In this paper, a new technology for on-orbit cold forming of space truss rods is proposed. For the cold roll forming process of asymmetric cross sections of thin strips, the effects of roll gap and roll spacing on the forming of asymmetric cross sections of strips were investigated using ABAQUS simulation + experiments. The study shows the following. When forming a strip with a specific asymmetric cross section, the stresses are mainly concentrated in corners 2/4/6, with the largest strain value in corner 2. With increasing forming passes, when the roll gap is 0.3 mm, the maximum equivalent strain values are 0.09, 0.24, 0.64 sequentially. Roll gaps of 0.4 mm and 0.5 mm equivalent strain change amplitude are relatively similar, and their maximum equivalent strain values are approximately 0.07,0.15, 0.44. From the analysis of the stress-strain history of the characteristic nodes in corners 2/4/6, it can be seen that the stress and strain changes in the deformation process mainly occur at the moment of interaction between the upper and lower rollers, where the stress type of node 55786 shows two tensile types and one compressive type, the stress type of nodes 48594 and 15928 shows two compressive and one tensile type, and the strain of the three nodes is in accordance with the characteristics of plane strain. When the roll gap is about 0.4 mm, the forming of the strip is relatively good. With increased roll spacing, the strip in the longitudinal stress peak through the rollers shows a small incremental trend, but the peak stresses are 380 Mpa or so. When the roll spacing is 120 mm, the longitudinal strain fluctuation of the strip is the most serious, followed by the roll spacing at 100 mm, and the minimum at 140 mm. Combined with the fluctuation in strip edges under different roll spacings, manufacturing cost and volume and other factors, a roll spacing of 100 mm is more reasonable. It is experimentally verified that when the roll gap is 0.4 mm and the roll spacing is 100 mm, the strip is successfully prepared in accordance with the cross-section requirements. When the rolling gap is 0.3 mm, due to stress-strain concentration, the strip is prone to edge waves in forming. The top of corner 2 of the flange triangular region is susceptible to intermittent tear defects, and the crack extension mechanism is mainly based on the cleavage fracture + ductile fracture.
Keywords: cold roll forming process; concentration of strain; roll gap; roll spacing; tearing crack; truss rods.