Flexural vibration analysis of a sandwich beam specimen with a partially inserted viscoelastic layer

The flexural vibration characteristics of a sandwich beam system with a partially inserted viscoelastic layer were quantitatively studied using the finite element analysis in combination with the sine-sweep experiment. Asymmetric mode shapes of the flexural vibration were visualized by holographic interferometry, which agreed with those obtained by the finite element simulation. Effects of the length and the thickness of the partial viscoelastic layer on the system loss factor (η_s) and resonant frequency (f_r) were significantly large for both the symmetric and asymmetric modes of the beam system.     

A method for analysis of head cover deformation and vibration amplitude in Francis hydro-turbine system by combination of CFD and FEA

It is of great importance to predict the deformation and vibration characteristics of the hydro-turbine structure accurately for the stable operation when the turbine is running under the alternating load of the flow field. In this paper, we proposed a methodology for analysis of the head cover deformation and vibration amplitude in the high-head Francis hydro-turbine system, in which Computational fluid dynamics (CFD) is employed to simulate the complex flow field in the head cover flow passage and the CFD-captured pressure distribution is provided for Finite element analysis (FEA) as a new load input to obtain more accurate head cover deformation and vibration calculation results. The results obtained by this method are compared with the results of the conventional algorithm and laboratory experimental results, demonstrated a better consistency. The great advantage of this method is that it allows vibration amplitude analysis and predictions under varied working conditions by adjusting the flow field parameters according to the specific working conditions. Therefore, it has supportive significance in optimization of the hydro-turbine structural turbine design as well as stabilizing operations at hydropower stations.

     

A case study: passive component inspection using a 1D wavelet transform

This paper exploits a wavelet-based scheme to inspect the surface defects and basic dimensions of 0805 Multi-layer Ceramic Chip capacitors (MLCC) using machine vision. The image of a passive component is initially processed to show only two solder plates (terminations). Then, the covariance matrix eigenvector for each boundary point generates the 1D θ-p representation to describe the angle variations at the boundaries of each termination. The 1D θ-p representation is further decomposed directly by a one-dimensional wavelet transform (1D WT). Since a single corner (an intersection of two boundary edges) and the jag corners (the surface defects) are local deviations on termination boundaries, their locations are represented as intensive and have a highly fluctuated wavelet energy at the 1st detail scale. Concerning a 0805 MLCC type of passive component, the surface defects and single corners on termination boundaries can be captured by appropriate thresholds (e.g., in wavelet energy). The basic dimensions of a passive component are simply the direct distance between located single corners. Real 0805 MLCCs are testing samples to evaluate the performance of the proposed approach. Experimental results show that the proposed method achieves a precise identification of the surface defects and measurements for basic dimensions. The proposed approach is invariant with respect to the orientation, easy to implement and free from a primitive-matching process. Therefore, it is especially suitable for various types of passive components that are similar to the 0805 MLCC in small-batch production.     

Effect of Interfacial Properties on EHL Under Pure Sliding Conditions

This paper presents an experimental study of the effect of boundary slip on the lubricating film shape and friction of an elastohydrodynamic lubrication (EHL) contact under isothermal conditions. Ball and disc pure sliding experiments were carried out with a high viscosity polybutene oil using a conventional optical EHL test rig. The film shape and friction were measured simultaneously. The results obtained from two discs with different coatings were compared. One disc was coated only with Cr, the partially reflective layer, and the other had an extra layer of SiO₂ coating on top. When running under mild conditions of low load and speed, there was no evidence of any boundary slip effect. However, when the load increased, the Cr-coated disc produced lower film thickness and friction than the SiO₂-coated disc. The Cr-coated surface had a larger contact angle, i.e., smaller surface energy, than the SiO₂ surface, which reflects the weak bonding between the molecules of the surface and the lubricant. The study concludes that surfaces with low surface energy promote boundary slip at the EHL contact, leading to a reduction in friction and film thickness.     

Cryogenic drilling of aluminum-based printed circuit boards: a review and analysis

Abstract

An aluminum-based printed circuit board (Al-PCB) is a composite material comprising a copper layer, an insulating layer, and an aluminum base layer. In the drilling of Al-PCBs, exit burrs are formed because of the plastic deformation of the remnant aluminum under high drilling temperatures. In this work, a new method using cryogenic media is suggested to prevent exit burrs in Al-PCB drilling. The effects of cryogenic media, such as cold air, supercritical carbon dioxide solvent (scCO₂), and liquid nitrogen (LN₂), on the drilling temperature, chip removal, tool wear and exit burr formation were observed and analyzed. The Al-PCB drilling temperature could be effectively reduced when drilling with cold air, scCO₂ or LN₂. The chip removal and tool wear could be improved when drilling with cold air or LN₂. The exit burr formation when drilling with scCO₂ or LN₂ was greater than that when drilling under cooling and cold air conditions. A cold air matching composite wood backup board (MW-0.5) could effectively control the exit burr formation within 20?μm. This is the first study on the effects of three different cryogenic media on PCB drilling and is expected to provide a good reference for the cryogenic drilling of PCBs.     

