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In this paper, we investigate the time-dependent drainage of a thin film of Eyring fluid of variable thickness, flowing down a vertical plate. The exact solutions for the velocity distribution, flow rate, mean thickness, average velocity, vorticity vector, and stress are obtained. Graphical results are presented and discussed for various flow variables like the velocity profile and the variable thickness. PACS Nos.: 01, 47. Nous etudions ici le drainage dependant du temps d'un film mince de fluide de Eyring d'epaisseur variable qui s'ecoule le long d'une plaque verticale. Nous obtenons les solutions exactes pour la distribution de vitesse, le taux d'ecoulement, l'epaisseur moyenne, la vitesse moyenne, le vecteur tourbillon et l'effort de contrainte. Nous presentons les resultats de facon graphique et discutons differentes variables, comme le profil de vitesse et l'epaisseur variable., 1. Introduction The problem of unsteady drainage of a linearly viscous fluid down a vertical wall was originally studied by Jeffreys [1]. He assumed that the inertial forces were negligibly [...]

In this paper, we model a steady thin film flow of an Oldroyd 8-constant fluid on a vertically moving belt. The governing nonlinear differential equation is first integrated exactly and then solved by applying the variational iteration method and the Adomian decomposition method. The numerical results obtained by these methods are then compared through graphs and tables and no visible difference is observed. This study highlights the significant features of the proposed methods and their ability for solving nonlinear problems arising in non-Newtonian fluid mechanics. Moreover, a reasonable estimation for the belt speed to lift the non-Newtonian fluid is also recorded. This estimation can be used for experimental verification. PACS Nos.: 47.50.-d, 66.20.-d, 47.40.-x, 47.85.-g. Nous modelisons ici l'ecoulement d'un fluide d'Oldroyd a 8 constantes sur une courroie se deplacant verticalement. L'equation differentielle directrice non lineaire est d'abord integree exactement et ensuite solutionnee numeriquement a l'aide de la methode d'iteration variationnelle et de la methode de decomposition d'Adomian. Les valeurs numeriques obtenues de ces methodes sont alors comparees via tables et graphiques et nous n'observons aucune difference. Cette etude souligne les caracteristiques significatives de ces methodes et leur capacite a resoudre des problemes non lineaires rencontres en mecanique des fluides non newtoniens. Nous notons aussi l'estimation raisonnable de la vitesse de courroie necessaire pour elever le fluide. Cette estimation peut etre utilisee pour verification experimentale. [Traduit par la Redaction], 1. Introduction During the past few decades, significant research efforts have been devoted to investigating thin film flows of non-Newtonian fluids in a variety of situations. Specifically, such flows are [...]

The analysis of the mechanical properties of thin films by nanoindentation has been recently subject of numerous theoretical and phenomenological studies as well as numerical simulations. In this work, we report on the application of the Winkler elastic foundation theory to analyze atomic force microscope nanoindentations of poly(n-butyl methacrylate) films with thicknesses of 90, 196, and 485 nm. The elastic moduli of the samples were found to be 1.13 ± 0.43 GPa, 1.34 ± 0.32 GPa and 1.23 ± 0.24 GPa, respectively, after indentations of at least 50% of the film thickness. These data rely on the independent determination of the mechanical properties of 485-nm thick films, using Sneddon's model at low penetration depth (yielding 1.27 ± 0.37 GPa). Our data show that the substrate effects begins to be noticeable only after indenting to a depth of more than 40% of the film thickness. POLYM. ENG. SCI., 51:1507-1512, 2011. © 2011 Society of Plastics Engineers, INTRODUCTION Indentation techniques have been very frequently used in the past to study the mechanical properties of materials and films, ranging from the macroscale down to the nanoscale (1), Macrohardness [...]

This work employs a shear and stress sensitive film (S3F) to investigate the suction surface flow features associated with a higher-lift low-pressure turbine airfoil (L2F). Well-behaved higher-lift low-pressure turbine designs suffer from an inability to accurately predict the transition location above the suction surface, and the separation onset locations obtained with the S3F sensor herein allow the validation of the separated-flow transition model used in the L2F design cycle. Improvements to the S3F measurement technique are explained in this work, and results are compared over a range of Reynolds numbers at 3.3% freestream turbulence including skin friction measurements at the trailing edge of the airfoil. Results demonstrate an improvement to the S3F data reduction process by accounting for the tunnel and model vibration, which will allow a greater range of sensor application. DOI: 10.2514/1.37579

Thin film shape memory alloys have recently become a promising material for the actuation of devices on the microscale such as micropumps and microvalves. Their utilization, however, has been limited due to the difficulty in tailoring their properties for different applications. Control over the transformation temperatures as well as mechanical and shape memory properties is required to enable their widespread Use. This study examines the effects of heat treatment time and temperature on the properties of amorphous, Ti-rich NiTi thin films on silicon substrates. The effects on the transformation temperatures are investigated through the use of temperature dependent optical microscopy and temperature dependent X-ray diffraction. The indentation modulus and hardness, as well as dissipated energy and depth recovery, are obtained through nanoindentation and atomic force microscopy. The role of microstructure and composition in altering both the mechanical and shape memory properties of the films is discussed. [DOI: 10.1115/1.4002189]

