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Plaster detachment is serious problem with strong influence on the structure durability. This contribution describes numerical simulation of the plaster detachment. The simulation is based on the coupled thermo-hydro-mechanical analysis of masonry and plaster. Interface finite elements are used between the masonry and plaster. Material parameters were obtained from laboratory test. [ABSTRACT FROM AUTHOR]

In this work, we present the implementation of a front-tracking variant of the lattice Boltzmann method to model water entry problems. In this method, the fluid is considered incompressible, the gas dynamics is neglected and the free surface is represented through a layer of interface cells, whose dynamics is described using the mass and momentum fluxes across it. The consistency and accuracy of the computations is demonstrated through comparisons with theoretical solutions and experimental data reported in the literature. [ABSTRACT FROM AUTHOR]

The appearance of cracks exposed to severe environmental conditions can be critical for concrete structures. The research is to validate Particle Flow Code(PFC2D) method in the context of concrete thermally-induced cracking simulations. First, concrete was discreted as meso-level units of aggregate, cement mortar and the interfaces between them. Parallel bonded-particle model in PFC2D was adapted to describe the constitutive relation of the cementing material. Then, the concrete mechanics meso-parameters were obtained through several groups of biaxial tests, in order to make the numerical results comply with the law of the indoor test. The concrete thermal meso-parameters were determined by compared with the parameters in the empirical formula through the simulations imposing a constant heat flow to the left margin of concrete specimens. At last, a case of 1000mm×500mm concrete specimen model was analyzed. It simulated the formation and development process of the thermally-induced cracks under the cold waves of different durations and temperature decline. Good agreements in fracture morphology and process were observed between the simulations, previous studies and laboratory data. The temperature decline limits during cold waves were obtained when its tensile strength was given as 3MPa. And it showed the feasibility of using PFC2D to simulate concrete thermally-induced cracking. [ABSTRACT FROM AUTHOR]

Docking of two protein molecules is induced by intermolecular interactions. Our purposes in this study are: designing binding interfaces on the two proteins, which specifically interact to each other; and inducing intermolecular interactions between the two proteins by mixing them. A 4-helix bundle structure was chosen as a scaffold on which binding interfaces were created. Based on this scaffold, we designed binding interfaces involving charged and nonpolar amino acid residues. We performed molecular dynamics (MD) simulation to identify suitable amino acid residues for the interfaces. We chose YciF protein as the scaffold for the protein-protein docking simulation. We observed the structure of two YciF protein molecules (I and II), and we calculated the distance between centroids (center of gravity) of the interfaces' surface planes of the molecules I and II. We found that the docking of the two protein molecules can be controlled by the number of hydrophobic and charged amino acid residues involved in the interfaces. Existence of six hydrophobic and five charged amino acid residues within an interface were most suitable for the protein-protein docking. [ABSTRACT FROM AUTHOR]

There is a need to improve the understanding of the role of interface conditions on eddy current inspections for cracks in multilayer aircraft structures. This paper presents initial experimental and simulated results studying the influence of gaps and contact conditions between two plates with a notch in the second layer. Simulations show an amplification of the eddy current signal for a subsurface notch adjacent to an air gap as opposed to a submerged notch in a solid plate. [ABSTRACT FROM AUTHOR]

The purpose of the present work is to investigate the coupled CFD/DSMC method using the existing CFD and DSMC codes developed by the authors. The interface between the continuum and particle regions is determined by the gradient-length local Knudsen number. A coupling scheme combining both state-based and flux-based coupling methods is proposed in the current study. Overlapping grids are established between the different grid systems of CFD and DSMC codes. A hypersonic flow over a 2D cylinder has been simulated using the present coupled method. Comparison has been made between the results obtained from both methods, which shows that the coupled CFD/DSMC method can achieve the same precision as the pure DSMC method and obtain higher computational efficiency. [ABSTRACT FROM AUTHOR]

Near-surface dopant pile-up at Si/SiO2 interfaces during post-implant annealing can affect the electrical performance of devices with shallow dopant profiles. Pile-up results from alterations in the charge state of dopant-related point defects, induced by near-surface band bending. The effects of annealing conditions on the evolution of pile-up are little known. The present work employs continuum simulations coupled with experiments in the case of B implanted into Si to show that annealing temperature, ramp rate, interface potential and annihilation probability, besides other factors, determine the growth kinetics and extent of pile-up. Annealing conditions under which pile-up is absent have also been identified. [ABSTRACT FROM AUTHOR]