The effect of mechanical vibration and drift on the reconstruction of exit waves from a through focus series of HREM images

Experimental HREM images can show a limited resolution as a result of mechanical vibration and drift. In this paper the effect of such mechanical vibrations on the accuracy of the through focus exit wave reconstruction method is investigated for different thicknesses of a test structure of La₃Ni₂B₂N₃. A through-focus series of HREM images for this structure is simulated for different kinds of mechanical vibration corresponding to an information limit g of about 7 nm⁻¹: (1) no mechanical vibration, (2) isotropic mechanical vibration, and (3) several anisotropic mechanical vibrations. From these through-focus series the reconstructed exit wave is calculated (Ultramicroscopy 64 (1996) 109). The above isotropic and anisotropic mechanical vibrations have a large effect on the reconstructed exit waves when compared with the reconstructed exit wave without mechanical vibration, i.e. the range of amplitudes and phases in a reconstructed exit wave decreases and the background intensity increases. The initial thickness and orientation can be obtained using a least-squares refinement procedure (Acta Crystallogr. A 54 (1998) 91) when there is no mechanical vibration present. In the case of isotropic or anisotropic vibration, the refined thickness and orientation are likely to give wrong results depending on the size of the vibrations and on the number of significant reflections (which is related to the size of the unit cell, the thickness and the misorientation).     

Heat transfer enhancement of pool boiling for a horizontal U-tube using TiO2-R141b nanofluid

An experimental investigation is performed into the pool boiling heat transfer performance of TiO₂-R141b nanofluid containing 0 vol%, 0.0001 vol%, 0.001 vol%, and 0.01 vol% TiO₂ nanoparticles. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) observations reveal that some of the TiO₂ nanoparticles adhere to the heated surface during the boiling process. As a result, the heat transfer performance is poorer than that obtained using pure R141b as the working fluid. Accordingly, a further investigation is performed in which the heated surface is vibrated ultrasonically. It is shown that the ultrasonic vibration creates an acoustic cavitation effect, which inhibits the formation of the nano-sorption layer and improves the heat transfer performance as a result.

     

Novel manufacturing process for anti-glare of LCD cover and development of haze model

This paper proposes a novel manufacturing process for an AG (Anti-glare) coating for LCD cover glasses. The proposed coating method uses silk screen printing equipment and the sintering step of the tempered LCD cover glass manufacturing procedure. In general, AG films have been widely used for dealing with glare but this is not proper for an outdoor LCD display due to low durability. To keep the same durability of tempered glass, glass frit was prepared and the tempering process was applied after silk screen printing. A ZBS (ZnOB₂O₃-SiO₂) glass frit was used and it was coated on using a silk screen process. Also, herein the performance of the proposed method is evaluated by comparing the haze values that were produced under various silk screening conditions. Based on the comparison results, the main parameters that characterize the AG effect of the proposed method were determined and a haze model was developed.

     

Characterisation of ZrO2 layers deposited on Al2O3 coating

The paper describes a method of coating combining two different layer types. The first layer is Al₂O₃ produced by plasma spraying with a thickness of around 200 μm which was deposited on a stainless steel substrate. Subsequently, ZrO₂ layers were deposited on to the Al₂O₃ coating by a sol–gel process using a dip coating technique. The dip coating process was repeated in order to see the influence of the number of ZrO₂ layers. Moreover, the effect of annealing temperature was investigated. In order to study their tribological behaviour, the coatings were subjected to micro-scale abrasion, scratch testing and ball-on-disc tests. The result shows that sol–gel ZrO₂ top layers reduce friction and enhance the wear resistance of the coating system.     

Investigation on the aerodynamic performance and boundary layer characteristics of high deflection industrial turbine cascade at off-design conditions

This research leads to reach the effects of the off-design operation on the aerodynamic performance, boundary layer behavior, and associated loss occurring in a high deflection industrial turbine blade. Numerical simulations, proved opposed to experimental results, are used to achieve the detailed flow field of the cascade, incidence angels ranging from −15° to +10° at inlet chord Reynolds number varied from 9.63E+04 to 2.24E+05. Boundary layer specifications covering thickness, displacement thickness, and momentum thickness are achieved in the 15 points on the suction side and talk about detail on the authority of numerical simulations in various flow conditions. Results indicate that profile loss is forcefully increased by the rising up the incidence angle mostly in the positive range. Studying the effect of incidence angle on the boundary layer behavior indicates that as incidence angle varies from negative to positive, all three characteristics of the boundary layer increase gradually.

