An investigation on worn surfaces of chopped glass fibre reinforced polyester through SEM observations

The wear mechanisms of chopped strand mat (CSM) glass fibre reinforced polyester (CGRP) composite subjected to dry sliding against smooth stainless steel counterface (R_a=0.06 μm) were studied using a pin-on-disc technique. The effects of normal load (30-90 N), sliding velocity (2.8-3.9 m/s) and sliding distance (0.7-3.5 km) on friction and wear behaviour of the CGRP composite in two different CSM orientations (parallel and anti-parallel) were measured. The worn surfaces of the CGRP composite specimens for each specific test condition were examined using scanning electron microscopy (SEM).Sliding in P-orientation exhibited lower friction coefficient at lower load and higher speed compared to AP-orientation. Meanwhile, sliding in AP-orientation exhibited (15%) less friction coefficient at higher load compared to P-orientation. At higher range of all tested parameters, AP-orientation exhibited less mass loss (16%) compared to the P-orientation.Interestingly, SEM observations showed various wear mechanisms that predominated by abrasive nature. Damage of different features in the matrix and CSM glass fibre associated with higher values of load, speed, and sliding distance such as micro- and macro-cracks in the matrix, interface separation, fibre debonding and fracture, and different sizes of fractured fibres were evident.     

Effect of analysis direction on the measurement of interfacial mixing in thin metal layers with atom probe tomography

The accuracy and precision of thin-film interfacial mixing as measured with atom probe tomography (APT) are assessed by considering experimental and simulated field-evaporation of a Co/Cu/Co multilayer structure. Reconstructions were performed using constant shank angle and Z-scale reordering algorithms. Reconstruction of simulated data (zero intermixing) results in a 10-90% intermixing width of ∼0.2 nm while experiential intermixing (measured from multiple runs) was 0.47±0.19 and 0.49±0.10 nm for Co-on-Cu and Cu-on-Co interfaces, respectively. The experimental data were collected in analysis orientations both parallel and anti-parallel to film growth direction and the impact of this on the interfacial mixing measurements is discussed. It is proposed that the resolution of such APT measurements is limited by the combination of specimen shape and reconstruction algorithms rather than by an inherent instrumentation limit.     

A large deflection and high payload flexure-based parallel manipulator for UV nanoimprint lithography: Part I. Modeling and analyses

This paper presents a flexure-based parallel manipulator (FPM) that delivers nanometric co-planar alignment and direct-force imprinting capabilities to automate an ultra-violet nanoimprint lithography (UV-NIL) process. The FPM is articulated from a novel 3-legged prismatic-prismatic-spherical (3PPS) parallel-kinematic configuration to deliver a θ_x–θ_y–Z motion. The developed FPM achieves a positioning and orientation resolution of ±10 nm and 0 . 05″ respectively, and a continuous output force of 150 N/Amp throughout a large workspace of 5°×5°×5 mm. Part I mainly focuses on a new theoretical model that is used to analyze the stiffness characteristics of the compliant joint modules that formed the FPM, and experimental evaluations of each compliant joint module. Part II presents the stiffness modeling of the FPM, the performance evaluations of the developed prototype, and the preliminary results of the UV-NIL process.     

Atomic-scale anisotropy of nanoscratch behavior of single crystal iron

In this paper a parallel molecular dynamics (MD) model has been developed to investigate the nanoscratch process of single crystal iron. The simulations were performed for two cases with different crystallographic orientations and scratch directions. In Case I the scratch plane is (1 0 0) and the scratch direction is [0 0 1]. In Case II the scratch plane and the scratch direction are (1,−1,2) and [1 1 1], respectively. To validate the MD simulation the nanoscratch testing was conducted using the TriboIndenter. The simulation results reveal that the vertical force and the lateral force tend to increase with the scratch displacement for both cases. Case I has smaller forces than Case II. However, the coefficient of friction for both cases is similar, which is in good agreement with the experimental value. The crystallographic orientation also affects the scratch hardness. The scratch hardness of Case I is smaller than that of Case II.     

