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NANOSTRUCTURED SURFACES THAT CAN KILL BACTERIA Engineers at Purdue University, West Lafayette, Ind., have developed a laser treatment method with the potential to transform metal surfaces into bacteria killers. The [...]

An analytical solution is developed for thermal stress in exponentially time decaying laser short-pulse heating of a metallic surface. Because the heating duration is short, a nonequilibrium heating model incorporating the electron kinetic theory approach is used to formulate the temperature distribution during the laser heating pulse. Thermomechanical coupling is introduced in the analysis to formulate the thermal stress field. Thermodynamic irreversibility is considered and the entropy generation rate due to heat transfer and thermal stress field is formulated during the heating process. It is found that temperature decays gradually in the surface region and becomes sharp as the distance increases towards the solid bulk. Thermal stress is compressive in the irradiated region. Thermodynamic irreversibility due to heat transfer dominates thermodynamic irreversibility because of the thermal stress field. PACS No.: 44.10.+i. Nous presentons une solution analytique pour la contrainte thermique due a une impulsion laser a decroissance exponentielle sur une surface metallique. Parce que le chauffage est de courte duree, nous utilisons un modele de chauffage hors d'equilibre incorporant la theorie cinetique des electrons afin de formuler la distribution de temperature pendant l'impulsion laser. L'introduction d'un couplage thermomecanique permet de decrire le champ de contrainte thermique. Nous tenons compte de l'irreversibilite thermodynamique et nous formulons le taux de generation d'entropie du au transfert de chaleur et au champ de contrainte thermique pendant le processus, pour trouver que la diminution de temperature qui est graduelle dans la region du chauffage devient rapide a distance. La contrainte thermique est compressive dans la region du chauffage. L'irreversibilite thermodynamique due au transfert de chaleur est plus importante que celle due a la contrainte thermique. [Traduit par la Redaction], Introduction Laser short pulse heating of metallic surfaces involves nonequilibrium energy transport in the irradiated region. Electron and lattice subsystems separate thermally because of electron temperature increases through energy absorption [...]

We analyze the focusing properties of Fresnel zone plates fabricated over steel tapes using laser ablation. Our intention is to implement the use of micro-optical elements when the use of conventional chrome-glass elements is not indicated. Because of the manufacture process, the surface presents a certain anisotropic roughness, which reduces the focusing properties. First, we develop numerical simulations by means of the Rayleigh--Sommerfeld approach, showing how roughness in both levels of the Fresnel zone plate affects the focalization of the lens. We also manufacture Fresnel zone plates over steel tape, and perform experimental verification that corroborates the numerical results. [c] 2010 Optical Society of America OCIS codes: 050.1965, 240.3990, 240.5770.

Nonadiabatic coupling of nuclear motion to electronic excitations at metal surfaces is believed to influence a host of important chemical processes and has generated a great deal of experimental and theoretical interest. We applied a recently developed theoretical framework to examine the nature and importance of nonadiabatic behavior in a system that has been extensively studied experimentally: the scattering of vibrationally excited nitric oxide molecules from a Au(111) surface. We conclude that the nonadiabatic transition rate depends strongly on both the N-O internuclear separation and the molecular orientation and, furthermore, that molecule-surface forces can steer the molecule into strong-coupling configurations. This mechanism elucidates key features of the experiments and provides several testable predictions regarding the dependence of vibrational energy transfer on the initial vibrational energy, molecular orientation, and incident angle. 10.1126/science.1179240

Reflectance micro-Fourier transform infrared (FT-IR) analysis has been applied to characterize biofilm formation of Aquabacterium commune, a common microorganism present on drinking water distribution systems, onto the increasingly popular pipe material stainless steel EN1.4307. The applicability of the reflectance micro-FT-IR technique for analyzing the bacterial functional groups is discussed, and the results are compared to spectra obtained using more conventional FT-IR techniques: transmission micro-FT-IR, attenuated transmitted reflectance (ATR), and KBr pellets. The differences between the infrared spectra of wet and dried bacteria, as well as free versus attached bacteria, are also discussed. The spectra obtained using reflectance micro-FT-IR spectroscopy were comparable to those obtained using other FT-IR techniques. The absence of sample preparation, the potential to analyze intact samples, and the ability to characterize opaque and thick samples without the need to transfer the bacterial samples to an infrared transparent medium or produce a pure culture were the main advantages of reflectance micro-FT-IR spectroscopy.

