A new analytical formulation of retention effects on particle diffusion processes

The ultimate purpose of this paper is to present a new analytical formulation to simulate diffusion with retention in a reactive medium under stable thermodynamic conditions. The analysis of diffusion with retention in a continuum medium is developed after the solution of an equivalent problem using a discrete approach. The new law may be interpreted as the reduction of all diffusion processes with retention to a unifying phenomenon that can adequately simulate the retention effect namely a circulatory motion. It is remarkable that the governing equation requires a fourth order differential term as suggested by the discrete approach. The relative fraction of diffusion particles β is introduced as a control parameter in the diffusion-retention law as suggested by the discrete approach. This control parameter is essential to avoid retention isolated from the diffusion process. Two matrices referring to material properties are introduced and related to the real phenomenon through the circulation hypothesis. The governing equation may be highly non-linear even if the material properties are constant, but the retention effect is a function of the concentration level, that is, β is a function of the concentration.

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Reliability-Based Design Optimization of Microstructures With Analytical Formulation

Journal of Mechanical Design ◽

10.1115/1.4040881 ◽

2018 ◽

Vol 140 (11) ◽

Cited By ~ 7

Author(s):

Pinar Acar

Keyword(s):

Design Optimization ◽

Material Properties ◽

Optimization Problem ◽

Optimization Under Uncertainty ◽

Reliability Based Design Optimization ◽

Case Scenario ◽

Worst Case ◽

Analytical Formulation ◽

Reliability Based Design ◽

Safe Approach

Microstructures are stochastic by their nature. These aleatoric uncertainties can alter the expected material performance substantially and thus they must be considered when designing materials. One safe approach would be assuming the worst case scenario of uncertainties in design. However, design under the worst case conditions can lead to over-conservative solutions that provide less effective material properties. Here, a more powerful design approach can be developed by implementing reliability constraints into the optimization problem to achieve superior material properties while satisfying the prescribed design criteria. This is known as reliability-based design optimization (RBDO), and it has not been studied for microstructure design before. In this work, an analytical formulation that models the propagation of microstructural uncertainties to the material properties is utilized to compute the probability of failure. Next, the analytical uncertainty solution is integrated into the optimization problem to define the reliability constraints. The presented optimization under uncertainty scheme is exercised to maximize the yield stress of α-Titanium and magnetostriction of Galfenol, respectively.

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Comparison between Glaser Method and Heat, Air and Moisture Transient Model for Moisture Migration in Building Envelopes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.887.385 ◽

2019 ◽

Vol 887 ◽

pp. 385-392 ◽

Cited By ~ 1

Author(s):

Michele Libralato ◽

Onorio Saro ◽

Alessandra de Angelis ◽

Simone Spinazzè

Keyword(s):

Moisture Content ◽

Material Properties ◽

Moisture Transfer ◽

Building Envelope ◽

Assessment Procedure ◽

Moisture Migration ◽

Building Envelopes ◽

Transient Model ◽

Percentage Difference ◽

Real Phenomenon

The Glaser method is an assessment procedure for the risk of moisture accumulation in building mono-dimensional structures, that could be used to evaluate mould risk and interstitial condensation risk.It is based on a simplified model that does not represent the real phenomenon and its limitations are well-known qualitatively.This work provides a comparison in terms of moisture content between the Glaser method and WUFI Pro, an advanced heat, air and moisture transfer prediction tool. First the influence of material properties is evaluated on four fictitious materials walls, then six different building envelope typologies for six weather files from Central and Southern Europe are modelled to evaluate the Glaser method results.The effects of the Glaser method simplifications are quantified in terms of moisture content percentage difference.

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Analytical formulation of optimum material properties for viscoelastic damping

Smart Materials and Structures ◽

10.1088/0964-1726/1/2/003 ◽

1992 ◽

Vol 1 (2) ◽

pp. 113-122 ◽

Cited By ~ 29

Author(s):

H H Hilton ◽

Sung Yi

Keyword(s):

Material Properties ◽

Viscoelastic Damping ◽

Analytical Formulation ◽

Optimum Material

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Microscopic pathways for stress relaxation in repulsive colloidal glasses

Science Advances ◽

10.1126/sciadv.aaz2982 ◽

2020 ◽

Vol 6 (12) ◽

pp. eaaz2982

Author(s):

F. Dallari ◽

A. Martinelli ◽

F. Caporaletti ◽

M. Sprung ◽

G. Grübel ◽

...

Keyword(s):

Metallic Glasses ◽

Material Properties ◽

Control Parameter ◽

Mechanical Response ◽

Primary Control ◽

Full Understanding ◽

Small Length ◽

Particle Mobility ◽

Glassy Materials ◽

Colloidal Glasses

Residual stresses are well-known companions of all glassy materials. They affect and, in many cases, even strongly modify important material properties like the mechanical response and the optical transparency. The mechanisms through which stresses affect such properties are, in many cases, still under study, and their full understanding can pave the way to a full exploitation of stress as a primary control parameter. It is, for example, known that stresses promote particle mobility at small length scales, e.g., in colloidal glasses, gels, and metallic glasses, but this connection still remains essentially qualitative. Exploiting a preparation protocol that leads to colloidal glasses with an exceptionally directional built-in stress field, we characterize the stress-induced dynamics and show that it can be visualized as a collection of “flickering,” mobile regions with linear sizes of the order of ≈20 particle diameters (≈2 μm here) that move cooperatively, displaying an overall stationary but locally ballistic dynamics.

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Meridional Circulation, Turbulence, and Diffusion Processes in Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100080477 ◽

1976 ◽

Vol 32 ◽

pp. 109-116 ◽

Cited By ~ 1

Author(s):

S. Vauclair

Keyword(s):

Convection Zone ◽

Diffusion Processes ◽

Meridional Circulation ◽

Diffusion Time ◽

Work In Progress ◽

First Results ◽

Stellar Envelopes ◽

And Diffusion ◽

Turbulence And Diffusion ◽

Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

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Grain boundary segregation in metals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130651 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1204-1205

Author(s):

C.L. Briant

Keyword(s):

Fracture Surface ◽

Grain Boundary ◽

Grain Boundaries ◽

Material Properties ◽

Electron Spectroscopy ◽

High Vacuum ◽

Boundary Segregation ◽

Grain Boundary Segregation ◽

Local Concentration ◽

The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

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Relationships Between Grain Boundary Structure and Material Properties

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600001550 ◽

1980 ◽

Vol 38 ◽

pp. 366-369

Author(s):

Brian Ralph ◽

Barlow Claire ◽

Nicola Ecob

Keyword(s):

Grain Boundary ◽

Material Properties ◽

Main Property ◽

Grain Structure ◽

Boundary Structure ◽

Grain Boundary Structure ◽

Property Changes

This brief review seeks to summarize some of the main property changes which may be induced by altering the grain structure of materials. Where appropriate an interpretation is given of these changes in terms of current theories of grain boundary structure, and some examples from current studies are presented at the end of this paper.

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