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  • 1
    Electronic Resource
    Electronic Resource
    Thermoreversible gelation of atactic polystyrene solutions (1983)
    s.l. : American Chemical Society
    Macromolecules 16 (1983), S. 28-34 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00235a006
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The mechanical behaviour of thin polyimide films on a silicon substrate under point loading (1989)
    Springer
    Journal of materials science 24 (1989), S. 3273-3279 
    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 technique has been developed to measure submicrometre displacements of a stylus into a thin polymeric film bonded to a rigid structure under point loading. The technique was utilized to study the point-loading behaviour of a thin polyimide film (20μm thick) spun cast on to a silicon wafer as a function of applied load. The displacement against time behaviour, along with the microscopic evidence, indicates that the deformation behaviour follows three regimes. The microscopic evidence suggests that below a contact stress of 0.1 G Pa the material responds in a reversible manner. Progressive increase in the contact stress causes the material to deform in an elasto-plastic fashion. At high contact stresses material flow is exhibited along with crack formation at the boundary of the stylus. At contact stresses greater than 1.29 GPa, failure of the film is observed
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01139052
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  • 3
    Electronic Resource
    Electronic Resource
    Determining fracture toughness of polyethylene from fatigue (1993)
    Springer
    Journal of materials science 28 (1993), S. 2981-2988 
    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 newly developed fatigue method of determining the value of the J-integral at crack initiation, J 1C, was tested on single-edge-notch-tension (SENT) specimens of a high-density polyethylene (HDPE). The fatigue method is able to propagate plane-strain brittle cracks in thin specimens which more closely approximate the “in-use” thickness, and hence the “in-use” morphology, of the polymer. This newly developed fatigue method was compared to ASTM standard procedure E813 (the ASTM method), which employs thick single-edge-notch-bend (SENB) specimens. Because of the similar size and shape of the crack-tip damage zone, the J 1C values for both methods were nearly identical (J 1C=1.8 kJ m−2, 1.4 kJ m−2 for the ASTM method and fatigue method, respectively).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00354703
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    An evaluation of the use of infrared heating for contouring 30% short carbon-fibre-reinforced PEEK (1992)
    Springer
    Journal of materials science 3 (1992), S. 88-94 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The ability to contour reinforced composites at specific points would allow these low modulus, high strength materials to be utilized in a wide variety of new applications. Contourable materials of this type would be especially suitable for orthopaedic applications such as internal fixation of fractures where plate removal due to stress shielding and bone resorption are major concerns. To this end, the high-temperature contourability of 30% short carbon-fibre-reinforced PEEK was investigated. The use of infrared radiation to heat this material to temperatures suitable for contouring was developed and refined into a protocol for heating and bending 12.4×6.4 mm injection-moulded flexural testing bars. To evaluate the heating, contouring and cooling effects of this processing on the material's mechanical and physical properties, five specimen groups were tested: control, extended heat only, cyclical heat only, repeated contouring, and repeated contouring-quenched. Each group's flexural properties, fracture toughness, post-contouring matrix crystallinity and extent of fibre-matrix wetout were monitored. The two heat only groups showed no significant changes in any properties compared to control. For the contoured groups, the quenched subgroup showed a minimal 0–9% decrease in all categories. The non-quenched group showed only a 0–6% change. The resilience of short carbon-fibre-reinforced, PEEK after severe thermo-mechanical cycling is convincing evidence of this material's suitability for structural applications, especially in which contourability and fast processing are required. This study demonstrates the thermoductility of CFR PEEK.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705274
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of residual stress on crack propagation in MDPE pipes (1987)
    Springer
    Journal of materials science 22 (1987), S. 3873-3879 
    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 Crack propagation behaviour in single edge notched specimens prepared from medium-density polyethylene (MDPE) pipe is examined under creep condition. The crack grown from an exterior notch (inbound) initiated faster than that grown from an interior notch (outbound). Subsequently, the outbound crack propagated monotonically to ultimate failure. The inbound crack showed anomalous behaviour involving two arrest stages prior to ultimate failure. The pipe is found to possess substantial residual stresses. The energy release rate for each case was calculated taking into account the respective residual stream distribution. The fact that the rates of crack propagation are not a unique function of the energy release rate indicates that the fracture is also influenced by morphological gradients imposed by processing conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133334
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    On the constancy of the specific enthalpy of fracture (1988)
    Springer
    Journal of materials science 23 (1988), S. 2321-2324 
