Furrows in the wake of propagating d-cones

We investigate the formation dynamics of plastic creases in thin elasto-plastic sheets. In contrast to the commonly accepted description of crumpled thin sheets, which asserts that creases form only by elastic interaction between two d-cones, the creases we study in this letter are created by plastic deformations left in the wake of a single propagating d-cone. Upon application of load, a d-cone initially remains stationary and responds by deforming globally. However, above a critical load, the d-cone undergoes a sharpening transition that focuses the stresses at its tip, allowing it to propagate along the sheet, leaving a furrow-like scar in its wake. Our results show that the dynamics of plastic defect creation are important for predicting the final geometry and statistics of a defect network in a crumpled thin sheet.