Optimization study of single point incremental forming process of low carbon steel/CP-Titanium bimetallic sheets using grey relational analysis and response surface methodology

Abstract

Single-point incremental forming (SPIF) of bilayer sheets is an inventive manufacturing technique. The formability and deformation behavior of an incrementally formed composite sheet are not sufficiently explored. In this paper, the incremental forming of CP-titanium/low-carbon steel bimetallic sheets are studied both experimentally and numerically. The results demonstrated that the deformation mechanisms are different from the deformation behavior of a monolithic metal sheet. The inner layer is deformed according to the layer in contact with the numerically controlled punch. In addition, the study reveals that the layer arrangement strongly influences the process. The grey relational analysis (GRA) and the global approach based on response surface methodology (RSM) are used to optimize the process parameters, namely the total initial sheet thickness of all the considered layers, the wall-drawing angle, and the vertical step size. Hence, the forming force and the thinning of the sheet material are considered responses to the output model. The results are given for both modes of layer positioning, depending on the material layer in contact with the tool. Moreover, this investigation aims to identify the influence of the process parameters on the grey relational grade (GRG) response through the analysis of variance (ANOVA). Additionally, the optimal conditions for both layer stacking approaches, contributing to achieving the minimum values of both responses and corresponding to the highest grey relational grade, are determined using the proposed optimization methodology to improve bimetal sheet formability. Finally, it could be observed that the optimization results proved the appropriateness and reliability of the developed techniques.