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  • 1990-1994  (3)
  • 1980-1984  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    The determination of the lateral compliances and Poisson's ratios for highly oriented polyethylene sheets (1982)
    Springer
    Journal of materials science 17 (1982), S. 1125-1130 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The extensional and lateral compliances have been determined for a series of oriented linear polyethylene sheets. For the measurements the sheet samples were mounted in a dead-loading creep apparatus fitted with a Hall effect lateral extensometer. The results agree well with those obtained previously on similar materials using other techniques. The values of the elastic constants are considered in the light of theoretical estimates based on force constant calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00543532
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A double-torsion study of the fracture of polyethersulphone (1984)
    Springer
    Journal of materials science 19 (1984), S. 3796-3805 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fracture studies of polyethersulphone have been undertaken using the double torsion geometry, in particular to establish the effects of ageing and crack speed on fracture toughness. The stability of crack growth was found in all cases to be very dependent on initial notching. If by suitable techniques, e.g. fatigue, a craze was formed at the notch root the subsequent crack growth was found to be stable, with a craze ahead of the growing crack. Under these conditions only a slight dependence of fracture toughness on crack speed was observed, with no significant differences between material aged for 5 years at room temperature and freshly moulded samples. The dimensions of the observed craze were found to be very similar to those of crazes observed in a parallel study using compact tension geometry and lead to comparable values for craze stress and crack opening displacement. In many instances unstable crack growth was observed, often described as “stick-slip”. This was often associated with the absence of a craze at the crack tip, perhaps due to a damage zone created during razor notching. The initiation load and load for crack arrest were determined and used to calculate initiation and arrest values for the fracture toughness as a function of the applied deformation rate. It was found that these values converged at high crosshead speeds to a value independent of ageing, although for the freshly moulded material the initiation values were significantly higher, and the arrest values lower. Electrically conducting grids were used to establish that crack speeds up to 400 m sec−1 occur during stick-slip crack growth. A detailed discussion is presented of conditions required for stable and unstable crack growth in polyethersulphone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552293
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The fracture toughness of tough polyethylenes by a novel high pressure technique (1984)
    Springer
    Journal of materials science 19 (1984), S. 413-422 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The failure of two grades of polyethylene has been studied using the technique of torsion under superposed hydrostatic pressure. The behaviour of unnotched samples of both grades was ductile at all pressures and strain-rates. However, at sufficiently high pressures both grades of polyethylene (including a tough copolymer) failed in a brittle manner when a surface notch was exposed to a suitable pressure fluid. Measurement of fracture stresses for various notch depths lead to a value for a critical stress intensity factor at each of several pressures. A linear extrapolation was then used to estimate the critical stress intensity factor at atmospheric pressure to be 1.11±0.05 MN m−3/2 and 1.68±0.08 MN m−3/2 for the homopolymer and copolymer, respectively. An independent measurement at atmospheric pressure for the homopolymer using compact tension geometry yielded a value of 1.28±0.02 MN m−3/2 confirming the accuracy of the extrapolation procedure and that the effect of the environment on the behaviour was not substantial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553564
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Measurement and analysis of the fracture of a liquid crystal polymer (1992)
    Springer
    Journal of materials science 27 (1992), S. 3969-3976 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The fracture initiation behaviour of injection-moulded plaques of a liquid-crystal polymer is described. Attention is restricted to cracks in the plane of the plaques propagating along the mould fill direction. The material is both anisotropic and inhomogeneous; the latter factor is accommodated by adopting a skin-core model of the plaque structure. The inhomogeneity leads to mixed mode (Modes I and II) fracture in some cases, and both single and mixedmode testing is used. The results can be represented in terms of either stress intensity or strain energy release rate by simple mixed-mode failure criteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00545482
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Effect of hydrostatic pressure on the yield and fracture of polyethylene in torsion (1981)
    Springer
    Journal of materials science 16 (1981), S. 1689-1699 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Yield and fracture of polyethylene have been studied in torsion tests under superposed hydrostatic pressures. Two ductile-to-brittle transitions have been observed. At high strain rates and pressures, a conventional ductile-to-brittle transition was found with increasing strain rate and pressure. A second ductile-to-brittle transition was observed at low strain rates with decreasing strain rate. The yield stress showed a region of low, relatively constant, rate dependence at low strain rates, high temperatures and low pressures and a second region of higher strain-rate dependence at high strain rates and pressures. In contrast, the fracture stress was found throughout to have a relatively constant strain-rate dependence of intermediate value between those obtained for the yield stress. These features confirmed that failure can be considered as competition between yield and fracture processes. The fracture stress became lower than the yield stress at both high and low strain rates where brittle fracture was observed, with fully ductile behaviour resulting in intermediate conditions where the fracture stress exceeded the yield stress. The pressure, strain rate and temperature dependence of the yield stress was well described by two Eyring processes acting in parallel, both processes being pressure dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396889
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    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Effect of hydrostatic pressure on the yield and fracture of polyethylene in torsion (1981)
