Hyperplasticty Main Page

Summary

The work described in these associated pages is related to a different approach to metal forming, one where impulse and impact are used instead of the more common approaches involving large static forces and slow displacement. Over the past several years we have shown materials can be stretched to much higher strains at high velocity compared to what is available in conventional quasi-static stretching. We refer to this extended ductility in high velocity conditions as hyperplasticity. An example of this is shown on the top right, where a rounded rectangular depression requiring over 75% extension is imparted in a 6061-T4 aluminum sheet with a single intense fluid-based electrohydraulic impulse with water into a one-sided steel die.

One of the most elegant methods of imparting very controlled high velocity to a sheet metal component is with electromagnetic forming. This non-contact launch method is shown on the lower left and is discussed in much ore detail on the associated pages. Electromagnetic forming coils can be used in a wide variety of ways. They can be embedded in traditional stamping toolsets and used to change strain distributions. This can greatly extend the limits of what kinds of components can be fabricated and can reduce reliance on lubricants. The example on the top left shows how an un-lubricated hybrid elecromagnetically-augmented press system can produce deeper part depths than lubricated conventional forming.

Electromagnetic forming can also be used to generate high velocities that can cause impact with a forming die. The example on the top left shows impact embossing an optical diffraction grating into copper and aluminum. A high magnification view of the original grating and its reproduction are also shown. and are almost indistinguishable. This method is very appropriate for microforming or surface decoration.

Electromagnetic methods are easily directly applied to high conductivity materials such as aluminum, copper, ferritic steels, magnesium alloys and so on. For lower conductivity materials such as austenitic stainless steels or nickel-based alloys additional tricks must be employed. For materials like high strength steels, EM methods are appropriate if judiciously applied. The example on the center left shows springback correction in a high strength steel. Local operations such as flanging, hemming and cutting are also possible with high strength steels.

Electromagnetic and impulse methods especially facilitate Agile Sheet Metal Forming, or: using a minimum set of easily or modified hard tools to manufacture high value sheet metal articles that meet conventional dimensional and property specifications.

The associated pages describe our work and this general technology area. inquiries and questions are welcome.

Glenn Daehn

+1 614 292 6779

Daehn.1@osu.edu

Impulse-Based Metal Forming

Research Thrust of Prof. Glenn S. Daehn

Department of Materials Science and Engineering

The Ohio State University

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