Theoretical investigation on the crushing performances of tailor rolled tubes with continuously varying thickness and material properties

Abstract

By adopting the variable gauge rolling (VGR) technology and the annealing process, the tailor rolled blanks (TRBs) with both continuously varying thickness and inhomogeneous material properties could be obtained. Through the procedure of subsequent forming and laser welding technology on TRBs, the tailor rolled tubes (TRTs) with axially varying thickness and material properties were successfully produced, and performed by the quasi-static axial crushing afterwards. On the basis of the microstructural transformation at different thickness locations, the relationships between the material properties and thicknesses were analyzed. Moreover, the failure mode and the deformation mechanism of TRTs have been discussed. It is noted that the progressively increased distances between the top and bottom of the plastic hinges is the essential characteristic. Combined with the classical crushing theories and models, a novel predictive mathematical model considering the thickness variation, changing material properties and variety heights of folding elements has been established. Compared with the series conventional computing models, this novel model performed better. On this foundation, the effects of different thickness transition form and distribution of material properties on the crushing performances were investigated. Besides, detailed effects of the tube structure and with or without changing material properties on the crushing capacity were also studied by introducing the concept of equivalent strength and equivalent thickness.