Fluid•DTU seminar, Tuesday, Oct. 20, 2009, at 11:00, Bldg. 306 Aud. 34

Volume alteration in solid materials is a common cause of material failure. Here we investigate the crack formation in thick and thin elastic layers. In thin films attached to a substrate, we show that small variations in the volume contraction and substrate restraining forces can produce widely different crack patterns ranging from spirals to complex hierarchical networks. In thick layers of cooling or drying solids, which loose heat or moist at the surface, a differential shrinkage can eventually lead to cracking of the solid. These cracks often form an intricate polygonal pattern such as the columnar joints formed in cooling lava. Calculations of the characteristic length scale and simulations of the formation of columnar joints are presented.