A modified single edge V-notched beam method for evaluating surface fracture toughness of thermal barrier coatings

The surface fracture toughness is an important mechanical parameter for studying the failure behavior of air plasma sprayed(APS)thermal barrier coatings(TBCs).As APS TBCs are typical multilayer porous ceramic materials,the direct applications of the traditional single edge notched beam(SENB)method that ignores those typical structural characters may cause errors.To measure the surface fracture toughness more accurately,the effects of multilayer and porous characters on the fracture toughness of APS TBCs should be considered.In this paper,a modified single edge V-notched beam(MSEVNB)method with typical structural characters is developed.According to the finite element analysis(FEA),the geometry factor of the multilayer structure is recalculated.Owing to the narrower V-notches,a more accurate critical fracture stress is obtained.Based on the Griffith energy balance,the reduction of the crack surface caused by micro-defects is corrected.The MSEVNB method can measure the surface fracture toughness more accurately than the SENB method.

Surface and thermal effects on vibration of embedded alumina nanobeams based on novel Timoshenko beam model

This paper deals with the free vibration analysis of circular alumina （Al2O3） nanobeams in the presence of surface and thermal effects resting on a Pasternak foun- dation. The system of motion equations is derived using Hamilton＇s principle under the assumptions of the classical Timoshenko beam theory. The effects of the transverse shear deformation and rotary inertia are also considered within the framework of the mentioned theory. The separation of variables approach is employed to discretize the governing equa- tions which are then solved by an analytical method to obtain the natural frequencies of the alumina nanobeams. The results show that the surface effects lead to an increase in the natural frequency of nanobeams as compared with the classical Timoshenko beam model. In addition, for nanobeams with large diameters, the surface effects may increase the natural frequencies by increasing the thermal effects. Moreover, with regard to the Pasternak elastic foundation, the natural frequencies are increased slightly. The results of the present model are compared with the literature, showing that the present model can capture correctly the surface effects in thermal vibration of nanobeams.

E-Beam Graft Polymerization of Hydrophilic PEG-Methacrylate on the Surface of PMMA

The graft polymerization of hydrophilic monomers on the surface of hydrophobic PMMA was performed using an electron beam (e-beam). The dose of e-beam irradiation, reaction concentration, temperature, and reaction time were used to study the effect of variables on the graft density of poly (ethylene glycol)-methacrylate. The results demonstrated that the weight percentage of graft polymer increased with increasing temperature, time and monomer concentration. However, the weight of the graft polymer did not increase with the increasing dose of e-beam irradiation. The change of the contact angle of the water droplet on the PMMA surface was monitored as a function of a reaction time. The results showed that the contact angle decreased up until a specific time and then leveled off to an approximately constant value after a certain reaction time of the graft polymerization. Transmission electron microscopy proved that the constant value of the contact angle was due to the local survival of surface radicals followed by the perpendicular diffusion of monomers only into the bulk of the surface-modified area on the sheet surface.

Designing analysis of the polarization beam splitter in two communication bands based on a gold-filled dual-core photonic crystal fiber

We design a novel kind of polarization beam splitter based on a gold-filled dual-core photonic crystal fiber （DC-PCF）. Owing to filling with two gold wires in this DC-PCF, its coupling characteristics can be changed greatly by the second-order surface plasmon polariton （SPP） and the resonant coupling between the surface plasmon modes and the fiber-core guided modes can enhance the directional power transfer in the two fiber-cores. Numerical results by using the finite element method show the extinction ratio at the wavethlengths of 1.327 μm and 1.55 μm can reach -58 dB and -60 dB and the bandwidths as the extinction ratio better than -12 dB are about 54 nm and 47 nm, respectively. Compared with the gold-unfilled DC-PCF, a 1.746-mm-long gold-filled DC-PCF is better applied to the polarization beam splitter in the two communication bands of λ = 1.327 μm and 1.55 μm.

Application of Electron Beam Surface Technologies in the Automotive Industry

Progress in the beam deflection technique opens up new possibilities for the application of electron beam (EB) surface and welding technologies in the automotive industry. This development is based on three-dimensional high-speed beam deflection and fully automatic online process control. So, in the EB surface treatment three-dimensional energy transfer fields can be realised which take into account the contour of a component, the conditions of heat conduction and the load conditions. High flexibility, precision and reproducibility are typical characteristics. High productivity is achieved by the simultaneous interaction of the EB in several processing areas or by carrying out several processes simultaneously. EB surface treatment is becoming more and more attractive and important especially in the automotive industry, and also in comparison to laser technologies. This paper deals with different EB surface technologies, for example hardening, remelting, surface alloying, dispersing or cladding of different materials such as steel, cast iron and different alloys of Al, Mg and Ti. Examples of applications in the automotive industry, especially engine components, will be discussed.

