An automated approach for measuring in situ two-dimensional strain fields was developed and validated for its application to cartilage mechanics. This approach combines video microscopy, optimized digital image correlation (DIC), thin-plate spline smoothing (TPSS) and generalized cross-validation (GCV) techniques to achieve the desired efficiency and accuracy. Results demonstrate that sub-pixel accuracies can be achieved for measuring tissue displacements with this methodology with a measurement uncertainty ranging from 0.25 to 0.30 pixels. The deformational gradients (from which the strains are determined) can be evaluated directly using the optimized DIC, with a measurement uncertainty of In actual measurements of strain in cartilage, TPSS and differentiation can be used to achieve a more accurate measurement of the gradients from the displacement data. Using this automated approach, the two-dimensional strain fields inside immature bovine carpometacarpal joint cartilage specimens under unconfined compression were characterized The depth-dependent apparent elastic modulus and Poisson’s ratio were also determined and found to be smallest at the articular surface and increasing with depth. The apparent Poisson’s ratio is found to decrease with increasing compressive strain, with values as low as 0.01 observed near the articular surface at 25% compression. The variation of the apparent Poisson’s ratio with depth is found to be consistent with a theoretical model of cartilage which accounts for the disparity in its tensile and compressive moduli.
An Automated Approach for Direct Measurement of Two-Dimensional Strain Distributions Within Articular Cartilage Under Unconfined Compression
Contributed by the Bioengineering Division for publication in the JOURNAL OF BIOMECHANICAL ENGINEERING. Manuscript received May 2001; revised manuscript received May 2002. Associate Editor: L. J. Soslowsky.
- Views Icon Views
- Share Icon Share
- Cite Icon Cite
- Search Site
Wang , C. C., Deng , J., Ateshian , G. A., and Hung, C. T. (September 30, 2002). "An Automated Approach for Direct Measurement of Two-Dimensional Strain Distributions Within Articular Cartilage Under Unconfined Compression ." ASME. J Biomech Eng. October 2002; 124(5): 557–567. https://doi.org/10.1115/1.1503795
Download citation file:
- Ris (Zotero)
- Reference Manager