Hahn, T.T.HahnKuepper, F.F.KuepperWissenbach, KonradKonradWissenbach2022-03-082022-03-081993https://publica.fraunhofer.de/handle/publica/302836A process or an arrangement for the increase of alternating torsion stress of a component (23) provided with a groove (22) provides for a hardening of only the groove bottom edge areas (20, 21) by at least one energy-rich beam (24, 25), whereby inert gas is introduced into the groove (22) (Figure 2) by means a nozzle (28) in order to avoid surface changes in the component (23).de608621patent1991-4142216