Enhancing radial strain uniformity of thin-walled cylinder by the dual asymmetric active counter-roller spinning process

Aiming at the problem of uneven forces on the inner and outer surfaces during counter-roller spinning (CRS) of thin-walled cylinders, which affects the spinning stability and forming quality, a new dual asymmetric active counter-roller spinning (DAACRS) process is proposed. It enhances the radial strain uniformity through more consistent contact of the inner and outer rollers and the material flow on the inner and outer surfaces. The theoretical analytical model of the influence of the spinning structural and process parameters on the contact condition and the oriented relationship is established. On this basis, the Kriging predictive surrogate model under the coupling influence of these parameters is established, and the spinning parameters optimized by the multi-objective particle swarm optimization (MOPSO) algorithm in the global continuous variables are obtained. The radial strain gradient effect of traditional spun parts is basically eliminated under this process parameters. Additionally, an active counter-roller spinning (ACRS) machine is independently developed and a comprehensive macro-micro quality evaluation method is proposed. The ACRS process can transform the material from dispersed {001}<110> low-strength plate texture to more standard {001}<100> high-strength plate texture, and obtain balanced axial and circumferential tensile strengths. Moreover, the new DAACRS process resulted in more balanced forming accuracy, inner and outer surface grain size, texture strength, and isotropic mechanical properties due to the high radial strain uniformity. Compared with the traditional completely symmetric active counter-roller spinning (CSACRS), the L, O, U-D, U-T{100}, U-T{110}, and U-T{111} are improved by 0.08265 mm(,) 0(.)00335 mm, 4.83(%), 10.55%, 11.54%, and 16.34%, respectively. Further analysis provides that the allowable values of strain uniformity for the higher quality thin-walled cylinders are [U-epsilon(PEEQ)]=0.365 and [U-epsilon(Max Principal)]=0.438. These results increase the understanding of the strain change, microstructure evolution, and mechanical properties change mechanism of the CRS process, thereby providing important guidance for improving the CRS process and forming quality.