Digital Image Correlation and Tracking

Free MATLAB® code for DIC and DDIT is available online.

 

Accurate tensile testing requires direct strain measurement in the gage section of the specimen and in small-scale testing this can be achieved by non-contact strain measurement methods. Notable approaches include the interferometric strain displacement gage (see ISDG, W.N. Sharpe), tracking of diffraction spots from gratings deposited on specimen surfaces, digital image correlation (DIC), and differential digital image tracking (DDIT). These techniques also allow for the measurement of the lateral strain to measure Poisson’s ratio. Digital image correlation and DDIT have the advantage of full-field capability giving local fidelity (e.g., strain heterogeneities near grain boundaries). These techniques measure the strain even after tensile necking extending the measurable stress-strain behavior beyond the maximum engineering stress. In the case of in situ tensile testing, DIC and DDIT are ideal methods for strain measurement, as the SEM, FIB, or AFM can be used as image sources during the test. Thus, quantitative information can be extracted in addition to imaging the deformation morphology during testing.

The basic premise of DIC is as follows, and a representative image demonstrating good surface contrast on a microspecimen is shown in the Figure below. The correlation coefficients of subsets of consecutive images (typically between 10 × 10 to 40 × 40 pixels²) are calculated and plotted versus their position. Biquadratic functions, for instance, can be used to locate the maximum correlation coefficient (with sub-pixel resolution) that is representative of the optimal fit between the subsets of the two images. Differential digital image tracking requires intensity peaks in the source images that can be tracked by a peak fitting algorithm (Figure 5b). This method can achieve a resolution of up to a thousandth of a pixel, which allows for good strain fidelity even in the absence of many pixels (e.g., AFM images with ~200 × 200 pixels² resulting in strain resolutions of up to Δε = 10^–5). Ultimately, the resolution of DIC and DDIT primarily hinge on the noise present in the imaging system. Differential digital image tracking is typically less susceptible to local image noise since features are tracked that span multiple pixels.

 

This text is part of a review on small scale tensile testing:

http://www.tms.org/pubs/journals/JOM/0903/gianola-0903.html

 

 

ISI Publications, C. Eberl, 2005-2011

Under Review:

C. Eberl, X. Wang, D.S. Gianola, M.Y. He, A.G. Evans, K.J. Hemker, ‘In Situ Measurement of the Toughness of the Interface Between a Thermal Barrier Coating and a Ni Alloy’, Journal of American Ceramic Society.

S. Burger, C. Eberl, A. Siegel, A. Ludwig, O. Kraft, 'A Novel High-Throughput Fatigue Testing Method for Metallic Thin Films’, Science and Technology of Advanced Materials.

 

Accepted:

J. Prokop, C. Eberl, M. Funk, P. Prüfe, J. Lorenz, V. Piotter, M. Welz, H.-J. Ritzhaupt-Kleissl, 'Investigation of Micro-testing samples produced by a new LiGA related process chain', Mic. Syst. Tech..

C. Eberl, D.S. Gianola, X. Wang, M.Y. He, A.G. Evans, K.J. Hemker, 'A Method for In Situ Measurement of the Elastic Behavior of a Columnar Thermal Barrier Coating', Acta Materialia.

M. Funk, K. Ma, C. Eberl, J. M. Schoenung, M. Göken, K. J. Hemker, 'High Temperature Mechanical Behavior of End-of-life Cryomilled NiCrAlY Bond Coat Materials', Met. Trans. A..

M. Funk, C. Eberl, 'Investigations on the Fatigue Behavior of Nanocrystalline Metals',  Key Eng. Mat., Proc. of sixth Int. Conf. on MAT. STRUCT. & MICROMECH. OF FRACT. 2010, accepted.

S. Burger, B. Rupp, A. Ludwig, O. Kraft, C. Eberl, 'Fatigue Testing of Thin Films', Key Eng. Mat., Proc. of sixth Int. Conf. on MAT. STRUCT. & MICROMECH. OF FRACT. 2010, accepted.

 

2010

18. C. Eberl., T. Saif, ‘In Situ Mechanical Testing of Biological andor Inorganic Materials at the Microscale and -/Nanoscale’, Guest Ed., MRS Bullettin, 35, 5 347-350 (2010).

17. C. Eberl, H. Riesch-Oppermann, R. Spolenak, F. Kubat, W. Ruile, D. Courty, O. Kraft, ‘In situ observations and quantitative analysis of short circuit probability due to ultra high frequency fatigue’, IEEE Transactions on Device and Materials Reliability, PP, 99 (2010).

16. C. Eberl, D. S. Gianola, K. J. Hemker, ‘Mechanical characterization of coatings using microbeam bending and digital image correlation techniques’, Exp. Mech., 50, 1 (2010).

 

2009:

15. T. J. Balk, C. Eberl, Y. Sun, K. J. Hemker, and D. S. Gianola, ’Tensile and Compressive Microspecimen Testing of Bulk Nanoporous Gold’, JOM, 24-30, Dec (2009).

