Lüders band

[1] First reported by Guillaume Piobert, and later by W. Lüders,[2] the mechanism that stimulates their appearance is known as dynamic strain aging, or the inhibition of dislocation motion by interstitial atoms (in steels, typically carbon and nitrogen), around which "atmospheres" or "zones" naturally congregate.

As internal stresses tend to be highest at the shoulders of tensile test specimens, band formation is favored in those areas.

However, the formation of Lüders bands depends primarily on the microscopic (i.e. average grain size and crystal structure, if applicable) and macroscopic geometries of the material.

[4] The visible front on the material usually makes a well-defined angle typically 50–55° from the specimen axis as it moves down the sample.

[6] The formation of Lüder bands can occur again with a deformation over time, since the interstitial atoms accumulate by diffusing processes called precipitation hardening (or aging).

**Figure 1:** Measured strain distribution of a tensile test (shape memory alloy) during loading and unloading shows moving Lüders bands. The measurement was performed with a LIMESS Digital image correlation system.