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  • 1
    Electronic Resource
    Electronic Resource
    Strain Rate and Test Temperature Dependence on the Flow Properties of La〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Doped Tungsten (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 59 (Dec. 2008), p. 319-325 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Tungsten and tungsten alloys are promising metals as protective materials for the armour in future fusion reactors. These metals exhibit the highest melting point, superior thermo-mechanical properties, low erosion and moderate neutron activation properties. The main drawback is their intrinsic brittleness at room temperature and their low recrystallization temperature. During thermal shock events in ITER, tungsten materials will exhibit various crack formations and failure mechanisms. The extensive heat loads on the surface of the material will create high thermal stresses, huge temperature rises and therefore large strain rates in the subsurface layers. This paper deals with the flow properties combining both temperature and strain rate effects of a lanthanum oxide dispersion strengthened tungsten material and the influence of grain orientation on its ductility. Promising results were obtained using a yield strength model based on a thermally-activated slip process that rationalizes the data
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/41/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.59.319.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of the geometry dependence of fracture toughness at cracking initiation by comparison of circumferentially cracked round bars and SENB tests on Copper (2000)
    Springer
    International journal of fracture 103 (2000), S. 205-225 
    Details
    ISSN: 1573-2673
    Keywords: Ductile fracture ; constraint ; fracture toughness ; voids ; CTOD ; size scale ; triaxiality ; precracking.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In the first part of the paper, the use of circumferentially cracked round bars (CRB geometry) for characterizing fracture toughness of a ductile material, namely copper, is assessed experimentally through a comparison with the single edge notched bend (SENB) geometry. The J R curve method with multiple-specimens was applied, but, as unstable cracking appeared very early in the CRB specimen, an engineering definition of fracture toughness was not pertinent. Unloaded specimens were analyzed metallographically to determine the CTOD at physical cracking initiation. The fracture toughness measured using the CRB geometry was 50% larger than using the SENB geometry. The second part of the paper aims at justifying this difference of fracture toughness at cracking initiation. Finite element simulations revealed a slightly higher constraint in the SENB specimens. The main difference between the two specimen geometries lies in a 50% larger extension of the finite strain zone with respect to the CTOD in the case of the SENB specimens. Based on the observation that, in the studied material, the critical CTOD is one order of magnitude larger than the void spacing, we conclude that the geometry dependence of the fracture toughness is caused by the difference in the finite strain zone extension rather than by a stress triaxiality effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007668030117
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  • 3
    Electronic Resource
    Electronic Resource
    Fracture toughness analysis of circumferentially-cracked round bars (2000)
    Springer
    International journal of fracture 104 (2000), S. 145-168 
    Details
    ISSN: 1573-2673
    Keywords: Fracture toughness ; circumferentially-cracked round bars ; η-factor ; loss of constraint ; micromechanical modelling.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The accuracy and the domain of applicability of approximate formulae used to evaluate the fracture toughness of circumferentially-Cracked Round Bars (CRBs) are established using finite element calculations. In the elastic plastic fracture mechanic (EPFM) domain, new formulae are developed which increase largely the accuracy and the domain of applicability. The loss of constraint is evaluated through the Q-factor allowing to determine the domain of validity of one-parameter fracture toughness characterisation. At the same time, an appropriate ‘crack length to bar radius’ ratio is proposed. A micromechanical model of cleavage fracture in the transition region is proposed where both the specimen size and loss of constraint correction are taken into account. This model allows to measure plane strain fracture toughness using small CRB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007625612644
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Damage work as ductile fracture criterion (1994)
    Springer
    International journal of fracture 66 (1994), S. 155-164 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper treats the ductile failure initiation in circumferentially-notched tension specimens and explores the local damage model that is able to represent the continuous degradation of the deforming material. With the aid of finite element calculations, the notched specimens have been simulated numerically and the whole strain-stress history for each geometry derived. This allows determination of the evolution of strain-stress fields until fracture occurs. Two damage models were evaluated: the Rice and Tracey cavity growth model and a model which combines the latter with the plastic strain work, to derive an intrinsic parameter called ‘damage work’. These models could predict the location where the crack will initiate as well as the crack initiation step which is reached for a relatively constant value of the critical damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020080
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