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  • 1
    Electronic Resource
    Electronic Resource
    Damage mode analysis of MCrAlY overlay coatings subjected to isothermal stepwise tensile testing by using in situ video imaging and acoustic emission monitoring (2004)
    PO Box 1354, 9600 Garsington Road, Oxford OX4 2XG, UK. : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 27 (2004), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The mechanical performance of gas turbine material systems consisting of a Ni-base superalloy substrate with three different MCrAlY overlay coatings with various Al contents was assessed, close to service temperature spectrum, by means of stepwise tensile tests. Furthermore, acoustic emission (AE) activity was monitored during the tensile testing. Tensile tests were performed for all three types of coated systems at four different temperatures (300, 500, 700 and 900 °C). The AE data were analysed by means of a standardized k-means algorithm with respect to nine parameters (such as amplitude, number of counts, duration, rise time, energy, etc.). In conjunction with in situ video imaging of the specimen surface and postmortem microstructural analysis of the samples, the classification of AE data has provided a means for damage identification and performance assessment of the substrate-coating material systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.2004.00749.x
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  • 2
    Electronic Resource
    Electronic Resource
    Coherent Propagative Structures in Plastic Deformation: A Theory of Lüders Bands in Polycrystals (1992)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 23-24 (Jan. 1992), p. 385-402 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/25/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.23-24.385.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Self-Organization of Defect Structures under High-Temperature Irradiation-A Theory of Void Lattices (1992)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 23-24 (Jan. 1992), p. 203-219 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/25/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.23-24.203.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Theory of radiation-induced self-organization of defect structures (1994)
    Springer
    Applied physics 58 (1994), S. 11-19 
    Details
    ISSN: 1432-0630
    Keywords: 61.80.Fe ; 61.70.Ph ; 64.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract During high-dose electron irradiation of thin Ni foils at 520 K, groups of about 10 Stacking-Fault Tetrahedra (SFT) are formed, which are referred to as patches. Within the patches the SFT occupy the sites of a square lattice whose sides are parallel to the two 〈100〉 directions of the crystalline host lattice in the foil plane. A theory of this planar square lattice of SFT is the subject matter of the preceding paper (Part I). The patches themselves are arranged in a planar face-centred cubic lattice that also shares its orientation with the host lattice. In the present paper (Part II) a mesoscopic theory is presented that accounts for this ordering of SFT-lattice patches in terms of an instability of disordered patch arrangements that results from a point-defect-mediated dynamic patch-patch interaction. This interaction arises from the competition of SFT-lattice patches for static crowdions migrating one-dimensionally along close-packed host lattice directions and for three-dimensionally diffusing vacancies and dumbbell interstitials. The so far exclusive occurrence of ordered SFT-lattice patches in Ni is related to the low packing density of this material, which leads to a high stability of the static crowdions and thus to a long range of the dynamic interaction between SFT-lattice patches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331512
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  • 5
    Electronic Resource
    Electronic Resource
    Stochastic dislocation patterning during cyclic plastic deformation (1996)
    Springer
    Applied physics 63 (1996), S. 45-55 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 62.20 ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A dislocation dynamical theory is developed for the formation of dipole dislocation patterns during cyclic plastic deformation in single glide. The stochastic dislocation dynamics adopted is suitable to account, in terms of a fluctuating effective medium, for the effects of long-range dislocation interactions on a mesoscopic scale. The theory can explain the occurrence of a matrix structure and persistent slip bands as a result of evolutionary processes, it gives the intrinsic strain amplitudes and the characteristic wavelength of these structures, and it allows for an interpretation of the structural changes associated with changes of the deformation conditions. Quantitative results are in good agreement with experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01579745
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  • 6
    Electronic Resource
    Electronic Resource
    Theory of solitary plastic waves (1994)
    Springer
    Applied physics 58 (1994), S. 49-58 
    Details
    ISSN: 1432-0630
