3D numerical model of tube-tubesheet joint roller expansion process

The tube-tubesheet joint by roller expansion process is widely used for the manufacturing of heat exchangers. The industry experiences quality issues with the joint, due to over or under expansion of the tubes. The paper focuses on the numerical modelling of the rolling process, and verification by experiments. The numerical model is simulated using LS-DYNA, where the motion of the rollers is included to simulate the step-wise plastic deformation of the tube. The model is built in 3D, with plane strain assumption for a section of the tube-tubesheet. The tubesheet structure is included in the model to obtain a realistic and appropriate stiffness behaviour. The experiments are investigated using optical measuring equipment, where the Micro Vickers Hardness and the grain structure of the tube in the plastic deformed zone are evaluated. The paper investigates the validity of modelling the tube-tubesheet expansion process with inclusion of the rollers.