单轴载荷下X80钢的包申格效应研究

A Study on Bauschinger Effect of X80 Steel under Simple Axial Loading

本文通过单轴拉伸和压缩试验研究了X80管线钢的包申格效应(BE)。采用正向与反向加载方法研究材料变形历史特性。测定了X80钢的简单拉伸试验曲线,其应力-应变关系表明,该材料具有理想弹塑性特点。为了得到X80钢的BE,在不同预变形下对几个试件分别进行加载,并当给定的预应变值分别达到0.63%,0.67%,0.95%,1.27%和1.55%时就卸载。随后再进行反向加载实验,并记录应力应变曲线。该钢材反向加载时出现加工硬化,且屈服强度比正向加载时要低。正反向加载之间的屈服强度差值随着预应变增加而增大;当预应变超过0.95%时,反向屈服强度达到恒量。实验表明,X80钢的反向加载特性可用Remberg-Osgood关系拟合。最后给出了屈服强度降和预塑性应变之间的经验公式。

The Bauschinger effect （BE） of X80 pipeline steel was studied in this paper through simple axial tension and compression tests. Forward and reverse axial loading schemes were conducted to investigate the character of the material deformation history. A typical curve of X80 steel in simple tension testing was determined. The stress-strain response showed the perfect elastic-plastic character of this material. To acquire the BE of X80 steel, several specimens were firstly loaded separately under the control of different pre-deformation. It was not unloaded until the given pre-strain value on the specimens reached 0.63%, 0.67%, 0.95%, 1.27% and 1.55% respectively. The reverse loading experiments were performed subsequently and the stress-strain curves were also recorded. It is clearly found that the material is work-hardening under the reverse loading and the yield strength is lower than that of the first forward loading test. The differences of yield strength between forward and reverse loadings increase as the pre-strains grow. When the pre-strain surpasses 0.95%, the reverse yield strength reaches to a constant. The testing results of X80 steel show that the constitutive relation of the reverse loading could be defined by the Remberg-Osgood relation. The experiential formula of the relationship between the yield strength reduction and the pre-plastic strain amplitude is derived at the last.