Three-dimensional (3D)--steady-developing-laminar-isothermal--and gravity-driven thin liquid film flow adjacent to an inclined plane is examined and the effects of film flow rate, surface tension, and surface inclination angle on the film thickness and film width are presented. The film flow was numerically simulated using the volume of fluid model and experimental verification was conducted by measuring film thickness and width using a laser focus displacement instrument. The steady film flow that is considered in this study does not have a leading contact line, however, it has two steady side contact lines with the substrate surface at the outer edge of its width. Results reveal that the film width decreases and the average film thickness increases as the film flows down the inclined plane. The film thickness and width decrease but its streamwise velocity increases as surface inclination angle (as measured from the horizontal plane) increases. A higher film flow rate is associated with a higher film thickness, a higher film width, and a higher average film velocity. Films with higher surface tension are associated with a smaller width and a higher average thickness. A ripple develops near the side contact line, i.e., the spanwise distribution of the film thickness exhibits peaks at the outer edges of the film width and the height of this ripple increases as the surface tension or the film flow rate increases. The width of the film decreases at a faster rate along the streamwise direction if liquid film has higher surface tension. Measurements of the film thickness and the film width compare favorably with the numerically simulated results. [DOI: 10.1115/1.4002109]

The effects of ultraviolet (UV) radiation on degradation of bitumen have received much attention from both academic and industrial points of view. However, quantitative evaluations of bitumen photo-oxidation in pavements have apparently not been determined. In this study, the effects of photo-oxidation of bitumen were investigated by exposing pressed thin films of bitumen. The data for thermal aging only were compared with corresponding data for photo-oxidation from exposure to UV radiation. The levels of aging were evaluated by following increases in the carbonyl functional group, and increases in viscosity. The results indicated that both thermal and UV aging occurred during exposure in the UV radiation oven test for thin bitumen films of both unmodified and SBS-modified bitumen. UV aging had a significant effect on bitumen properties, particularly when the bitumen film thickness was less than 150 [micro]m. Results also showed that the level of UV irradiation intensity had a significant influence on the level of photo-oxidation of the bitumen. DOI: 10.1061/(ASCE)MT.1943-5533.0000010 CE Database subject headings: Asphalts; Aging; Ultraviolet radiation; Temperature effects; Laboratory tests. Author keywords: Bitumen; Aging; Ultraviolet radiation; Film thickness; Temperature.

Thermomechanical analysis of global and local buckling is presented to show temperature effects on the stress/strain and shape of a film-on-substrate system. First, the strain is expressed as a function of three key temperatures (room, working, and deposit temperatures). Through sensitivity analysis on temperature, polydimethylsiloxane (PDMS) selection is determined to theoretically design film-on-substrate systems with the minimum variation in stress caused by temperatures. Then, the wrinkling behaviors are studied to establish the relationships of critical strain, wavelength, and amplitude with temperature. In addition, the critical working temperature is determined for local buckling. The approximate semi-analytical solution and the finite element simulation are compared by the use of a two-dimensional case of film on a half-space substrate. [DOI: 10.1115/1.4000927] Keywords: flexible electronics, thermomechanical buckling, thin film, multiphysics simulation, elastomer

A computational model developed based on the phase-field approach is used to model domain structures in ferroelectric thin films and to quantify the effects of strain and applied electric field on the microstructural evolution, and on the induced dielectric, electrostrictive, and piezoelectric film properties. Theoretically predicted vortex-like poly-domain and experimentally observed bidomain and monodomain film morphologies are modeled using the continuum phase-field approach. A nonlinear finite element method is used to solve the boundary value problems relevant to ferroelectric thin films. The computed results agree with the Kittel law for specific ranges of film strain. Simulations that track the domain structure evolution and compute ferroelectric thin film properties given the film dimensions and the imposed electromechanical boundary conditions are also reported. [DOI: 10.1115/1.4000925] Keywords: ferroelectrics, thin films, phase-field modeling, finite element methods, vortex domain structure

The buckling solutions for a stressed thin film deposited on a semi-infinite rigid substrate have been determined in the framework of the Foppl--von Karman's theory of thin plates and the perturbed bifurcation theory when pressures are applied onto the lower and upper free surfaces of the buckled film. It is found that the equilibrium solutions of the film are modified compared with the classical case of the Euler column, as well as the critical stress above which the film buckles. [DOI: 10.1115/1.4000923]

This article presents some experimental data indicating the possibility of depositing nanocrystalline γ-[Al.sub.2][O.sub.3] thin films on 304L stainless steel, at low temperatures, using magnetron sputtering (MS) in a reactive atmosphere [...]

Whereas considerable interest exists in self-assembly of well-ordered, porous 'inverse opal' structures for optical, electronic, and (bio)chemical applications, uncontrolled defect formation has limited the scale-up and practicality of such approaches. Here we demonstrate a new method for assembling highly ordered, crack-free inverse opal films over a centimeter scale. Multilayered composite colloidal crystal films have been generated via evaporative deposition of polymeric colloidal spheres suspended within a hydrolyzed silicate sol-gel precursor solution. The coassembly of a sacrificial colloidal template with a matrix material avoids the need for liquid infiltration into the preassembled colloidal crystal and minimizes the associated cracking and inhomogeneities of the resulting inverse opal films. We discuss the underlying mechanisms that may account for the formation of large-area defect-free films, their unique preferential growth along the (110) direction and unusual fracture behavior. We demonstrate that this coassembly approach allows the fabrication of hierarchical structures not achievable by conventional methods, such as multilayered films and deposition onto patterned or curved surfaces. These robust Si[O.sub.2] inverse opals can be transformed into various materials that retain the morphology and order of the original films, as exemplified by the reactive conversion into Si or Ti[O.sub.2] replicas. We show that colloidal coassembly is available for a range of organometallic sol-gel and polymer matrix precursors, and represents a simple, low-cost, scalable method for generating high-quality, chemically tailorable inverse opal films for a variety of applications. coassembly | colloidal assembly | crack-free films | inverse opals | nanoporous doi/ 10.1073/pnas.1000954107

