Hall-Petch equation

Etymology
Independently discovered by English scientists Eric O. Hall and Norman J. Petch, in 1951 and 1953 respectively.

Proper noun

 * 1)  A relationship between the yield point and grain size of a material given by the equation σ$y$ = σ$0$ + k$y$ * d$-0.5$, where σ$y$ is the yield stress, d is the average grain diameter, and σ$0$ and k$y$ are constants specific to a particular material.