     

Characterisation,by the PIXE Method,of Trace Elements During Physicochemical Reactions at the Periphery of Bioactive Glass Pastilles in Contact with Biological Fluids

Abstract

The prerequisite for bioactive glasses to bond to living bone is the formation of biologically active apatites on their surface in the body. Reactions and bioactivity mechanisms between bioactive glasses and bone depend on the glass composition. We study a glass in the SiO₂‐Na₂O‐CaO‐P₂O₅‐K₂O‐Al₂O₃‐MgO system. To characterise physicochemical reactions at the materials periphery, we immersed the glass pastilles into biological fluids for periods of 5, 10, and 20 days. The surface changes were studied at the micrometer scale by a Particle Induced X‐ray Emission (PIXE) method associated with Rutherford Backscattering Spectroscopy (RBS). After 20 days of immersion, elemental maps showed the formation of a calcium‐phosphate layer at the surface of the glass pastilles. The thickness of this layer was around 15 µm. Thanks to the PIXE method, we demonstrated the presence of traces of Mg in this layer. The glass doped with MgO leads to the formation of an apatite which incorporates magnesium. Formation of this Ca‐P‐Mg layer represents the bioactive properties of the studied glass. This biologically active layer improves the properties of the glass and will permit a chemical bond between the ceramic and bone.     

Effect of Y2O3 content on Ni60 alloy cladding layer

Six kinds of Ni60 alloy coatings with different percentage of Y₂O₃ were prepared by laser cladding. A metallurgical microscope was used to analyze the morphology of the cladding layer. Scanning electron microscopy and EDS energy spectrum analysis were used to characterize the microstructure and element segregation of the cladding layer. A Vickers microhardness tester was used to measure the hardness of the cladding layer. Finally, a friction and wear tester established the friction and wear properties of the cladding layer. The study results show that Y₂O₃ can significantly reduce the height of the cladding layer and increase the width of the cladding layer; it can also improve the structure refinement and element segregation of the cladding layer. The microhardness of the cladding layer is significantly improved compared to the Ni60 alloy coating without Y₂O₃, thereby enhancing the wear resistance of the coating.

     

Free vibration analysis of solar functionally graded plates with temperature-dependent material properties using second order shear deformation theory

Second-order shear deformation theory (SSDT) is employed to analyze vibration of temperature-dependent solar functionally graded plates (SFGP’s). Power law material properties and linear steady-state thermal loads are assumed to be graded along the thickness. Two different types of SFGP’s such as ZrO₂/Ti-6Al-4V and Si₃N₄/SUS304 are considered. Uniform, linear, nonlinear, heat-flux and sinusoidal thermal conditions are imposed at the upper and lower surface for simply supported SFGPs. The energy method is applied to derive equilibrium equations, and solution is based on Fourier series that satisfy the boundary conditions (Navier’s method). Non-dimensional results are compared for temperature-dependent and temperature-independent SFGP’s and validated with known results in the literature. Numerical results indicate the effect of material composition, plate geometry, and temperature fields on the vibration characteristics and mode shapes. The results obtained using the SSDT are very close to results from other shear deformation theories.     

Architecture of superthick diamond-like carbon films with excellent high temperature wear resistance

A plasma-enhanced chemical vapor deposition system was used to deposit super thick diamond-like carbon (DLC)-based films ((Si_x-DLC/Si_y-DLC)_n). The aim of this work is to investigate the properties of super thick films to verify that increasing the thickness of DLC films offers the possibility of improving their properties at high temperatures. The investigation revealed that superthick (Si_x-DLC/Si_y-DLC)_n film exhibited excellent tribological property up to 500 °C. One reason is that a thin layer that consists of nanocrystals SiC is formed on the top of wear track. Another is that the stress mostly concentrates near the top surface.     

