Extension of existing material and computational models for lifetime prediction of exhaust turbocharger hot parts under thermoemechanical loading

  • In this project, the transfer of material and computational models to a different material class, i. e. to an austenitic cast iron with spherical graphite, was studied to predict the lifetime of exhaust turbocharger hot parts under TMF load. Therefore, the alloy EN-GJSA-XNiSiCr35-5-2 (Ni-Resist D-5S) was chosen. Firstly, an experimental database was established for this material because it was insufficient at the beginning of the project. Tensile, creep, LCF and TMF tests were carried out, which served the calibration of the models. The TMF tests were used to validate the deformation model. The investigated material showed a strongly deviating behavior under TMF conditions compared to the ferritic SiMo alloys investigated in the previous project: Ni-Resist exhibited a comparable strength under OP- and IP-TMF loading, while the ferritic alloys showed a distinct higher strength under IP-TMF load. Evidence for creep damage was found for Ni-Resist with increasing temperatures and holdIn this project, the transfer of material and computational models to a different material class, i. e. to an austenitic cast iron with spherical graphite, was studied to predict the lifetime of exhaust turbocharger hot parts under TMF load. Therefore, the alloy EN-GJSA-XNiSiCr35-5-2 (Ni-Resist D-5S) was chosen. Firstly, an experimental database was established for this material because it was insufficient at the beginning of the project. Tensile, creep, LCF and TMF tests were carried out, which served the calibration of the models. The TMF tests were used to validate the deformation model. The investigated material showed a strongly deviating behavior under TMF conditions compared to the ferritic SiMo alloys investigated in the previous project: Ni-Resist exhibited a comparable strength under OP- and IP-TMF loading, while the ferritic alloys showed a distinct higher strength under IP-TMF load. Evidence for creep damage was found for Ni-Resist with increasing temperatures and hold times under tensile load. This is also a distinct difference to the SiMo alloys. The stress-strain behavior of the LCF and TMF tests is well described by the model for the new material in most cases. The same is true for the lifetime prediction, which is within a factor of two, except for 900 °C. The model was verified by a thermal shock test of an exhaust man-ifold. The aim of the simulation was in particular to predict the crack locations. An accurate prediction of the cycle number was not expected, as the component is afflicted with a casting skin, while the test pieces were not. The predominant number of experimentally determined locations were predicted. A fundamental objective of this project was to study the effect of HCF vibrations on the TMF lifetime experimentally in further detail and to extend the existing lifetime model to account for superimposed HCF load. In a first step, the database of the previous project based on SiMo 4.05 was considerably extended to determine the different influencing parameters. A proce-dure was developed which reproduces the lifetime reduction by the superimposed HCF vibra-tions during a TMF cycle. It is assumed that the superimposed HCF load accelerates the crack propagation considerably after exceeding a certain crack length. The time when the accelera-tion occurs, is significant for the lifetime reduction. This approach allows predicting the lifetimes in good agreement with the experiments for both materials.zeige mehrzeige weniger

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Metadaten
Autoren/innen:Danilo Uckert
Koautoren/innen:Kathrin Matzak, Hans-Joachim Kühn, Birgit Rehmer, Frauke Peter, Bernard Fedelich, Rainer Falkenberg, Cetin Haftaoglu, Vitaliy Kindrachuk, Birgit Skrotzki
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Englisch
Jahr der Erstveröffentlichung:2016
Organisationseinheit der BAM:5 Werkstofftechnik
5 Werkstofftechnik / 5.2 Experimentelle und modellbasierte Werkstoffmechanik
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Ermüdung; LCF; Modellierung; Schädigung; Simulation; TMF
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Degradation von Werkstoffen und Materialien
Veranstaltung:FVV Frühjahrstagung 2016
Veranstaltungsort:Bad Neuenahr
Beginndatum der Veranstaltung:14.04.2016
Enddatum der Veranstaltung:14.04.2016
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:19.04.2016
Referierte Publikation:Nein