Fabrication of 3D electronic structures in the micrometer-to-millimeter range is extremely challenging due to the inherently 2D nature of most conventional wafer-based fabrication methods. Self-assembly, and the related method of self-folding of planar patterned membranes, provide a promising means to solve this problem. Here, we investigate self-assembly processes driven by wetting interactions to shape the contour of a functional, nonplanar photovoltaic (PV) device. A mechanics model based on the theory of thin plates is developed to identify the critical conditions for self-folding of different 2D geometrical shapes. This strategy is demonstrated for specifically designed millimeter-scale silicon objects, which are self-assembled into spherical, and other 3D shapes and integrated into fully functional light-trapping PV devices. The resulting 3D devices offer a promising way to efficiently harvest solar energy in thin cells using concentrator microarrays that function without active light tracking systems. 3D structure | microfabrication | self-folding | photovoitaics | capillary force www.pnas.org./cgi/doi/10.1073/pnas.0907390106

The optimization of the surface shape for a slider to meet the specified load demands under an ultra-thin film lubrication condition has been performed in this study. The optimization process is developed based on the conjugate gradient method in conjunction with a direct problem solver, which is built based on the rarefied-flow theory. The direct problem solver is able to predict the pressure distributions of the rarefied gas flows in the slip-flow, transition-flow, and molecular-flow regimes with a wide range of characteristic inverse Knudsen number. First, the validity of the direct problem solver has been verified by a comparison with the existing information for some particular cases, and then the developed direct problem solver is incorporated with the conjugate gradient method for optimizing the shape profile of the slider surface. The performance of the present optimization approach has also been evaluated. Results show that the shape profile of the slider surface can be efficiently optimized by using the present approach. Thus, a number of cases under various combinations of influential parameters, involving the characteristic inverse Knudsen number and the bearing numbers in the x- and y-directions, are investigated. [DOI: 10.1115/1.3213528] Keywords: slider, optimization, ultra-thin film, rarefied' flow, conjugate gradient method

Mechanical and thermoelastic properties of optical films are very important to ensure the performance of optical interference filters and optical coating systems. We systematically study the growth and the mechanical and thermoelastic characteristics of niobium oxide ([Nb.sub.2][O.sub.5]), tantalum oxide ([Ta.sub.2][O.sub.5]), and silicon dioxide (Si[O.sub.2]) thin films prepared by dual ion beam sputtering. First, we investigate the stress ([sigma]), hardness (H), reduced Young's modulus ([E.sub.r]), and scratch resistance. Second, we focus on the methodology and assessment of the coefficient of thermal expansion (CTE) and Poisson's ratio (v) using the two-substrate method. For the high refractive index films, namely, [Nb.sub.2][O.sub.5] (n at 550 nm = 2.30) and [Ta.sub.2][O.sub.5] (n at 550 nm = 2.13), we obtained H ~ 6 GPa, [E.sub.r] ~ 125 GPa, CTE = 4.9 x [10.sup.-6] [degrees][C.sup.-1], v = 0.22, and H ~ 7 GPa, [E.sub.r] ~ 133 GPa, CTE = 4.4 x [10.sup.-6][degrees][C.sup.-1], and v = 0.27, respectively. In comparison, for Si[O.sub.2] (n at 550 nm = 1.48), these values are H ~ 9.5 GPa, [E.sub.r] ~ 87 GPa, CTE = 2.1 x [10.sup.-6][degrees][C.sup.-1], and v = 0.11. Correlations between the growth conditions (secondary beam ion energy and ion current), the microstructure, and the film properties are discussed. OCIS codes: 310.6870, 310.6860.

The wrinkling and delamination of stiff thin films adhered to a polymer substrate have important applications in 'flexible electronics.' The resulting periodic structures, when used for circuitry, have remarkable mechanical properties because stretching or twisting of the substrate is mostly accommodated through bending of the film, which minimizes fatigue or fracture. To date, applications in this context have used substrate patterning to create an anisotropic substrate-film adhesion energy, thereby producing a controlled array of delamination 'blisters.' However, even in the absence of such patterning, blisters appear spontaneously, with a characteristic size. Here, we perform well-controlled experiments at macroscopic scales to study what sets the dimensions of these blisters in terms of the material properties and explain our results by using a combination of scaling and analytical methods. Besides pointing to a method for determining the interfacial toughness, our analysis suggests a number of design guidelines for the thin films used in flexible electronic applications. Crucially, we show that, to avoid the possibility that delamination may cause fatigue damage, the thin film thickness must be greater than a critical value, which we determine. adhesion | elasticity | stretchable electronics | blistering | buckling

A system consisting of a circular multilayered thin-film elastic plate and a piezoelectric actuator, which is used for ultrasound generation in air, is analyzed and the effects of the electrode dimension of a circular thin-film piezoelectric actuator lying on a clamped multilayered elastic plate are examined. The results have shown that the deflection of the elastic plate is optimized by adjusting the radius of the top electrode.

