FE analysis of tube forming process with experimental verification

Purpose: of this paper: The paper presents some results of extensive investigation of steel seam-welded tubes forming process, by applying combined treatment of material narrowing and expansion. The objective of executed numerical FE and experimental investigations was to determine the optimal technology for production of tubular product at simple tools and at the standard forming processing machines, without defects and with demanded dimensional accuracy. Design/methodology/approach: Tube forming was done in one phase, in tool with two shaping spherical parts, that enables the expansion of the specimen’s central zone and the filling of the die due to narrowing of the specimen ends, when certain conditions are achieved and with appropriate combination of influential process parameters (outer diameter, height and tube’s wall thickness, as well as friction conditions). Series of physical and numerical FE experiments was performed. Findings: Optimal dimensions of tubular product, with required process stability, were obtained this way. Also, results of experiments pointed out that the best process stability and die filling is achieved with specimens whose surfaces had previously been chemically treated. Results of numerical FE simulations of process are quite verified by experiments. Practical implications: Obtained results have practical significance in solving similar processing problems. It also enables to investigate and broaden the knowledge on stability of these kinds of processes, beyond the scope of experimental investigations. Tubular product that is subjected to numerical-experimental investigation in this paper is prepared by narrowing it at both ends thus excluding the possibility to apply holder inside the tube. Originality/value: Proposed method offers possibility for production of tubular products at simple forming machines and tools, without complex and expensive hydroforming equipment.