用于金属阻尼器的Q235钢材循环硬化应变幅相关特性

STRAIN AMPLITUDE-DEPENDENT HARDENING PROPERTY OF Q235 STEEL FOR METALLIC DAMPERS

  • 摘要: 金属阻尼器作为一种成本较低的减震构件被广泛应用于各类工程结构之中,通常采用低强度高延性钢材制作。在地震作用下,金属阻尼器会经历随机的循环塑性变形历程,其材料力学性能会发生变化,产生循环硬化或软化。为了探究常用于金属阻尼器的Q235钢材在各类循环应变幅下的力学性能,该文对Q235钢材在常应变幅、升应变幅与降应变幅循环荷载下的力学性能进行了试验研究,最大应变幅达到10%,分析了加载应变幅值和应变历史对钢材硬化性能的影响。结果表明,Q235钢材的硬化能力与加载应变幅相关,较大应变幅下积累的塑性变形会提高后续较小应变幅下钢材的硬化量,升应变幅荷载下钢材的硬化能力与加载历史无关。在此基础上,通过MATLAB优化工具箱标定了各个常应变幅试件的最优化CHABOCHE模型参数,参数结果表明仅考虑各向同性硬化的应变幅依赖效应即可准确反映Q235钢材在各个应变幅下的循环力学响应。以剪切阻尼器为例,基于有限元软件ABAQUS,通过编制子程序USDFLD考虑了材料硬化的应变幅依赖效应,分析对比了是否考虑钢材硬化应变幅依赖特性对阻尼器性能预测的影响。分析表明Q235钢材的循环硬化的应变幅相关特性对阻尼器性能分析影响很大,需要在分析中考虑。

     

    Abstract: Metallic damper has been widely used as a cheap seismic reduction technology in various engineering structures, and it is usually made from steel with low yield strength but high ductility. Under seismic loading, metallic dampers would experience stochastic cyclic loading paths with its strain amplitude varying significantly, and in such case the steel material experiences cyclic hardening and cyclic softening. Experimental studies including constant strain amplitude, ascending strain amplitude, and descending strain amplitude were firstly conducted on steel Q235 to investigate its mechanical performance under various cyclic loading protocols. The largest strain amplitude exceeds 10% of the original value, and the influence of strain amplitude and strain history was extensively scrutinized. The results demonstrate that: the hardening capacity of Q235 steel depends strongly on strain amplitude, and the plastic strain cumulated under larger strain amplitude would increase the hardening capacity of it under smaller strain amplitude tests followed while the influence of deformation history can be ignored in ascending strain amplitude tests. Furthermore, the Chaboche model parameters of Q235 steel under different constant strain amplitudes were calibrated using the optimization toolbox in software MATLAB. The optimized parameters indicate that simply considering the strain amplitude-dependent property of isotropic hardening is enough to describe hysteretic behavior of steel Q235. Using the shear damper as an example, the strain amplitude dependence property of material hardening capacity was considered by programming the subroutine USDFLD upon finite element software ABAQUS. The importance of considering this hardening property in predicting the performance of shear dampers is analyzed. It shows that the strain-amplitude dependent properties of cyclic hardening of Q235 steel have a significant impact on the analysis of damper performance and need to be concerned.

     

/

返回文章
返回