Reynolds equation in polar cylindrical (polar) coordinates is used for numerous tribological applications that feature thin fluid films in sliding contacts, such as chemical mechanical polishing and pin-on-disk testing. Although unstated, tribology textbooks and literal' resources that present Reynolds equation in polar coordinates often make assumptions that the radial and tangential entrainment velocities are independent of the radial and tangential directions, respectively. The form of polar Reynolds equation is thus typically presented, while neglecting additional terms crucial to obtaining accurate solutions when these assumptions are not met. In the present investigation, the polar Reynolds equation is derived from the cylindrical Navier-Stokes equations without the aforementioned assumptions, and the resulting form is compared with results obtained from more traditionally used forms of the polar Reynolds equation. The polar form of Reynolds equation derived in this manuscript yields results that agree with the commonly used Cartesian form of Reynolds equation but are drastically different from the typically published form of the polar Reynolds equation. It is therefore suggested that the polar form of Reynolds equation proposed in this technical note be utilized when entrainment velocities are known to vary with either radial or angular position. [DOI: 10.1115/l.3118783] Keywords: Reynolds equation, polar coordinates, pin-on-disk, chemical mechanical polishing

End seals in squeeze film dampers (SFDs) aid to increase their damping capability while maintaining low lubricant flow rates and reducing the severity of air ingestion. This paper presents measurements of the forced response in a SFD integrating a contacting end seal and with closed flow ports, i.e., no lubricant through flow. The system motion is nonlinear due to the dry-friction interaction at the mechanical seal mating surfaces. Single parameter characterization of the test system would yield an equivalent viscous damping coefficient that is both frequency and motion amplitude dependent. Presently, an identification method suited for nonlinear systems allows determining simultaneously the squeeze film damping and inertia force coefficients and the seal dry-friction force. The identification procedure shows similar (within 10%) force coefficients than those obtained with a more involved two-step procedure that first requires measurements without any lubricant in the test system. The identified SFD damping and inertia force coefficients agree well with model predictions that account for end flow effects at recirculation grooves. The overall test results demonstrate that the nonrotating end seal effectively eliminates side leakage and avoids air ingestion, thus maintaining a consistent damping performance throughout the test frequency range. The nonlinear identification procedure saves time and resources while producing reliable physical parameter estimations. [DOI: 10.1115/1.2967498]

In order to evaluate the importance of stress relaxation on device performance of capacitive RF MEMS switches, stress relaxation has been measured in 1.2-[micro]m-thick Au films using a membrane bulge technique. When the residual stress in the films is small, the stress relaxation is fully recoverable and is well described by linear anelasticity (viscoelasticity) theory. A 27% reduction in the effective elastic modulus occurs over a three-day period under constant strain conditions at room temperature. The time dependence of the relaxation can be represented by a series of time constants with values extending from seconds to days. Linear superposition of the anelastic response can be used to accurately predict the stress under any time dependence of the strain. The prediction is accurate even during cyclic loading and unloading, and even when the strain is cycled at rates that are fast compared with any of the relaxation times. The restoring force available to open a capacitive RF MEMS switch is modeled for two different switch designs. The restoring force is shown to drop by approximately 7% or 20% at room temperature for the two cases presented. [2008-0263] Index Terms--Materials reliability, microelectromechanical devices, RF switch, stress measurement.

The strong stiction of adjacent surfaces with meniscus is a major design concern in the devices with a microsized interface. The present research concerns the elastic adhesion of rough fractal surfaces in the presence of a thin liquid film. A rough fractal surface is characterized with a two-variable Weierstrass-Mandelbrot fractal function. The microcontact model of the single asperity is established in terms of the fractal parameters. The adhesion model from meniscus is developed with the Dugdale approximation of the Laplace pressure to consider the adhesive interaction within/outside the contact area. Then the Maugis-Dugdale model and its extension are used to solve the elastic adhesive interaction for the two approaching fractal surfaces by incorporating the fractal surface model. Simulations of the external force versus the interface stiffness, surface roughness, and relative humidity are performed, respectively. The simulation results show that the interface stiffness, surface topography, and relative humidity can heavily influence the interface adhesion of rough surfaces with meniscus. [DOI: 10.1115/1.3084213] Keywords: meniscus, adhesion, fractal, microsized interface, Maugis-Dugdale model

The formation of a thin liquid film onto a moving substrate is a commonly encountered industrial process, and one that is encountered in lubrication, oil extraction processes, and coating flows. The formation of such a film is analyzed via the analytical Stokes flow solution for the flow in a wedge bounded on one side by a free surface and on the other by a moving surface. The full solution is obtained by numerically integrating a set of ordinary differential equations from far downstream, in the region of the final film thickness. The results show excellent agreement with the results obtained by the Bretherton equation, the Ruschak equation, the Coyne and Elrod model, and a two-dimensional free surface finite element simulation of the problem. [DOI: 10.1115/1.3089540]

The rupture of a 3D stationary free liquid film under the competing effects of surface tension and van der Waals forces is studied as a linearized stability problem in a purely irrotational analysis utilizing the dissipation method. The results of the foregoing analysis are compared with a 2D long-wave approximation that has given rise to an extensive literature on the rupture problem. The irrotational and long-wave approximations are here compared with the exact 2D solution. The exact solution and the two approximate theories give the same results for infinitely long waves. The problem considered depends on two dimensionless parameters, the Hamaker number and the Ohnesorge number. The Hamaker number is a dimensionless number defined as a measure of the ratio of van der Waals forces to surface tension. The exact solution and the two approximate solutions differ by thin film | irrotational flow | dissipation method

