Research of Effect of Peculiarities of Creasing a Polymer Sheet Material on a Rigid Base on Parameters of a Folding Operation

Folded elements are widespread in design of various products. They are made of sheet metal, cardboard, plastics or other materials. For example, heat exchangers, printed products, cardboard or plastic folders, folded fillers for three- or multilayered panels, which are made of paper, cardboard or plastics material can be mentioned. Although folded fillers are significantly advanced in terms of structural or operational performance, their wide application is hindered by poor mastering of the mass production technology. At present, the process of shaping folded fillers using a creasing operation on a rigid base is the most prospective. However, the creasing operations on polymer materials while manufacturing folded fillers are performed with deformations significantly exceeding a uniform strain limit. There are no research works on the subject in the known technical literature. Therefore, the work intended to resolve the matters filling the gap is relevant. The purpose of the research is to obtain results enabling to develop optimal processes for shaping folded fillers of polymer materials taking into account considerations on the creasing on a rigid base. Based on the analysis of the initial and the final condition of the material at the creasing area, a mechanism of strain has been developed, objectives of determinations of the final shape in the creasing area have been solved analytically using an equilibrium equation adopted for the objectives in question; conditions for incompressibility, true (logarithmic) strain values, flat cross-section hypothesis have also been determined. As a result of the research, analytic dependences have been obtained for determinations of the residual thickness, curvature of the material at the creasing area, residual interfacial angle after release of the load. Experimental studies of the above parameters were carried out and comparisons with calculated values are shown.