(in lingua inglese)
Cracking requires tensile stress to propagate. High residual compressive stress counteracts tensile stress and hinders the growth of cracks. Any measure which increases residual compressive stress should increase the life of a mandrel by suppressing cracking. Shot peening treatments introduce residual compressive stresses in the surface layer and prolong the fatigue life of a component. Furthermore, the condition of the surface of the tool is extremely important in addressing fatigue failures.