This paper describes the measurement of lubricant-film thickness in a rolling element bearing using a piezoelectric thin film transducer to excite and receive ultrasonic signals. High frequency (200 MHz) ultrasound is generated using a piezoelectric aluminum nitride film deposited in the form of a very thin layer onto the outer bearing raceway. This creates a transducer and electrode combination of total thickness of less than 10 [micro]m. In this way the bearing is instrumented with minimal disruption to the housing geometry and the oil-film can be measured noninvasively. The high frequency transducer generates a fine columnar beam of ultrasound that has dimensions less than the typical lubricated contact ellipse. The reflection coefficient from the lubricant-layer is then measured from within the lubricated contact and the oil-film thickness extracted via a quasistatic spring model. The results are described on a deep groove 6016 ball bearing supporting an 80 mm shaft under normal operating conditions. Good agreement is shown over a range of loads and speeds with lubricant-film thickness extracted from elastohydrodynamic lubrication theory. Keywords: piezoelectric thin films, rolling bearing, oil-film thickness measurement, reflection coefficient, condition monitoring

Calculating the fluid flow and pressure field in thin fluid films, lubrication theory can be applied, and Reynolds fluid film equation has to be solved. Therefore, boundary conditions have to be formulated. Well-established mass-conserving boundary conditions are the Jakobsson--Floberg--Olsson (JFO) boundary conditions. A number of numerical techniques, which have certain advantages and certain disadvantages, have been developed to solve the Reynolds equation in combination with JFO boundary conditions. In the current paper, a further method is outlined, which may be a useful alternative to well-known techniques. The main idea is to rewrite the boundary value problem consisting of the Reynolds equation and the JFO boundary conditions as an arbitrary Lagrangian--Eulerian (ALE) problem. In the following, an ALE formulation of the Reynolds equation with JFO boundary conditions is derived. Based on a finite element implementation of the governing boundary value problem, numerical examples are presented, and pressure fields are calculated for a plain hydrodynamic journal bearing with an axial oil groove. Keywords: Reynolds equation, fluid film theory, hydrodynamic journal bearing, Jakobsson--Floberg--Olsson (JFO) boundary conditions, moving mesh, arbitrary Lagrangian--Eulerian (ALE)

A bulge testing system was developed to mechanically characterize the deformation behaviors and elastic moduli of multilayered films, mainly composed of polycrystalline silicon (polysilicon) and lead zirconate titanate (PZT), used in a multilayer actuator of a piezoelectric inkjet head. In the tests, commercial inkjet heads including a few tens of multilayer actuators were directly pressurized by air, and the corresponding deflections were measured via full-field optical measurement techniques. An analytic solution derived from a thin-plate theory and finite-element analysis were used to describe pressure-deflection behaviors of films, and the results were compared with the experimental data to evaluate the elastic modulus of individual film. The results showed that the elastic moduli of polysilicon and PZT films are ~110 and ~49 GPa, respectively. These values were consistent with the nanoindentation results. For polysilicon films, about 30% reduction in elastic modulus, compared with that calculated from single-crystal elastic constants, was observed, and this was most likely attributed to the presence of microdefects like voids and microcracks at grain boundaries between columnar grains. [2008-0056] Index Terms--Bulge test, full-field optical measurement, multilayered films, piezoelectric inkjet head.

The bulge test is successfully extended to the determination of the fracture properties of silicon nitride and oxide thin films. This is achieved by using long diaphragms made of silicon nitride single layers and oxide/nitride bilayers, and applying a comprehensive mechanical model that describes the mechanical response of the diaphragms under uniform differential pressure. The model is valid for thin films with arbitrary z-dependent plane-strain modulus and prestress, where z denotes the coordinate perpendicular to the diaphragm. It takes into account the bending rigidity and stretching stiffness of the layered materials and the compliance of the supporting edges. This enables the accurate computation of the load-deflection response and stress distribution throughout the composite diaphragm as a function of the load, in particular at the critical pressure leading to the fracture of the diaphragms. The method is applied to diaphragms made of single layers of 300-nm-thick silicon nitride deposited by low-pressure chemical vapor deposition and composite diaphragms of silicon nitride grown on top of thermal silicon oxide films produced by wet thermal oxidation at 950 [degrees]C and 1050 [degrees]C with target thicknesses of 500, 750, and 1000 nm. All films characterized have an amorphous structure. Plane-strain moduli [E.sub.ps] and prestress levels [[sigma].sub.o] of 304.8 [+ or -] 12.2 GPa and 1132.3 [+ or -] 34.4 MPa, respectively, are extracted for [Si.sub.3][N.sub.4], whereas [E.sub.ps] = 49.1 [+ or -] 7.4 GPa and [[sigma].sub.o] = -258.6 [+ or -] 23.1 MPa are obtained for Si[O.sub.2] films. The fracture data are analyzed using the standardized form of the Weibull distribution. The [Si.sub.3][N.sub.4] films present relatively high values of maximum stress at fracture and Weibull moduli, i.e., [[sigma].sub.max] = 7.89 [+ or -] 0.23 GPa and m = 50.0 [+ or -] 3.6, respectively, when compared to the thermal oxides ([[sigma].sub.max] 0.89 [+ or -] 0.07 GPa and m = 12.1 [+ or -] 0.5 for 507-nm-thick 950 [degrees]C layers). A marginal decrease of [[sigma].sub.max] with thickness is observed for Si[O.sub.2], with no significant differences between the films grown at 950 [degrees]C and 1050 [degrees]C. Weibull moduli of oxide thin films are found to lie between 4.5 [+ or -] 1.2 and 19.8 [+ or -] 4.2, depending on the oxidation temperature and film thickness. [2007-0269] Index Terms--Bulge test, fracture, pooled Weibull analysis, silicon nitride ([Si.sub.3][N.sub.4]), silicon oxide (Si[O.sub.2]).