Quasi-plane-hypothesis of strain coordination for RC beams seismically strengthened with externally-bonded or near-surface mounted fiber reinforced plastic

The application of fiber reinforced plastic（FRP）,including carbon FRP and glass FRP,for structural repair and strengthening has grown due to their numerous advantages over conventional materials such as externally bonded reinforcement（EBR） and near-surface mounted（NSM） strengthening techniques.This paper summarizes the results from 21 reinforced concrete beams strengthened with different methods,including externally-bonded and near-surface mounted FRP,to study the strain coordination of the FRP and steel rebar of the RC beam.Since there is relative slipping between the RC beam and the FRP,the strain of the FRP and steel rebar of the RC beam satisfy the quasi-plane-hypothesis;that is,the strain of the longitudinal fiber that parallels the neutral axis of the plated beam within the scope of the effective height（h 0） of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of the FRP and steel rebar satisfies the equation：ε FRP =βε steel,and the value of β is equal to 1.1-1.3 according to the test results.

Double linear strain distribution assumption of RC beam strengthened with external-bonded or near-surface mounted fiber reinforced plastic

Rehabilitation of existing structures with fiber reinforced plastic(FRP)has been growing in popularity because they offer superior performance in terms of resistance to corrosion and high specific stiffness.The strain coordination results of 34 reinforced concrete beams(four groups)strengthened with different methods were presented including external-bonded or near-surface mounted glass or carbon FRP or helical rib bar in order to study the strain coordination of the strengthening materials and steel rebar of RC beam.Because there is relative slipping between concrete and strengthening materials(SM),the strain of SM and steel rebar of RC beam satisfies the double linear strain distribution assumption,that is,the strain of longitudinal fiber parallel to the neutral axis of plated beam within the scope of effective height(h0)of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of SM and steel rebar satisfies the equation εGCH=βεsteel,where the value of β is equal to 1.1-1.3 according to the test results.

Research on the Surface Modification of Pure Zirconium by Electron Beam

In this paper, the changes of surface morphology, microstructure, hardness and corrosion resistance of industrial pure zirconium before and after surface modification by high current pulsed electron beam were discussed. The microstructure evolution and surface morphologies of the samples were characterized by using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM). The experimental results show that sample by high current pulsed electron beam treatment surface melting, martensitic phase transformation occurred, and volcanic crater morphology and fine microstructure in the remelted layer surface;with the increase of number of pulses, after processing the microhardness of the samples also with the increase, 15-pulsed sample microhardness than the original sample increased by 30.9%. Corrosion resistance of samples was studied with the impedance diagram and polarization curve. The electrochemical results show that corrosion resistance of samples by high current pulsed electron beam treatment presents different degrees of change, the 5-pulsed sample in 1 mol HNO3 solution corrosion of the best, and 15-pulsed sample corrosion resistance is even lower than the original sample. Grain refinement, martensite transformation, dislocation and deformation twins are the main reasons for improving the micro hardness and corrosion resistance of the samples.

Investigation on the Effect of Film Thickness on the Surface Morphology, Electrical and Optical Properties of E-Beam Deposited Indium Tin Oxide (ITO) Thin Film

The following article has been retracted due to the fact that the authors practise fraud. The scientific community takes a very strong view on this matter, and the Advances in Materials Physics and Chemistry treats all unethical behavior seriously. This paper published in Vol. 4 No. 10 194-202, 2014 has been removed from this site. ? Title: Investigation on the Effect of Film Thickness on the Surface Morphology, Electrical and Optical Properties of E-Beam Deposited Indium Tin Oxide (ITO) Thin Film ? Authors: Golam Saklayen, Shahinul Islam, Ferdous Rahman, Abu Bakar

Explicit frequency equations of free vibration of a nonlocal Timoshenko beam with surface effects

Considerations of nonlocal elasticity and surface effects in micro-and nanoscale beams are both important for the accurate prediction of natural frequency. In this study, the governing equation of a nonlocal Timoshenko beam with surface effects is established by taking into account three types of boundary conditions： hinged–hinged, clamped–clamped and clamped–hinged ends. For a hinged–hinged beam, an exact and explicit natural frequency equation is obtained. However, for clamped–clamped and clamped–hinged beams, the solutions of corresponding frequency equations must be determined numerically due to their transcendental nature. Hence, the Fredholm integral equation approach coupled with a curve fitting method is employed to derive the approximate fundamental frequency equations, which can predict the frequency values with high accuracy. In short,explicit frequency equations of the Timoshenko beam for three types of boundary conditions are proposed to exhibit directly the dependence of the natural frequency on the nonlocal elasticity, surface elasticity, residual surface stress, shear deformation and rotatory inertia, avoiding the complicated numerical computation.

