Chernov-Lüders Lines

(Lüders’ lines), thin, dark lines that appear on the polished surface of a steel specimen when the yield point is reached during cold plastic deformation. During extension or compression they are oriented at an angle of approximately 45° to the axis of the specimen; that is, they coincide with the direction of the planes of the principal shearing stresses. The lines were first described by L. Lüders of Germany in 1859 and independently by D. K. Chernov in 1884. They are also known as stretcher strains, deformation bands, Hartmann lines, and Piobert lines.