Yong,
You are right recently DIC is receiving high interest for dynamic deformations measurement, and in my opinion, there are two driving factors.
1) The current improvement and capability of high speed imaging. Currently, there are cameras that can take images at a framing rate above 1 million per second and at a spatial resolution of 400×250 pixel2. . At this speed, a high-quality deformation can be measured. For example, in Hopkinson bar experiment, where the loading duration is in the order of 100 µs, we can get above 100 high-quality images for DIC analysis.
The main challenge as far as DIC as high rate loading is, measuring small deformation/strain. Small deformation is still challenging at quasi-static loading conditions, but by image averaging the data/noise ratio can be improved. Since there will be no time to take multiple images at the same loading, during high strain rate loading, noise reduction by averaging is difficult and accurate deformation/strain measurement using DIC is challenging. In the case of large deformation, the limit was the imaging system but it is improving year by year.
A detail information regarding high-speed DIC can be obtained in the paper by F. Pierron · M.A. Sutton · V. Tiwari, Experimental Mechanics (2011) 51:537–563 http://link.springer.com/article/10.1007%2Fs11340-010-9402-y#/page-1
2) Another reason for recent increase interest in high-speed DIC is the need for understanding failure mechanisms in materials at meso-scale (between Nano and macro) including at high strain rate condition. Heterogeneous materials, like granular materials, even polycrystalline metal at mesoscale, required a full field method to capture the local deformation.
As far as I know, the first high-speed DIC based on ultrafast/high-speed X-ray is by Lu, et al (http://scitation.aip.org/content/aip/journal/rsi/85/7/10.1063/1.4887343). Using PCI/radiograph x-ray and DIC they quantitatively the 3D strain fields in materials with strain noise error in the order of 10-3. Based on an optical system, I think the first high magnification DIC work is by Bodelot et al (http://www.sciencedirect.com/science/article/pii/S0749641915000984). Using a high-speed camera, HPV-2, and Infinity K2 long-distance microscope they could map the deformation field in a copper. They achieved a spatial resolution of 15.2 μm/pixel at 500, 000 frames/sec. Recently we used HPVX-2 with Navitar lens and achieved a spatial resolution of 10.2 μm/pixel at 1 million frames/sec (http://link.springer.com/article/10.1007/s40870-016-0051-9).
There are some challenges such as, getting the right speckle size, lighting issue and depth of field of the cameras as you go higher magnification, otherwise full field local deformation can be measured even at higher resolution.
I would like to hear from others working in the field.
Yong,
You are right recently DIC is receiving high interest for dynamic deformations measurement, and in my opinion, there are two driving factors.
1) The current improvement and capability of high speed imaging. Currently, there are cameras that can take images at a framing rate above 1 million per second and at a spatial resolution of 400×250 pixel2. . At this speed, a high-quality deformation can be measured. For example, in Hopkinson bar experiment, where the loading duration is in the order of 100 µs, we can get above 100 high-quality images for DIC analysis.
The main challenge as far as DIC as high rate loading is, measuring small deformation/strain. Small deformation is still challenging at quasi-static loading conditions, but by image averaging the data/noise ratio can be improved. Since there will be no time to take multiple images at the same loading, during high strain rate loading, noise reduction by averaging is difficult and accurate deformation/strain measurement using DIC is challenging. In the case of large deformation, the limit was the imaging system but it is improving year by year.
A detail information regarding high-speed DIC can be obtained in the paper by F. Pierron · M.A. Sutton · V. Tiwari, Experimental Mechanics (2011) 51:537–563 http://link.springer.com/article/10.1007%2Fs11340-010-9402-y#/page-1
2) Another reason for recent increase interest in high-speed DIC is the need for understanding failure mechanisms in materials at meso-scale (between Nano and macro) including at high strain rate condition. Heterogeneous materials, like granular materials, even polycrystalline metal at mesoscale, required a full field method to capture the local deformation.
As far as I know, the first high-speed DIC based on ultrafast/high-speed X-ray is by Lu, et al (http://scitation.aip.org/content/aip/journal/rsi/85/7/10.1063/1.4887343). Using PCI/radiograph x-ray and DIC they quantitatively the 3D strain fields in materials with strain noise error in the order of 10-3. Based on an optical system, I think the first high magnification DIC work is by Bodelot et al (http://www.sciencedirect.com/science/article/pii/S0749641915000984). Using a high-speed camera, HPV-2, and Infinity K2 long-distance microscope they could map the deformation field in a copper. They achieved a spatial resolution of 15.2 μm/pixel at 500, 000 frames/sec. Recently we used HPVX-2 with Navitar lens and achieved a spatial resolution of 10.2 μm/pixel at 1 million frames/sec (http://link.springer.com/article/10.1007/s40870-016-0051-9).
There are some challenges such as, getting the right speckle size, lighting issue and depth of field of the cameras as you go higher magnification, otherwise full field local deformation can be measured even at higher resolution.
I would like to hear from others working in the field.