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@PHDTHESIS{Seibel:171851,
      author       = {Seibel, Thomas},
      title        = {{E}influss der {P}robengröße und der {K}ornorientierung
                      auf die {L}ebensdauer einer polykristallinen
                      {N}i-{B}asislegierung bei {LCF}- {B}eanspruchung},
      volume       = {227},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2014-05408},
      isbn         = {978-3-89336-986-7},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {II, 131 S.},
      year         = {2014},
      note         = {RWTH Aachen, Diss., 2014},
      abstract     = {In the present work the LCF (Low Cycle Fatigue) crack
                      initiation life of the conventionally cast Ni-base alloy
                      RENE 80 was analyzed as a function of specimen size and
                      grain orientation. Five specimen geometries with distinctly
                      different gauge sections were used: 3 geometries with
                      cylindrical gauge section (G1-G3) and two notched geometries
                      with a stress concentration factor of $\alpha$1 = 1,62 (KG1)
                      and $\alpha$2 = 2,60 (KG2), resulting in a maximum
                      difference of the damage relevant surface area up to a
                      factor of approximately 72. Correction factors were
                      determined by FEM calculations for all specimen geometries
                      with highly reduced gauge sections where direct strain
                      measurement was not possible. Additionally a uniform failure
                      criterion with a relatively small crack size of 0,962
                      mm$^{2}$ was defined. Totally, 116 isothermal LCF tests were
                      carried out at the different specimen types at a temperature
                      of 850°C in total strain control with a load ratio (minimum
                      strain / maximum strain) of R$_{ε}$ = -1. The load cycles
                      were applied with triangular waveform at a frequency of 0.1
                      Hz for high strain amplitudes and 1 Hz for low strain
                      amplitudes, respectively. After the LCF-Tests the fracture
                      surfaces of all samples were analyzed in more detail by SEM
                      to identify the crack initiation mechanisms as well as the
                      crack initiation sites. In this context it could be shown,
                      that fatigue cracks were generally initiated at slip bands
                      in surface grains. Accordingly, the grain orientations at
                      the crack initiation sites were measured by electron back
                      scatter diffraction (EBSD) and the maximum shear stresses in
                      the respective principal slip system (111) <110> was
                      calculated using the Schmid approach. For this, longitudinal
                      sections were be prepared exactly at the crack initiation
                      sites of samples loaded with low strain amplitudes where
                      clearly defined single crack initiation sites were observed.
                      Afterwards the maximum shear stress in the principal slip
                      system at the crack initiation site was correlated to the
                      lifetime behavior, resulting in a distinct decrease of
                      scatter and size influence compared to the conventional
                      representation total strain vs. cycles to failure.},
      keywords     = {Dissertation (GND)},
      cin          = {IEK-2},
      cid          = {I:(DE-Juel1)IEK-2-20101013},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/171851},
}