3. Inertial friction

3.1 Principle

Inertia friction was developed later and initially disseminated under the name of Inertia welding. It stems from the idea of operating in short times to enhance the welding characteristics of certain high-strength metals with low thermal diffusivity.

Experience shows that for these materials, weldability is excellent when higher forging forces are applied than with controlled friction under different thermal conditions.

The principle is based on the following observations:

• if we want to obtain uniform friction and heating conditions across the entire cross-section of an assembly of two solid bars, we need to vary the speed of rotation from a high speed, effective near the axis,...