低合金汽车结构钢动态响应模型研究

Study on Dynamic Response Model of Low Alloy Automobile Structural Steel

目的研究低合金汽车结构钢不同应变速率下的动态响应行为,并提供一种简单准确的动态增长因子的预测方法,为内高压成形工艺提供参考。方法进行高应变速率拉伸(动态拉伸)实验,并用高速摄像机和扫描电子显微镜对材料的拉伸行为和断口形貌进行表征,利用实验数据建立一系列结构钢的动态响应模型,研究不同应变速率下的响应特性。结果随着应变速率的不断增大,应力-应变曲线出现周期性波动衰减,通过模型分析,发现在高应变速率下材料变形具有两阶段特征,与应力波传播的往返次数特征相似。结论与Cowper-Symonds(C-S)模型拟合结果对比发现,所提出的两段式模型得到的实际结构钢屈服强度动态增长因子拟合度更高,可更好地对材料屈服强度进行预测。在实际内高压成形过程中应保证应变速率不宜过高,避免因应变速率过高导致的不均匀变形,影响材料成形质量。

The dynamic response behavior of low-alloy automotive structural steel under different strain rates is studied,and a simple and accurate method for predicting the dynamic growth factor is provided,which provides a reference for the hydroforming process.High strain rate tensile(dynamic tensile)experiments were carried out,and the tensile behavior and fracture morphology of the materials were characterized by high-speed camera and scanning electron microscope.A series of dynamic response models of structural steel were established by using the experimental data to study the response characteristics under different strain rates.With the increase of strain rate,the stress-strain curve appears periodic fluctuation attenuation.Through the model analysis,it is found that the material deformation has two-stage characteristics at high strain rate,which is similar to the characteristics of stress wave propagation.Compared with Cowper-Symonds model fitting,the two-stage model fitting the dynamic growth factor of yield strength of actual structural steel has higher fitting degree and better prediction of material yield strength.It is pointed out that the strain rate should not be too high in the actual hydroforming process,so as to avoid the effect of the non-uniform deformation caused by too high strain rate on the forming quality of materials.