Determining electrophysical characteristics of metal-oxide-semiconductor structures from the data of voltage-capacitance analysis of the depletion region of a semiconductor surface

The oxide layer in nanotransistors with metal-oxide-semiconductor (MOS) structures may be as thin as 20Å. The physical diagnostics of such structures via conventional methods of voltage-capacitance characteristics (VFCs) is impossible without taking into account the usually disregarded effects of degeneracy and dimensional quantization of the electron gas. However, as the oxide-layer thickness decreases, these effects make an increasingly substantial contribution to capacitance C of the MOS structure not only at C?C _i (where C _i is the “oxide capacitance”) but also at C < C _i . In this study, we have developed a general method for determining the principal characteristics of MOS structures from the data of analysis of the VFCs in the region of the Schottky depletion layer. The doping level, the surface potential, the semiconductor surface charge, the voltage of “flat bands,” oxide capacitance C _i , the voltage drop across the oxide, and the sign and density of the charge fixed in it can be found at an accuracy of ?0.1% within the framework of a single experiment regardless of the oxide-layer thickness and without using fitting parameters and a priori assumptions concerning the properties of the electron gas in the accumulation and inversion layers. The stages and results of the implementation of this method are demonstrated by the results of experiments performed on an n-Si-based MOS structure with a 171.2 Å-thick oxide layer.     

Improvement of dimensional accuracy of blu-ray disc cover layer

In order to obtain uniform thickness of a blu-ray disc cover layer, a CFD analysis and an experimental comparison of the cover layer thickness distribution during the spin-coating process were conducted. The blu-ray disc, a next generation optical disc format having 25GB capacity over, consists of a thermoplastic polymer substrate layer which has a thickness of 1.1mm, a sputtered reflective metal layer and UV polymer cover layer which has a thickness of 100μm. Especially, the cover layer, which primarily governs the optical quality of the disc, is made by a precise spin coating process. However, it is still hard to get a satisfactory coating uniformity, typically, the thickness variation of the cover layer should be maintained under ±3μm, because of the unavoidable bump formed around the rim of the disc. In order to improve the dimensional accuracy of the cover layer, first, through the CFD analyses of spin coating process, the optimal spin coating conditions were obtained; and second, the edge of the disc substrate was modified into various shapes, such as chamfer, round, step, the height of the bump can be kept under the desired accuracy.     

Surface morphology and interdiffusion of LiF in Alq3-based organic light-emitting devices

Highly efficient organic light-emitting devices (OLEDs) have been realized by insertion of a thin insulating lithium fluoride (LiF) layer between aluminum (Al) cathode and an electron transport layer, tris-(8-hydroxyquinoline) aluminum (Alq₃). In this paper, we study the surface morphology of LiF on Alq₃ by synchrotron X-ray scattering and atomic force microscopy (AFM) as a function of thickness of LiF. We also study the interdiffusion of LiF into Al cathode as well as into Alq₃ layer as a function of temperature. Initially, LiF molecules are distributed randomly as clusters on the Alq₃ layer and then gradually form a layer as increasing LiF thickness. The interdiffusion of LiF into Al occurs more actively than into Alq₃ in annealing process. LiF on Alq₃ induces the ordering of Al to (1 1 1) direction strongly with increasing LiF thickness.     

Thermal characteristic evaluation of functionally graded composites for PSZ/metal

The functionally graded material (FGM) is the new concept for a heat resisting material. FGM consists of ceramics on one side and metal on the other. A composition and microstructure of an intermediate layer change continuously from ceramics to metal at the micron level. This study is carried out to analyze the thermal shock characteristics of functionally graded PSZ/metal composites. Heat-resistant property was evaluated by gas burner heating test using C₂H₂/O₂ combustion flame. The ceramic surface was heated with burner flame and the bottom surface cooled with water flow. Also, the composition profile and the thickness of the graded layer were varied to study the thermomechanical response. Furthermore, this study carried out the thermal stress analysis to investigate the thermal characteristics by the finite element method. Acoustic emission (AE) monitoring was performed to detect the microfracture process in a thermal shock test.     

To the Question about the Thickness of Informative Layer in Magnetic-Noise Testing

The question about the thickness of informative layer under magnetic-noise testing of hardened layers is considered in [1–7], where it is estimated to be up to 800 μm. This paper presents experimental studies of the thickness of informative layer using instances of technologies used for surface-deformation and laser thermal hardening processes. It is shown that in the latter case, the thickness of informative layer is of greater importance. Applied mechanical stresses practically do not change the thickness of informative layer for a wide class of steels.

     

An analysis of heat transfer in the thin-layer transducer used for the measurements of EHD contact parameters

Thin-layer transducers, which are mainly used for the measurement of the EHD contact parameters, have to be attached to an isolating layer separating it from the steel roller. The isolating layer, made of SiO_x or Al₂O_3, disturbs heat flow in relation to the real contact. This paper presents a solution for the system of two heat conduction equations for a two-layer body: SiO_x-steel. The boundary conditions reflect the real situation during the measurements carried out by means of these transducers. The solution was obtained for an assumed temperature distribution of the isolating layer surface. Computation results for two different temperature distributions of the surface and for various values of the SiO_x-layer thickness are also presented.