Wrinkling prediction of aluminum alloy tubes during reduced diameter compression forming

Wrinkling is a significant challenge associated with the forming of tubes via diameter reduction. The work reported herein employed elastoplastic principles to assess the external pressure diameter reduction forming process by generating a strain diagram showing the occurrence of critical instability. This diagram can be used to effectively predict the appearance of wrinkling defects during forming. The Donnell linear buckling theory together with a bilinear material model was used to derive an expression for the critical external pressure leading to wrinkling instability, employing constant tube end conditions and a uniform external pressure, and the effects of forming conditions and material parameters on wrinkling were explored. During experimental trials, AA6061 tubes were formed via diameter reduction in conjunction with varying heat treatment conditions using the solid granule medium forming process. A Vialux portable mesh strain tester was employed to collect relevant data to verify the critical instability points, and the effects of various factors on resistance to wrinkling were investigated. An analysis of the experimental results demonstrates that the conclusions of the theoretical analysis are correct.