A chemicurrent is a flux of fast (kinetic energy [??] 0.5-1.3 eV) metal electrons caused by moderately exothermic (1-3 eV) chemical reactions over high work function (4-6 eV) metal surfaces. In this report, the relation between chemicurrent and surface chemistry is elucidated with a combination of top-down phenomenology and bottom-up atomic-scale modeling. Examination of catalytic CO oxidation, an example which exhibits a chemicurrent, reveals 3 constituents of this relation: The localization of some conduction electrons to the surface via a reduction reaction, 0.5 [O.sub.2] + [delta][e.sup.-] [right arrow] [O.sup.[delta]-] (Red); the delocalization of some surface electrons into a conduction band in an oxidation reaction, [O.sup.[delta]-] + CO [right arrow] C[O.sup.[delta]-.sub.2] [right arrow] C[O.sub.2] + [[delta]e.sup.-] (Ox); and relaxation without charge transfer (Rel). Juxtaposition of Red, Ox, and Rel produces a daunting variety of metal electronic excitations, but only those that originate from C[O.sub.2] reactive desorption are long-range and fast enough to dominate the chemicurrent. The chemicurrent yield depends on the universality class of the desorption process and the distribution of the desorption thresholds. This analysis implies a power-law relation with exponent 2.66 between the chemicurrent and the heat of adsorption, which is consistent with experimental findings for a range of systems. This picture also applies to other oxidation-reduction reactions over high work function metal surfaces. heterogeneous catalysis | hot electrons | metal surfaces | surface science | transition metals

The effect of facial ring jewelry is investigated on the energy absorbed in the head when illuminated by communications-enabled personal data assistant (PDA)-type devices. We study the relative changes in specific absorption rates in the head due to perturbing metallic rings in proximity to the face illuminated by a 1.8 GHz dipole and a monopole on a conducting box. Simple and complex head models used in a validated finite-difference time-domain (FDTD) simulation are compared with measurements from an industry standard DASY4 SAR measurement system. Both simulation and measurement ate referred to the IEEE specific anthropomorphic mannequin head. Results show that metallic rings may alter specific absorption rates (SAR) level distributions within the head. Results are given for several common ring sizes. Index Terms--DASY4, finite-difference time-domain (FDTD), metallic jewelry, personal data assistant (PDA), specific absorption rates (SAR).

The article discusses the synthesis and the properties of the chiral metal surfaces, which are commonly employed in enantioselective catalysis.

Solid panicle erosion of metal surfaces is a major problem in several fluid handling industries due to unpredicted equipment failure and production loss. The prediction of erosion is difficult even in a single-phase flow. The complexity of the problem increases significantly in a multiphase flow due to the existence of different flow patterns where the spatial distribution of the phases changes with the change of phase flow rates. Earlier predictive means of erosion in single and multiphase flows were primarily based on empirical data and were limited to the flow conditions of the experiments. A mechanistic model has been developed for predicting rosion in single-phase and multiphase flows considering the effects of solid particle impact velocities that cause erosion. Local fluid velocities and simplified equations are used to calculate erosion rates assuming a uniform distribution of solid particles in the liquid phase in the multiphase flow. Another assumption was that the solid particle velocities are similar to the velocity of the fluids surrounding the particles. As the model is based on the physics of multiphase flow and erosion phenomenon, it is more general than the previous models. The predicted erosion rates obtained by the mechanistic model are compared to experimental data available in the literature showing a reasonably good agreement. [DOI: 10.1115/1.2767336]

The robustness of the hole target against laser parameter changes in a laser spot size and in a laser pulse length against a contaminated proton source layer and against a laser alignment error are described. The multiple-hole target is robust against a laser alignment error and a target positioning error and it has served as a robust target for practical uses to produce a collimated proton beam.