Bending of functionally graded nanobeams incorporating surface effects based on Timoshenko beam model

The bending responses of functionally graded （FG） nanobeams with simply supported edges are investigated based on Timoshenko beam theory in this article. The Gurtin-Murdoch surface elasticity theory is adopted to analyze the influences of surface stress on bending response of FG nanobeam. The material properties are assumed to vary along the thickness of FG nanobeam in power law. The bending governing equations are derived by using the minimum total potential energy principle and explicit formulas are derived for rotation angle and deflection of nanobeams with surface effects. Illustrative examples are implemented to give the bending deformation of FG nanobeam. The influences of the aspect ratio, gradient index, and surface stress on dimensionless deflection are discussed in detail.

Compounded Surface Modification of ZK60 Mg Alloy by High Current Pulsed Electron Beam+Micro-plasma Oxidation

In this study, compounded surface modification technology-high current pulsed electron beam （HCPEB） ＋ micro-plasma oxidation （MPO） was applied to treat ZK60 Mg alloys. The characteristics of the microstructure of ZK60 Mg alloy after single MPO and HCPEB＋MPO compounded treatment were investigated by SEM. The results showed that the density of the ceramic layer of HCPEB＋MPO-treated ZK60 Mg alloy was improved and defects were reduced compared to that under MPO treatment alone. Surface modified layer of ZK60 Mg alloys treated by HCPEB＋MPO was divided into three zones, namely the top loose ceramic zone, middle compact zone and inside HCPEB-induced melted zone. Corrosion resistance of ZK60 Mg alloy before and after the compounded surface modification was measured in a solution of 3.5% NaCl by potentiodynamic polarization curves. It was found that the corrosion current density of ZK60 Mg alloys could be reduced by about three orders of magnitude, from 311μA/cm^2 of the original sample to 0.2μA/cm^2 of the HCPEB＋MPO-treated sample. This indicates the great application potential of the HCPEB＋MPO compounded surface modification technology in improving the corrosion resistance of ZK60 Mg alloys in the future.

Microstructure and property modifications in surface layers of a Mg-4Sm-2Al-0.5Mn alloy induced by pulsed electron beam treatments

In this work,surface modification of a Mg-4Sm-2Al-0.5Mn alloy with high current pulse electron beam(HCPEB)under different number of pulses were investigated.The evolution in microstructure,composition and phase components and properties in the surface layer before and after HCPEB treatment were characterized.It was found that the Al 11 Sm 3 and Al 2 Sm phases in the surface layer were gradually dissolved during HCPEB treatment,leading to the formation of a chemical homogeneous melted layers.Besides,deformation bands were formed in the treated layer due to the thermal stress generated during treatment.After 15 pulses treatment,the surface hardness increases to the maximum value of about 62.2 HV,about 61.2%higher than that of the untreated state.Electrochemical results show that the 15 pulses treated sample presents the best corrosion resistance in the 3.5wt%NaCl water solution by showing the highest corrosion potential(E_(corr))of-1.339V SEC and the lowest corrosion current density(I_(corr))of 1.48×10^(-6)A·cm^(-2).The results prove that the surface properties of the Mg-4Sm-2Al-0.5Mn alloy can be significantly improved by the HCPEB treatments under proper conditions.

The scanning tunneling microscopy and spectroscopy of GaSb_(1-x)Bi_(x) films of a few-nanometer thickness grown by molecular beam epitaxy

The ultrahigh vacuum scanning tunneling microscope(STM)was used to characterize the GaSb_(1-x)Bi_(x) films of a few nanometers thickness grown by the molecular beam epitaxy(MBE)on the GaSb buffer layer of 100 nm with the GaSb(100)substrates.The thickness of the GaSb_(1-x)Bi_(x) layers of the samples are 5 and 10 nm,respectively.For comparison,the GaSb buffer was also characterized and its STM image displays terraces whose surfaces are basically atomically flat and their roughness is generally less than 1 monolayer(ML).The surface of 5 nm GaSb_(1-x)Bi_(x) film reserves the same terraced morphology as the buffer layer.In contrast,the morphology of the 10 nm GaSb_(1-x)Bi_(x) film changes to the mound-like island structures with a height of a few MLs.The result implies the growth mode transition from the two-dimensional mode as displayed by the 5 nm film to the Stranski-Krastinov mode as displayed by the 10 nm film.The statistical analysis with the scanning tunneling spectroscopy(STS)measurements indicates that both the incorporation and the inhomogeneity of Bi atoms increase with the thickness of the GaSb_(1-x)Bi_(x) layer.