    Springer
    Journal of materials science 16 (1981), S. 1689-1699 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Yield and fracture of polyethylene have been studied in torsion tests under superposed hydrostatic pressures. Two ductile-to-brittle transitions have been observed. At high strain rates and pressures, a conventional ductile-to-brittle transition was found with increasing strain rate and pressure. A second ductile-to-brittle transition was observed at low strain rates with decreasing strain rate. The yield stress showed a region of low, relatively constant, rate dependence at low strain rates, high temperatures and low pressures and a second region of higher strain-rate dependence at high strain rates and pressures. In contrast, the fracture stress was found throughout to have a relatively constant strain-rate dependence of intermediate value between those obtained for the yield stress. These features confirmed that failure can be considered as competition between yield and fracture processes. The fracture stress became lower than the yield stress at both high and low strain rates where brittle fracture was observed, with fully ductile behaviour resulting in intermediate conditions where the fracture stress exceeded the yield stress. The pressure, strain rate and temperature dependence of the yield stress was well described by two Eyring processes acting in parallel, both processes being pressure dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553984
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The fracture toughness of tough polyethylenes by a novel high pressure technique (1984)
    Springer
    Journal of materials science 19 (1984), S. 413-422 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The failure of two grades of polyethylene has been studied using the technique of torsion under superposed hydrostatic pressure. The behaviour of unnotched samples of both grades was ductile at all pressures and strain-rates. However, at sufficiently high pressures both grades of polyethylene (including a tough copolymer) failed in a brittle manner when a surface notch was exposed to a suitable pressure fluid. Measurement of fracture stresses for various notch depths lead to a value for a critical stress intensity factor at each of several pressures. A linear extrapolation was then used to estimate the critical stress intensity factor at atmospheric pressure to be 1.11±0.05 MN m−3/2 and 1.68±0.08 MN m−3/2 for the homopolymer and copolymer, respectively. An independent measurement at atmospheric pressure for the homopolymer using compact tension geometry yielded a value of 1.28±0.02 MN m−3/2 confirming the accuracy of the extrapolation procedure and that the effect of the environment on the behaviour was not substantial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02403227
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Influence of molecular weight and branch content on the fracture behaviour of polyethylene (1992)
    Springer
    Journal of materials science 27 (1992), S. 2799-2806 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The fracture behaviour of a range of polyethylenes with different molecular weights and side group content has been studied by means of a novel high-pressure tensile testing facility. The normally ductile specimens became brittle at high pressures, e.g. 700 MPa, so that the test results could be studied by means of linear elastic fracture mechanics. Oriented specimens were prepared by die-drawing to draw ratios of 5∶1 and 9.5∶1. The performance of the isotropic and oriented (longitudinal and transverse directions) materials were assessed using their K IC values. Results were carefully compared in order to study the effects of molecular weight and low concentrations of small side groups on the fracture behaviour of polyethylene. The structure of the oriented polymers was characterised using wide-angle X-ray diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540707
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    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Transitions between crazing, fracture and yield under hydrostatic pressure (1980)
    Springer
    Journal of materials science 15 (1980), S. 2471-2477 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A simple model is proposed to explain transitions from crazing or fracture to shear yielding and vice-versa with increasing superposed pressure. The model is based on an estimate of the local tensile component of stress in the vicinity of a flaw, distinguishing between the different physical situations which arise depending on whether or not the pressurizing medium penetrates the flaw. The model explains naturally many observations of specimens failing in a brittle manner in nominally compressive stress fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550749
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    A double-torsion study of the fracture of polyethersulphone (1984)
    Springer
    Journal of materials science 19 (1984), S. 3796-3805 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fracture studies of polyethersulphone have been undertaken using the double torsion geometry, in particular to establish the effects of ageing and crack speed on fracture toughness. The stability of crack growth was found in all cases to be very dependent on initial notching. If by suitable techniques, e.g. fatigue, a craze was formed at the notch root the subsequent crack growth was found to be stable, with a craze ahead of the growing crack. Under these conditions only a slight dependence of fracture toughness on crack speed was observed, with no significant differences between material aged for 5 years at room temperature and freshly moulded samples. The dimensions of the observed craze were found to be very similar to those of crazes observed in a parallel study using compact tension geometry and lead to comparable values for craze stress and crack opening displacement. In many instances unstable crack growth was observed, often described as “stick-slip”. This was often associated with the absence of a craze at the crack tip, perhaps due to a damage zone created during razor notching. The initiation load and load for crack arrest were determined and used to calculate initiation and arrest values for the fracture toughness as a function of the applied deformation rate. It was found that these values converged at high crosshead speeds to a value independent of ageing, although for the freshly moulded material the initiation values were significantly higher, and the arrest values lower. Electrically conducting grids were used to establish that crack speeds up to 400 m sec−1 occur during stick-slip crack growth. A detailed discussion is presented of conditions required for stable and unstable crack growth in polyethersulphone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02396953
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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