Untersuchung der Entstehung und Umlagerung von mechanisch und thermisch induzierten Eigenspannungen für die Nickelbasis-Legierung Inconel® 718

Research output: ThesisDiploma Thesis

Abstract

As residual stresses can have significant consequences in terms of strength on components in operation, research in this topic is very important but just as challenging. A lot of experience and know-how about the development of residual stresses is necessary. To increase the knowledge this thesis contains simulation-models that investigate residual stresses in the nickel-based alloy Inconel® 718, a high-temperature material used in aviation and aerospace. Additional experiments verify the results of the simulation. The first part concentrates on mechanically induced residual stresses, inserted by stretching a notched specimen. Subsequent removal of material at the surface causes redistribution of the stresses in the specimen. The main focus is put on thermally induced residual stresses though, which occur during rapid cooling down from high temperatures. Here the relaxation and regeneration of stresses takes place when cooled-down forged components get heat-treated. After considerations about applicable procedures for the experiments, Inconel® 718-specimens get water-quenched from 1.000 °C and 950 °C. Their temperature-curve gets recorded over the whole period. The simulation-model is based on a thermal-mechanical decoupled method. The accuracy of the residual-stresses-computation is essentially dependent on how realistic the local cooling-curves in the simulation are. And this again is affected by the location- and temperature-dependent heat-transfer coefficients. As the heat transfer has to be as realistic as possible, an optimization-tool is designed for adaptation of the heat-transfer coefficients to reality. The most significant results in this thesis are the simulation of stress-redistribution after material-removal, the development of an experimental setup to get thermally induced residual stresses and the calculation of the heat-transfer coefficients.

Details

Translated title of the contributionResearch of development and redistribution of mechanically and thermally induced residual stresses for the nickel-based-alloy Inconel® 718
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
Award date22 Mar 2013
Publication statusPublished - 2013