3.4 Pinned-pinnned resonance corrugation
“Pinned-pinned resonance” corrugation arises from excitation of a resonance of the rail in which it vibrates as a beam with nodes almost at the sleepers. Examples are shown of this type of corrugation on ballasted track and on a metro, where there is a mix of both pinned-pinned resonance and P2 resonance corrugation. This type of corrugation occurs primarily on straight track and on the high rail in curves. High dynamic loads result from the dynamically stiff support, so corrugation is often worse on the approach to sleepers than at the more flexible mid-span position, where dynamic loads are lower.
Pinned-pinned resonance corrugation is often associated with a loud “roaring” noise inside and outside the train (thereby giving rise to the term “roaring rails”).
The pinned-pinned resonance has the highest frequency of common wavelength-fixing mechanisms.