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51.
Fabrizio Davì Morton E. Gurtin 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1990,41(6):782-811
Mullins, in a series of papers, developed a surface dynamics for phase interfaces whose evolution is controlled by mass diffusion within the interface. It is our purpose here to embed Mullins's theory within a general framework based on balance laws for mass and capillary forces in conjunction with a version of the second law, appropriate to a purely mechanical theory, which asserts that the rate at which the free energy increases cannot be greater than the energy inflow plus the power supplied. We develop an appropriate constitutive theory, and deduce general and approximate equations for the evolution of the interface.
Sommario Mullins, in una serie di articoli inerenti la morfologia delle superfici di interfaccia tra fasi, ha sviluppato una dinamica delle superfici la cui evoluzione è governata dal fenomeno di diffusione di massa all'interno dell'interfaccia. Scopo di questo articolo è inscrire la teoria di Mullins in uno schema più generale basato su leggi di bilancio della massa e delle azioni capillari nonchè su una formulazione puramente meccanica del secondo principio della termodinamica, asserente ehe l'incremento di energia libera non possa essere superiore al flusso di energia ed alla potenza fornite all'interfaccia. Viene successivamente sviluppata una appropriata teoria costitutiva, e vengono dedotte le equazioni di evoluzione sia in forma generale che approssimata.相似文献
52.
J. Stan Morton James B. Westmoreland April Rhineheart 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(2):483-486
Tritiated water is probably the most mobile manmade nuclide found in the environment. The low-energy beta decay produces few
health concerns except at extremely high concentrations of tritium. However, because of the ubiquitous nature of tritiated
water, when identified in the bionetwork, it can be viewed as a precursor of nuclides with greater health risks. For this
reason alone it becomes desirable to determine tritium concentrations many orders of magnitude below that considered a health
concern. A devise is described that eliminates the need for large water-filled chest freezers used as coolers. The enrichment
cells can be employed individually or in series. 相似文献
53.
Morton E. Gurtin 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1991,42(3):370-388
This paper discusses the formulation of balance laws for mass, force, and energy in conjunction with a law of entropy growth for the motion of a sharp evolving phase interface within a continuum framework.
Zusammenfassung In dieser Arbeit werden Erhaltungssätze für Masse, Kraft und Energie sowie eine Entropieungleichung für die räumliche Ausbreitung einer scharfen Phasengrenzschicht im Rahmen eines kontinuierlichen Modells diskutiert.相似文献
54.
S. Yu. Kun D. J. Hinde M. Dasgupta J. R. Leigh J. C. Mein C. R. Morton J. O. Newton B. A. Robson H. Timmers A. V. Vagov 《Zeitschrift für Physik A Hadrons and Nuclei》1997,359(3):263-270
Excitation functions for the strongly dissipative collision 19 F(E lab = 135–140 MeV)+89 Y with an energy step of 250 keV in the lab. system have been measured. The data are consistent with previous measurements and exhibit oscillations, which are interpreted as an indication of quantum chaotic phenomena in dissipative heavy-ion collisions. The Fourier component of the energy autocorrelation of the total projectile-like angle-integrated dissipative yield has been calculated and is found to have a pulsing behaviour with a time interval between sequential pulses equal to the period of the coherent nuclear rotation. This provides another possibility of experimentally detecting quantum chaos in dissipative heavy-ion collisions. 相似文献
55.
This study develops a small-deformation theory of strain-gradient plasticity for single crystals. The theory is based on: (i) a kinematical notion of a continuous distribution of edge and screw dislocations; (ii) a system of microscopic stresses consistent with a system of microscopic force balances, one balance for each slip system; (iii) a mechanical version of the second law that includes, via the microscopic stresses, work performed during viscoplastic flow; and (iv) a constitutive theory that allows:
- •
- the free energy to depend on densities of edge and screw dislocations and hence on gradients of (plastic) slip;
- •
- the microscopic stresses to depend on slip-rate gradients.
56.
A method of combining moiré interferometry and the finite-element method to effect localized stress analysis is presented.
The displacement data from local regions of interest in the optical experiment are used as boundary conditions for the finite-element
stress analysis.
The stability of the method is examined with data from simple numerical models one of which corresponded to the stress analysis
of a pin-loaded plate with friction. These studies show that the method requires the sensivity of moiré interferometry for
successful implementation, i.e., displacement data accuracy within 0.1 μm or 4 μin.
This localized hybrid method of stress analysis provides a powerful and efficient method for the reduction of experimental
data. 相似文献
57.
We formulate integral statements of force balance, energy balance, and entropy imbalance for an interface between a body and
its environment. These statements account for interfacial energy, entropy, and stress but neglect the inertia of the interface.
Our final results consist of boundary conditions describing thermomechanical interactions between the body and its environment.
In their most general forms, these results are partial differential equations that account for dissipation and encompass as
special cases Navier’s slip law, Newton’s law of cooling, and Kirchhoff’s law of radiation. When dissipation is neglected,
our results reduce to the well-known zero-slip, free-surface, zero-shear, prescribed temperature, and flux-free conditions.
Dedicated to James K. Knowles: teacher, colleague, friend 相似文献
58.
Gurtin recently proposed a strain-gradient theory for crystal plasticity in which the gradient effect originates from a defect energy that characterizes energy storage due to the presence of a net Burgers vector. Here we consider a number of different possibilities for this energy: specifically, working within a simple two-dimensional framework, we compare predictions of the theory with results of discrete-dislocation simulations of stress relaxation in thin films. Our objective is to investigate which specific defect energies are capable of capturing the size-dependent response of such systems for different crystal orientations. 相似文献
59.
A series of experiments has been conducted to determine the effect of loading variables such as cyclic frequency, load ratio, and material on acoustic emission from fatigue-crack propagation. It is shown that the applied-stress intensity range (ΔK) is the controlling parameter for all materials studied while the other parameters have lesser effects. Two potential methods for engineering application of acoustic emission during fatigue loading are described. 相似文献
60.
A theory of strain-gradient plasticity for isotropic, plastically irrotational materials. Part I: Small deformations 总被引:1,自引:0,他引:1
This study develops a small-deformation theory of strain-gradient plasticity for isotropic materials in the absence of plastic rotation. The theory is based on a system of microstresses consistent with a microforce balance; a mechanical version of the second law that includes, via microstresses, work performed during viscoplastic flow; a constitutive theory that allows:
- •
- the microstresses to depend on , the gradient of the plastic strain-rate, and
- •
- the free energy ψ to depend on the Burgers tensor .