Performance prediction of a nozzled and nozzleless mixed-flow turbine in steady conditions

This paper presents a meanline model to predict the performance parameters of a turbocharger turbine under steady state conditions. The turbine was developed at Imperial College and the design was based on a commercial nozzleless unit that was modified into a variable geometry single-entry turbine.The wide range of tests data from the Imperial College Turbocharger Group dynamometer enabled the evaluation of the model in the areas of the turbine map where currently no previous comparison had been made in the literature. This facility is designed to allow testing over a wide range of velocity ratios (0.3-1.1) previously unavailable with conventional test stands.The nozzleless turbine model was validated against experimental results spanning an equivalent speed range of 27.9 and 53.8 rev/s √K while for the nozzled case the model was validated against one single speed (43.0 rev/s √K) and three different vane angle settings (40°, 60° and 70°).The results of the model simulation showed that the performance can be predicted with excellent accuracy for different turbine speeds and vane angles. Based on the model prediction, a breakdown aerodynamic loss was performed.     

A large deflection and high payload flexure-based parallel manipulator for UV nanoimprint lithography: Part II. Stiffness modeling and performance evaluation

This paper presents a flexure-based parallel manipulator (FPM) that delivers nanometric co-planar alignment and direct-force imprinting capabilities to automate an ultra-violet nanoimprint lithography (UV-NIL) process. The FPM is articulated from a 3-legged Prismatic-Prismatic-Spherical (3PPS) parallel-kinematic configuration to deliver a θ_x–θ_y–Z motion. The developed FPM achieves a positioning and orientation resolution of ±10 nm and 0.05″, respectively, and a continuous output force of 150 N/A throughout a large workspace of 5°×5°×5 mm. Part I mainly focuses on a new theoretical model that is used to analyze the stiffness characteristics of the compliant joint modules that formed the FPM, and experimental evaluations of each compliant joint module. Part II presents the stiffness modeling of the FPM, the performance evaluations of the developed prototype, and the preliminary results of the UV-NIL process.     

Multi-scale parallel finite element analyses of LDH sheet formability tests based on crystallographic homogenization method

A multi-scale parallel finite element (FE) procedure based on the crystallographic homogenization method was applied to the LDH sheet formability test analysis. For the multi-scale structure, two scales are considered. One is a microscopic polycrystal structure and the other is a macroscopic elastic plastic continuum. The analysis code can predict the formability of sheet metal in macro-scale, simultaneously the crystal texture and hardening evolutions in the micro-scale (Nakamachi E et al. Int J Plasticity 2007;23:450-8). Since huge computation time is required for the nonlinear dynamic multi-scale FE analysis, parallel computing technique based on domain partitioning of FE model for macro-continuum is introduced into the multi-scale code using the message passing interface (MPI) library and PC cluster (Kuramae H et al. In: Proceedings of the eighth international conference on computational plasticity, Part 1, 2005. p. 622-5). The explicit time stepping solution scheme in the nonlinear multi-scale FE dynamic problem is well-suited for parallel computing on distributed memory environment such as PC cluster because solving simultaneous equation is not required. We measured crystal morphologies of four automotive sheet metals, aluminum alloy sheet metals A6022-T43 and A5182-O, an asymmetrically rolled aluminum alloy sheet metal A6022-ASR, and mild steel HC220YD, by using the scanning electron microscope (SEM) with electron back scattered diffraction (EBSD) analyses, and defined a three-dimensional representative volume element (RVE) of micro polycrystal structure, which satisfy the periodicity condition of crystal orientation distribution. We evaluate not only macroscopic formability of the automotive sheet metals by the multi-scale LDH test analysis, but also microcrystalline texture evolution during plastic deformation. Furthermore, a relationship between the macroscopic formability and the microcrystal texture evolution was discussed through looking at multi-scale FE results. It is concluded that the mild steel HC220YD was the highest formability than the aluminum alloy sheet metals because of remaining and generating the γ-fiber texture, such as {1 1 1}〈1 1 0〉-{1 1 1}〈1 1 2〉 orientations, during plastic deformation.     

Prediction of calcium concentration in human blood serum using an artificial neural network

A predictive method, based on artificial neural network (ANN) has been developed to study absorbance and pH effects on the equilibrium of blood serum. This strategy has been used to analyze serum samples and to predict the calcium concentration in blood serum. A dedicated data acquisition system is designed and fabricated using a LPC2106 microcontroller with light emitting diode (LED) as source and photodiode as sensor to measure absorbance and to calculate the calcium concentration. A multilayer neural network with back propagation (BP) training algorithm is used to simulate different concentration of calcium (Ca²⁺) as a function of absorbance and pH, to correlate and predict calcium concentration. The computed calcium concentration by neural network is quite satisfactory with correlations R² = 0.998 and 0.995, standard errors of 0.0127 and 0.0122 in validation and testing stages respectively. Statistical analysis are carried out to check the accuracy and precision of the proposed ANN model and validation of results produce a relative error of about 3%. These results suggest that ANN can be efficiently applied and is in good agreement with values obtained with the current clinical spectrophotometric methods. Hence, ANN can be used as a complementary tool for studying metal ion complexion, with special attention to the blood serum analysis.     

