Background

Measuring true stress–strain curve over a large-strain-range is essential to understand mechanical behavior and simulate non-linear plastic deformation. The digital image correlation (DIC) technique, a non-contact full-field optical measurement technique, is a promising candidate to obtain a long-range true stress–strain curve experimentally.

Objective

This paper proposes a method for measuring true stress–strain curves over a large-strain-range during tensile testing using DIC.

Methods

The wide-strain-range true stress–strain curves of dual-phase and low carbon steels were extracted on the transverse direction in the neck region. The axial strain on the neck section was estimated by averaging the inhomogeneous deformation on the cross-section of the tensile specimen. The true stress was calculated from the engineering stress and the cross-sectional area of the neck.

Results

The validity of the proposed method was assessed by comparing the experimental load–displacement responses during tensile testing with the finite element method (FEM) simulation results. The stress and strain on the neck section estimated using the FEM and DIC, respectively, were proven to satisfy the uniaxial condition and successfully obtained.

Conclusions

The experimental results agree well with the FEM results. The proposed concept can be applied to various deformation modes for accurately measuring long-range true stress–strain curves.

中文翻译：

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使用颈部截面测量法获得宽应变范围的真实应力-应变曲线

背景

测量大应变范围内的真实应力-应变曲线对于理解机械行为和模拟非线性塑性变形至关重要。数字图像相关 (DIC) 技术是一种非接触式全场光学测量技术，是通过实验获得远程真实应力-应变曲线的有希望的候选技术。

客观的

本文提出了一种在拉伸试验期间使用 DIC 测量大应变范围内真实应力-应变曲线的方法。

方法

在颈部区域的横向上提取双相钢和低碳钢的宽应变范围真应力-应变曲线。通过平均拉伸试样横截面的不均匀变形来估计颈部的轴向应变。真实应力由工程应力和颈部的横截面积计算。

结果

通过将拉伸试验期间的实验载荷-位移响应与有限元方法 (FEM) 模拟结果进行比较，评估了所提出方法的有效性。分别使用 FEM 和 DIC 估计的颈部应力和应变被证明满足单轴条件并成功获得。

结论

实验结果与有限元结果非常吻合。所提出的概念可应用于各种变形模式，以准确测量远程真实应力-应变曲线。