A method to detect minute flaws on metal parts is proposed to remove defective parts before assembling in a factory. The input grayscale images of metal parts are directly used to recognize flaws without any image conversion to shorten recognition time. The recognition problem to find flaws and detect their position on the metal parts is converted to another problem that searches for the maximum peak and the variables producing the peak. Then, the recognition problem can be treated as an optimization problem, and this conversion allows us to utilize high genetic algorithm performances in optimization. The effectiveness and problems of the proposed method are studied on the standing points of recognition speed and quantitative recognition ability. Based on the analysis, we furthermore improved our system to increase the flaw detection rate; the lighting direction was changed to find the best lighting condition that can emphasize the contrast between the metal surface and the flaw by using the reflection character of the hairline on the metal, which is resulted by a polishing process. Index Terms--Genetic algorithm (GA), metal surface inspection, model-based matching.

Hemming is a manufacturing process of folding a panel onto itself or another sheet. Quality of hemming is characterized by geometry and formability. This paper presents a response surface study of three-dimensional (3D) curved-surface-curved-edge hemming of an aluminum alloy, AA6111-T4, using finite-element ( FE) analysis. Solid elements and explicit FE solver are used for simulations of flanging, pre- and final hemming, and shell elements with implicit solver are deployed for springback prediction. A novel procedure called 'solid-to-shell mapping' is developed to bridge the solid elements with the shell elements. Verified to be accurate and efficient, the model is utilized in a central composite design to quantitatively explore the relationships between certain key process variables and the hem dimensional quality and formability. The most significant variables are identified as: (i) prehemming angle on roll-in/roll-out; (ii) nominal surface curvature on sheet springback; and (iii) initial sheet strain and flanging die radius on the maximum hemline surface strain of the produced hem. These results provide insights for process parameter selections in designing and optimizing 3D hems under material formability constraints. [DOI: 10.1115/1.2515430] Keywords: aluminum hemming, dimensional quality, formability, solid-to-shell mapping, central composite design

In the present paper the applicability of state and rate dependent friction laws in describing the phenomena of high speed slip at metal-on-metal interfaces is investigated. For the purpose of model validation, results of plate-impact pressure-shear friction experiments were conducted by Irfan in 1998 and Irfan and Prakash in 2000 using a Ti6AI4V and Carpenter Hampden tool-steel tribo pair are employed. In these experiments high normal pressures (1-3 GPa) and slip speeds of approximately 50 m/s were attained during the high-speed slip event. Moreover, these experiments were designed to investigate the evolution of friction stress in response to step changes in normal pressure and also in the applied shear stress during the high-speed slip event. A step drop in normal pressure is observed to result in an exponential decay of the friction stress to a new steady-state characteristic of the current normal pressure and the current slip velocity. A step drop in applied shear stress is observed to lead to an initial drop in friction stress, which later increases toward a new steady-state friction stress level. In response to the step drop in applied shear stress the slip velocity initially increases and then decreases to a new steady-state level consistent with the new friction stress level. A modified rate and state dependent friction model that employs both velocity and normal stress dependent state variables is used to simulate the experimental results. A good correlation is found between the experimental results and the predictions of the proposed state and rate dependent friction model. [DOI: 10.1115/1.2401217] Keywords: mathematical modeling, high speed frictional slip, plate impact friction experiments, state and rate dependent friction

The major limiting factor in the transmission of high-power microwave (HPM) has been the interface between dielectric-vacuum or, even more severely, between dielectric-air, if HPM is to be radiated into the atmosphere. Extensive studies have identified the physical mechanisms associated with vacuum-dielectric flashover, as opposed to the mechanisms associated with air-dielectric flashover, which are not as well known. Surface-flashover tests involving high field enhancement due to the presence of a triple point have shown that volume breakdown threshold (dielectric removed) is approximately 50% higher than the flashover threshold with a dielectric interface over the 90-760 torr range. In order to quantify the role of field enhancement in the flashover process independent of electron injection from metallic surfaces, the effects of the triple point are minimized by carefully choosing the geometry, and in some cases, the triple point is 'removed' from the flashover location. Experimental results were presented, including the impact of gas pressure and the presence of UV illumination, along with temperature analysis of the developing discharge plasma and temporally resolved images of the flashover formation. These results are compared with literature data for volume breakdown in air, with discussion on the similarities and differences between the data. Index Terms--Atmospheric, breakdown, dielectric surface, high-power microwave (HPM), surface flashover.

