Rubber pad tube straining as a new severe plastic deformation method for thin-walled cylindrical tubes

Abstract

A novel severe plastic deformation technique entitled rubber pad tube straining is proposed suitable for manufacturing of high-strength ultrafine-grained and nanostructured thin-walled cylindrical tubes. A punch with a convex portion in the middle is pressed down into a tube constrained with a hollow cylindrical rubber supported by a rigid cylinder. Tube diameter increases and decreases incrementally when the punch is pressed down, and the rubber pressure pressed back the tube diameter to its initial size. This process was performed on a commercially pure aluminum tube. Finite element results revealed that the equivalent plastic strain of about 1 could be reached at the end of the first cycle of rubber pad tube straining while having a good strain homogeneity along the thickness and length. Experimental results showed that the yield and ultimate strengths were increased to about 172 and 182 MPa from the initial values of about 80 and 128 MPa, respectively. Also, the hardness was increased to ∼55 HV from ∼44 HV.