2. Empirical models

2.1 Establishing models

This approach is not based on solving equations, even in simplified form, but on analyzing experimental results. These are either systematic production surveys, or tests carried out specifically in the laboratory to measure and correlate the desired quantity (e.g. flat-rolling widening) with the parameters of the operation (e.g. thickness/width ratio, cylinder radius, reduction). These test campaigns are carried out either on steel, or on a simulation material (lead, modeling clay). In the latter case, it should be borne in mind that problems of similarity can degrade the quantitative prediction