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  • 1
    Electronic Resource
    Electronic Resource
    Influence of atmospheric moisture on slow fatigue crack growth at ultrasonic frequency in aluminium and magnesium alloys (2002)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 25 (2002), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The deleterious influence of atmospheric moisture on the fatigue properties of an aluminium wrought alloy AlZnMgCu1.5-T6, an aluminium cast alloy AlSi9Cu3 and magnesium cast alloys AM60 hp, AZ91 hp and AS21 hp has been studied at a cycling frequency of 20 kHz. Atmospheric moisture accelerates fatigue crack growth and decreases the threshold stress intensities to 55–75% of the respective values in vacuum. In ambient air, fatigue crack growth rates were up to two decades higher than those in vacuum. Accelerated crack growth was found at propagation rates below about 2 × 10−9 m cycle−1 in aluminium alloys and below about 3 × 10−8 m cycle−1 in magnesium alloys. As the threshold regime is approached, fatigue cracks in ambient air either propagate at a minimum mean growth rate on average of approximately one lattice spacing per cycle or they stop propagating, whereas mean growth rates of 10−12 m cycle−1 were found in vacuum. Crack initiation and slow fatigue crack growth mainly determine lifetimes in the high cycle regime, and endurance data obtained at ultrasonic frequency in ambient air of 40–60% relative humidity are similar to lifetimes measured at conventional frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.2002.00571.x
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  • 2
    Electronic Resource
    Electronic Resource
    FATIGUE CRACK GROWTH BEHAVIOUR OF FIBRE-METAL LAMINATE GLARE-1 AND METAL LAMINATE 7475 WITH DIFFERENT BLUNT NOTCHES (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 20 (1997), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The fatigue crack growth behaviour of the fibre metal laminate “GLARE-1” has been investigated for different blunt notches in Constant Amplitude (CA) tests. In order to investigate the influence of the fibres, the same laminate material but containing no fibres (Laminate 7475) was also tested. The fatigue crack growth properties of GLARE-1 are superior to those of Laminate 7475. GLARE-1 shows lower crack growth velocities at the same Knom values and in addition the crack growth rates decrease with increasing crack length. The Laminate 7475 shows typical metal behaviour for single crack propagation and accelerating crack growth with increasing crack length. In GLARE-1, multiple crack propagation takes place. The cracks propagate independent of each other and have similar crack growth rates, in part due to closure effects caused by the unbroken fibre layers.The crack growth rates of specimens having a small root radius are higher in both materials than in specimens with a large notch radius. In GLARE-1, the superiority of a larger notch radius is more pronounced than in the Laminate 7475 and is attributed to a stronger crack closure effect owing to fibre bridging. The reason for the higher bridging capability in specimens containing larger notches is that less fibres are broken or damaged in the notch vicinity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1997.tb01512.x
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  • 3
    Electronic Resource
    Electronic Resource
    INFLUENCE OF TRANSFORMATION-INDUCED CRACK CLOSURE ON SLOW FATIGUE CRACK GROWTH UNDER VARIABLE AMPLITUDE LOADING (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 18 (1995), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fatigue crack growth under constant and random loading conditions was investigated for a metastable austenitic-bainitic steel in comparison with a ferritic chromium steel at very low crack growth rates. Experimentally determined random crack growth was compared with linear Miner calculations on the basis of constant amplitude results. It was found that the measured crack growth rates in transforming material are a