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  • 1980-1984  (12)
  • 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
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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)
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  • 4
    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)
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  • 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/BF00553984
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    Paper (German National Licenses)
    Fulltext
  • 6
    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
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    Paper (German National Licenses)
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  • 7
    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
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    Paper (German National Licenses)
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  • 8
    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
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    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    A novel technique for measuring the impact properties of a tough polyethylene (1983)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 708-712 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A novel technique is described which enables reliable fracture toughness measurements to be made in impact test on relatively small specimens of a tough polyethylene. Composite specimens have been made in which a tough polyethylene is sandwiched between two layers of a more brittle polyethylene. The overall fracture toughness is interpreted on the basis of simple additivity of the strain energy release rate associated with each of the component layers. Brittle plane strain failures were obtained for specimens in which the relative thickness of the layers was varied over a substantial range and the fracture toughness of each layer determined by suitable extrapolation. The fracture toughness of the brittle layer obtained in this way agreed well with direct measurements on that material.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760231304
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    A study of the drawing behavior of poly(ethylene terephthalate) (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 25 (1980), S. 1381-1390 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Cold-drawn and hot-drawn samples of poly(ethylene terephthalate) were studied by means of measurements of shrinkage stress, birefringence and differential scanning calorimetry (DSC). The values of shrinkage stress were comparable for both types of sample, implying that the deformation of a molecular network is important for both cold drawing and hot drawing. The DSC results indicate that substantial crystallization occurs in hot drawing for other than the lowest draw ratios, and this crystallization gives rise to an additional peak in the shrinkage stress measurements. In addition to temperature, strain rate is also an important variable, and changes in strain rate caused significant changes in both hot-drawn and cold-drawn samples.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1980.070250712
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    Paper (German National Licenses)
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