Interrupted pulse electromagnetic expanding ring test for sheet metal

José Imbert,Michael Worswick,Taamjeed Rahmaan,E Cadoni

doi:10.1051/epjconf/20159401048

Abstract

This paper describes the development of an interrupted pulse electromagnetic (EM) expanding ring experiment to study the high rate properties of AA5182 aluminum commercial sheet alloys at strain rates in excess of 5,000 s −1 . Experiments are performed to compare two commonly adopted methods of driving the expanding ring: EM expansion versus an exploding wire. After studying and testing both methods, it was determined that EM expansion had the greatest potential for being developed into a test that would result in free-flight of the samples. By interrupting the current pulse in the EM expanding ring test, the ring is allowed to achieve free-flight, thus eliminating the need to determine the induced EM forces and significantly reducing the uncertainty of the stress-strain behaviour determined from the test. Once the free-flight condition is established, the stress-strain behaviour of the material is determined from the free-flight deceleration of the sample, as calculated from the velocity measured using a Photon Doppler Velocimeter (PDV). Results are presented for AA5182 at strains rates between 1,000 to 5,500 s −1 and exhibit low strain rate sensitivity, are comparable to tensile split-Hopkinson bar results at strain rates of 1,000 s −1 .

Highlights

The current push for automotive vehicle light weighting has resulted in considerable interest in the application of aluminum alloys and advanced high strength steels in automotive mass production
When these high speed techniques are used to form material into a die, strain rates in excess of 10,000 s−1 are predicted to occur during the interaction of the tool with the sheet [3, 4]
The mechanisms that result in the observed increases in formability are not yet fully understood, in part due to the lack of understanding of the properties of sheet metals at such high rates of strain, which significantly limits the ability to model these processes

Summary

Introduction

The current push for automotive vehicle light weighting has resulted in considerable interest in the application of aluminum alloys and advanced high strength steels in automotive mass production. These material exhibit only moderate formability when compared to traditional low carbon steel alloys. The formability of some of these alloys has been shown to increase with the use of high speed forming techniques [1,2,3,4] such as electromagnetic (EM) and electrohydraulic forming. The expanding ring technique is one of a few with potential to satisfy this need and it is the subject of this work

Methods

Results

Conclusion