Imaging in-plane and normal stresses near an interface crack using traction force microscopy

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Wiki entry by : Dongwoo Lee, AP225 Fall 2010.

Paper in this Wiki : Imaging in-plane and normal stresses near an interface crack using traction force microscopy Y. Xu, W. C. Engl, E. R. Jerison, K. J. Wallenstein, C. Hyland, L. A. Wilen, E. R. Dufresne Proceedings of the National Academy of the Sciences (2010)

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Summary

This paper describes a new technique to study fracture mechanics of systems that has complex spatially and temporally varying mechanical properties; "traction force microscopy" was used to image the stress near the tip of an advancing interface crack. In the paper, the authors tried to draw the 3D displacement and stress distributions of a system that consists of colloidal coating. As the coating dries, a crack was created, and image analysis was performed for entire history of the crack propagation. Fig. 1 A shows the schematic diagram of the system in the paper, and fig. 1 B and C shows the interface crack in a colloidal coating for side view and top view, respectively. Using the image data in Fig. 1, it is possible to draw three dimensional displacement and stress distribution as shown in the Fig. 2. As expected, the stress shoots up rapidly just ahead of cracking. This technique allows scientists to see the spatially and temporally heterogeneous mechanical properties of materials.

Discussion

Image analysis is a good tool to figure out the mechanical property of a material when the resolution is sufficient. The authors used the technique to a system as colloid in it dries and succeed to draw 3D stress distribution. This is helpful for studying the fracture mechanics. Once the resolution of this technique is improved, it would be possible to probe the mechanical properties of homogeneous materials because the lattice parameters of a system would vary when it deforms. This may give remarkable knowledge expansion in material science.