Numerical method is presented for simulation of the deformation, drainage and rupture of axisymmetric film (gap) between colliding drops in the presence of film soluble surfactants under the influence of van der Waals forces at small capillary and Reynolds numbers and small surfactant concentrations. The mathematical model is based on the lubrication equations in the gap between drops and the creeping flow approximation of Navier-Stokes equations in the drops, coupled with velocity and stress boundary conditions at the interfaces. A non-uniform surfactant concentration on the interfaces, related with that in the film, leads to a gradient of the interfacial tension which in turn leads to additional tangential stress on the interfaces (Marangoni effects). Both film and interface surfactant concentrations, related via adsorption isotherm, are governed by a convection-diffusion equation. The numerical method consists of: Boundary integral method for the flow in the drops; Finite difference method for the flow in the gap, the position of the interfaces and the surfactant concentration on the interfaces, as well as in the film. Second order approximation of the spatial terms on adaptive non-uniform mesh is constructed in combination with Euler explicit scheme for the time discretization. For the convection-diffusion equation in the film first order implicit and Crank-Nicolson time integration schemes are used as well. Tests and comparisons are performed to show the accuracy and stability of the presented numerical method. [ABSTRACT FROM AUTHOR]

In previous work we introduced an approach for simulating ultrasonic pulse/echo immersion inspections of multi-layer armor panels. Model inputs include the thickness, density, velocity and attenuation of each armor layer, the focal properties of the transducer, and a measured calibration signal. The basic model output is a response-versus-time waveform (ultrasonic A-scan) which includes echoes from all interfaces including those arising from reverberations within layers. Such A-scans can be predicted both for unflawed panels and panels containing a large disbond at any given interface. In this paper we continue our testing of the simulation software, applying it now to an armor panel consisting of SiC ceramic tiles fully embedded in a titanium-alloy matrix. An interesting specimen of such armor became available in which some tile/metal interfaces appear to be well bonded, while others have disbonded areas of various sizes. We compare measured and predicted A-scans for UT inspections, and also demonstrate an extension of the model to predict ultrasonic C-scans over regions containing a small, isolated disbond. [ABSTRACT FROM AUTHOR]

This paper presents the theoretical and numerical analyses of the propagation characteristics of the longitudinal modes excited by the point source in the three-layered cylindrical ultrasonic transmission rod model. The phase velocity and group velocity dispersion curves, and displacement distributions of the Stoneley mode and the quantized Stoneley mode segments are numerically simulated. The results show that the quantized Stoneley mode segments are analogous to the non-dispersive Stoneley wave propagating along the second cylindrical interface. [ABSTRACT FROM AUTHOR]

Delamination is one of the critical failure modes that laminated composites structures encounter during their fabrication and/or in-service. When guided Lamb wave (Ao) is employed for sizing of delamination, it is necessary to understand the wave interaction with the defect. Studies were carried out on the interaction of Ao mode with symmetric and asymmetric delaminations and transmission of turning modes in the sub-laminates. An attempt was also made to understand the propagation of Ao mode in composite structural T-joint. During the interaction of Ao mode with structural discontinuity in a T-joint, generation of a new mode, So, and propagation of turning modes were observed. Length and width of interface delamination in composite T-joint have been worked out using D-scan and B-scan respectively. All studied were carried out through numerical simulations and experimental verifications through Non- Contact Ultrasound (NCU) technique. [ABSTRACT FROM AUTHOR]

Interfaces are given considerable attention in the field of nanotechnology, as many of the preferred material properties that are observed at the nanoscale are attributed to the high surface to volume ratio that is present at sub-micron scales. The optoelectronic properties of semiconductors, for example, depend on the number of dislocations that are present at the interface between the nano-sized doping elements and the matrix. In the present paper a first step is taken towards understanding the interface-dislocation interactions. The theoretical framework used is that of gradient plasticity framework, enhanced with a separate interface energy term. This interface energy depends on the plastic strain at the interface and defines an interface yield-like criterion which indicates the stress at which the interface begins to deform plastically. Experimentally this interfacial yielding is captured through nanoindentation experiments near the grain boundary of crystalline materials, namely Fe-2.2wt%Si. Fitting the theoretical analytical expression to the experimental data allows the determination of the key material parameters; for Nb it gives the internal length to be approximately 1.4μm, and in fact for pure (single phase) materials the dislocation source distance is approximated as 1.5μm. In order to further render the interface-dislocation interactions, discrete dislocation dynamics simulations are presented for a micron-scale tri-crystal with rigid/non-deforming grain boundaries. The resulting strain distribution profile from the simulation coincides with the predicted plastic strain of the gradient plasticity framework, while the best fit results when the internal length in the analytical expression is chosen to be the same as the value of the dislocation source distance used in the simulation. Hence, the gradient plasticity model that considers an interface energy term has been validated using experimental and numerical investigations. [ABSTRACT FROM AUTHOR]