factor of 10 lower than the calculated values, whereas the difference is only a factor of 2 for the ferritic steel. The reason for the pronounced crack growth retardation in the metastable alloy is transformation of part of the austenitic phase into martensite in the stress field of the crack tip, accompanied by a volume increase and, consequently, residual compressive stresses. Rare high load cycles in the random sequence increase the closure level, which then leads to pronounced retardation of fatigue crack growth for the numerous successive low amplitude cycles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.1995.tb00918.x
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  • 4
    Electronic Resource
    Electronic Resource
    Variable amplitude loading in the very high-cycle fatigue regime (2002)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 25 (2002), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Ultrasonic fatigue testing is appropriate to perform random loading tests in the regime of very high numbers of cycles. It has been shown that neither an endurance limit nor a threshold stress intensity exists under loading with randomly varying amplitudes even for materials that do show these limits under constant amplitude loading conditions. The technical features of the ultrasonic testing technique in order to perform random fatigue tests are shortly described. Endurance tests were performed on smooth specimens of AlSi7Mg (A356.0) aluminium alloy and on notched AISI 4142 and C45 steel specimens. The previous studies of crack propagation and threshold behaviour on AISI 420 ferritic chromium steel and GGG 100-B cast iron are included. Experimental results on lifetime and fatigue crack growth measurements under randomly varying amplitudes, as well as lifetime predictions, based on constant amplitude measurements and damage accumulation calculations are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.2002.00570.x
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  • 5
    Electronic Resource
    Electronic Resource
    In-vitro evaluation of fatigue failure of locking screws in solid tibial nails (1999)
    Springer
    Der Unfallchirurg 102 (1999), S. 29-34 
    Details
    ISSN: 1433-044X
    Keywords: Key words Solid tibial nail • Locking screws • Fatigue failure • Mechanical fatigue testing ; Schlüsselwörter Solide Tibianägel • Verriegelungsbolzen • Ermüdungsbrüche • Biegeschwellfestigkeitsprüfung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Im Rahmen der Frakturbehandlung mit soliden Tibianägeln in unaufgebohrter Technik sind Ermüdungsbrüche der Verriegelungsbolzen wesentlich häufiger als ein Versagen des Verriegelungsnagels selbst. Infolge dieser Ermüdungsbrüche sind konsekutive Reoperationen oder zumindest eine verminderte Belastung der stabilisierten Extremität bis zur knöchernen Konsolidierung erforderlich. Anhand einer Materialprüfungsstudie wurden Verriegelungsbolzen 6 unterschiedlicher solider Tibianägel (biorigider Tibianagel/aap, UTN/ace, STN/Howmedica, TLN/Howmedica, ΔR & T-Tibianagel/Smith & Nephew, AO/ASIF UTN/Synthes) einer Biegeschwellbelastung unterzogen, die jener im Knochen-Implantat-Verbund zu erwartenden entspricht. Unsere Ergebnisse zeigten einerseits die direkte Korrelation des Bolzendurchmessers im Vergleich zur Ermüdungsfestigkeit des Implantates und andererseits das Faktum, daß Bolzen selben Durchmessers mit einem durchgehenden Gewinde eine signifikant niedrigere Lebensdauer aufweisen als Bolzen mit einem kopfnahen bzw. kopffernen Gewinde. Anhand unserer Ergebnisse konnten wir folgern, daß bis zum Erreichen der knöchernen Konsoliderung mit allen geprüften Implantaten, unter Verwendung der vorgesehenen Anzahl an Verriegelungsbolzen eine Mobilisierung mit halbem durchschnittlichen Körpergewicht von 35 kg möglich ist, ohne daß es zum Ermüdungsbruch der Verriegelungsbolzen kommt. Mit einigen der getesteten Implantate ist eine Mobilisierung mit vollem Körpergewicht möglich, allerdings ohne eine zusätzliche Belastung, wie es z. B. ein Laufmuster darstellt, zu erlauben.