The trend that group 13 metals prefer pentagonal -bipyramidal skeleton, rather than an icosahedron is explained by orientation of the [pi]-orbitals of the ring in both cases. The overlap between ring [pi]-orbitals and cap orbitals is improved by the out-of-plane bending of ring hydrogens and five-membered ring of pentagonal bipyramid makes better overlap with the diffuse orbital of metals effectively than that of isoashedron.

In the field of industrial vision, the three-dimensional inspection of highly reflective metallic objects is still a delicate task. We deal with a new automated three-dimensional inspection system based on polarization analysis. We first present an extension of the shape-from-polarization method for dielectric surfaces to metallic surfaces. Then, we describe what we believe to be a new way of solving the ambiguity concerning the normal orientation with an active lighting system. Finally, applications to shape-defect detection are discussed, and the efficiency of the system to discriminate defects on specular metallic objects made by stamping and polishing is presented. OCIS code: 110.6880

A new conformal finite-difference time-domain (CFDTD) updating scheme for metallic surfaces nonaligned in the grid is presented in this paper. In contrast to existing conformal models, the new model can be formulated with the original Yee FDTD update equation. Therefore, the proposed scheme can be easily added in standard FDTD codes even if the codes are already parallelized or hardware-accelerated. In addition, based on the commonly used conventional stability criterion, a derivation of the stability is presented and based on the conformal geometric information, a time step reduction formula is presented. The time step reduction is used as a user-defined parameter to tradeoff speed versus accuracy. The achievable geometric precision is optimized to a given time step. Therefore, even with the conventional time step (no reduction) the presented scheme profits from the conformal discretization. To show the performance and the robustness of the proposed scheme canonical validations and two real world applications were investigated. A broadband low profile (circular) antenna was successfully simulated showing the benefit of the conformal FDTD method compared to the conventional scheme. Furthermore, a CAD based mobile phone was conformally discretized and successfully simulated showing that the proposed scheme is highly suited for the simulation of advanced engineering problems. Index Terms--Conformal finite-difference time-domain (CFDTD) method, finite-difference time-domain (FDTD) method, subcell.

Recently, there has been an increased interest in the problem of wave transmission through sub-wavelength apertures, following successful experimental demonstration by several groups for enhancing optical power transmission through nano-scale holes in metallic screens due to properly designed periodic corrugation. Oliner, Jackson, and their co-workers explained and justified this phenomenon as the result of the excitation of the leaky waves supported by the corrugated screen. Here we discuss in detail the mechanism and analysis for another setup we have recently proposed, in which metamaterial layers with special parameters may be utilized as covers over a single sub-wavelength aperture in a perfectly electric conducting (PEC) flat screen in order to increase the wave transmission through this aperture, and we provide a detailed physical insights and analytical explanation for this aperture setup that may lead to similar, potentially even more pronounced effects when the proper metamaterial layers are used in the entrance and the exit face of the hole in the flat PEC screen with no corrugation. Some numerical results confirming this theory are presented and discussed. We also investigate the sensitivity of the transmission enhancement to the geometrical and electromagnetic parameters of this structure. Index Terms--Aperture coupling, aperture enhancement, leaky wave, metamaterials, polariton, sub-wavelength aperture.

We use the finite-difference time-domain (FDTD) method to model the spectral properties of frequency-selective surfaces (FSSs) at normal incidence in the 1-10 [micro]m wavelength. At these wavelengths the usual assumption that the metallic portions of a FSS are infinitesimally thin perfect conductors are no longer valid. We include the effects of dispersive complex conductivity for real metals and dispersive permittivity for dielectric materials by developing a unified approach that is especially suited for use in FDTD simulations. We concentrate on the finite nature of the metallic conductivity and its variation with wavelength in FSS structures. Our simulation results indicate that the resonant spectrum of a FSS in this wavelength range depends not only on the geometry of the structure and the dielectric substrate present, but also critically on the dispersive properties of the metal species used for the conductors. OCIS codes: 000.4430, 160.3900, 160.4760, 260.2030, 260.3910.

