大型直缝焊管多次三点弯曲压力矫直控制策略

为了减少大型直缝焊管的直线度误差,提出了一种针对大型管件多次三点弯曲压力矫直工艺的定量控制策略．首先,基于所建立的平面弯曲弹复理论及过弯矫直等价原理,给出了基于管件初始挠度曲线分布的理论矫直弯矩,并揭示了多次压力矫直工艺的矫直机理:以锯齿形折线分布弯矩逼近理论矫直弯矩光滑曲线．基于此,提出了多次压力矫直控制策略,依据该策略只需一次性测量管件初始挠度分布,即可给出多次三点弯曲压力矫直所需的工艺参数．其次,为提高矫直效率且保证矫直精度,提出了载荷修正系数的概念．实验结果表明:当矫直次数一定时,随着修正系数的增加,管件的残余挠度减小;而随着矫直次数的增加,将管件矫直所需的修正系数逐渐减小．以小尺寸管件的物理模拟试验验证了多次压力矫直控制策略的可行性、可靠性,这为大型管件矫直过程的自动化、智能化提供了理论依据．

Press straightening control strategy of multi-step three-point bending for LSAW pipes

To minimize the straightness error of deflected Longitudinally Submerged Arc Welding (LSAW) pipes, a quantitative control strategy of pressure straightening process with multi-step three-point bending is studied. Based on the springback equation of small curvature plane bending and the equivalent principle for over-bend straightening, this paper proposes a theoretical straightening moment which corresponds with the initial deflection distribution of pipes. The principle of the multi-step pressure straightening process is revealed, and the parameters in three-point bending process for each step can be obtained only by measuring the initial deflection distribution once. To improve the straightening efficiency and ensure the straightening accuracy, the concept of load correction coefficient is firstly proposed. Experimental results show that when the number of straightening step is fixed, the residual deflection of the pipe is reduced with the growth of load correction coefficient. Meanwhile, as the number of straightening step increases, the load correction coefficient decreases. The feasibility and the reliability of the control strategy are verified by the physical simulation experiments of small pipes.