![](https://s3images.coroflot.com/user_files/individual_files/585147_5nhylpziffe47dmtvykcp7o7o.png)
The expanding tube experiment consists of discharging a large alternating current through a copper coil encased in epoxy resin. A cylindrical aluminum tube sample is placed over the coil. The aluminum sample has a circular pattern etched on its surface. The tube can be coated with a polymer.
The coil is connected to a capacitor bank. During the test, the capacitor bank is discharged through the coil, inducing a current in the aluminum specimen. The Lorentz force interaction causes the specimen to expand radially outward at very high speeds.
![](https://s3images.coroflot.com/user_files/individual_files/585147_5nv9t7nyd2jhk_buo0lyvkthn.png)
A high-speed camera and a flash system are used to record the expansion of the specimen. A conical mirror is placed behind the specimen such that the surface of the specimen is reflected in the mirror and captured in the high-speed camera footage.
![](https://s3images.coroflot.com/user_files/individual_files/585147_otnooyhhkgyksypqsbg9wh5tj.jpg)
This image shows an example of the specimen as it expands. The expansion follows a uni-axial tension stress state.
![](https://s3images.coroflot.com/user_files/individual_files/585147_i2avu4owtsqstrqbvlnnanflg.jpg)
The reflection of the sample in the conical mirror is unwrapped through mapping of pixels in image post processing.
![](https://s3images.coroflot.com/user_files/individual_files/585147_caw8hc3937dtiizkaujbmb9sp.jpg)
The unwrapped images allow for local strain measurements of the surface of the specimen to be performed, as well as track localization and fragmentation of the sample.
![](https://s3images.coroflot.com/user_files/individual_files/585147_hb4cg5mwm89jl0o_5mjapieb4.jpg)
Local and global (from sample diameter evolution) strain measurements can then me compared to better understand the dynamic behavior of the material.
![](https://s3images.coroflot.com/user_files/individual_files/585147_0lxlnelikzqggqprxwio_noeo.jpg)
Variations to the experiment described were performed. The first deviation aimed at creating a plane-strain loading condition on longer tube specimens.
![](https://s3images.coroflot.com/user_files/individual_files/585147_xdrym9iqjkga5vjhreuy_hw5r.jpg)
This sequence shows the expansion of the longer tube.
![](https://s3images.coroflot.com/user_files/individual_files/585147_gabufj_wqe98ceziqkpevty3o.jpg)
Post-mortem image of the plane-strain condition test specimen.
![](https://s3images.coroflot.com/user_files/individual_files/585147_fswaaait8ep8clwyza2hij24v.jpg)
The second variation of the experiment looked at using a flat coil to accelerate a flat plate.
![](https://s3images.coroflot.com/user_files/individual_files/585147_mftmxbosw4qgzeahjdsffprl0.jpg)
This image shows the of the flat plate specimen being accelerated by the flat coil.
![](https://s3images.coroflot.com/user_files/individual_files/585147_bfbhfejffkcvunkg5nvlzfsa4.jpg)
Post-mortem image of flat plate specimen.
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