Strain-stress Relation of Medium-thickness Steel Plates Including Necking Stages

Abstract

Abstract: In order to make up for the defects of extensometer in measuring necking processes, a cross-sectional analysis method was proposed based on three dimensional digital image correlation(3D-DIC) technique. The medium-thickness steel plate QStE700 whose rolling degree was as 0°was taken as the research object, based on the cross-sectional analysis method, the sectional geometry and area during tensile processes were obtained, the necking time under tensile loading was determined, the stress-strain evolution including necking stages and the changing rules of necking area were analyzed. The modified Bridgeman equation was adopted to transform the true stress-strain curves into the equivalent stress-strain curves, and the modified equivalent stress-strain curves including necking stages were obtained. The finite element model was established based on the traditional exponential curves and the modified equivalent stress-strain curves respectively, the relationship between section area and time and the relationship between load and displacement were both obtained. It shows that the results of the finite element model based on the modified stress-strain curve are in good agreement with the experimental results, the cross-sectional analysis method based on the 3D-DIC technique is verified. This method may be applied to describe the tensile deformation processes including necking stages.

Key words: medium-thickness steel plate, automobile lightweight, cross-sectional analysis method, necking, stress-strain relation

摘要：

为弥补传统引伸计在颈缩区域测量方面的不足，提出一种基于三维数字图像相关（3D-DIC）技术的截面分析方法。以轧制方向为0°的QStE700中厚钢板为研究对象，采用截面分析方法获得单向拉伸过程中截面几何形貌及面积，确定颈缩失稳发生时刻，并分析包含颈缩失稳的应力应变演化过程及截面积变化规律。利用改进的Bridgeman方程对颈缩失稳后的真实应力应变曲线进行校正，获得包含颈缩失稳的中厚钢板等效应力应变曲线。分别以传统的幂指硬化曲线和改进的等效应力应变曲线为本构模型，建立中厚钢板单向拉伸有限元仿真模型，获得截面积随时间变化曲线及载荷与位移关系曲线。结果表明，以改进的等效应力应变曲线为本构模型的仿真结果与试验结果吻合较好，验证了基于3D-DIC技术的截面分析方法的正确性。此方法可用于描述包含颈缩失稳的整个拉伸过程。

关键词: 中厚钢板, 汽车轻量化, 截面分析方法, 颈缩失稳, 应力应变关系

CLC Number:

TG156

ZHU Chuanmin1;GU Peng1;LIU Dinghao1;ZHANG Heng2 . Strain-stress Relation of Medium-thickness Steel Plates Including Necking Stages[J]. China Mechanical Engineering.

朱传敏1;顾鹏1;刘丁豪1;张恒2. 包含颈缩失稳的中厚钢板应力应变关系[J]. 中国机械工程.

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