Dibyendu Mal

Formation of crack patterns in clay films : Desiccation and relaxation

A study of crack patterns in laponite films of different thickness is presented. Two cracking regimes are observed. The earlier, with a higher rate of desiccation and shrinking, has predominantly 4-fold vertices in the crack network, while the later regime has less volume shrinking and forms mainly 3-fold vertices. The pattern shows a self-similarity under coarse-graining. The graph of the area covered by cracks versus minimum crack-width resolved, scales with the film thickness. Curves representing crack area for different thickness thus collapse onto a single curve.

Desiccation cracks on different substrates: simulation by a spring network model

Crack patterns formed due to desiccation of clay or similar materials show distinctive reproducible patterns. If one measures the cumulative area Acum covered by the cracks with widths ?Wmin, then Acum plotted against Wmin shows a typical reproducible shape. In a log?log plot, this curve has two roughly linear regions with different slopes. For a polypropylene (PP) substrate, there is a sharp change from a nearly horizontal line to a very steep line, whereas for a glass substrate, which is smoother, there is a gradual changeover between the two regions. We propose a simple one-dimensional spring chain model, in which reducing the natural length of the springs corresponds to the desiccation process. Springs may break, or slip against the substrate to accommodate strain beyond a specified threshold. The model successfully reproduces the successive stages of crack formation and behaviour of the cumulative area curve, as observed in experiments. The difference in the qualitative nature of the patterns on smooth and rougher substrates is also obtained.

FRACTAL CRACK PATTERNS IN LAPONITE FILMS AND THEIR SCALING BEHAVIOR

We study crack patterns in laponite films of different thickness. The patterns show a self-similarity under coarse-graining, the fractal dimension determined by box-counting has a value around 1.66, independent of film thickness. The cracks on layers of different thickness show a remarkable scaling bahavior. We have measured the cumulative area covered by the cracks versus minimum crack-width resolved. Curves representing crack area for different thickness collapse onto a single curve, when the crack widths are scaled by the film thickness.

ERRATUM: "Fractal Crack Patterns in Laponite Films and Their Scaling Behavior"

ERRATUM Correction to: “Fractal Crack Patterns in Laponite Films and Their Scaling Behavior” DIBYENDU MAL,∗ SUPARNA SINHA,∗ TAPATI DUTTA,‡ S. MITRA† and SUJATA TARAFDAR∗,§ ∗Condensed Matter Physics Research Centre, Physics Department †Department of Geological Sciences Jadavpur University, Kolkata 700032, India ‡Physics Department, St. Xavier’s College, Kolkata 700016, India §sujata tarafdar@hotmail.com The above-titled article published in Vol. 14, No. 4 (December 2006), pp. 283–288 contains an incorrect Fig. 6. The correct version is appended below: