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  • 1
    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 By employing a single thick molybdenum fibre-copper matrix composite with very weak interfacial bonding, it was confirmed that flow stress, internal stress, effective stress and change in flow stress due to change in strain rate of the composite obey the simple rule of mixtures; strain-hardening exponent, stress exponent of strain rate, effective stress exponent of dislocation velocity and activation volume obey the modified rule of mixtures in the whole range of plastic deformation of the composite. This means that the inherent features of the fibre in the present composite were conserved beyond the failure strain of the fibre tested alone, and the above deformation parameters of the composite were, to a first approximation, determined by the inherent parameters of the fibre and the matrix.
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  • 2
    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 embedded molybdenum fibre in a copper matrix composite was elongated apparently uniformly although the interface was so weak that necking in the fibre could not be suppressed by the matrix. To explain this result, a possible mechanism was suggested where suppression of necking in the fibre is caused by strain hardening of the composite as a whole and by an increment in strain rate in the cross-section where the fibre starts necking, but the incremental deformation amount and the incremental strain rate of the cross-section are small. On the basis of this mechanism, and with the aid of Hart's criterion, a new instability approach to tensile behaviour of the composite is presented. It was found that the stability of the composite is determined mainly by the strain-hardening exponent of the composite, which is determined by the modified rule of mixtures. The present derived condition of instability of the composite is in good agreement with that proposed by Mileiko.
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  • 3
    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 fracture behaviour of centre-notched (0/± 45/0)S and (0/90)2S laminates with increasing notch length has been studied. Two test series have been investigated: specimens of constant width (W=20 mm) and small notch length (2a ⩽ 12 mm), and specimens with various notch lengths (5 ⩽ 2a ⩽ 35 mm) and a constant relative notch length (2a/W=0.5). An X-ray technique showed that the damage at the notch tip, which is formed at increasing load, consists mainly of subcracks parallel to the fibres of the constituent layers. The damage zone causes the crack opening displacement (COD) to deviate from the original linearity. TheK R curve concept has been applied assuming that the COD deviation from linearity is completely the result of original crack extension. This approach fails to describe the notch length effect, because a tangent point between theK R andK curves was not found and because of a strong dependency of the maximum fracture resistanceK Rmax on notch length. The fracture behaviour of 20 mm wide specimens could be explained with the point and average stress criteria, based on characteristic lengths which are independent of notch length. At various notch lengths at a constant 2a/W=0.5, however, the characteristic lengths increased with increasing notch length.
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  • 4
    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 An experimental study was carried out on the effects of notch length, specimen thickness, ply thickness and type of defect (centre-notch or hole) on the fracture toughness of graphite-epoxy composites with lay-up sequences of 0/±45°/0 and 0/90°. Three fracture-mechanical concepts were applied: the Waddoups-Eisenmann-Kaminski (WEK) model, the Whitney-Nuismer model (point and average stress cirteria) and the K R-curve method. An increase of notch length as well as an increase of ply thickness led to a higher toughness, whereas a change in specimen thickness did not noticeably affect the toughness. Furthermore, the hole caused a smaller strength reduction than a notch. The applicability of the above-mentioned concepts is probably restricted mainly because of the fact that they do not, or do only insufficiently, regard the damage zone near the border of the defect, if a large damage zone usually leads to larger material parameters of the investigated concepts, namely the inherent flaw size, the characteristic lengths of the point and average stress criterions and the K R -value at fracture.
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  • 5
    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 structure of a Fe90Zr10 amorphous alloy was investigated by means of small angle X-ray scattering as well as large-angle diffraction measurements. For as-quenched specimens, SAXS was found to be relatively weak, but spread over a wide scattering angle. After quantitative analysis, it was concluded that a compositional fluctuation occurs on a fine scale of about 0.6 nm. When the specimen was heat treated below the crystallization temperature, the amorphous structure changed to a more stable dual structure consisting of pure iron and a structure similar to Fe3Zr. By prolonged heat treatment, the iron-rich regions crystallized initially from the amorphous state. An apparent correspondence was found to exist between the changes in the amorphous structure and in the mechanical properties. The microscopic phase separation within the amorphous state resulted in an increase of ultimate tensile strength and fracture toughness. The deterioration of mechanical properties was suggested to be attributed to the gradual crystallization of iron-rich regions.
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  • 6
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Inclusive Λ production in $$\bar p$$ p interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c is studied. The inclusive cross sections for Λ and Λ $$\bar \Lambda $$ production are measured. The differential cross sections as functions ofx, y, andP T 2 are given for each beam momentum. It is found that the contribution of indirect production of Λ from resonance decay is considerably enhanced in the region of higher missing mass against Λ. The negative polarization is observed for Λ with largerP T and lower missing mass, and is found to be mainly from two body reactions. Inclusive cross sections for∑ ±(1385) production and the fraction of indirect Λ from∑ ±(1385) decay are measured. The ratio between the cross sections for∑ +(1385) and∑ −(1385) productions is found to be almost constant for wide range of beam momenta.
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  • 7
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract InclusiveK s 0 andK s 0 K s 0 production in $$\bar pp$$ interactions at 3.0, 3.5, 4.0 and 4.5 GeV/c are studied. Cross sections ofK s 0 , K s 0 K s 0 andK *±(892) are presented for each incident momentum. The production ofK s 0 andK *±(892) through annihilation process is investigated. It is found that the annihilation process is dominant but decreases with incident momentum. The annihilation process is compared withe + e − interactions. Remarkable similarity between them is found in the $${{x_0 = 2E(K_s^0 )} \mathord{\left/ {\vphantom {{x_0 = 2E(K_s^0 )} {\sqrt s }}} \right. \kern-\nulldelimiterspace} {\sqrt s }}$$ distribution. Events with two detectedK s 0 's are analyzed. The result shows theK s 0 K s 0 pairs are produced in the central region of c.m. system and there is a clearS * signal in theK s 0 K s 0 effective mass distribution.
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  • 8
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The energy density of the central products in the ultra-relativistic heavy ion collisions are calculated. In our estimation, the special attention is paid to the space-time extension of the emission points of the secondary hadrons which are originate in the successive nucleon-nucleon interactions within the finite size of colliding nuclei. The average collision number per produced particle, in the final state interaction, is also calculated and is used as a criterion whether the system is thermalized or not. It turns out that the attainable energy density in the central heavy ion collision is sensitive to the spacetime extension of the emission points. However, if the incident energy and the mass numbers of colliding nuclei are high and large, we can get high enough energy density for the phase transition from a hadronic state to a quark-gluon plasma state.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 70 (1980), S. 165-169 
    ISSN: 1573-5117
    Keywords: Dissolved organic matter ; monosaccharides ; gas chromatography versus spectrophotometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstracts The concentrations of carbohydrates measured by gas chromatography in lakes of three different trophic levels have a tendancy to be lower than those measured by spectrophotometry. The concentrations of glucose and galactose were high in the euphotic zone of eutrophic lakes and the rhamnose was relatively high in the profundal zone. The ratio of the concentrations of each monosaccharide was relatively uniform from surface to bottom in a dystrophic lake. Glucose and galactose freshly produced in the euphotic zone might well be easily decomposed.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 71 (1980), S. 95-97 
    ISSN: 1573-5117
    Keywords: dissolved organic matter ; carbohydrates ; amino acids ; lake water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dissolved organic matter in natural water was classified into a labile and a refractory fraction according to the decomposition properties for microorganisms. In decomposition experiments of dissolved organic matter from an eutrophic small lake in Japan, dissolved amino acids and dissolved carbohydrates fractions could be confirmed to be the labile fractions of dissolved organic matter.
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