Infeed swaging is a type of rotary swaging process. It is usually used to reduce the cross section from the beginning to the end of the tube. Compared with the infeed swaging with mandrel, the infeed swaging without mandrel has the advantages of less-loading, chipless forming, giving high production rate and low tool costs. It has been widely used in aeronautic and automotive industries. In this paper, using the finite element (FE) simulation code, TRANSVALOR FORGE 2011, three-dimensional (3D) FE model and experiment were developed to investigate the stress state and deformation pattern during the infeed swaging of tube without mandrel. Results show that the stress state varies with the regions. In the sinking zone, the stress state in the middle of the tube is biaxial compressive, while that at the other regions is triaxial. In the forging zone, the material suffers from tensile axial stress, compressive thickness stress and circumferential stress. After unloading, tensile residual stresses occur at the forging zone and the inner surface in the sinking zone. The maximum tensile residual stress is 69.5MPa, which is 77.3% of the yield stress. In the sinking zone, more metal flows radially inside and the deformation type is compressive. In the forging zone, more material tends to flow along the axial direction. The deformation type in the forging zone is tensile. Moreover, experiments were also conducted to validate the FE model. The experimental and simulated results have a good agreement. After the infeed swaging, the microstructure of the tube became smaller and denser. The metal flow lines are continuous, contributing to improve the strength and the fatigue life of tube.

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