Interface separation mechanism in bimetal clad pipes under hard object extrusion

Abstract

To investigate the interface separation mechanism of bimetallic clad pipes under external hard object extrusion, the model for the bimetallic pipe under a conical triangular punch was established. The effects of extrusion angle, inner pipe wall thickness, forming clearances, and forming internal pressure on interface separation were studied. The results show that interface separation is non-linearly related to extrusion angle. For the axial interface, the maximum separation of 37.25 mm and 35.17 mm occurs at an extrusion angle of 90° under load and after rebound, respectively. For the transverse interface, the maximum separation of 5.95 mm occurs at 60° under load, and 6.40 mm at 75° after rebound. Separation is negatively correlated with inner pipe wall thickness. Axial separation is positively correlated with forming clearances. The maximum transverse separation occurs at 1 mm forming clearances under load and at 1.5 mm after rebound. The internal forming pressure 60 MPa significantly increases maximum axial separation but reduces transverse separation. Secondary extrusion leads to a further increase in maximum interface separation, though the increase is non-linearly related to punch displacement.