|
|
||
|
|
|
|
From: Michael Marder, Robert D. Deegan and Eran Sharon, "Crippling, buckling and cracking: Elasticity of thin sheets", Physics Today, , February 2007, pp. 33-38
(a) A plastic sheet ripping apart elastic-plastically is viewed with polarized light. Short-wavelength free-edge buckles (wrinkles) form a small distance away from the unrelaxed biaxially tensioned tip of the tear. In this partially relaxed region a little distance away from the crack tip there still exists some residual tension parallel to the new edge of the tear. At some point away from the crack tip the residual tension parallel to the crack and at the new edge of the material reaches zero. Internal residual tension parallel to the tear is then most efficiently further relieved by out-of-plane deformation (buckling/wrinkling) of the new edge, out-of-plane deformation the amplitude of which increases with increasing distance from the crack tip as more and more residual tension is relieved.
(b) A complex "multi-generational" buckling pattern forms in the wake of an elastic-plastic tear. In this photograph we see about eight "long" half-waves from top to bottom. Within each "long" half-wave is superposed a very local short-wavelength edge wrinkling.
(c) A plastic sheet placed in a cup and poked with a pencil buckles elastically inextensionally, that is, into a new developable surface. The maximum buckling deflection occurs at the edge, and the radial lines remain straight during the buckling process.
Page 24 / 360