    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 specific enthalpy of fracture due to ductile crack propagation in commercial polycarbonate sheet is calculated as γ* =A 1c/R 1c, whereA 1c is the critical energy release rate associated with the onset of unstable crack propagation andR 1c is the corresponding amount of damage (yielded material) formed per unit crack extension.A 1c andR 1c are determined from fatigue crack propagation experiments conducted at different maximum loads, load ratios and frequencies. The value of γ* obtained from all experiments is found to be 9.8±1.4 cal g−1 (1cal = 4.184 J) which indicates that γ* is a material constant. This finding substantiates predictions of the crack layer theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01111883
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  • 7
    Electronic Resource
    Electronic Resource
    Damage mechanisms of fatigue fracture in a metastable beta Ti-15-3 alloy (1991)
    Springer
    Journal of materials science 26 (1991), S. 2615-2620 
    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 mechanism of crack tip deformation in metastable beta Ti-15-3 alloy under fatigue loading has been examined. In spite of the small thickness of the test specimens (1 mm), the plastic zone revealed plane strain conditions which was transformed to a plane stress zone when its size became 0.25 of the crack length. Slip processes whose density increased with crack length were the dominant microscopic feature of crack tip plasticity. Microcracks emanating from the main crack appeared as a result of extensive slip damage. Transmission electron microscopy (TEM) and X-ray evidence indicate the absence of twinning or phase transformation and that dislocation processes constitute the microstructural origin of crack propagation resistance in the alloy. Energy calculations show that the specific energy of slip, 20 MJ m−3, exceeds that of microcracking by three orders of magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00545545
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  • 8
    Electronic Resource
    Electronic Resource
    Accelerated fatigue fracture mechanism of medium density polyethylene pipe material (1991)
    Springer
    Journal of materials science 26 (1991), S. 5671-5680 
    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 Fatigue crack propagation studies were performed in medium density polyethylene pipe to elucidate the damage mechanism associated with pipe failure. Past pipe testing methods required up to several years to produce failures which mimicked those observed in the field. However, by fatiguing a specially designed test specimen, brittle failure, resembling that observed under service conditions, was produced in only three days. It was determined that the method of loading and the crack plane orientation greatly affect the degree and extent of brittle crack propagation. In some specimen geometries, the initial brittle fracture may undergo a transition to a more ductile failure mode. The damage which precedes the crack tip during brittle cracking is a root craze and two smaller side crazes; these crazes are primarily composed of yielded membranes which are oriented normal to the crack propagation direction, rather than being composed of fibrils. The number and length of these crazes was shown to be dependent on the chosen test geometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553673
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  • 9
    Electronic Resource
    Electronic Resource
    Accelerated fatigue fracture mechanism of medium density polyethylene pipe material (1991)
    Springer
    Journal of materials science 26 (1991), S. 5671-5680 
    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 Fatigue crack propagation studies were performed in medium density polyethylene pipe to elucidate the damage mechanism associated with pipe failure. Past pipe testing methods required up to several years to produce failures which mimicked those observed in the field. However, by fatiguing a specially designed test specimen, brittle failure, resembling that observed under service conditions, was produced in only three days. It was determined that the method of loading and the crack plane orientation greatly affect the degree and extent of brittle crack propagation. In some specimen geometries, the initial brittle fracture may undergo a transition to a more ductile failure mode. The damage which precedes the crack tip during brittle cracking is a root craze and two smaller side crazes; these crazes are primarily composed of yielded membranes which are oriented normal to the crack propagation direction, rather than being composed of fibrils. The number and length of these crazes was shown to be dependent on the chosen test geometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02403972
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Mechanistic analysis of fatigue crack initiation in medium-density polyethylene (1993)
    Springer
    Journal of materials science 28 (1993), S. 3617-3625 
    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 Kinetics parameters of craze evolution preceding fatigue crack initiation (FCI) in mediumdensity polyethylene (MDPE) pipe materials were determined and analysed within fracture mechanics theory. A single craze initially preceded the notch tip, a root craze, which subsequently became accompanied by a few side crazes. Crack initiation transpired after the craze-zone growth had reached its fully developed configuration. The length of the root craze of the fully developed zone was found to be equal to the length of the first discontinuous crack band on the fracture surface. The growth of the root-craze length and the crack-tip opening displacement (CTOD) followed a power law over the major portion (94%) of the FCI time. Measurable rupture of the craze material was only noted within the final portion of the FCI time and was associated with exponential increase of the CTOD. The Dugdale/Barenblatt model overestimated the craze length by 30% and underestimated the CTOD by 50% which was hypothesized to be due to multiple crazing at the notch tip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01159845
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    Paper (German National Licenses)
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