Multimaterial Eulerian and Arbitrary Lagragian-Eulerian (ALE) codes usually use volume fractions of materials to track individual components in mixed cells. Material advection usually is calculated either by interface capturing, where a high-order van Leer-like slope reconstruction technique is applied, or interface tracking, where a normal reconstruction technique is applied. The former approach is more appropriate for gas-like substances, and the latter is ideal for solids and liquids, since it does not smear out material interfaces. A wide range of problems involves both diffuse and sharp interfaces between substances and demands a combination of these techniques. It is possible to treat all substances that can diffuse into each other as a single material and only keep mass fractions of the individual components of the mixture. The material response can be determined based on the assumption of pressure and temperature equilibrium between components of the mixture. Unfortunately, it is extremely difficult to solve the corresponding system of equations. In order to avoid these problems one can introduce an effective gamma and employ the ideal gas approximation to calculate mixture response. This method provides reliable results, is able to compute strong shock waves, and deals with complex equations of state. Results from a number of simulations using this scheme are presented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A numerical modeling of an interface including a local imperfection and simulation of the ultrasonic wave propagation through the interface are described in this paper. We propose an imperfection model with the interface condition depending on displacement-stress states. This phenomenon generates superharmonics in the transmitted wave through the interface. The interface model is incorporated into a time domain boundary element method and transmitted waveforms are calculated. Simulation results show that the amplitude ratio of superharmonic waves changes according to the initial opening gap and the length of the imperfection area. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The properties of a product result at the end of the production chain. To predict these properties as accurate as feasible every process step has to be described in the exactest way possible. The big challenge for the simulation technique is to realistically depict the actual circumstances in the process chain as well as in the process depth. Usually, simulations are calculated for single process steps of an entire process chain. The aim of recent research is to combine these steps to a complete simulation of a plant even using the calculated results of the previous step as input data for the next one. An useful method to combine simulations and to present the results is the Virtual Reality tool. It offers the possibility to show a three dimensional model of the whole complex plant. Combined with results of logistic simulations the VR-model can visualize the whole production process. For the combination of calculations at several accuracy levels a hierarchical structure was developed. At selectable parts it is possible to go deeper into the process (vertical) and to integrate the above mentioned single process step calculations (horizontal). This horizontal and vertical enlargement of the simulation finally leads to an overall description of the production process of a product. The present manuscript at first describes the new medium Virtual Reality used for representation of complex production facilities in different visualization levels. The hierarchical model matrix with the interfaces is presented. Exemplified for the vertical refinement of the overall model the interaction workpiece/tool in rolling and the link of finite element method with physical material models is shown. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

A numerical strategy for the finite element simulation of the flow of two immiscible fluids has been developed based on unstructured triangular meshes. The tracking of the interface between the two fluids is accomplished by means of an advection equation for the volume fraction of one of these fluids. An accurate description of the interface is achieved by means of an automatic mesh refinement procedure developed for the simulation of fluid flow in twin-screw extruders. The advantage of this technique comes from the use of one single reference mesh. At each time iteration, this reference mesh is adapted by splitting up the elements in the vicinity of the interface into sub-elements. Local refinement can then be carried out with one single mesh to be generated before the simulation is started. First, the method will be presented in detail. It will then be applied to two-dimensional classical benchmark problems: the advection skew to the mesh and the transport of a square. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Numerical simulations of laser-generated guided elastic waves in two-layer bonded plates are presented by modeling adhesive bond layer as a spring model. The transient waveform is expressed by the two-layer normal mode expansion method (NME), and then the sensitivity of each mode and transient waveform on the stiffness coefficients characterizing cohesive quality are analyzed in details. This method provides a new promising way for the characterization of the cohesive quality in bonded plates. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

First-principles molecular dynamics simulations have advanced microscopic understanding of the electrochemical reactions as well as the electrode/electrolyte interfaces. Those simulations describe the properties of the inner Helmholtz layer successfully. By contrast, the description of the electrochemical reaction is not yet accurate enough, prompting further improvement of the modeling. [ABSTRACT FROM AUTHOR]