Research

Lifetime predictions for exhaust gas turbocharger hot parts

Using conventional design methods, manufacturers of turbo-machinery are not able to realistically predict the failure behaviour of components, e.g. exhaust gas turbocharger hot parts. By developing new operating material and calculation models for lifetime forecasting, new insights have been gained in this project. The investigations concentrate on ferritic materials of the type EN-GJS SiMo and the austenitic cast iron EN-GJSA-XNiSiCr35-5-2 (Ni-Resist D-5S). As part of tensile, creep, LCF (Low Cycle Fatigue) and TMF (Thermo Mechanical Fatigue) tests, a comprehensive database was determined. A further focus of the project was to experimentally test the influence of HCF vibrations on TMF service life and to extend the service life model to HCF (High Cycle Fatigue) overlap. There was a good correlation between test and simulation results.

» With our work we could dramatically expand our understanding of TMF and TMF-HCF damage and to develop praxis-oriented lifetime prediction models, and in this way clearly make the design of turbo-machinery more efficient. «
Dr. Heiko Haase (MTU Friedrichshafen)

Motivation

Reliable and applicable service life models are essential for manufacturers of turbo-machinery so that they can recognise weaknesses in a component early on and better understand failure mechanisms. The methods currently used to assess the service life of exhaust gas turbocharger hot plates only consider low-frequency elasto-plastic fatigue loading. The objective of the project was therefore to integrate the relevant stresses TMF and HCF into a new lifetime prediction model.

Methodology

The basis of the work involved tensile, creep, LCF and TMF tests, which created a broad experimental database. The tests were conducted using samples of two types of materials – ferritic turbine casing materials of the type EN-GJS SiMo and austenitic cast iron EN-GJSA-XNiSiCr35-5-2 (Ni-Resist D-5S). The newly developed material model for lifetime prediction was verified with measurement data and component tests on a turbine casting and an exhaust manifold. A further focus was to test, during the experiment, what influence HCF vibrations have on TMF service life. A fracture mechanical approach served for the theoretical description. It depicted the reduced service life through the overlapping HCF vibrations in the TMF cycle.

Result

The new calculation model clearly demonstrates the load-deformation behaviour and the service life in the LCF and TMF tests for both material classes. The same is true for the overwhelming number of fracture locations in the exhaust manifold which were experimentally acquired during the component tests. Furthermore, it was possible to extend the new service life model to HCF overlap. With this approach, the service life for the SiMo-materials as well as for the Ni-Resist could be predicted in good agreement with the experiment. The modelling approach is available as a user-defined sub-routine for component analysis for commercial programs and thus can be directly used in industrial practice. It makes an important contribution to turbo-machinery being designed more efficiently and to reducing the length of product development cycles.

Documentation

TMF lifetime calculation of exhaust-gas turbocharger hot parts | Development of simulation models for lifetime prediction of materials for exhaust-gas turbocharger hot parts under thermo mechanical fatique loading and transfer to the application to components | Project No. 916

TMF lifetime calculation of exhaust-gas turbocharger hot parts II | Expansion of existing materials and computational models for life prediction of hot exhaust gas turbocharger parts under thermomechanical fatigue loading | Project No. 1100

Themis

Status
Finalised

Programme
Public Funding

Budget
760.000,00 EUR

Time Period
2006-08-01 to 2009-09-30 Part I
2012-01-01 to 2015-06-30 Part II

German Federation of Industrial Research Associations (AiF) e. V.

Bayenthalgürtel 23
50968 Cologne
Germany

Federal Ministry for Economic Affairs and Energy (BMWi)

Scharnhorststrasse 34-37
10115 Berlin
Germany

Industrie

Dr.-Ing. Heiko Haase
MTU Friedrichshafen

Forschungsstellen

Bundesanstalt für Materialforschung und -prüfung (BAM), Senior Scientific and Technical Federal Institute with responsibility to the Federal Ministry for Economic Affairs and Energy (BMWi)

Head of Research:
Prof. Dr. Birgit Skrotzki

Bundesanstalt für Materialforschung und -prüfung

Unter den Eichen 87
12205 Berlin
Germany

Project Management

Stefanie Jost-Köstering

FVV
+49 (0) 69 6603 1531
+49 (0) 69 6603 2531

Research Association for Combustion Engines eV

Lyoner Strasse 18
60528 Frankfurt am Main
Germany
T +49 69 6603 1345