| Details: |
We present results from a study of the compression of a
quasi-two-dimensional aqueous foam in a Hele-Shaw cell. Our results
show that during compression, the (spatially-averaged) normal-stress
difference localizes in bands with a wavelength of the order of the
mean diameter of a bubble. Stress field colormaps are constructed by
image analysis and used to visualize the bands. We investigate the
phenomenon by varying the mean bubble diameter and polydispersity.
We quantify the extent of (global) compression by measuring the
average of an anisotropy ratio for the strain eigenvalues, and find
the probability distribution of the angle between corresponding
eigenvectors of the stress and strain tensors. We show that these
stress bands are ruptured in regions in which avalanches of
neighbour-switching T1 events occur, which suggests local stress
relaxation in these regions. |