Micron-scale static friction and wear coefficients, surface roughness, and resulting wear debris have been studied for sliding wear in polycrystalline silicon in ambient air at micro-Newton normal loads using on-chip sidewall test specimens, fabricated with the Sandia SUMMIT V[TM] process. With increasing number of wear cycles friction coefficients increased by a factor of two up to a steady-state regime, concomitant with a decay (after an initial sharp increase) in the wear coefficients and roughness. Wear coefficients were orders of magnitude smaller than reported macroscale values, suggesting that the wear resistance is higher at micrometer dimensions. Based on our observations, a sequence of micron-scale wear mechanisms is proposed involving: 1) a short adhesive wear regime (< [10.sup.4] cycles), where the oxide is worn away and the first silicon debris particles form and 2) a regime dominated by abrasive wear, where silicon particles (50-100 nm) are created by fracture through the grains (~500 nm). These particles subsequently oxidize and agglomerate into larger debris clusters, while 'ploughing' by this debris leads to abrasive grooves associated with local cracking events rather than plastic deformation. [2007-0292] Index Terms--Friction, microelectromechanical systems (MEMS), silicon, thin films, wear.

Phase-change materials have been extensively used for optical data storage in commercial rewritable compact disks and digital video disks. These materials are also widely considered for next-generation phase-change random access memories to replace current Flash memories. We suggest a different application of phase-change materials in optically triggered microactuators. The suggested device consists of a thin film of a phase-change material deposited on a microfabricated cantilever. A laser-induced phase transformation in the fill initiates a cantilever deflection since the transformation is accompanied by a large density change. We analyze quantitative criteria for material selection and optimization of device dimensions for the largest possible actuation angles and deflections. The resulting analytical model is both verified numerically and applied experimentally. Furthermore, we show that these cantilevers offer a convenient way to measure film stresses and film strains associated with laser-induced phase transformations. [2007-0276] Index Terms--Actuators, laser annealing, stress measurement, tellurium alloys.

In this study, the contact problems of thin films and cover plates are considered. In these problems, the loading consists of any one or combination of stresses caused by uniform temperature changes and temperature excursions, far field mechanical loading, and residual stresses resulting from film processing or welding. The primary interest in this study is in examining stress concentrations or singularities near the film ends for the purpose of addressing the question of crack initiation and propagation in the substrate or along the interface. The underlying contact mechanics problem is formulated by assuming that the film is a 'membrane' and the substrate a graded elastic continuum, and is solved analytically by reducing it to an integral equation. The calculated results are the interfacial shear stress between the film and the graded substrate, the Mode II stress intensity factor at the end of the film, and the axial normal stress in the film. The results indicate that grading the material properties of the substrate helps to decrease the film stresses and the stress intensity factors at the free edges and to lower the axial normal stresses at the midsection where the film is most likely to crack. [DOI: 10.1115/1.2936237] Keywords: thin film, contact stress, functionally graded material, cover plate, stress intensity factor

The influence of inertia and boundary conditions on the steady state and stability of isothermal film casting of viscoelastic fluids is examined using a Phan-Thien-Tanner rheological model. The elongational flow between the die exit and the take-up point is investigated. In general, the steady-state film tends to contract for low-inertia flow; this contraction, however, is significantly diminished by inertia. The polymeric normal stresses and primary normal stress difference decrease in the most of the air gap as inertia increases. In contrast, the stress and stress difference increase considerably near the take-up point due to a dramatic increase in the elongation rate. The linear stability analysis for two-dimensional disturbances is carried out. For a polymer with no degradation, and in the absence of inertia (Re = 0), the analysis predicts critical draw ratios that form an envelope to an unstable region. This region of unstable conditions reduces as inertia increases. Two branches of neutral stability curve are observed for higher-inertia flow as opposed to a single curve for Re = 0. The unstable region expands as a increases, where a is a measure of polymer degradation. When a becomes sufficiently large, the elasticity tends to destabilize the flow. It is also found that boundary conditions have an important influence on the steady-state profiles and stability region, particularly for high-elasticity fluids. [DOI: 10.1115/1.2956592]

The special methods to model the electrodes at the crystal interface of an AT cut crystal are described. The electrode thin film approximations facilitated the accurate analyses of larger problems by reducing the overall size of the problem and the time of computations.

The fracture toughness, fracture strength, and stress corrosion cracking behavior of thin-film amorphous silicon dioxide (Si[O.sub.2]) deposited on silicon wafers via plasma-enhanced chemical vapor deposition have been measured using specimens with length scales comparable to micromachined devices. Clamped--clamped microtensile specimens were fabricated using standard micromachining techniques. These devices exploit residual tensile stresses in the film to create stress intensity factors at precrack tips and stress concentrations at notches, in order to measure fracture toughness and fracture strength, respectively. The fracture toughness of thin-film Si[O.sub.2] was 0.77 [+ or -] 0.15 MPa * [m.sup.1/2], and the fracture strength was 0.81 [+ or -] 0.06 GPa. Stress corrosion cracking (slow crack growth) was also measured in the Si[O.sub.2] devices with sharp precracks subjected to residual tensile stresses. These data are used to predict lifetimes for a Si[O.sub.2]-based microdevice. Index Terms--Ceramics, corrosion, microelectromechanical devices, stress, thin films.

