轴向冲击下开口薄壁冷弯钢构件多模态屈曲及相互作用

Dynamic buckling of open cross-section thin-walled members subject to axial impact involves strain rate effect of material, stress wave propagation (inertial effects), interaction of multimode buckling and initial imperfection. That is because that, 1) high strain rate can evidently change the yield strength of steel; 2)the stress wave begin to propagating in the structure, it makes the occur of buckling and its transition; 3) at the period of post buckling, multimode buckling occur in members, their interaction should be considered; 4)the open cross-section thin-walled members are very susceptive to imperfections..The existing dynamic buckling criterion either has no theoretical foundation such as the Volmir criterion, or too conservative such as the B-H criterion or too inconvenience to implement such as Kleiber - Kotula - Saran dynamic buckling criterion. The project is to establish a numerical algorithm which has a comprehensive consideration of strain rate effect of the material, the interaction of stress wave propagation and dynamic buckling, the interaction of multimode buckling and the influence of initial imperfection. It can be used to study the dynamic response of open cross-section thin-walled members subject to axial impact. Comparing the numerical results with experimental results, it proposes a recognized dynamic buckling criterion based on dynamic buckling and post-buckling equilibrium path.

轴向冲击下，开口薄壁冷弯钢构件的动态屈曲问题需要考虑材料的应变率效应、应力波传播(惯性效应)、多屈曲模态的相互作用以及初始缺陷的影响。这是因为1)高应变率可显著改变钢材的屈服强度；2)轴向冲击后，应力波开始在结构中传播，使结构发生屈曲及屈曲跃迁；3)后屈曲阶段，构件中存在多模态屈曲，需考虑它们的相互作用；4)轴压下的开口薄壁构件对于缺陷非常敏感。.已有的动态屈曲准则或没有理论依据如Volmir准则，或过于保守如B-H准则，或不便使用如Kleiber–Kotula–Saran动态失稳准则。本项目建立一个全面考虑材料的应变率效应，应力波传播与动态屈曲的相互作用，多模态屈曲相互作用以及初始缺陷的影响的数值算法，研究轴向冲击下开口薄壁构件的动态响应。并用实验结果和数值结果进行对比分析，在研究动态屈曲和后屈曲平衡路径的基础上提出一个公认的动态屈曲准则。

轴向冲击下，开口薄壁冷弯钢构件的动态屈曲问题需要考虑材料的应变率效应、应力波传播(惯性效应)、多屈曲模态的相互作用以及初始缺陷的影响。这是因为1)高应变率可显著改变钢材的屈服强度；2)轴向冲击后，应力波开始在结构中传播，使结构发生屈曲及屈曲跃迁；3)后屈曲阶段，构件中存在多模态屈曲，需考虑它们的相互作用；4)轴压下的开口薄壁构件对于缺陷非常敏感。.本项目建立一个全面考虑材料的应变率效应，应力波传播与动态屈曲的相互作用，多模态屈曲相互作用以及初始缺陷的影响的数值算法，研究轴向冲击下开口薄壁构件的动态响应。并用实验结果和数值结果进行对比分析，在研究动态屈曲和后屈曲平衡路径的基础上提出了一个动态失效公式。.此外，由于试样的设计和优化依赖于构件畸变屈曲临界应力模型的准确建立，本课题对畸变屈曲模型的贡献填补了国内外规范的空白，优化编程的实现为工程应用提供了极大的便利。落锤和Hopkinson压杆实验还发现了动态屈曲往往伴随着撕裂这一失效模式同时发生，完善了材料本构和实效准则以后，可以较为准确地通过有限元重现这一耦合现象。里面的机理还需要今后进一步研究。