Investigation of the deformation stability in the incremental sheet forming process

S Ai,H Long,J Chen,B Lu,H Ou,Y Qin,S J Yuan,T A Dean,J Lin,F Vollertsen

doi:10.1051/matecconf/20152104012

Abstract

Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. One of the unique characters of the ISF process is the improved formability comparing to conventional sheet forming process. This may be due to the localized deformation nature, which increases the deformation stability in the ISF process. Although many hypotheses have been proposed, there is no direct modelling and calculation of the ISF deformation stability. Aiming to obtain a better understanding of the ISF process, an analytical model was developed to investigate and analyse the material deformation stability in this work. Based on the analytical evaluation of stress variations and force equilibrium, a mathematical relationship between the maximum forming angle and the process stability condition was established. To validate the developed model, experiments were carried out by forming a hyperbolic part made of AA1100 material. The maximum forming angle, as an indicator to the ISF formability, was employed compare the analytical evaluation and experimental result. It was found that the ISF deformation stability is one of the key factors that affect the ISF formability.

Highlights

Incremental sheet forming (ISF) is a flexible process for manufacturing of small-batched and customized sheet metal products
The above published literatures identified that the major SPIF deformation mechanism is the combination of bending, stretching and shearing deformation depending on process conditions
Severe necking appears at the final stage of forming. It can be concluded for material AA1100 that the fracture in the ISF process is due to the instability of sheet deformation: with the increase of the forming angles, the part wall becomes thinner and thinner

Summary

Introduction

Incremental sheet forming (ISF) is a flexible process for manufacturing of small-batched and customized sheet metal products. One unique characterization of the ISF process is the increased formality This high ISF formability has been investigated with many theories proposed. Ackson and Allwood [7] demonstrated that the material deformation of ISF is due to the combination of bending, stretching and shearing. Eyckens et al [10] argued that the dominant material deformation mechanism (i.e. shearing or bending) depends on the specific process conditions. Fang et al [12] established an analytical model to analyse the effects of bending and material hardening on the SPIF formability. The above published literatures identified that the major SPIF deformation mechanism is the combination of bending, stretching and shearing deformation depending on process conditions. The results are examined and the mechanism of the ISF deformation stability is discussed to further enhance the understanding of the ISF process

Theoretical investigation

Experimental validation

Findings

Conclusions