Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 21 (1986), S. 4081-4088 
    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 crack opening displacement against time was measured in linear polyethylene as a function of stress, notch depth, and temperature for three-point bending under plane strain conditions. The experimental conditions were accurately controlled so that the scatter in the rate of damage was within ±20%. Microscopic observations showed that the shape of the damaged zone was triangular for stresses less than one-half the yield point and that the length was predictable from measurements of the crack opening displacement. The initial rate of damage prior to crack growth was constant up to crack opening displacement = 15 to 25Μm. The entire shape of the crack opening displacement-time curve and the time to complete failure could be predicted from the initial damage rate. A theory based on the observed microcrazing is presented which explains the dependence of damage rate on stress intensity and microstructural parameters.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 21 (1986), S. 2423-2429 
    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 rate of notch opening was observed in single-edge notched tension specimens of linear high-density polyethylene under plane strain conditions as a function of applied stress and notch depth. The initial rate of notch opening was 22K 4.3 μm min−1 (where units ofK are MN m−3/2). The initial rate of notch opening was constant until the opening at its root was 25 to 30μm for all stresses and notch depths. The accelerating part of the notch opening against time curve and the time to failure could be predicted from the initial rate of notch opening. It is concluded that the same mechanism governs the initiation stage and the subsequent crack growth rate.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 24 (1989), S. 2467-2472 
    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 existence of a threshold stress intensity for failure by slow crack growth under plane strain conditions for single-edge notched tensile specimens and for three-point bending was investigated at 42° C. It was found that the threshold for the nucleation of damage was between 0.074 and 0.063 MPa m1/2 and the threshold for complete failure was about 0.08 MPam1/2.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 25 (1990), S. 411-416 
    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 failures of ethylene-hexene copolymer single-edge notch tensile specimens were observed under a constant tensile load. The notch opening was measured against time over a range of stress. Three failure modes were observed: ductile, brittle and transitional. The microscopic changes at the notch tip were correlated with each of the modes of failure. Early in the test the ultimate mode of failure can be predicted from the microstructural changes in the notch. In the transition region, the lifetime increases as the stress increases because the blunting of the notch offsets the effect of the applied stress-stress field. The ductile failure is controlled by the macroscopic creep behaviour and the brittle failure occurs by slow crack growth that starts at a craze.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 23 (1988), S. 643-648 
    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 slow crack-growth behaviours of a high-density polyethylene and an ethylene-hexene copolymer with 4.5 butyl chains per 1000 carbon atoms are compared. The slow crack-growth rate in the copolymer is about 102 to 103 times slower than for the homopolymer. The two polymers are compared with respect to their kinetics of slow crack growth, the morphology of the damage zone that grows from a notch, the stress-strain behaviour and the temperature dependence of the rate of damage. The results suggest that the major effect of the butyl branches is to decrease the rate of disentanglement which governs the process of slow crack growth.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 25 (1990), S. 29-34 
    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 ductile-brittle transition of an ethylene-hexene copolymer was measured from 80 to 24° C. The basic curves of stress against time to failure could all be unified in terms of a single equation based on normalizing the stress relative to the transition stress between the ductile and brittle regions and using a single thermal activation parameter. This unity is based on the observations which show that the ductile and brittle failure processes are both associated with a shear process. The unifying equation is $$\left( {\frac{\sigma }{{\sigma _{\text{c}} }}} \right)^n = \left( {\frac{{t_{\text{R}} }}{{t_{\text{f}} }}} \right){\text{ exp }}\left[ {{\text{85 500/}}R\left( {\frac{1}{T} - \frac{1}{{T_{\text{R}} }}} \right)} \right]$$ where σ c is the minimum stress for ductile failure at an arbitrary temperature, T R; t R is the time to failure at an arbitrary reference temperature T R; n equals 34 and 3.3 for the ductile and brittle regions, respectively and R is in J mol−1 K−1.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 21 (1986), S. 4081-4088 
    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 crack opening displacement against time was measured in linear polyethylene as a function of stress, notch depth, and temperature for three-point bending under plane strain conditions. The experimental conditions were accurately controlled so that the scatter in the rate of damage was within ±20%. Microscopic observations showed that the shape of the damaged zone was triangular for stresses less than one-half the yield point and that the length was predictable from measurements of the crack opening displacement. The initial rate of damage prior to crack growth was constant up to crack opening displacement = 15 to 25Μm. The entire shape of the crack opening displacement-time curve and the time to complete failure could be predicted from the initial damage rate. A theory based on the observed microcrazing is presented which explains the dependence of damage rate on stress intensity and microstructural parameters.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2349-2354 
    ISSN: 0887-6266
    Keywords: polyethylene ; slow crack growth ; γ-irradiation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of γ-irradiation on slow crack growth (SCG) in a medium density polyethylene (MDPE) was measured and compared with behavior of high density polyethylene (HDPE) and a recrystallized HDPE (RCHDPE). The three materials exhibited the same dependence on dose up to 3 Mrd. The HDPE became brittle above 50 Mrd. The resistance to SCG of MDPE and RCHDPE increased very rapidly with dose above 3 Mrd, until at 50-80 Mrd their resistance to SCG became extraordinarily high. This high resistance to SCG was accompanied by a transition from crazing to shear deformation at the root of a notch. It was found that for the same concentration, crosslinks are more effective than short chain branches for increasing resistance to SCG. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2349-2354, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 109-115 
    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: Slow crack growth was measured in the perpendicular and parallel directions relative to the extrusion direction of the pipe. For five pipes from different manufacturers, the anisotropy factor, the lifetime to fracture in the perpendicular direction divided by lifetime in the parallel direction, varied from 1.2 to 4.7 for complete fracture and 1.4 to 4.0 for crack initiation. The degree of molecular orientation was determined by measuring the shrinkage that occured when a pipe specimen was heated near its melting point. The amount of shrinkage correlated with the anisotropy factor for slow crack growth. The shape change after shrinkage was related to the flow pattern of the resin during extrusion and the cooling rate after extrusion.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 1175-1179 
    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: The time for brittle failure by slow crack growth for 22 polyethylene copolymers was measured in Igepal and air. The notched tensile tests were conducted in Igepal and air at 50°C and 4.2 MPa and in air at 80°C and 2.4 MPa. For failure times less than 103 min, the difference between the Igepal and air environments was not measurable. As the failure time increased beyond 103 min, the ratio of failure in air compared to that in Igepal increased so that for the very highest failure times of 5 × 105 to 108 min in air, the failure time in Igepal was reduced by 25 - 50 times. The correlation between the Igepal and air tests was generally good with respect to all types of polyethylene. However, a separation of the polyethylenes with respect to their comonomer, butene, hexene, or octene improved the correlation. The resistance to slow crack growth of all the current commercial polyethylene copolymers can be assessed by a notched tensile test in Igepal in about a week or less.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...