Surface finish of micro punch with ion beam irradiation

Ion beam irradiation was adopted for surface treatment of the micro punch manufactured by precision machining.Ar plasma was used for the ion irradiation process,which was generated by the electron cyclotron resonance(ECR)equipment.The surface finish processes of micro punch were carried out at irradiation angles of 45°and 10°,respectively.The surface roughness and topography were measured to estimate the quality of surface finish.The results show that the ion irradiation is very effective to reduce the surface roughness,which can be improved more significantly at irradiation angle of 10°than at 45°.The technology of surface finish with ion beam irradiation is suitable for the surface treatment of micro die.

Stiction of a Nano-Beam with Surface Effect

Nanowire stiction is a crucial bottleneck for the development of M/NEMS devices.We present a model of a nano-beam stuck to the substrate in consideration of both surface elasticity and residual surface stress.The critical detachment length can be derived from the transversality condition using the variational method.The effects of the surface parameters on the adhesion of the nano-beam are discussed in detail.These analyses provide some suggestions for engineers in the design and fabrication of more accurate M/NEMS instruments.

Mn DEPLETION IN THE SURFACE LAYER OF STAINLESS STEEL 304 LN AT THE TEMPERATURE 1200 K

The Mn component of stainless steel 304 LN has been found to be severely depleted in the surface layer during heating at the temperature 1200 K. The surface concentrations of Mn were reduced by about 2- 3 orders of magnitude in comparison with the bulk value, as was revealed by a secondary ion mass spectroscopy (SIMS) system. And the Mn concentration gradient in the surface layer was examined, too, by SIMS. Massive preferential losses of Mn have been determined by using the catcher technique and proton induced X- ray emission (PIXE). A theoretical model has been proposed for calculating the surface concentration changes for a component in an alloy under heating. A comparison shows a good agreement between the calculation and experimental results from SIMS and catcher technique.

Study of MPI based on parallel MOM on PC clusters for EM-beam scattering by 2-D PEC rough surfaces

This paper firstly applies the finite impulse response filter （FIR） theory combined with the fast Fourier transform （FFT） method to generate two-dimensional Gaussian rough surface. Using the electric field integral equation （EFIE）, it introduces the method of moment （MOM） with RWG vector basis function and Galerkin＇s method to investigate the electromagnetic beam scattering by a two-dimensional PEC Gaussian rough surface on personal computer （PC） clusters. The details of the parallel conjugate gradient method （CGM） for solving the matrix equation are also presented and the numerical simulations are obtained through the message passing interface （MPI） platform on the PC clusters. It finds significantly that the parallel MOM supplies a novel technique for solving a two-dimensional rough surface electromagnetic-scattering problem. The influences of the root-mean-square height, the correlation length and the polarization on the beam scattering characteristics by two-dimensional PEC Gaussian rough surfaces are finally discussed.

Low Temperature Nitriding of 304 Austenitic Stainless Steel Using RF-ICP Method: the Role of Ion Beam Flux Density

The significant role of ion beam flux during nitriding 304 austenitic stainless steel has been investigated by using a radio frequency inductively-coupled plasma reactor into which a sample with negative bias voltage was inserted. A milliammeter is used to detect tile current of ions which collide with the sample and optical emission spectroscopy is used to discern the reactive species included in the nitrogen plasma. The nitriding efficiency is indicated by X-ray diffraction and the microhardness test. The reported data reveal that the ion beam flux density as well as the deposition pressure, bias voltage and time can strongly affect the nitriding of stainless steel via tile expanded multiphase microstructure inside the nitrided layer. The increase in the density of ion flux results in an ascent in the intensity of the expanded peak and a simultaneous decline in the intensity of the 3＇ austenite peak. The evolution trend of ion beam flux density is described as a function of tile operating pressure and the bias voltage. The maxinmm ion flux density has been achieved at 10 Pa pressure and 500 V bias voltage. A reasonable nitriding region has been, consequently, suggested after comparing this work with previously reported results.

Characterizing modified surface layer of 316L stainless steel treated by high current pulsed electron beam

High current pulsed electron beam(HCPEB) is now developing as a useful tool for surface modification of materials.When concentrated electron flux transferring its energy into the surface layer of target material within a short pulse time,coupled thermal and stress processes would lead to the formation of metastalbe microstructure with improved properties.In the present work,HCPEB treatment of 316L stainless steel(SS) was carried out and the microstructural changes in modified surface layer were characterized with optical microscopy,X-ray diffractometry and electron backscatter diffractometry(EBSD) techniques.The corrosion resistance of modified surface was measured in a 5wt.% salt solution.The evolution regularity of surface craters and grain refinement effect,as well as the preferred orientation of(111) crystal plane occurring in the HCPEB treatment under different working parameters were discussed along with their influence on corrosion resistance.