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Deformations and forces analysis of single point incremental sheet metal forming

Petek A., Kuzman K., Kopač J.

Archives of Materials Science and Engineering

2009

Vol. 35, nr 2

107-116

Purpose: In this paper the experimental equipment and design of the system for deformation and forming force measuring by single point incremental sheet metal forming are described. Beside this the analysis results of the impact of the wall angle, tool rotation, vertical step size, tool diameter and lubrication on the magnitude of forming force and plastic logarithmic strain are presented. Design/methodology/approach: The incremental sheet metal forming process was performed on the CNC controlled milling machine Moiri Seiki with the FANUC MSC-521 control system. The forming forces were measured using specially designed force measuring system which is connected with the milling machine. In contrast to force measuring, the deformations of the specimen were measured by using the graphometric analysis based on the size and direction investigation of the major strains of the particular sheet metal area. Findings: The results show that the forming force is very small in comparison to the deep drawing process and it does not depend on the product size. That is why the production of very large products is absolutely appropriate for forming. Beside this, the deformations and forces distribution are mostly dependent on the size of the wall angle of forming, tool diameter and vertical step sizes of the tool. Research limitations/implications: The deformations and forces analyses are researched only for the steel DC05 of 1 mm in thickness. Practical implications: The analysis results will help to improve the choice of the appropriate equipment and to setting of the optimal process parameters on the strain distribution and the size of needed forming force. By this the production time of the product could be reduced, which is otherwise by this process very long. Originality/value: A detailed deformations and forces analyses of single point incremental sheet metal forming for some combinations of process parameters used are original.

Numerical determination of the forming limit diagrams

Pepelnjak T., Kuzman K.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 20, nr 1-2

375-378

Purpose: At present the industrial practice demands a reliable determination of forming limits which assures the prediction of properly selecting the forming process in a digital environment. Therefore, technological limits defined with the forming limit diagrams (FLDs) have to be known. The experimental evaluation of FLDs for sheet metal is time consuming and demands expensive equipment. The experimental work could be omitted by predicting the FLD with numerical simulations. Design/methodology/approach: The paper presents a methodology to determine the entire range of the FLD for sheet metal in a digital environment. The Marciniak testing procedure simulated with the FEM program ABAQUS was selected to determine the FLD. To assure the reliability of the developed method, different materials were analysed: two types of deep drawing steel, an aluminium 3000 alloy, and a Ti-alloy. The selected materials have different mechanical properties and sheet thicknesses ranging from 0.5 mm to 1.23 mm. For the verification of numerically obtained results parallel experimental determinations of the FLDs were performed showing a good correlation between the FLDs obtained by both approaches. Findings: A specially developed method for the evaluation of the thickness strain as a function of time as well as the first and the second time derivation of the thickness strain enable the determination of the onset of necking. Research limitations/implications: The presented method of the digital evaluation of the FLDs is still in a developmental phase and needs further improvements for industrial practice. However, in some cases the numerical approach had already been used for a fast prediction of the FLD prior to performing the experiments. At the current level the developed program still needs an expert to support it in some critical decisions. Originality/value: Considering some methological improvements and automation procedures the developed method could be used in everyday practice.