The shape of a crumpled paper ball can be described by a network of straight folds, connected at point defects termed 'd-cones'. When the ball is opened up, the sharper folds leave the familiar plastic creases seen in crumpled papers (right image - 1). Upon closer inspection, a different type of crease can be observed; considerably sharper and more ragged than the usual creases (right image - 2). They are created when a d-cone propagates across the sheet and 'plows' the paper, leaving a sharp furrow like scar in its wake. We are interested in the formation dynamics of these creases, which bears many similarities to the propagation of cracks in solids. Another question regarding these odd creases is what role do they play in determining the full pattern of creases formed in a crumpled sheet of paper.

 

 

 

Extra furrows stuff:

Furrows creation in crumpled paper:  Paper kvetch

A d-cone propagating in a Mylar sheet - notice the abrupt sharpening of the d-cone accompanying the initiation of propagation: D-cone propagating in Mylar

Furrows in the wake of propagating d-cones (PDF)