Time-dependent springback of high strength titanium tubular materials: Experiment and modeling

Abstract

• Residual stress and dislocation evolution of HSTT during bending and springback comprehensively obtained. • Compression-tension uneven axial residual stress-driven creep mechanism of time-dependent springback for HSTT revealed. • Viscoelasticity-Kelvin constitutive model considering stress attenuation developed for modeling time-dependent springback. • Combining Viscoelasticity-Kelvin with SIM and Chord modulus models for accurate prediction of time-dependent springback. • Deformation-history dependent effects of time-dependent springback for spatial multi-bending tubes clarified. Although time-dependent springback is minor compared with instantaneous springback, its deformation-history dependent effects may deteriorates the compactness of parts assembly and poses potential hazards to the safety and stability of the equipment systems especially under harsh service conditions. However, time-dependent springback still has not been paid enough attention, and how to accurately predict this phenomenon is still a challenge needed to be solved urgently. In this work, taking high-strength Ti-3Al-2.5V titanium tubular materials (HSTT) upon bending as a case, the experimental exploration of the physical mechanisms and the prediction modeling for time-dependent springback of the HSTT were conducted. First, the residual stress and dislocation evolution of HSTT during bending, instantaneous springback and time-dependent springback are comprehensively experimentally obtained, and the compression-tension uneven residual stress-driven creep deformation mechanism of time-dependent springback for HSTT was revealed. Then, considering stress attenuation, a Viscoelastic-Kelvin constitutive model for time-dependent springback was developed and combined with the stress invariant-based model (SIM) and Chord modulus model to accurately predict the whole process of bending, instantaneous springback and time-dependent springback of the HSTT. Finally, the verified model is employed to explore the evolution rules of time-dependent springback and residual stress of HSTT upon bending, and the deformation-history dependent effects of time-dependent springback for spatial multi-bending component are clarified. The findings and methods of this study could aid in achieving higher precision manufacturing of high performance tubular components.