In this paper we investigate developable cones ( $d$-cones) topology. From profilometer measurements, we found that for a sample of a finite thickness the singularity is never pointlike but has a form of a crescent. Measurements of the sheet local curvature revealed that the $d$-cone tip is rejected by a distance which characterizes the singularity size. High deformations of the $d$-cone lead to a plastic regime equivalent to a decrease in the singularity size characterized from curvature and profile analysis.

• Received 21 August 1997

DOI:https://doi.org/10.1103/PhysRevLett.80.2354