An improved method for manufacturing sheet-tube connection structure by double-sided annular sheet squeezing

Sheet-tube connection structures are widely applied in chemical, petroleum, medicine, and other industries. Its reliable connection and manufacturing are of great significance for the function of the corresponding equipment. To avoid the occurrence of too deep pits and easy warpage during the single-sided annular sheet squeezing process, an improved method to join sheets to tubes by double-sided annular sheet squeezing is proposed in this paper. The joining process is to squeeze the sheet through the top and bottom dies simultaneously, resulting in radial metal plastic flow, forming the interlock between the sheet and the tube. By experimental and numerical simulation, the joining process of Al6061-T6 sheet and tube under different process parameters using double- and single-sided annular sheet squeezing was conducted and compared. The pull-out test is used to evaluate the quality of sheet-tube joints. Results showed that using the double-sided annular sheet squeezing method can obtain a symmetrical interlocking structure rather than an asymmetric structure by single-sided squeezing, effectively reducing the pit depth on the sheet surface. In addition, the improved method can effectively reduce about 25% of the joining force, but the pull-out strength is about 1.5kN lower than that obtained by the single-sided squeezing method. The joining strength is comprehensively affected by the thickness of the die annulus, punch stroke, and squeezing type. The influence mechanism of process parameters on pull-out strength is discussed. This study provides a new and efficient joining way for the manufacture of sheet-tube connection structures.