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Mechanics of Materials in High-Temperature Applications: Modelling and Characterisation for Realistic Thermomechanical Conditions

In certain high temperature applications, such as gas turbine components, load and temperature cycles are often such that the material tends to viscoplastic behaviour. The modelling and characterisation of materials used in such conditions is a rather difficult and expensive matter. Traditionally material data have been obtained through low cycle fatigue testing and the modelling has therefore focused on reproducing the behaviour in these tests. However, when compared to the conditions found in the actual component, the strain rates have been too high in the traditional tests while the hold times at high temperature, on the other hand, have been too short. This leads to the missing of phenomena such as dynamic strain ageing, ageing and rafting. Further, the extrapolation of the models from the test domain to the actual domain of use leads to parameter uncertainties.

The project aims at improved constitutive modelling of materials for high temperature applications and at the implementation of new models into a finite element computational environment.

Within the project, modelling of the high- and intermediate-temperature behaviour of the nickel based superalloy IN792 has been done. The tests upon which the characterisation and calibration are based, are in the form of step relaxation tests where the strain rates have been chosen on the basis of strain rates found in gas turbine blades during start up. A servo hydraulic test rig for high temperature materials testing has been set up for the continuing test program.

Page responsible: Bo Torstenfelt
Last updated: 2008-02-07