A novel acquisition strategy of process parameters for spatial tubes with variable curvature formed by free bending technology

Free bending technology is an important bending process for forming spatial tubes with variable curvature. By continuously adjusting the position of the die, tube axis with complex shapes can be formed, so accurately obtaining process parameters is crucial for precisely forming complex tubes. According to the geometric characteristics of tubes formed by free bending technology, the tubes are divided into stable segments with constant curvature and transitional segments with variable curvature, and the process parameters and geometric parameters of the formed tubes are described by the parameter sets. In this paper, based on the knowledge base, a new acquisition strategy was proposed to obtain the process parameters of spatial tubes with variable curvature. Aim at forming transitional tubes, in order to establish an effective correlation between process and geometric parameters, a surrogate model based on SVD-RBF has been proposed to quickly predict the axis shape of the transitional tube. In addition, applying this strategy to the forming experiment of the typical tube, it was found that the shape deviation E_max/L is 0.7806%, which verifies the feasibility of this strategy.