Application of Functionally Graded Structural Members in constructions

by Rafal Ortwein (Cracow University of Technology (PL))

Tuesday 25 Jun 2013, 14:00 → 15:00 Europe/Zurich

30/7-010 (CERN)

Functionally Graded Structural Members (FGSM) are new kind of materials obtained from austenitic stainless steels via strain induced phase transformation at cryogenic temperatures. This process leads to change from the initial austenitic microstructure to martensitic one. It has been theoretically described in a constitutive model developed by B. Skoczeń [1], where the creation of FGSM by torsion of a cylindrical bar at cryogenic temperatures is described. The structure created this way has many advantages compared to the classical untransformed element. They exhibit higher strength and stability, better properties of the surface thanks to the harder martensitic phase and better resistance to fracture. A series of experiments to verify these predictions was conducted. A set-up has been created allowing torsion tests at room and cryogenic temperatures. Afterwards microscopic, micro-hardness, and martensite content measurements have been performed on 304 stainless steel cylindrical samples. To test the influence of the transformed microstructure to mechanical properties tensile test and stability, tests have been performed as well. It has been concluded that it is possible to create the FGSM by monotonic and cyclic torsion at cryogenic temperatures. The distribution of martensite along the radius of the cross-section was also measu. Newly created FGSMs have enhanced properties but also a few drawbacks. Further study to minimize unwanted effects is still necessary.

Slides Ortwein_seminar_FGSM.pdf