We present a procedure that compensates for phase aberrations in digital holographic microscopy by computing a polynomial phase mask directly from the hologram. The phase-mask parameters are computed automatically without knowledge of physical values such as wave vectors, focal lengths, or distances. This method enables one to reconstruct correct and accurate phase distributions, even in the presence of strong and high-order aberrations. Examples of applications are shown for microlens imaging and for compensating for the deformations associated with a tilted thick plate. Finally we show that this method allows compensation for the curvature of the specimen, revealing its surface defects and roughness. Examples of applications are shown for microlenses and metallic sphere imaging. OCIS codes: 090.1760, 090.1000, 180.0180, 120.5050, 120.3620.

A density matrix treatment is presented for the vibrational relaxation of the frustrated translational mode of a molecule adsorbed on a metal system. The system is modeled as a vibrating adsorbate oscillator coupled to a bath of harmonic oscillators representing either phonons or electronic density fluctuations.

The electronic structure, adsorption and bonding of two isomer molecules, orthocarborane and metacarborane are compared. Significant differences in the experimental binding energies are noticed

Scuffing or scoring is an important form of damage leading to component replacements in lubricated mechanical systems such as power drives, gears, bearings, cams and followers, piston rings etc. Since scuffing necessarily involves localized welding of asperities, suitable surface modifications or coating can impart a good resistance to scuffing. A new class of low temperature salt bath nitriding process provides good resistance to scuffing. The current work is on evaluation of the scuffing resistance of AISI 4340 steels imparted with two such treatments. Experimental investigations were conducted on Sursulf and Arcor treated AISI 4340 steel specimen using a pin on ring test system under boundary lubrication condition. Continuous monitoring of friction records and (near surface) bulk temperature were done under step loading. Limiting loads and load velocity relations were evaluated and using the data generated and a thermo-mechanical wear model, performance is indexed. Off line studies on surface finish, hardness variations and surface transformations were also accomplished. Some salient aspects of the investigation and data generated are presented here. Onset of scuffing was observed to be far delayed with pin specimen imparted with these treatments compared to hardening. [DOI: 10.1115/1.1504089]

One of the failings of the pressure die casting process is that variable surface quality is a common result. This paper provides evidence that die vibrant can be used to polish castings as they form during solidification. Evidence is obtained from experiments performed on a purpose built rig that is designed to be representative of the pressure die casting process. The rig's design is such that part of the casting face can be subjected to tangential vibration at prespecified frequencies and amplitudes. The castings made are viewed under a microscope and micrographs produced. These combined with Talysurf readings show that die vibration can be used to generate casting surfaces with a quality significantly superior to that of the die. Supporting evidence is also provided by thermocouple readings and the solution of the inverse parabolic heat equation. The expected increase in the interfacial heat transfer coefficient is obtained with improved casting surface quality. Established in the paper is the effect of vibration frequency and amplitude on the Ra value of the casting surface. It is shown that threshold values for frequency and amplitude exist, below which surface improvement is diminished. [DOI: 10.115/1459085]

Anomalous field enhancement occurs between two-plasmon-resonant surfaces. This model is expected to be useful for metal surfaces having roughness.

The dissociative chemisorption of hydrogen on metal surfaces is examined in the light of quantum mechanics using density functional theory for interpreting molecule-surface interaction and quantum dynamics for simulating hydrogen atom motion.

