A coordination model of the in-plane bending of strip metal under unequal compression

The in-plane bending of a strip metal workpiece under unequal compression can be developed into an advanced precision forming process with high quality, high efficiency, low consumption, good flexibility for size changes, and a high forming limit, where the forming is difficult to carry out using any other conventional process. To establish a coordination model of the process for the investigation and understanding of the coordinated development of unequal deformation and its contribution to in-plane bending forming is one of the key problems urgently to be solved in the research and development of this advanced in-plane bending process. In this paper, on the basis of the rectilinear state of the unequally compressive deformation conducted with two conical rollers and the contribution of the unequal deformation to the in-plane bending forming, a coordination coefficient function of the unequal deformation is proposed, and further a coordination model of the in-plane bending of strip metal under unequal compression is established. Experimental research is carried out by means of the apparatus made in the authors’ laboratory for performing the in-plane bending process under the unequal compression with LF21M and LD2M strip workpieces in order to validate the model. The results obtained show the following: (1) The predictions by using the model are in good agreement with the experimental results. The model as a basic equation describing the process, characterizing the quantitative relationships between the deformation conditions and the forming results, reveals the precision forming law produced by the unequal deformation with its coordination. (2) The greater the unequally compressive deformation, the greater is its contribution to the stable in-plane bending forming. The proposed coordination coefficient used for describing this physical phenomenon is found to be practicable and sound. (3) The more notable the unequal compressive state, the higher the stable in-plane bending forming limit obtained, and the model provides the basis for the determination and optimization of the in-plane bending process. (4) The method described for establishing the coordination model is also of general significance to non-rectilinear states of unequally compressive deformation.