Modelling of instability defects in thermo-bending of polymer-based tubes

This study presents an integrated experimental–numerical framework to predict and mitigate instability defects in thermo-bending of polymer-based tubes. A differential local thermal control system was developed to regulate thermo-mechanical behaviour across the glass transition temperature. A modified constitutive model was calibrated for polyamide 12 (PA12) and polyvinyl chloride (PVC), capturing strain softening and hardening regimes. Results show that PA12 provides a wide processing window, while PVC requires asymmetric heating to shift the neutral axis and suppress wrinkling, necking and ovalisation. The framework enables reliable prediction and improved control of thermo-bending processes.