Investigation on the effects of process parameters on the through-thickness shear strain in single point incremental forming using dual level FE modelling and statistical analysis

Single point incremental forming (SPIF) is a process with the capability to form complex geometries using a tool of very simple geometry, without the need for a matching die. At present, through-thickness modes of deformation and effects of process parameters on through-thickness shear are not clear. The objectives of this report are firstly, to define the most critical working parameters that influence the through-thickness shear strains and secondly to obtain the optimal combination of these parameters that achieve maximum through-thickness shear deformation. Through-thickness shear strains are considered a direct indication of formability in the SPIF process. A design of experiment (DOE) approach is used to develop the study of various process parameters, in particular step-down size, sheet thickness, tool diameter, friction coefficient and strength coefficient. The example used is the manufacture of a truncated cone by SPIF. A dual-level FE modelling technique is used to simulate the process and obtain the corresponding shear strains for each combination of process parameters. The Analysis of Variance ANOVA method is used to analyze the results and obtain the most critical factors. The results show that the shear deformation, and hence the formability, could be increased by increasing the coefficient of friction and sheet thickness and decreasing the step-size down and tool diameter.