<p>The tube spinning process is an incremental plastic rotary metal forming process used to manufacture axisymmetric and non-axisymmetric products and other industrial applications. Process design for tube spinning is inherently challenging due to its complexity in many process control parameters, most of which are interrelated. Accuracy of final product shape and dimensional stability are connected between process parameters and configuration of the process. The progress of predictive experiment design of elevated temperature forming processes is critically dependent on the exact description of the deformation zone's boundary conditions, that is, roller pass. Moreover, due to closed incremental type deformation, it is difficult to predict shape and thickness experimentally. This situation makes the use of virtual process models highly attractive to eliminate the need for trial and error. In this study, a noble manufacturing method is introduced for producing jointless spherical vessels for a space rocket fuel tank. The research is conducted by&nbsp;multi-pass mandrel-free tube spinning&nbsp;to form cylindrical shape to spherical shape at elevated temperature. The experiments are used a very thin wall tube diameter to thickness ratio (d/t =140). Flame induction heating method is used for heating the tube. The target shape is formed by multi-pass linear spinning passes from aluminium alloy AA6061-T6 tube at 400 °C. After forming the full spherical vessel, the shape and thickness are measured. Based on these findings from observations of experimental results, it is confirmed that the plastic deformation of the process is highly localized, but the shape and thickness of the deform tube are like an axisymmetric one. For enhancing computational efficiency, the spinning process is approximated by an axisymmetric model. The implicit commercial FE code Abaqus/Standard is used to simulate the multi-pass mandrel free spinning process. Uniaxial tensile tests at different temperatures are conducted for the development of the material model. The post-necking hardening curves of the material are identified using a hybrid experimental-numerical approach. &nbsp;The stress-strain defined in this way is described by a hybrid Swift/Voce hardening law combined with a form of Johnson-Cook strain-rate dependence. FEA model is validated up to half spherical part. Good agreement is obtained on the shape and thickness change in the mandrel-free, multi-pass tube spinning. Both experiments and FEA results show that the thickness change in the spherical region is homogeneous but thickening at the conical region. The outcomes provide a guide for smooth forming cylindrical to spherical shape by mandrel free multi-passes tube spinning at elevated temperature.</p>

Multi-Pass Mandrel-Free Tube Spinning at Elevated Temperature for Producing Space Rocket Fuel Tank

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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