Application to high strain rate testing
It is a real challenge to perform photomechanics at very high rates of loading because of the poorer quality
of the images provided by ultra high speed cameras. It is even more challenging to process such measurements with the VFM to
extract properties because of the presence of inertia effects.
For the moment, this activity is still very much exploratory but two projects are underway.
- Use of a Hopkinson bar in tension to test composites (notched and unnotched).
Full-field measurement is performed by the grid method and images are captured by a Cordin 550-62
ultra high speed camera (up to 4 million fps at a 1 Mpixel spatial resolution, 62 images can be recorded). This project is in collaboration with the ACCIS group at the University of Bristol (Prof. M.R. Wisnom and Dr S.R. Hallett). It has been supported by the EPSRC through grant EP/G001715/1. A first idea of the results can be found on the following presentation from the 2009 SEM conference
The first reference below can also be downloaded here (2009 SEM conference).
- Exploring new test configurations at very high rates. The idea is to move away from the standard Hopkinson bar tests with new procedures to identify load and constitutive parameters. This project is underway in collaboration with the University of South Carolina (Prof. Michael A. Sutton). For instance, here is a video showing 16 images taken at a rate of 10 microseconds with an IMACON200 camera. The test is a three point bending test on an aluminium bar. Image correlation is then preformed using the VIC2D software. The processing of the results is underway.
Three point bending at high rate (frame rate: 10 microseconds)
References
- Moulart R., Pierron F., Hallett S., Wisnom M.,
Full-field strain measurements at high rate on notched composites tested with a tensile Hopkinson bar,
Procceedings of the Annual SEM Conference (Society for Experimental Mechanics),
1-4 June 2009 in Albuquerque (New Mexico), USA.