中频感应加热消除薄板焊接失稳变形的机理研究

In production of lightweight ship structures, inherent deformation generated by welding will make stiffened ship panel buckle, which is fabricated with thin plates of high tensile strength steel; medium frequency induction heating moving with welding torch simultaneous, can effectively mitigate welding induced buckling. With modelling of temperature field generated by induction heating, and coupling analysis of temperature fields generated by induction heating and welding heating, the influence mechanism of induction heating on the whole distribution of temperature is obtained. Average temperatures of the whole temperature fields caused by different induction heating processes and identical welding heating are measured and calculated, to establish the mathematical model between induction heating and average temperature, and to clarify the nature of the phenomenon of whole temperature field changing with induction heating. By measurement and FE analysis of welding distortion, welding induced inherent deformations with induction heating processes are evaluated, to preliminarily reveal the intrinsic mechanism of the phenomenon that induction heating mitigates the welding induced buckling. Three-bar model is employed to examine the welding process with induction heating; with incorporating generation mechanism of inherent strain, the intrinsic mechanism of that inherent strain of main-bar decreases when temperature of side-bar elevates due to induction heating is clarified. This project which bases on inherent deformation, clarifies the intrinsic mechanism of mitigation of welding induced buckling with medium frequency induction heating; provides theoretical basis to constitute manufacturing specification with high productivity and quality of stiffened ship panel; has an essential meaning for our country to enhance the market competition of advanced ship fabrication.

在“轻量化造船”中，焊接产生的固有变形使得高强钢薄板制造的船体加筋板发生失稳；而伴随焊枪移动的中频感应加热，可有效地消除焊接失稳变形。通过感应加热温度场的模拟，以及感应加热和焊接加热温度场的耦合分析，得出感应加热对整体温度场分布的影响机理。通过对不同感应加热和焊接加热下整体温度场平均温度的测量和计算，建立感应加热和平均温度关系的数学模型，阐明感应加热时，整体温度场变化的现象本质。通过焊接变形的测量和有限元分析，估算感应加热作用下的焊接固有变形，初步揭示感应加热消除焊接失稳变形的内在机理。三根棒力学模型分析感应加热时的焊接过程，结合固有应变的产生机理，解释侧棒温度因感应加热升高时，主棒固有应变减小的内在机制。本项目以固有变形为依据，阐明了感应加热作用时，焊接失稳变形消除的内在机理；为高质高效的船体加筋板制造工艺的制定，提供理论依据；对提升我国高新船舶制造的市场竞争力具有重要意义。

水面舰艇及远洋高技术客船的轻量化建造，使得高强钢薄板结构的应用逐步增多；高强钢薄板在满足船体结构强度和刚度的同时，会因厚度的锐减，在建造过程中发生失稳屈曲现象，影响船舶建造的精度和周期。.本研究基于焊接失稳变形预测及力学机理的分析，提出使用中频感应加热，在远离焊缝的区域，产生同步的附加热源；增加整个焊接接头的平均温度，进而减小母材对焊缝的自约束强度，得到较小的焊接纵向收缩力，避免焊接失稳变形的产生。.通过多组薄板焊接试验、温度场及面外失稳变形的测量，分析了焊接温度场与感应加热温度场之间的耦合效应；提出了焊接纵向收缩力的精确评估方法，建立了焊接固有变形数据库；基于三根棒模型和平均温度的概念，解释了附加热源降低焊接接头自约束，及减小焊接纵向收缩力的内在机理。使用高效的热-弹-塑性有限元计算，研究了附加热源强度和位置等过程参数对消除焊接失稳变形的影响，建立了虚拟的多变量试验空间，实现过程工艺参数的优化分析。.基于基金项目的研究，一方面，提出了感应加热热源模型，预测了瞬态温度场及其产生的残留变形；采用塑性应变积分法，获得焊接及感应加热过程耦合作用下的纵向收缩力；同时，从力学机理上阐述了辅助感应加热增加焊接接头平均温度、减小母材的自约束强度，以及消除高强钢薄板焊接失稳变形等科学问题；另一方面，建立了感应加热工艺参数（热源强度和加热位置）的虚拟试验空间，通过大通量的热-弹-塑性有限元计算得到了优化的工艺参数组合，为实际工程问题的解决，提供了必要的理论指导，且具有一定的借鉴意义。