Z型Q345冷弯钢构件率相关本构模型下的动态冲击失稳研究

以Z型Q345薄壁冷弯钢构件为研究对象, 首先测试了试验钢在10-4~102s-1应变率内的材料力学属性, 并拟合得到了由Johnson-Cook本构模型表述的材料本构参数, 同时对拉伸断裂的试件断口做了微观形貌分析. 接着, 在落锤装置上对Z型冷弯钢构件做不同速度的轴向冲击试验, 研究构件受到冲击的动态失稳变形情况. 然后, 通过ABAQUS软件建立了可以反映锤头冲击构件过程的仿真模型, 考虑应变率效应和初始缺陷等因素, 分析了构件主要部位端部质点的位移和速度变化情况以及应力波传播效应的影响. 结果表明 薄壁冷弯钢构件受到外部冲击作用会产生动态屈曲, 随着冲击载荷增大, 发展为明显的塑性变形. 应力波的传播效应对动态屈曲模态的阶跃起着关键的作用.

Dynamic impact instability of Z-shaped Q345 cold-formed steel members under rate-dependent constitutive model

Z-shaped Q345 cold-formed steel members were chosen as the research object. Firstly, the mechanical constitutive properties of the experimental steel in the range of strain rates 10-4~10-2s-1 were obtained, and the material parameters expressed by the Johnson-Cook constitutive model were also obtained by fitting. At the same time, the micro-morphology of the fracture of the tensile specimens was analyzed. Then, the axial impact tests of the Z-shaped cold-formed steel members at different speeds of drop hammer were carried out to study the dynamic instability and deformation of the members under impact. Next, the finite element models that can reflect the impact processes of the drop hammer tests were established by ABAQUS software, whereby the factors such as strain rate effects and initial defects were taken into account. The displacement and velocity changes of the particles at the end of the main part of the component and the influence of the stress wave propagation effect were analyzed. The results showed that dynamic buckling occurred in the thin-walled cold-formed steel members when subjected to external impact, and obvious plastic deformation developed with the increase of the impact loads. The propagation effect of stress waves played a key role in the phase step of dynamic buckling models.