ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
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
    Fracture of synthetic diamond (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 3083-3088 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fracture behavior of synthetic diamond has been investigated using indentation methods and by the tensile testing of pre-notched fracture-mechanics type samples. Specifically, the fracture toughness of free-standing diamond plates, grown by chemically-vapor deposited (CVD) methods, was measured using Vickers indentations and by the use of disk-shaped compact-tension specimens; the latter method provides an evaluation of the through-thickness fracture properties, whereas the indentation method was performed on the nucleation surface of the sample. Measured fracture toughness (Kc) values were found to be approximately 5–6 MPa(square root of)m by both methods, indicating that the fracture resistance of CVD diamond does not vary appreciably with grain size (within the certainty of the testing procedures). Complications, however, arose with the fracture-mechanics testing regarding crack initiation from a relatively blunt notch; further work is needed to develop pre-cracking methods to permit more reliable fracture toughness testing of diamond. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360060
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Cyclic fatigue-crack growth behaviour of short cracks in SiC-reinforced lithium aluminosilicate glass-ceramic composite (1990)
    Springer
    Journal of materials science 9 (1990), S. 719-725 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00721814
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Cyclic fatigue-crack propagation in a silicon carbide whisker-reinforced alumina composite: role of load ratio (1993)
    Springer
    Journal of materials science 28 (1993), S. 3258-3266 
    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 characteristics of subcritical crack growth by cyclic fatigue have been examined in a silicon carbide whisker-reinforced alumina composite, with specific reference to the role of load ratio (ratio of minimum to maximum applied stress intensity, R=K min/K max); results are compared with similar subcritical crack-growth data obtained under constant load conditions (static fatigue). Using compact-tension samples cycled at ambient temperatures, cyclic fatigue-crack growth has been measured over six orders of magnitude from ∼10−11–10−5 m cycle−1 at load ratios ranging from 0.05–0.5. Growth rates (da/dN) display an approximate Paris power-law dependence on the applied stress-intensity range (ΔK), with an exponent varying between 33 and 50. Growth-rate behaviour is found to be strongly dependent upon load ratio; the fatigue threshold, ΔK TH, for example, is found to be increased by over 80% at R=0.05 compared to R=0.5. These results are rationalized in terms of a far greater dependency of growth rates on K max(da/dN ∞ K max 30 ) compared to ΔK(da/dN ∞ ΔK 5), in contrast to fatigue behaviour in metallic materials where generally the reverse is true. Micromechanisms of crack advance underlying such behaviour are discussed in terms of timedependent crack bridging involving either matrix grains or unbroken whiskers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00354244
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Cyclic fatigue in monolithic alumina: mechanisms for crack advance promoted by frictional wear of grain bridges (1995)
    Springer
    Journal of materials science 30 (1995), S. 643-654 
    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 microstructural basis of cyclic fatigue-crack propagation in monolithic alumina has been investigated experimentally and theoretically. A true cyclic fatigue effect has been verified, distinct from environmentally assisted slow crack growth (static fatigue). Microstructures with smaller grain sizes were found to promote faster crack-growth rates; growth rates were also increased at higher load ratios (i.e. ratio of minimum to maximum applied loads). Using in situ crack-path analysis performed on a tensile loading stage mounted in the scanning electron microscope, grain bridging was observed to be the primary source of toughening by crack-tip shielding. In fact, crack advance under cyclic fatigue appeared to result from a decrease in the shielding capacity of these bridges commensurate with oscillatory loading. It is proposed that the primary source of this degradation is frictional wear at the boundaries of the bridging grains, consistent with recently proposed bridging/degradation models, and as seen via fractographic and in situ analyses; specifically, load versus crack-openingdisplacement hysteresis loops can be measured and related to the irreversible energy losses corresponding to this phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356324
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Fatigue-crack propagation behavior in monolithic and composite ceramics and intermetallics (1995)
    Springer
    Materials science 30 (1995), S. 277-300 
    Details
    ISSN: 1573-885X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We study microstructural mechanisms of fatigue crack growth in advanced monolithic and composite ceramics and intermetallics. Much attention is devoted to the contribution of cycling loading to the hindrance of mechanisms that lead to a considerable increase in toughness (crack-tip shielding) of these materials. For example, in intermetallics with a ductile phase, such as β-TiNb-reinforced γ-TiAl or Nb-reinforced Nb3Al, a significant increase in toughness caused by the presence of uncracked ductile phase inside a crack is retarded under cyclic loading because ductile particles immediately fail by fatigue. Similarly, in monolithic ceramics, e.g., in alumina (aluminum oxide) or silicon nitride, the significant plasticization appearing under monotonic loading is greatly diminished under cyclic loading due to gradual wear at the grain-matrix interface. In fact, the nature of fatigue in such low-plasticity materials differs essentially from the well-known mechanisms of fatigue in metals and is governed, first of all, by a decrease in shielding, which depends on the loading cycle and time. The susceptibility of intermetallics and ceramics to fatigue degradation under cyclic loading affects seriously the possibility of structural use of these materials in practice. In particular, in this case, it is difficult to apply strength calculation methods that take into account the presence of defects and to implement life-prediction procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00569681
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Toughness and fatigue of encapsulation-processed silicon carbide-polymer matrix particulate composites (1993)
    Springer
    Journal of materials science 28 (1993), S. 2196-2206 
