The deformation behaviour of the super duplex stainless steel SAF2507 (UNS S32750)
under successive uniaxial tensile loading-unloading was investigated with respect to load sharing
and inter-phase interactions. The steel consists of 58% austenite and 42% ferrite in volume. By insitu
X-ray diffraction experiment the evolution of phase-specific stresses with applied load was
monitored for three successive loading-unloading cycles with the maximum total strains being
0.34%, 0.75% and 1.63%, respectively. It was found that yielding occurred earlier in the austenitic
phase than in the ferritic phase during the first loading cycle. In the followed loading cycles, both
phases yielded under larger but similar applied stresses. Due to a similar behavior of the phases in
the elasto-plastic regime inter-phase interactions were relatively weak. Low microstresses induced
by the plastic straining resulted in somewhat larger stresses in the ferritic phase.
In this article we present the results of a research project of Volkswagen AG and Fraunhofer IWU. It shows new approaches in the development of active mass dampers for transmission applications. The proposed active controlled system enables to reduce the interior sound pressure level of the rear axle gear mesh order by more than 5 dB. By detailed pre-examination of the drivetrain vibrations and transfer paths we gained new insights into the phenomenon of rear axle gear whine. In order to develop solutions to realise the damping of the vibrations we designed and constructed a test bench which consists of the main components of the rear axle unit and its bearings. The vibration phenomenon was replicated by synthetic excitation. Thus we could acquire an adequate control concept combined with a corresponding actuator and experimentally established control parameters.Validations on an experimental vehicle under synthetic excitation and finally under real driving conditions adduced the evidence for the functionality of the proposed system.
KurzfassungDas in diesem Artikel beschriebene Forschungsprojekt der Volkswagen AG und des Fraunhofer IWU zeigt neue Ansätze bei der Entwicklung von aktiven Systemen zur Schwingungstilgung an Getrieben auf. Im Speziellen wurde der Geräuscheintrag einer bestimmten Zahneingriffsordnung des Hinterachsgetriebes in den Fahrgastraum eines PKWs um mehr als 5 dB gesenkt. Grundlage des Erfolges waren detaillierte Voruntersuchungen am Fahrzeug, mit deren Hilfe das Schwingungsphänomen eingegrenzt werden konnte. Mit dieser Kenntnis war es in einem weiteren Schritt möglich, Lösungsvorschläge zur Umsetzung der Schwingungstilgung zu entwickeln. Dazu wurde an einem Versuchstand, bestehend aus den Komponenten des hinteren Antriebsstrangs und deren Lagerung, das Schwingungsphänomen durch künstliche Anregung erzeugt. Auf dieser Basis wurden unterschiedliche Konzepte zur aktiven Schwingungstilgung untersucht sowie die Position des Aktors und Regelungsparameter versuchstechnisch abgestimmt. Abschließend konnte der Funktionsnachweis des Systems am Versuchsfahrzeug unter künstlicher Anregung und letztendlich unter realen Fahrbedingungen erbracht werden.
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