The solidification modulus establishes a relationship between the volume-surface ratio of a simple casting and its solidification time. The idea goes back to a famous article by Nicolas Chvorinov, whose birthday we want to commemorate today.

Nicolas Chvorinov was a Czech foundry engineer born on 15 November 1903. Chvorinov completed his graduation from the Mining Academy in Příbram - Czech Republic - in 1928 and became a well-known specialist in the field of crystallisation and solidification of castings.

In 1940, Chvorinov published his most important work called "Theorie der Erstarrung von Gußstücken" (Theory of the Solidification of Castings) in the German foundry journal GIESSEREI. This article brought him worldwide recognition and is still cited in many foundry-related works today. In his paper, Chvorinov proposed a physical relationship between the the solidification time of a simple casting and its volume-to-surface ratio. The ratio of a casting's volume (V) and its area (A) is known as the solidification modulus (M = V/A). The expression suggested by Chvorinov, which became known in the foundry world as Chvorinov's rule, is T = k⋅M², where T is the solidification time and k is the mold constant.

With the help of modern simulation technology, Chvorinov's rule allows the definition of a point-local modulus value and provides a method for its numerical computation. As such, a variant of it is still used as part of Visiometa's modulus analysis.

The legacy of Nicolas Chvorinov's contributions to the foundry world should always be remembered and appreciated. We have the privilege of combining the results of his work with modern simulation technology, making his central ideas accessible to all foundrymen.