    Keywords: 03.40.Kf ; 62.20.Fe ; 81.40.Lm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The paper deals with the dislocation dynamics of coherently propagating modes of plastic shear (Lüders bands) in single crystals oriented for single slip, in terms of a generalized Fisher-Kolmogorov equation. The role of (1) cross-slip and (2) non-axial stresses as propagation mechnisms is investigated, and the problem of propagation velocity selection is addressed. The phenomenon of slip band clustering which was observed in sufficiently thick tensile specimens is traced back to a propagative instability owing to non-axial stresses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331516
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  • 7
    Electronic Resource
    Electronic Resource
    Theory of radiation-induced self-organization of defect structures (1994)
    Springer
    Applied physics 58 (1994), S. 3-10 
    Details
    ISSN: 1432-0630
    Keywords: 61.80.Fe ; 61.70.Ph ; 64.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract During high-dose electron irradiation of thin foils of face-centred cubic metals and dilute alloys in a high-voltage electron microscope at temperatures above recovery stage III, planar ordering of Stacking-Fault Tetrahedra (SFT) in square lattices with the same orientations as the crystalline host lattices has been observed. In the present paper, a theory is presented that relates the formation of such SFT lattices to dynamic SFT interactions mediated by the anisotropic drift-diffusion of radiation-induced point defects in the SFT strain fields. Treating the SFT dynamics on the mesoscopic length scale of the ordering phenomenon, expressions for the interactions between the SFT are derived. As shown by linear stability analysis, there is a regime of control-parameter values in which these interactions induce a phase transition from a disordered SFT arrangement to a SFT lattice. The properties of this lattice and their dependences on parameters that can be controlled by experiment are investigated and compared to observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331511
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  • 8
    Electronic Resource
    Electronic Resource
    Theory of solitary plastic waves (1994)
    Springer
    Applied physics 58 (1994), S. 41-48 
    Details
    ISSN: 1432-0630
    Keywords: 03.40.Kf ; 62.20.Fe ; 81.40.Lm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A dislocation dynamical model of the reaction-diffusion type is used to describe the spatio-temporal dynamics of Lüders band propagation in polycrystals. The diffusive nature of dislocation glide is traced back to the random crystallographic orientation of the active slip systems. The role of pile-ups in dislocation multiplication is accounted for by a dynamical generalization of the Hall-Petch law. It is argued that Lüders bands in polycrystals are related to a bistable dynamics of mobile dislocations. Further results obtained cover the dependences on material parameters and deformation conditions of (1) the occurrence, (2) the strain, propagation velocity and width of Lüders bands, and (3) the upper and lower yield stresses. These results are in good agreement with experimental findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00331515
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  • 9
    Electronic Resource
    Electronic Resource
    Stochastic dislocation patterning during cyclic plastic deformation (1996)
    Springer
    Applied physics 63 (1996), S. 45-55 
    Details
    ISSN: 1432-0630
    Keywords: PACS61.70; 62.20; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. A dislocation dynamical theory is developed for the formation of dipole dislocation patterns during cyclic plastic deformation in single glide. The stochastic dislocation dynamics adopted is suitable to account, in terms of a fluctuating effective medium, for the effects of long-range dislocation interactions on a mesoscopic scale. The theory can explain the occurrence of a matrix structure and persistent slip bands as a result of evolutionary processes, it gives the intrinsic strain amplitudes and the characteristic wavelength of these structures, and it allows for an interpretation of the structural changes associated with changes of the deformation conditions. Quantitative results are in good agreement with experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01579745
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    On the foundations of stochastic dislocation dynamics (1996)
    Springer
    Applied physics 62 (1996), S. 473-481 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 61.70.Ga ; 62.20.-X ; 81.40.Ef
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  A stochastic approach to dislocation dynamics is proposed that starts off from considering the geometrically necessary fluctuations of the local stress and strain rate caused by long-range dislocation interactions during plastic flow. On a mesoscopic scale, a crystal undergoing plastic deformation is thus considered an effective fluctuating medium. The auto- and cross-correlation functions of the effective stress and the plastic strain rate are derived. The influences of dislocation multiplication, storage and cross slip on the correlation functions are discussed. Various analogies and fundamental differences to the statistical mechanics of thermodynamic equilibrium are outlined. Application of the theory of noise-induced transitions to dislocation dynamics gives new insight into the physical origin of the spontaneous formation of dislocation structures during plastic deformation. The results demonstrate the importance of the strain-rate sensitivity in dislocation patterning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050326
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