实应力-应变曲线进行归一化后，提出了一套描述高强度 S690 钢全范围本构模型的公式。最后，