Spontaneous polymerization (S-Poly) is a novel process to form protective polymer coatings on aluminum and other metals. Here we discuss polymerization and coating properties when two fluorinated monomers are introduced into the S-Poly system. The resulting coatings were characterized using attenuated total reflectance fourier transform infrared (ATR-FTIR), differential scanning calorimetry (DSC), optical microscope and other measurements. Fluorinated coatings showed excellent dielectric properties and strong hydrophobicity. Their dry adhesion strength was a little lower than the coatings in previous systems, but changed very little after immersion in hot water for several days. Some of the fluorinated coatings exhibited significantly improved corrosion resistance in most corrosion tests., Zheng, Haipeng (*) Guy D. Davis (+) James P. Bell (*) INTRODUCTION Coatings on metal surfaces are widely used in applications ranging from macro equipment to microelectronics devices. Among many [...]

Research into void dynamics in relation to the critical morphological evolution is presented. This work was designed to identify the circumstances under which premature failure of metallic thin interconnects arises. The significance of the surface diffusion anisotropy for the premature creation of a fatal open circuit configuration is highlighted.

The possibility of quantum control of surface photochemical reaction was demonstrated for the system of Cs/Cu(III). The report stated that the phase dependence of two-photon photoemission spectra demonstrated the control of desorptive motion of Cs atoms.

The Mode I stress intensity factor of a sector crack in a three-dimensional Voronoi polycrystal is computed by the body force technique. Microstructural stresses arising from the elastic anisotropy of grains (cubic and hexagonal) and the random grain orientations are estimated using the Eshelby procedure and incorporated in the stress intensity factor calculations. For metallic polycrystals, it is shown that the stress intensity factor depends significantly on the elastic anisotropy ratio, the grain orientations, the remote stress state, and the microstructural stresses. [S0021-8936(00)03401-2]

A theoretical model of the gap nucleation process during pure metal solidification on a deformable mold of finite thickness is presented. Both surfaces of the mold follow a sinusoidal lay for which the ratio of the amplitude to the wavelength, or aspect ratio, is much less than one. This makes the aspect ratio a convenient perturbation parameter for the thermal and mechanical problems since it is indicative of the spatial variation in the surfaces. The thermal and mechanical fields are coupled along the upper surface of the mold through a pressure-dependent thermal contact resistance. The main goal of the model is to develop a means for examining the contact pressure along the mold-shell interface and how variation of the mold surface wavelength affects the time and location of gap nucleation. Gaps, which result from irregular distortion of the shell due to the modest variation of the mold surface geometry, are assumed to nucleate when the contact pressure locally falls to zero. The model leads to two coupled differential equations for the shell thickness and contact pressure perturbations which are solved with a numerical scheme. Using a series solution methodology, it is shown that the contact pressure perturbation predicted by the present model reduces to that for a rigid, perfectly conducting mold (which was considered in another work) in the limit of zero mold thickness. In the companion paper, we specifically examine various combinations of pure materials acting either as the shell or the mold material. The concept of a critical wavelength, which separates those wavelengths that lead to gap nucleation at the crests, from those that lead to gap nucleation at the troughs, is introduced. The potential for development of design criteria for mold surface topographies using the present theoretical model as a limiting solution for finite element models of more complex casting processes is discussed. [S0021-8936(00)03201-3]

Research investigates spectra of the small molecules adsorbed onto single-crystal metal surfaces obtained under ultra-high vacuum using reflection absorption infrared spectroscopy. Instrumentation details and data on molecular structure ranging from qualitative to ab initio electronic structure determination of chemisorbed molecules are discussed.

A discussion on the dynamic processes occurring at metal surfaces in terms of theory and experimental approach is presented. The review covers a wide range of topics from inelasticitic-molecule-surface scattering to electron-induced dynamics at metal surfaces. Phonon and electron-hole pair dissipation with reference to adsorbate dynamics is discussed.

The changes in the microtopography of a metal surface during a corrosion process are measured by decorrelation of the scattered speckle fields under coherent illumination. For that purpose a quantitative relation between the decorrelation of the scattered light fields and the rate of corrosion is established in a theoretical model, based on the statistics of phase and reflectivity changes of point scatterers at the surface. The speckle fields are recorded by a CCD camera and processed numerically in a computer, yielding the standard deviation of the topography changes with nanometer sensitivity. From the analysis of a series of images taken at equal time intervals during the corrosion process, the degree of interrelation among subsequent topography changes is calculated.