In order to measure temperature fields on tool face during cutting, a cutting tool with built-in thin film thermocouples (TFTs) has been devised. The TFTs composed of a nickel and nichrome thin films were fabricated on the rake face near the cutting edge of a sintered alumina tool insert using a physical vapor deposition and photolithography technique. An empirical formula that shows Seebeck coefficient of a TFT depends on electrical resistance of the TFT circuit was established. Three different types of tools in number and size of TFTs were developed and temperature fields on the rake face in cutting of a plain carbon steel $45C were measured. The results of the cutting thermometry experiment reveal that the devised tool with built-in three TFTs can measure temperature fields on the tool face and can sense slight change in cutting situation. [DOI: 10.1115/1.2823066] Keywords: cutting temperature, thin film thermocouple, Seebeck coefficient, PVD coating

Steady two-dimensional thin-film flow of a Newtonian fluid is examined in this theoretical study. The influence of exit conditions and gravity is examined in detail. The considered flow is of moderately high inertia. The flow is dictated by the thin-film equations of boundary layer type, which are solved by expanding the flow field in orthonormal modes in the transverse direction and using Galerkin projection method, combined with integration along the flow direction. Three types of exit conditions are investigated, namely, parabolic, semiparabolic, and uniform flow. It is found that the type of exit conditions has a significant effect on the development of the free surface and flow field near the exit. While for the parabolic velocity profile at the exit, the free surface exhibits a local depression, for semiparabolic and uniform velocity profiles, the height of the film increases monotonically with streamwise position. In order to examine the influence of gravity, the flow is studied down a vertical wall as well as over a horizontal wall. The role of gravity is different for the two types of wall orientation. It is found that for the horizontal wall, a hydraulic-jump-like structure is formed and the flow further downstream exhibits a shock. The influence of exit conditions on shock formation is examined in detail. [DOI: 10.1115/1.2928387]

The delamination of thin coating films from substrates is a critical issue for the reliability of micro- and nanoelectronic devices. Indentation methods have the potential to measure interfacial strength in micro- and nanofilm thickness coating films. In this paper, indentation tests of layered structures are simulated using the damage-based cohesive zone model. When the delamination initiates, the indentation load and depth curve tend to deviate from the indentation load and depth curve for the perfectly bonded case. When the interface is stiffer than the coating film, a brittlelike delamination occurs on the interface; when the stiffness of the interface is smaller than that of the coating layer, a ductilelike delamination occurs on the interface. The ratio of shear moduli, [mu.sub.int]/[[mu].sub.PI], characterizes the delamination behavior on the interface during indentation tests. Focusing on the discontinuous point during the indentation tests and introducing the balance of energy before and after the onset of delamination, the evaluation method of the interfacial strength is proposed. The proposed method can be used to estimate the interfacial strength when the ratio of hardness and the yield stress of the coating film is 3.5 < [H.sub.A]/[[sigma].sub.y] < 4.5. Keywords: interface, thin film, indentation, finite element method, cohesive zone model, delamination, interfacial strength, plastic deformation, indentation hardness

This investigation proposes the use of the shadow moire method (SMM) to measure stress in a thin film that is coated on a flexible substrate. The technique defines the profile of the sample by contour lines without the application of an external force, and the radius of curvature is calculated from these contour lines. The SMM is insensitive to environmental noise and has the same advantages as the interference method, such as being nondestructive and easy to use. For A1 film with a thickness of 120 nm coated on a polyimide substrate by a DC magnetron sputtering system (800 W, room temperature), the stress is 0.45 [+ or -] 0.042 GPa. OCIS codes: 120.4120, 310.6870.

Mg[F.sub.2] films with a columnar microstructure are obliquely deposited on glass substrates by resistive heating evaporation. The columnar angles of the films increases with the deposition angle. Anisotropic stress does not develop in the films with tilted columns. The residual stresses in the films depend on the deposition and columnar angles in a columnar microstructure. OCIS codes: 310.6870, 310.4925, 310.1860.

Titanium oxide (Ti[O.sub.2]) thin films were prepared by different deposition methods. The methods were E-gun evaporation with ion-assisted deposition (IAD), radio-frequency (RF) ion-beam sputtering, and direct current (DC) magnetron sputtering. Residual stress was released after annealing the films deposited by RF ion-beam or DC magnetron sputtering but not evaporation, and the extinction coefficient varied significantly. The surface roughness of the evaporated films exceeded that of both sputtered films. At the annealing temperature of 300 [degrees]C, anatase crystallization occurred in evaporated film but not in the RF ion-beam or DC magnetron-sputtered films. Ti[O.sub.2] films deposited by sputtering were generally more stable during annealing than those deposited by evaporation. OCIS codes: 310.0310, 310.1860, 310.6860, 310.6870.

La[F.sub.3] thin films of different thicknesses were deposited on Ca[F.sub.2] (111) and silicon substrates at a relatively low substrate temperature of 150 [degrees]C. Optical (transmittance, reflectance, refractive index, and extinction coefficient) and mechanical (morphology and crystalline structure) properties have been investigated and are discussed. It is shown that La[F.sub.3] thin films deposited on Ca[F.sub.2] (111) substrates are monocrystalline and have a bulklike dense structure. Furthermore, it is presented that low-loss La[F.sub.3] thin films can be deposited not only by boat evaporation but also by electron beam evaporation. OCIS codes: 310.0310, 310.6870.

The effect of the characteristics of the Landau-Devonshire free energy and values of electrostatic and elastic interactions on the formation of different types of domain structures in ferroelectric thin films is examined with phase-field simulations. Findings reveal a minor role-played by the applied field strength and the thickness of the dead layer in the transition between 90 degree and 180 degree domain structures.

