# Effect of Geometrical Factors on Torsion in Cold Roll Forming of the Lower Side Beam of a Car
## 1 Introduction  
Cold bending forming is widely used in various fields due to its unique high efficiency. However, the technology has not been fully mastered, and there are many unnecessary defects in production, such as torsion. Torsion is a common defect in cold forming. In particular, in the creation of products with asymmetrical cross-sections, it is easy to produce torsion defects, causing high levels of resource waste in production. Therefore, the research on torsion has extraordinary guiding significance for cold forming. In cold forming production, the use of finite element simulation is essential [1] because the inefficient trial-and-error method is often used to obtain the process rules. These process rules mainly include whether the deformation method and deformation speed of the plate and strip are reasonable. In the process of cold roll forming, an edge will produce longitudinal extension, resulting in residual longitudinal strain, bending, torsion, and other defects when the material moves longitudinally in the roll. The greater the residual strain, the higher the defect rate will be [2]. Some researchers have already investigated the torsion defect in the cold roll forming process. [PERSON] [3] et al. found that the difference of longitudinal strain at the webs and the vertical edge of U-shaped steel had an essential effect on torsion by studying the bending and torsion defects in the cold forming of asymmetric U-shaped high-strength steel. They proposed the application of pressure to the web to improve the torsion. [PERSON] [4] et al. also studied the torsion defects of asymmetric U-shaped steel. They found that the long side and the short side did not contact the roller successively in the forming process, leading to different applying forces in the direction of thickness, resultingin torsion. They proposed changing the roll's shape to solve the torsion problem and found that the simultaneous change of longitudinal strain at the edge could effectively reduce the torsion. [PERSON] [5] et al. studied the influence of geometrical factors on the torque required to form grooved steel and found that the thickness had the most significant effect on the forming torque. The torque was closely related to the longitudinal strain of the edge but not to the transverse strain. [PERSON] et al. [6], considering the factors such as the crimping and uncoiling of the cold-formed strip, conducted a prediction study on the residual stresses of cold-formed steel members, and the residual stresses and strains showed a nonlinear increase trend with the increase of strip thickness. [PERSON] et al. [7] studied the influence of process parameters on the cold-forming quality of grooved steel, reduced the longitudinal strain at the edge, and weakened the redundant deformation by optimizing process parameters. [PERSON] et al. [8] studied the effects of yield strength, strip thickness, angular increment, flange width, and other factors on the required torque and vertical component force in cold forming. They found that decreasing the yield strength, strip thickness, and angular increment could reduce the sheer component force and required torque. Reducing the strip width could reduce the vertical component force and increase the total required torque. [PERSON] et al. [9] analyzed and studied the factors influencing the energy consumption of cold forming and found that the angle increment, rack spacing, and forming speed significantly influenced energy consumption. [PERSON] [10] studied the relationship between U-shaped steel edge longitudinal peak strain and deformation length and material yield strength. [PERSON] and [PERSON] [11] studied the influence of forming parameters on the longitudinal strain and bending of edges. They found that the longitudinal bending increased with the increase of the angle. The peak of longitudinal strain at the border increased with the increase of strip thickness and angular increments.