Barkhausen noise emission of AISI 304 stainless steel originating from strain induced martensite by shot peening

This study deals with magnetic Barkhausen noise emission produced by strain-induced martensite generated during shot peening of austenitic AISI 304 stainless steel. The transformation from the paramagnetic to ferromagnetic state and the corresponding birth of the magnetic domain structure are important with respect to irreversible motion of domain walls and the corresponding Barkhausen noise emission. Barkhausen noise is investigated and explained with respect to the residual stress state as well as the micro-structure expressed in terms of the martensite fraction, its crystallite size, preferred orientation, surface topography, and microhardness. The strength of the Barkhausen noise is mainly linked with the number of shot peening cycles, corresponding Almen intensity, and the associated volume fraction of strain-induced martensite as well as the extent of its depth. The role of the residual stress state in the martensite phase is minor. Surface strengthening expressed in terms of the microhardness in the near-surface region is very high for the medium shot peening intensity. A remarkable decrease in the near-surface microhardness as well as the presence of heavily thinned folds indicate over shot peen-ing and surface microcracking in the case of a longer shot peening time and the corre-sponding higher Almen intensity.Web of Science2076274

The Development of Mechanism with Hybrid Kinematic Structure Prototype

This paper deals with the development of mechanism with hybrid kinematic structure called trivariant and its subsystems. Hybrid machines are characterized by connecting advantages of both type mechanisms together - high dynamics of parallel mechanisms for positioning and high flexibility and high mobility range of serial mechanisms for orientation. At our department was built the small-scale mechanism prototype used for testing, functional verification, for education and training. There was created the simulation software and control system based on standard PC for this prototype. Our prototype can be applied like small CNC milling machine but it is possible to modify it also for the manipulation with objects like robot device