The main objective of this research is to analyze the variation of minimum film thickness in the inlet zone of roll-strip interface by incorporating starvation and viscous shear heating effects at high rolling speeds (5-20 m/s), reduction ratios (0.05-0.20), and slip values (varying up to 20%). An additional objective of this paper is to develop empirical relations for predictions of minimum film thicknesses (both isothermal and thermal) and maximum film temperature rise in the inlet zone of the lubricated roll strip contact as functions of roll-speed, reduction ratio, material parameter, slip, and starvation parameter. An efficient numerical method based on Lobatto quadrature technique is adopted for rigorous analysis of the present problem. The results reveal that the existence of starvation seems to be beneficial in terms of reduction in maximum film temperature rise as well as reduction in quantity of oil required for lubrication provided thin continuous film exists at the contact. Keywords: thermohydrodynamic analysis, high-speed cold rolling, minimum film thickness, starvation, film temperature rise, empirical relations

In this paper, the effects of rotation on the distribution of a layer of oil on a bearing raceway are analyzed in relation to the geometry of the raceway. The research is motivated by the need to understand the behavior of grease lubricated bearings. Some specific aspects of grease lubrication can be understood by approximating the contact as a starved lubricated elastohydrodynamic lubrication contact. In such a contact, the shape and thickness of the inlet layer of oil, supplied to the contact on the running track, are of crucial importance to the film formation and contact performance. Small changes in the distribution of lubricant on the rolling track, as a result of reflow or redistribution, may have a large (local) effect on the film thickness inside the contact. Starting from the Navier-Stokes equations, the free surface thin layer flow equation for axisymmetric rotating surfaces is derived. For the case of bearing applications, it is shown that a simple quasilinear equation can be derived for the layer thickness, as a function of location and time, which can be solved analytically. Experiments have been carried out, measuring the changes of a layer of oil on rotating raceways in time in relation to the rotational speed and the raceway geometry. It is shown that the simplified model accurately predicts the thin layer flow, except in a region near the outflow boundary, where the effect of the boundary condition on the layer shape is crucial. This is further illustrated by results of numerical simulations. Keywords: lubrication, roller bearing, thin film flow, centrifugal effects

A novel experimental method has been developed to investigate how model asperities, on opposing surfaces in an elastohydrodynamic (EHD) contact, interact to influence the lubricant film distribution. This technique allows direct measurements of lubricant film thickness during asperity-asperity collision. A surface having a single transverse ridge asperity was rubbed against a second surface having three different roughness features, a transverse ridge, multiple transverse ridges, and an array of hemispherical bumps to study the resultant micro-EHD films. This work reveals how the film thickness is greatly reduced when the peaks of opposing asperities coincide, and how asperities can combine to cause a larger volume of lubricant to be entrapped at their leading edges. The new technique described shows considerable promise for the study of mixed lubrication. Keywords: elastohydrodynamic lubrication, mixed lubrication, micro-EHL, thin film, surface roughness, asperity collision

This paper reports the mechanical properties and fracture behavior of silicon carbide (3C-SiC) thin films grown on silicon substrates. Using bulge testing combined with a refined load-deflection model of long rectangular membranes, which takes into account the bending stiffness and prestress of the membrane material, the Young's modulus, prestress, and fracture strength for the 3C-SiC thin films with thicknesses of 0.40 and 1.42 [micro]m were extracted. The stress distribution in the membranes under a load was calculated analytically. The prestresses for the two films were 322 [+ or -] 47 and 201 [+ or -] 34 MPa, respectively. The thinner 3C-SiC film with a strong (111) orientation has a plane-gstrain moduli of 415 [+ or -] 61 GPa, whereas the thicker film with a mixture of both (111) and (110) orientations exhibited a plane-strain moduli of 329 [+ or -] 49 GPa. The corresponding fracture strengths for the two kinds of SiC films were 6.49 [+ or -] 0.88 and 3.16 [+ or -] 0.38 GPa, respectively. The reference stresses were computed by integrating the local stress of the membrane at the fracture over edge, surface, and volume of the specimens and were fitted with Weibull distribution function. For the 0.40-[micro]m-thick membranes, the surface integration has a better agreement between the data and the model, implying that the surface flaws are the dominant fracture origin. For the 1.42-[micro]m-thick membranes, the surface integration presented only a slightly better fitting quality than the other two, and therefore, it is difficult to rule out unambiguously the effects of the volume and edge flaws. [2007-0191] Index Terms--Bulge test, fracture property, microelectromechanical systems (MEMS), silicon carbide (SIC) thin films, Weibull distribution function.

Current methodologies used for the inference of thin film stress through curvature measurements are strictly restricted to uniform film stress and system curvature states over the entire system of a single thin film on a substrate. By considering a circular multilayer thin film/substrate system subjected to nonuniform temperature distributions, we derive relations between the stresses in each film and temperature, and between the system curvatures and temperature. These relations featured a 'local' part that involves a direct dependence of the stress or curvature components on the temperature at the same point, and a 'nonlocal' part, which reflects the effect of temperature of other points on the location of scrutiny. We also derive relations between the film stresses in each film and the system curvatures, which allow for the experimental inference of such stresses from full-field curvature measurements in the presence of arbitrary nonuniformities. These relations also feature a 'nonlocal' dependence on curvatures making full-field measurements of curvature a necessity for the correct inference of stress. The interfacial shear tractions between the films and between the film and substrate are proportional to the gradient of the first curvature invariant, and can also be inferred experimentally. [DOI: 10.1115/1.2755178] Keywords: multilayer thin films, nonuniform film temperatures and stresses, nonuniform system curvatures, nonlocal stress-curvature relations, interfacial shears