计及相变的QP980钢的动态本构方程与断裂研究

发布时间：2018-10-26 09:45

【摘要】：本文研究了计及相变的QP980钢的动态本构方程与动态断裂。提出了一种应变受控的拉伸Hopkinson试验装置(TSHB),取得了高应变率拉伸下发生预设应变的QP980钢试件。对回收试件进行同步加速器X射线衍射(XRD)试验,结果表明,QP980钢在高应变率拉伸下,残余奥氏体的体积含量随应变的变化规律与准静态拉伸下的变化规律几乎一致。根据O-C马氏体相变理论,结合XRD试验分析结果,得到了高应变率拉伸下QP980钢的相变动力学方程。根据多相材料细观力学理论,由各组成相的弹塑性变形行为,构成计及相变的QP980钢的准静态本构方程。假设应变率与温度效应可分离,基于不同应变率及不同温度下的TSHB试验,建立了计及相变的QP980钢动态本构方程。由所建本构方程得出的应力-应变曲线与试验曲线进行了对比,验证了所建本构方程的有效性。采用高速摄影技术记录了QP980钢板条试件在TSHB试验中的颈缩与断裂,基于Batra和Wei的失稳判据以及所建立的动态本构方程,计算了QP980钢板条试件在TSHB试验中的非局部颈缩应变,并与测试结果进行了对比。通过进行不同温度、不同应变率下的拉伸试验,研究了QP980钢板条试件的断裂应变与应变率以及温度的依赖关系。通过对试件断裂区域的扫描电镜(SEM)观测,揭示了QP980钢在变形过程中的微空穴不同的演化机制。
[Abstract]:The dynamic constitutive equation and dynamic fracture of QP980 steel with phase transformation are studied in this paper. In this paper, a strain controlled tensile Hopkinson test device, (TSHB), has been developed to obtain QP980 steel specimens with preset strain under high strain rate tension. The results of synchrotron X-ray diffraction (XRD) test show that the volume content of residual austenite varies with strain in QP980 steel at high strain rate, which is almost the same as that under quasi-static tension. Based on O-C martensitic transformation theory and XRD test results, the transformation kinetics equation of QP980 steel under high strain rate tension is obtained. According to the mesomechanical theory of multiphase materials, the quasi-static constitutive equation of QP980 steel with phase transformation is constructed by the elastoplastic deformation behavior of each component phase. Assuming that the strain rate and temperature effect can be separated, the dynamic constitutive equation of QP980 steel with phase transformation is established on the basis of TSHB tests at different strain rates and different temperatures. The stress-strain curve derived from the established constitutive equation is compared with the experimental curve, and the validity of the established constitutive equation is verified. The necking and fracture of QP980 steel strip specimen in TSHB test were recorded by high-speed photography. Based on the instability criterion of Batra and Wei and the dynamic constitutive equation established, the non-local necking strain of QP980 steel strip specimen in TSHB test was calculated. The results are compared with the test results. The dependence of fracture strain on strain rate and temperature of QP980 steel strip specimens were studied by tensile tests at different temperatures and different strain rates. The different evolution mechanisms of microvoids in QP980 steel during deformation were revealed by scanning electron microscope (SEM) observation of the fracture zone of the specimens.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1

【参考文献】