  We present a mathematical method for identifying, separating and quantifying
the 3D significant distortions. Measurement of a gas quenched C-ring type
sample is performed by a Coordinate Measuring Machine (CMM). Quenching
simulation is done with the commercial software Forge 2008 TTT. After
comparisons, we notice that the distortions and their tendencies are the same
but not exactly the amplitudes. We only focus on distortions which have a
physical origin, like the pincers opening, often observed in the literature. As
a first explanation, we underline the role of phase transformations and volume
dilatation of the steel during quenching.
