锈蚀后Q235钢的滞回性能与循环本构模型研究

Hysteretic Behavior and Cyclic Constitutive Model of Q235 Steel After Corrosion

对大气腐蚀33年的Q235钢开展了循环加载试验,重点分析了锈蚀后钢材的断裂模式、耗能能力和骨架曲线随腐蚀程度的变化关系;对比分析了静力与循环加载作用下,腐蚀钢材的力学性能变化;阐明了腐蚀程度对其滞回性能的影响,并建立了腐蚀钢材的循环本构模型.试验结果表明:锈蚀后钢材的滞回曲线仍较饱满,但耗能能力随质量损失线性降低,最高降幅达15.51%;随着循环加载次数的增加,质量损失使耗能能力及塑性变形能力降低得越来越多,当质量损失率大于0.12时,试件受压向的骨架曲线硬化点应变由0.6%缩短至0.3%,降幅高达50%;受拉也有类似的情况;同时,受蚀坑影响循环加载下钢材的变形能力会显著降低(极限应变与伸长率分别降低36.47%和8.88%),但对极限强度和断裂强度的影响甚微.考虑到传统的Ramberg-Osgood模型不包含钢材的屈服阶段且无法准确判断钢材的屈服荷载,引入了包含弹性、屈服以及强化阶段的三段式骨架曲线.钢材的卸载阶段根据试验确定为线性,并建立了卸载刚度随循环应变与质量损失率的定量关系.最后,考虑腐蚀损伤与循环应变明确了重加载阶段的解析式,在此基础上提出了不同质量损失下的锈蚀钢材滞回本构模型,并且通过与试验值比较验证了该模型的准确性.为工程中评估腐蚀钢材的滞回性能提供了参考.

The cyclic loading test was conducted on Q235 steel specimens corroded in the atmosphere for 33 years.The relationships between corrosion degree and fracture mode,energy dissipation capacity,and skeleton curve of corroded steel were mainly analyzed,the variation of the mechanical properties of corroded steel was compared and analyzed under static and cyclic loading,the effect of corrosion degree on hysteretic behavior was clarified,and the cyclic constitutive model of corroded steel was established.Results showed that the hysteresis curves of corroded steel remain smooth and full,while the dissipation capacity linearly decreases with the mass loss,with a maximum decrease rate of up to 15.51%.The degradation of the energy dissipation and plastic deformation capacities caused by mass loss also becomes more significant with the increase in cyclic numbers.When the mass loss rate is greater than 0.12,the strain of the hardening point of the compression skeleton curves decreases from 0.6%to 0.3%,with a decrease of up to 50%.The tension skeleton curves also exhibit the same degradation condition.Moreover,cyclic loading significantly decreases the deformability of steel(i.e.,the ultimate strain and elongation decrease by 36.47%and 8.88%,respectively)but has only a slight influence on the ultimate and fracture strengths.Furthermore,given that the traditional Ramberg-Osgood model cannot determine the yield stage of steel and cannot accurately estimate the yield load,the three-stage skeleton curve is employed to plot the elastic,yield,and hardening stages.According to the test,the unloading stage is determined to be linear,and the quantitative relationship between unloading stiffness,cyclic strain,and mass loss rate is established.Finally,considering corrosion damage and cyclic strain,the analytical formula for the reloading stage is clarified.Based on this,the general hysteresis institutive model with different mass losses is established,and the accuracy of this model is verified by comparing it with the test.Therefore,an evaluation method of hysteretic behavior for corroded steel is provided in the field of engineering.