基于微观损伤断裂机理的高强钢材焊接空心球节点力学性能研究

The use of high strength steel materials has been more and more popular in large-span space structures. As the most important component in the space structure with the action of connecting members and transferring loadings, the design of joint is really a significant and difficult problem. In this project, performance of material, weld connection as well as joint are all investigated one after another to obtain the mechanical behavior of welded hollow spherical joints made of high strength steel. In order to achieve this goal, the relationship between micromechanics-based fracture theory and macro mechanical properties of joint is established, and both numerical simulation and experimental methods are employed hereby. First, monotonic tensile and electron microscopic tests will be carried out on a series of material specimens, extracted from base metal, welding seam and heat-affected zone of hot press molding Q460 high strength steels respectively, to build the strain-stress relationship and calibrate the parameters of the micromechanical fracture model; Then tensile experimental investigation on the T-shape welded connections of CHS members and end plate will be performed to develop precise numerical simulation method and validate the micromechanical fracture model; In addition, FEM. parameter analysis introducing micromechanics-based failure criterion will be performed on high strength welded hollow spherical joints, considering unidirectional axial loadings, bidirectional axial loadings, three-dimensional axial loadings as well as the combination loadings of axial force and bending moment, accompanying with a series experiments on behavior of joints. At last, the failure mechanism of high strength welded hollow spherical joints will be presented. The reasonable calculation formulas of the ultimate bearing capacity and of joints will be put forward. The mathematical description of nonlinear joint stiffness with clear physical meaning will be derived. Design suggestions on high strength welded hollow spherical joints will also be proposed. Research results of this project will apply scientific proof and technical support to the development or revision of technical specification for large span space structures.

高强钢材在大跨空间结构中应用日渐增多，而节点作为连接杆件、传递荷载的关键，将是高强大跨空间结构的设计重点和难点。本项目以高强钢材焊接空心球节点为研究对象，将钢材微观损伤断裂机理和节点宏观力学性能相联系，结合试验与精细化数值分析手段，从材料、焊缝连接和节点三个层面渐次开展研究工作。通过单向拉伸和电镜扫描试验，获取Q460热压成型、焊缝熔敷金属和热影响区钢材应力-应变关系和微观断裂预测模型参数；以T型钢管-端板焊接接头轴心和偏心受拉性能试验，探索高精度有限元建模方法和校验微观损伤断裂预测结果；分别进行单向轴力、双向轴力、轴力与弯矩共同作用以及空间多向等受力状态下的节点性能试验和参数分析，探索高强焊接空心球节点损伤破坏机理，提出准确、合理的静力承载力设计公式，建立有明确物理意义的节点刚度数学描述，并给出实用构造建议。项目成果将为未来大跨空间结构设计规范的修订提供有力科学依据和技术支撑。

高强钢材在大跨空间结构中应用日渐增多，而节点作为连接杆件、传递荷载的关键，将是高强大跨空间结构的设计重点和难点。本项目以高强钢材焊接空心球节点为研究对象，将钢材微观损伤断裂机理和节点宏观力学性能相联系，结合试验与精细化数值分析手段，从材料、焊缝连接和节点三个层面渐次开展研究工作。通过单向拉伸和剪拉性能试验，获取Q460钢板母材、焊缝熔敷金属和热影响区钢材应力-应变关系和微观断裂预测模型参数；以T型钢板对接接头、钢管-端板焊接接头轴心和偏心受拉性能试验，探索高精度有限元建模方法和校验微观损伤断裂预测结果；分别进行单向轴力、双向轴力、轴力与弯矩共同作用以及空间多向等受力状态下的节点性能试验和参数分析，探索高强焊接空心球节点损伤破坏机理，提出准确、合理的静力承载力设计公式。项目成果将为未来大跨空间结构设计规范的修订提供有力科学依据和技术支撑。