    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 new process for composite fabrication was developed which improves distribution of the particulate reinforcing phase by polymer encapsulation of the particulate prior to consolidation. The effect of such processing on the fatigue-crack propagation and fracture toughness behaviour of particulate thermoplastic composites was investigated. Composites of several particulate size ranges were fabricated into disc-shaped, compact tension specimens and tested under cyclic and monotonie loading conditions. For comparison, a composite was also fabricated using a standard casting technique. The observed fatigue-crack growth rates spanned three orders of magnitude (10−11 to 10−9 m per cycle) over an applied stress intensity range, ΔK, of 0.3 to 1.1 MPa m1/2. The measured fracture toughness values ranged from 0.69 to 2.95 MPa m1/2. Comparison of the two processing techniques indicated that encapsulation processing increased the fracture toughness of the composite by approximately 33%; however, the fatigue-crack growth behaviour was unaffected. In addition, a trend of increasing crack growth resistance (toughness) with increasing reinforcement particle size was observed. These results are discussed in the light of crack shielding and bridging models for composite toughening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367584
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Grain size effects on cyclic fatigue and crack-growth resistance behaviour of partially stabilized zirconia (1995)
    Springer
    Journal of materials science 30 (1995), S. 3291-3299 
    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 Cyclic fatigue crack growth and crack-resistance behaviour was studied in partially stabilized zirconia (PSZ) with three different cubic-phase grain sizes following sub-eutectoid heat treatments. Raman spectroscopy was used to determine the extent of phase transformation around the cracks for both cyclic and monotonic loading conditions. All tests were on “long”, through thickness cracks using compact-tension specimens. Predictions of crack-tip shielding were made following determination of toughening parameters using crackresistance data. It was found that the dominant factors affecting cyclic fatigue-crack growth were the level of crack-tip shielding, as a result of phase transformation, and the intrinsic toughness of the material. Grain size did not appear to significantly affect fatigue crack-growth behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349872
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Reliability of PMMA bone cement fixation: fracture and fatigue crack-growth behaviour (1997)
    Springer
    Journal of materials science 8 (1997), S. 473-483 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Fracture mechanics tests were performed to characterize the fracture toughness and fatigue crack-growth behaviour of polymethylmethacrylate (PMMA) bone cement, commonly used in joint replacement surgery. Compact tension specimens of various thicknesses were prepared and tested in both air and Ringer’s solution. Contrary to previous reports citing toughness as a single valued parameter, the PMMA was found to exhibit resistance-curve behaviour with a plateau toughness of ∼0.6 MPa m1/2 in air, and ∼2.0 MPa m1/2 in Ringer’s solution. The increased toughness in Ringer’s solution is thought to arise from the plasticizing effect of the environment. Under cyclic loads, the material displayed true mechanical fatigue failure in both environments; fatigue crack-growth rates, da/dN, were measured over the range ∼10-10 to 10-6 m/cycle and found to display a power-law dependence on the stress intensity range, ΔK. The cement was found to be more resistant to fatigue-crack propagation in Ringer’s solution than in air. Wear debris was observed on the fatigue fracture surfaces, particularly those produced in air. These findings and the validity of using a linear-elastic fracture mechanics approach for viscoelastic materials are discussed in the context of providing more reliable and fracture-resistant cemented joints.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018574109544
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Mechanical properties of carbonated apatite bone mineral substitute: strength, fracture and fatigue behaviour (1997)
    Springer
    Journal of materials science 8 (1997), S. 559-570 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The synthesis and properties of carbonated apatite materials have received considerable attention due to their importance for medical and dental applications. Such apatites closely resemble the mineral phase of bone, exhibiting superior osteoconductive and osteogenic properties. When formed at physiological temperature they present significant potential for bone repair and fracture fixation. The present study investigates the mechanical properties of a carbonated apatite cancellous bone cement. Flexural strength was measured in three and four point bending, and the fracture toughness and fatigue crack-growth behaviour was measured using chevron and disc-shaped compact tension specimens. The average flexural strength was found to be ∼0.468 MPa, and the fracture toughness was ∼0.14 MPa√m. Fatigue crack-growth rates exhibited a power law dependence on the applied stress intensity range with a crack growth exponent m=17. The fatigue threshold value was found to be ∼0.085 MPa√m. The mechanical properties exhibited by the carbonated apatite were found to be similar to those of other brittle cellular foams. Toughness values and fatigue crack-growth thresholds were compared to other brittle foams, bone and ceramic materials. Implications for structural integrity and longer term reliability are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018550831834
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Cyclic fatigue and fracture in pyrolytic carbon-coated graphite mechanical heart-valve prostheses: Role of small cracks in life prediction (1994)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 791-804 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A fracture-mechanics based study has performed to characterize the fracture toughness and rates of cyclic fatiguecrack growth of incipient flaws in prosthetic heart-valve components made of pyrolytic carbon-coated graphite. Such data are required to predict the safe structural lifetime of mechanical heart-valve prostheses using damagetolerant analysis. Unlike previous studies where fatiguecrack propagation data were obtained using through thickness, long cracks (∼2-20 mm long), growing in conventional (e.g., compact-tension) samples, experiments were performed on physically small cracks (∼100-600 μm long), initiated on the surface of the pyrolytic-carbon coating to simulate reality. Small-crack toughness results were found to agree closely with those measured conventionally with long cracks. However, similar to well-known observations in metal fatigue, it was found that based on the usual computations of the applied (far-field) driving force in terms of the maximum stress intensity, Kmax, small fatigue cracks grew at rates that exceeded those of long cracks at the same applied stress intensity, and displayed a negative dependency on Kmax; moreover, they grew at applied stress intensities less than the fatigue threshold value, below which long cracks are presumed dormant. To resolve this apparent discrepancy, it is shown that long and small crack results can be normalized, provided growth rates are characterized in terms of the total (near-tip) stress intensity (incorporating, for example, the effect of residual stress); with this achieved, in principle, either form of data can be used for life prediction of implant devices. Inspection of the long and small crack results reveals extensive scatter inherent in both forms of growth-rate data for the pyrolytic-carbon material. © 1994 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820280706
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...