Flattening of random rough surfaces on a workpiece undergoing bulk deformation has been analyzed using a model of the surface consisting of just two wavelength components. Asperities are flattened at a rate which depends on the ratio of the initial r.m.s, amplitudes of the long and short wavelength components. The flattening behavior of the long wavelength asperities only becomes important when the amplitude of the long wavelength asperities is much greater than that of the shorter wavelength asperities. The surface modification was investigated experimentally by cold rolling of aluminum strips. The power spectral density of the roughness was used to extract appropriate amplitudes for the short and long wavelength components of roughness. The change in roughness amplitudes showed excellent agreement with theory.

The influence of harmonic normal loads on sliding friction is investigated through analysis of contacts consisting of conical and spherical sliders of hard materials on softer metal surfaces. Friction for such contacts is assumed to result from a plowing component and a shearing component. Calculations and experiments show that the coefficient of friction is essentially independent of normal load for contacts with conical sliders. However, for spherical sliders the relation between the coefficient of friction and normal load is highly nonlinear. In the presence of harmonic variations in normal load, this non-linearity causes a shift in the average coefficient of friction. For ideal lubricated contacts, the shearing component of friction is very small and for this case, it is shown that the maximum average reduction in the coefficient of friction is ten percent. When the shearing component is more significant, as with dry contacts, the shift is less. For example, when the shear strength is one-sixth the hardness of the softer material, the maximum average reduction in the coefficient of friction is five percent.

Research is conducted to examine the applicability of an existing model created for coated metallic surfaces for use over the range of parameters utilized in an engine block. Experimental data is compared to a thermal contact conductance model created for plastic asperity deformation of uncoated surfaces. Results indicate that material composition, anisotropic surface roughness and interface porosity will cause the measured thermal contact conductance values to deviate from the values predicted by the two models.

A study was conducted to analyze electron transport in an atom-sized bridge between a metal surface and a tip of a scanning tunneling microscope. The perturbation technique was utilized to determine the self-energy against the Coulomb interaction within a single-site approximation. The electric current was then obtained by solving the Lippmann-Schwinger equation. Experimental results indicated that increases in temperature dependence correlated with the strength of the Coulomb interaction.

A study was conducted relating to research on the nature and occurrence of copper surface oxidation in aqueous solution-related ambient environments. Surface enhanced Raman spectroscopy was used to probe the surface structural changes linked to potential dependent oxidation and reduction of copper in alkaline, neutral and acidic media. Experimental methodology, findings and implications are discussed. Results are also compared with evidence derived from previous experiments which confirm adsorbed oxygen on copper electrodes.

The velocity, normal pressure, and slider size dependence of the coefficient of dry friction of metals in the range of high sliding velocities (V [greater than or equal to] 1 m/s) is investigated theoretically. Failure of the adhesive junctions by adiabatic shear banding is considered as the underlying process. The concept of asperity shearing by the adiabatic shear banding mechanism represents a new approach to unlubricated high velocity friction. Analytical solutions of a coupled thermomechanical problem are given for two constitutive relations. Numerical solutions for steel-on-steel friction showing a decrease of the coefficient of friction with the sliding velocity for different normal pressures are presented. The model is considered to be adequate in the velocity range of 1-10 m/s where friction enhanced oxidation or surface melting are believed not to interfere with the asperity shearing process.

Fretting is the tribological phenomenon observed in nominally-clamped components which experience vibratory loads or oscillations. Associated with fretting contacts are regions of small-amplitude relative motion or microslip that occurs at the edges of contact. A newly-available infrared technology capable of resolving temperatures fields finely, both spatially and temporally, is used to characterize the near-surface conditions associated with fretting contact between an aluminum alloy cylinder and fiat. Both frictional heating due to interfacial slip and the coupled-thermoelastic effect arising from strains in the material induce these temperatures. The experimental results provide insight into not only the magnitude and distribution of near-surface temperatures, but also the nature of the contact stress field and the mechanics of partial slip fretting contacts. Comparisons of the measured temperature fields are made with those predicted by considering both conduction of the frictional heat flux and coupled-thermoelastic theory.