Multiobjective Optimization of Single Point Incremental Forming: Comparison between Isotropic and Combined Hardening Behavior

Abstract

Single point incremental forming (SPIF) of sheet metal is a promising process to produce small batch production and prototyping. This process consists of a controlled process of displacement performed on a three-axis CNC milling machine. In former work, the most critical factors which affected single point incremental forming process were found to be formed shape, tool size, material type, material thickness and incremental step size. The present work is focused on an optimization strategy of (SPIF) process determined by a numerical study based on finite element analyses (FEA) according to a Box-Behnken Design of Experiments. Two types of hardening behaviour laws of material are used: isotropic and combined isotropic-kinematic hardening behaviour. To do so, a set of numerical simulations are carried out for an aluminum truncated cone as geometry of a benchmark model. The simulation results include some decisions about the mechanical resistance and geometrical quality of the parts such as the thickness distribution and the magnitude of springback. In this paper, the main objective is to present an overview of multiobjective design optimization of process parameters in single point incremental forming operation in order to minimize the sheet thinning rate and the springback simultaneously. In this investigation, the steps of optimization procedure include the using of Box-Behnken experimental design for sample producing, response surface model for coarse fitting and a developed Multiobjective Genetic Algorithm (MOGA) for exact solving of fitness functions. The results show that these methods are able to determine all the best possible compromise with respect several antagonistic objectives as well as generate the approximate Pareto optimal solutions. So these will make it possible to choose the appropriate process parameters according to the objectives functions to be minimized and consequently the improvement of the products formed by the process of incremental forming.

Parameters for the FEA simulations of single point incremental forming

“…Complicated shell theories are required to consider thickness and to make up for the developmental assumptions. In addition, the two-dimensional material law and the assumptions employed in the shells lead to inaccuracies in the description of through thickness variables (Arfa, Bahloul, and Belhadjsalah, 2014;Bahloul et al, 2013;Computational Finite Element Methods in Nanotechnology, 2012;Liu, Daniel, Li, Liu, & Meehan, 2014;Petek & Kuzman, 2010).…”

“…Shear locking and membrane locking can be avoided by using reduced integration (Arfa et al, 2014;Bahloul et al, 2013;Liu et al, 2014;Malhotra et al, 2012;Mirnia, Mollaei Dariani, Vanhove, & Duflou, 2013;Petek & Kuzman, 2010). It is the easiest way to avoid locking.…”

Multiobjective Optimization Problem of Dieless Incremental Forming

“…One of the most widely experimented forms of sheet metal forming process is called 'singlepoint incremental forming' or SPIF, in which a sheet is rigidly clamped around its edges but untied underneath and formed by a hemispherical tool [1]. The incremental sheet forming is restricted by different parameters: the wall angle, tool diameter, incremental size and the initial thickness [2]. Figure 1 show respectively a sketch of SPIF and its' geometrical errors.…”

Application of Response Surface Analysis and Genetic Algorithm for the Optimization of Single Point Incremental Forming Process

“…The application of numerical simulation based on the finite element method for SPIF process helped engineers to efficiently improve the process development. It allows an inexpensive study of arbitrary combinations of input parameters including design parameters and process conditions to be investigated [6]. In this sense, Dejardin et al [7] developed an experimental work and numerical modelling for improving knowledge of incremental sheet forming process for sheet metal parts.…”