桥梁钢厚板对/角接焊焊接接头残余应力空间分布及测试技术研究

To meet the requirements of carrying and cross capacity of steel bridges, the high-strength steel thick plate is also widely used. Welding is the main way to connect the bridge steel structure, but residual stress induced by welding in steel thick plate has a complex spatial distribution and large tensile stress near the yield strength. It will seriously affect the manufacture and installation precision for thick steel structure; also reduce fatigue life and durability of bridge structure. At present, researchers around the world usually assumed that the welding residual stress is uniform distributed along the thickness. The previous research results of our research group show that the spatial distribution of the residual stress in the steel thick plate is very complicated. The above assumption has little effect on the design and calculation for bridge steel sheet; however it is bound to bring a large design error for the thick steel plate, which leaves the safety risk for the bridge structure. Therefore, it is necessary to systematically study the formation mechanism, evolution process, spatial distribution state, and measurement technology of welding residual stresses in typical welded joints of thick steel plate. In this project, we will use the experimental measurement and numerical simulation to study the spatial distribution of residual stress in butt and angle weld joint for thick weld plate; establish the residual stress prediction theory of thick weld plate. We also plan to put forward technical measures to make the measurement and simulation methods more practical.

为满足钢结构桥梁承载和跨越能力的要求，高强钢厚板的应用越来越普遍。焊接是桥梁钢结构连接的主要方式，而钢厚板的焊接残余应力不仅数值较大，且空间分布复杂，这会严重影响厚板钢结构的制造、安装精度，也会对桥梁结构的疲劳寿命和耐久性等带来不利影响。当前，国内外研究者通常假定钢厚板的焊接残余应力沿板厚方向均匀分布，从课题组前期的研究成果来看，钢厚板的残余应力空间分布非常复杂。残余应力均匀分布的假定对桥梁钢薄板的设计计算影响较小，但是对桥梁钢厚板势必会带来较大的设计计算误差，给桥梁结构的长期正常使用留下安全隐患。因此，有必要对桥梁钢厚板典型焊接接头焊接残余应力的形成机理、演化进程、空间分布状态及测试技术进行系统研究。本项目拟采用实验测试和数值模拟相结合的办法，研究桥梁钢厚板对接焊和角接焊残余应力的空间分布状态，提出厚板焊接残余应力预测理论；从应用层面，提出残余应力空间分布测试和模拟的实用技术措施。

为满足钢结构桥梁承载和跨越能力的需求，高强钢厚板的应用越来越普遍。焊接是桥梁钢结构的主要连接方式，而焊后钢厚板中残留的焊接应力不仅数值较大，且空间分布复杂，这会严重影响钢桥厚板结构的制造、安装精度，也会对桥梁结构的服役安全性和耐久性等产生非常不利的影响。本项目在焊接残余应力测试方法、数值模拟方法、厚板残余应力空间分布及钢桥典型焊接接头疲劳寿命评估方法等方面开展了系统性的研究，主要研究内容包括：（1）焊接残余应力测试方法优化：讨论了应力双轴性对钻孔法测试精度的影响，提出了钻孔法偏心误差的修正方法；（2）厚板残余应力测试新方法：基于轮廓法与固有应变法，提出了可以重构厚板内三维残余应力的分步固有应变-轮廓法；（3）焊接残余应力数值模拟方法优化：在焊接模拟中考虑了相变的影响，并通过试验获得了准确的桥梁钢高温力学性能，提升了焊接模拟的准确性；（4）焊接残余应力空间分布与焊接变形：通过试验与数值模拟获了得超厚板对接焊接头、厚板T型接头、十字交叉焊缝、正交异性钢桥面板等钢桥典型构造的焊接残余应力空间分布规律以及钢箱杆件的焊接变形规律；（5）焊接残余应力稳定性：通过试验与数值模拟获得了自然时效与振动时效对正交异性钢桥面板焊接残余应力的影响规律；（6）钢桥腐蚀对疲劳寿命的影响规律：通过试验与数值模拟获得了腐蚀对钢桥力学性能与疲劳性能的影响规律；（7）钢桥腐蚀疲劳寿命预测方法：提出了腐蚀疲劳损伤演化模型和裂纹扩展模型，并基于上述模型建立了钢桥腐蚀疲劳寿命预测方法。上述研究成果可为钢桥的疲劳细节设计和服役耐久性评估提供有力的理论基础和技术支撑，对促进钢桥的发展具有重要意义。