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  • STRUCTURAL MECHANICS  (6)
  • Polymer and Materials Science  (3)
  • Animals
  • Humans
  • Models, Molecular
  • 1990-1994  (9)
  • 1
    Electronic Resource
    Electronic Resource
    The effect of the steric hindrance on metallic cation conduction in polymer electrolytes (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 879-885 
    Details
    ISSN: 0887-624X
    Keywords: polyisocyanates ; polymer electrolytes ; metallic cation conducting polymers ; steric hindered phenols ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,6-Di-t-butylphenol and oligo(ethylene oxide) bound covalently to polyisocyanate were synthesized and characterized. The ionic conductivities of their Li, Na, and K phenolates were studied at various temperatures. The conductivities were in the range of 10-7-10-5 S/cm at 30°C. The conductivity of Na and K salts was approximately 102 greater than that of the Li salts. The t-butyl groups serve to dissociate K and Na ions from the phenoxide. The cations, therefore, are more mobile as a result increasing the conductivity. The temperature dependence of ionic conductivity suggests that the migration of ions is controlled by segmental motion of the polymer, shown by linear curves obtained in Vogel-Tammann-Fulchere plots. The polyisocyanate backbone is a rather stiff structure, however, a flexible oligo(ethylene oxide) side chain forms complexes with metal ion. Since the ion transport is associated with the local movement of polymer segments, the rigidity of the polymer backbone does not have much influence on the ion mobility.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080300519
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of sorbed carbon dioxide on the impact strength of amorphous glassy polymers (1990)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 28 (1990), S. 7-12 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1990.140280102
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  • 3
    Electronic Resource
    Electronic Resource
    A study of oxygen-implanted Si0.5Ge0.5 alloy by XPS and thermodynamic analysis (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 149-154 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A thermodynamic study of oxygen-implanted Si0.5Ge0.5 alloy based on an XPS analysis is reported for the first time. The alloy was grown by molecular beam epitaxy (MBE) and was implanted with high-dose oxygen ions (up to 1.8 × 1018 cm-2) at an energy of 200 keV. The changes of Si, Ge and O activities with the concentration of oxygen were calculated using the THERMO-CALC program, and chemical potentials of these elements throughout the oxygen-buried region were plotted out according to the chemical state information obtained from XPS depth profiling results.Transport during implantation and in subsequent annealing follows the gradient of chemical potential: elemental Si migrates into the oxygen-rich layer to form SiO2 by the replacement of Ge in Ge oxides. This leads to a decrease of the total free energy for the system of Si, Ge and O in the sample. The description of the system in terms of activities and chemical potential enables true diffusion profiles to be used in place of phenomenological descriptions such as ‘snowplough’ or ‘pile-up’.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200209
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  • 4
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    Single-parameter characterization of discrete-dislocation pileup tipfield and its application to physically based micro-mechanics (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The equivalence between continuous dislocation pileups and cracks is reviewed. The force on the leading dislocation is defined and a general method of calculation of the force is proposed. The equivalence relations are given. Based on the analysis by Eshelby, Frank, and Nabarro and the numerical calculations by Chou and Li and Armstrong et al, it will be shown that the force, F, on the locked leading dislocation of a discrete pileup is capable of characterizing uniquely the stress, strain, and displacement fields at the tip of the pileup, including the positions of the discrete mobile dislocations behind the leading dislocation. Conversely, the positions of the mobile dislocations can be used to measure F. If the propagation of micro-slips and the initiation of micro-fractures at the tip of a pileup are controlled by resolved shear stress and normal cleavage stress respectively, the resolved shear stress intensity coefficient, ReSIC, and the resolved cleavage stress intensity coefficient, ReCIC, must be constant.
    Keywords: STRUCTURAL MECHANICS
    Type: In: Morris E. Fine Symposium, TMS Fall Meeting, Detroit, MI, Oct. 8-11, 1990, Proceedings (A93-12101 02-23); p. 375-381.