14. D. S. Gianola, C. Eberl, ‘Micro- and Nanoscale Tensile Testing of Materials’, invited overview for JOM, 24-35, March (2009).

13. S. P. Joshi, C. Eberl, B. Y. Cao, K.T. Ramesh, K. J. Hemker, ‘On the Occurrence of Portevin – Le Châtelier Instabilities in Ultrafine-Grained 5083 Aluminum Alloys’. Exp. Mech.,  49, 2 207-218 (2009).

 

2008:

12. J. Lohmiller, C. Eberl, O. Kraft, T.J. Balk ,‘Mechanical Spectroscopy of Nanocrystalline Nickel Near Room Temperature’, Scripta Mat., 59, 4 (2008).

11. A. C. Lewis, D. van Heerden, C. Eberl, K. J. Hemker, T. P. Weihs, ‚Creep Deformation Mechanisms in Fine-Grained Niobium’, Acta Mat., 56, 13(2008).

10. A. C. Lewis, C. Eberl, K. J. Hemker, T. P. Weihs, ‚Grain Boundary Strengthening in Copper/Niobium Multilayered Foils as a Function of Temperature and Strain Rate’, JMR, 23, 2 (2008).

9. K. J. Hemker, B. G. Mendis, C. Eberl, ‘Characterizing the microstructure and mechanical behavior of two-phase NiCoCrAlY bond coat for thermal barrier systems’, Mat. Sci. Eng. A, 483-484 (2008).

8. D.S. Gianola, C. Eberl, X. M. Cheng, K. J. Hemker, ‘Stress-driven surface topography evolution in nanocrystalline Al thin films’, Adv. Mat., 20, 2 (2008).

 

2007:

7. C. Eberl, R. Spolenak, O. Kraft, W. Ruile, E. Arzt, ‘Fatigue damage in thin film Al interconnects at ultra high frequency: a Finite Element Analysis approach’, ‘Thin Solid Films’, 515, 6 (2007).

6. W. N. Sharpe, Jr., J. Pulskamp, D. G. Gianola, C. Eberl, R. G. Polcawich, R, J, Thompson, ‘Strain measurement of silicon dioxide microspecimens by digital image processing’, Exp. Mech., 47, 5 (2007).

 

2006:

5. C. Eberl, R. Spolenak, O. Kraft, F. Kubat, Werner Ruile, E. Arzt, ‘Fatigue at ultra high frequencies in Al thin films’, J. Appl. Phys., 99, 11 (2006).

4. C. Eberl, R. Spolenak, E. Arzt, F. Kubat, A. Leidl, W. Ruile, O. Kraft, ‘Ultra high-cycle fatigue in pure Al thin films and line structures’, Mat. Sci. and Eng. A, 421 (2006).

 

2005:

3. S. Orso, U. G. K. Wegst, C. Eberl and E. Arzt, ‘Micrometer scale tensile testing of biological attachment devices’, Adv. Mat., 18 (2005).

2. F. Kubat, W. Ruile, C. Eberl, T. Hesjedal, L. M. Reindl, ‘Qualitative and quantitative analysis of acoustomigration effects in SAW-devices’, Micro Elec. Eng., 82 (2005).

1. R. Spolenak, L. Sauter, C. Eberl, ‘Reversible orientation – biased grain growth in thin metal films induced by a focused ion beam’, Scripta Mat., 53 (2005).

 

Begutachtete Tagungsbeiträge:

2010:

4. J. Prokop, C. Eberl, M. Funk, J. Lorenz, P. Prüfe, V. Piotter, H. J. Ritzhaupt-Kleissl, 'Mehrkomponentenspritzgießen mit Galvanoformung als Fertigungsalternative für komplexe Mikrobauteile', 2.Industriekolloquium der Forschergruppe 702 'Mikrobauteile', Karlsruhe, 24.Juni 2010. Tag.bd. S.25-35 Erlangen : Lehrstuhl f.Kunststofftechnik, (2010) ISBN 978-3-931864-49-1.

2006:

3. W.N. Sharpe, Jr., J. Pulskamp, D.S. Gianola, C. Eberl, R. Polcawich, R. Thompson, “Strain measurements of silicon dioxide microspecimens,” Proceedings of the 2006 SEM Annual Conference, St. Louis, MO, Session 46 (2006) Paper 54.

2. W. N. Sharpe, Jr., J. Pulskamp, B. G. Mendis, C. Eberl, D. S. Gianola, R. Polcawich, and K. J. Hemker, ' Tensile Stress-Strain Curves of Gold Film', ASME Conf. Proc. 2006, 533 (2006), DOI:10.1115/IMECE2006-13290.

2005:

1. Volkert, C.A., Eberl, C., Mönig, R., Walter, M., Kraft, O., 3D analysis of microstructures by focused ion beam microscopy, Gundlach, C. [Hrsg.]. Evolution of Deformation Microstructures in 3D : Proc.of the 25th Risoe Internat.Symp.on Materials Science, Roskilde, DK, September 5-10, 2004. Roskilde : Risoe National Laboratory, S.171-86, (2005).