    Notes: Summary Unreamed nailing with solid tibial nails is an accepted method of treatment for open tibial shaft fractures up to grade III and of closed tibial fractures with severe soft tissue damage. However, fatigue failure of the distal locking bolts is a frequent complication. We report a mechanical study investigating the fatigue limit of six different types of locking bolts used in solid tibial nails (Biorigid Tibial nail/aap, UTN/ace, STN/Howmedica, TLN/Howmedica, ΔR & T Tibial nail/Smith & Nephew, AO/ASIF UTN/Synthes). Our results prove a direct correlation between the bolt's diameter and mechanical properties. Further more we found that bolts with a continuing thread were weaker than bolts of the same diameter with only a short thread and an increased diameter at the nail's aperture. Our results suggest that mobilization with half of the average body weight (350N) allows osseous consolidation without fatigue failure of any of the tested locking bolts. Some of the tested locking bolts may even withstand full weight-bearing in a physiological walking cycle, but will not withstand the stress of a running cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001130050369
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  • 6
    Electronic Resource
    Electronic Resource
    Spiral angle of elementary cellulose fibrils in cell walls ofPicea abies determined by small-angle x-ray scattering (1998)
    Springer
    Wood science and technology 32 (1998), S. 335-345 
    Details
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The spiral angle of the elementary cellulose fibril in the wood cell wall, often called microfibril angle, is of primary importance for the mechanical properties of wood. While there are a number of methods to estimate this angle, x-ray diffraction (XRD) techniques have recently obtained a lot of attention because of their ability to provide information averaged over a significantly large specimen volume. Here, we present results from a related method, small-angle x-ray scattering (SAXS). The advantage of SAXS is that, unlike XRD, it does not require any assumption on the orientation of the cellulose crystal axis with respect to the fibril axis. Full three-dimensional scattering patterns were collected using an area detector by rotating the sample around one axis. The distribution of fibrillar orientations was seen to reflect the typical cross-sectional shape of the tracheids (square or circular). In the stem, the spiral angle was found 〈5° in earlywood and ≈20° in latewood. In branches the angle was ≈30° in the upper part and ≈40° in the lower part, which strongly supports the idea that the spiral angle has primarily mechanical function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702790
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of crack propagation in particleboard (1996)
    Springer
    Wood science and technology 30 (1996), S. 307-321 
    Details
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary In this paper the wedge-splitting-method (Tschegg 1986) for mode I-testing was applied to specimens of particleboard. Specimen geometry and loading-device used for this method allow testing under the condition of steady state crack propagation. Therefore the full load-displacement curves can be recorded. Using the loaddisplacement-curves, different ways of evaluation have been carried out to determine relevant fracture properties like the specific fracture energy Gf and the crack resistance Rc of the investigated material for two different orientations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223551
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  • 8
    Electronic Resource
    Electronic Resource
    Fracture characteristics of PARALLAM® PSL in comparison to solid wood and particleboard (1998)
    Springer
    Wood science and technology 32 (1998), S. 43-55 
    Details
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Typical fracture characteristic values like load-displacement curve and specific fracture energy of the new wood laminate compound PARALLAM® PSL were determined by using the wedge splitting technique. Comparison with the values of solid wood and particleboard showed the superiority of this wood composite in both “weak” transverse orientations. This result is explained by the favourably oriented wood strands in PARALLAM® PSL with a length up to 2.6 m, which give rise to crack arresting mechanisms. In addition the influence of specimen geometry on the critical load and corresponding loadpoint-displacement at crack initiation was calculated for both isotropic and orthotropic materials using linear elastic FE-models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702559
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  • 9
    Electronic Resource
    Electronic Resource
    Mode III fracture energy of wood composites in comparison to solid wood (1999)
    Springer
    Wood science and technology 33 (1999), S. 391-405 
    Details
    ISSN: 0043-7719
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A simple experimental setup for mode III and mixed mode (I + III) fracture tests with anisotropic materials under steady state crack propagation has been developed. Load-displacement curves can be recorded up to the complete separation of the specimen. From the load-displacement curves several mechanical material parameters can be derived. The tests have been performed for solid wood and different wood composites, being PARALLAM® PSL in different orientations, particleboard and INTRALLAM® LSL, and the fracture behaviour is characterised by the specific fracture energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002260050125
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  • 10
    Electronic Resource
    Electronic Resource
    Fracture characteristics of PARALLAM® PSL in comparison to solid wood and particleboard (1998)
    Springer
    Wood science and technology 32 (1998), S. 43-55 
    Details
    ISSN: 0043-7719
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Typical fracture characteristic values like load-displacement curve and specific fracture energy of the new wood laminate compound PARALLAM® PSL were determined by using the wedge splitting technique. Comparison with the values of solid wood and particleboard showed the superiority of this wood composite in both “weak” transverse orientations. This result is explained by the favourably oriented wood strands in PARALLAM® PSL with a length up to 2.6 m, which give rise to crack arresting mechanisms. In addition the influence of specimen geometry on the critical load and corresponding loadpoint-displacement at crack initiation was calculated for both isotropic and orthotropic materials using linear elastic FE-models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002260050058
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