    Format: text
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  • 5
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    A review of fatigue crack growth analyses (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Stress intensity factor range, Delta K, has been shown to correlate well with fatigue crack growth rate, da/dN. A number of fatigue crack growth theories have been developed for such correlations. Often, conjectory theories of fatigue crack growth are constructed from experimental data. On the other hand, fatigue crack growth theories can also be derived rigorously with deductive logic. Four such deductive theories are reviewed: (1) that for the growth of a small crack in a very wide homogeneous plate, (2) the theory of similitude for the correlation of da/dN with Delta K, (3) a theory of crack growth in homogeneous materials in small-scale yielding, and (4) the unzipping theory of fatigue crack growth. This paper synthesizes these four theories into a logic framework useful for fatigue crack growth analysis. The deductive theories and the conjectory theories complement each other in the advances of the understanding of fatigue crack growth. The applications of logic framework to formulating an overview of fatigue crack growth behavior and to defining the complex issues of the growth of small cracks and crack growth in composites are illustrated.
    Keywords: STRUCTURAL MECHANICS
    Type: Theoretical and Applied Fracture Mechanics (ISSN 0167-8442); 16; 91-108
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  • 6
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    Characterization of the tip field of a discrete dislocation pileup for the development of physically based micromechanics (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: It is shown, on the basis of calculations by Eshelby et al. (1951), Armstrong et al. (1966), and Chou and Li (1969), that a single parameter, such as the force on the leading dislocation (F), the crack extension force, or the stress intensity factor, is capable of characterizing uniquely the entire tip field of a discrete dislocation pileup, including the positions of mobile dislocations behind the locked leading dislocation at the tip. Conversely, the position of the i-th mobile dislocation X(i) is related to the value of F and is capable of characterizing the entire stress, strain, and displacement fields at the tip of a discrete dislocation pileup. If the interactions between dislocations are linear elastic, the measured positions of the mobile dislocations can be used to determine the value of F, which can then be used as a quantitative measure of the strength of a dislocation barrier resisting the propagation of a microslip or the nucleation of a microfracture.
    Keywords: STRUCTURAL MECHANICS
    Type: Metallurgical Transactions A - Physical Metallurgy and Materials Science (ISSN 0360-2133); 21A; 2087-208
    Format: text
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  • 7
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    The characterization of a crack-tip field (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The stress intensity factor, K, has been successfully used as a measure of fracture toughness, and stress intensity factor range, Delta K, correlates well with the fatigue crack growth rate. This paper gives a deductive logic to demonstrate rigorously that, in the case of small-scale yielding, K and Delta K are capable of characterizing the elastic-plastic crack-tip field both under a monotonic loading and cyclic fatigue loading. This capability to characterize the entire crack-tip field is the underlying reason for the successful application of K and Delta K to linear fracture mechanics.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics (ISSN 0013-7944); 39; 2 19
    Format: text
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  • 8
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    The equivalence between dislocation pile-ups and cracks (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Cracks and dislocation pile-ups are equivalent to each other. In this paper, the physical equivalence between cracks and pile-ups is delineated, and the relationshps between crack-extension force, force on the leading dislocation, stress-intensity factor, and dislocation density are reviewed and summarized. These relations make it possible to extend quantitatively the recent advances in the concepts and practices of fracture mechanics to the studies of microfractures and microplastic deformations.
    Keywords: STRUCTURAL MECHANICS
    Type: Theoretical and Applied Fracture Mechanics (ISSN 0167-8442); 12; 195-204
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  • 9
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    The development of physically based micro-mechanics - Based on the characteristic tip field of dislocation pileup (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Based on the analytical solution by Eshelby et al. (1951) and the numerical calculations by Chou and Li (1969) and Armstrong et al. (1962), it is shown that the force, F, on the locked leading dislocation of a discrete dislocation pileup is capable of characterizing uniquely the stress, strain, and displacement field at the tip of the pileup, including the positions of the discrete mobile dislocations next to the leading dislocation. Conversely, the positions of the mobile dislocations can be used to measure F. The F thus measured can be used to study micro-plastic deformation and micro-fractures at grain boundaries or any other dislocation barriers.
    Keywords: STRUCTURAL MECHANICS
    Type: Theoretical and Applied Fracture Mechanics (ISSN 0167-8442); 13; 181-191
    Format: text
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