Potential of kenaf fibres as reinforcement for tribological applications

This paper presents an attempt to use kenaf fibres as reinforcement for tribo-composite based on epoxy for bearing applications. Kenaf fibres reinforced epoxy (KFRE) composite was fabricated using a closed mould technique associated with vacuum system. Sliding wear and frictional behaviour of the composite were studied against polished stainless steel counterface using Block-On-Disc (BOD) machine at different applied loads (30–100 N), sliding distances (0–5 km) and sliding velocities (1.1–3.9 m/s). The effect of the fibre orientations, with respect to the sliding direction, was considered; these orientations are parallel (P-O), anti-parallel (AP-O) and normal (N-O). The morphology of the worn surfaces of the composite was studied using a scanning electron microscope (SEM). The result revealed that the presence of kenaf fibres in the composite enhanced the wear and frictional performance of the epoxy. Applied load and sliding velocity have less effect on the specific wear rate of the composite in all the three orientations. The composite exhibited better wear performance in N-O compared to P-O and AP-O.     

ANN-based prediction of surface and hole quality in drilling of AISI D2 cold work tool steel

This paper focuses on artificial neural network (ANN)-based modeling of surface and hole quality in drilling of AISI D2 cold work tool steel with uncoated titanium nitride (TiN) and titanium aluminum nitride (TiAlN) monolayer- and TiAlN/TiN multilayer-coated-cemented carbide drills. A number of drilling experiments were conducted at all combinations of different cutting speeds (50, 55, 60, and 65 m/min) and feed rates (0.063 and 0.08 mm/rev) to obtain training and testing data. The experimental results showed that the surface roughness (Ra) and roundness error (Re) values were obtained with the TiN monolayer- and TiAlN/TiN multilayer-coated drills, respectively. Using some of the experimental data in training stage, an ANN model was developed. To evaluate the performance of the developed ANN model, ANN predictions were compared with the experimental results. It was found that the determination coefficient values are more than 0.99 for both training and test data. Root mean square error and mean error percentage values were very low. ANN results showed that ANN can be used as an effective modeling technique in accurate prediction of the Ra and Re.     

Eddy current evaluation of air-gaps in aeronautical multilayered assemblies using a multi-frequency behavioral model

This paper reports on the estimation of the air-gap thickness between parts in an aeronautical multilayered metallic assembly, by the means of the eddy current method. A behavioral multi-frequency modeling of the interactions between the used cup core sensor and the multilayered structure was developed thanks to the analysis of experimental data, completed with finite element electromagnetic computations. The elaborated model was used to estimate the air-gap thickness (in the range of 0-500 μm) of a multilayered structure featured by a metallic coating of known thickness (1.5 mm) and a distant metallic layer of unknown thickness (in the range 1.5-3.5 mm). The obtained estimation error is smaller than a few percents, either for simulated or experimental data.     

Solid particle erosion of unidirectional carbon fibre reinforced polyetheretherketone composites

The solid particle erosion behaviour of unidirectional carbon fibre (CF) reinforced polyetheretherketone (PEEK) composites has been characterised. The erosion rates of these composites have been evaluated at different impingement angles (15–90°) and at three different fibre orientations (0, 45, and 90°). The particles used for the erosion measurements were steel balls with diameter of 300–500 μm and impact velocities of 45 and 85 m/s. The unidirectional CF reinforced PEEK composites showed semi-ductile erosion behaviour, with maximum erosion rate at 60° impingement angle. The fibre orientations had a significant influence on erosion rate. The morphology of eroded surfaces was examined by using scanning electron microscopy (SEM). Possible erosion mechanisms are discussed.     

Tribological performance evaluation of (1 1 1) preferred oriented TiN duplex coatings

The duplex surface coating of hot work tool steel, which comprises nitriding of a substrate and coating of a TiN layer, has been the subject of a series of studies as a potential surface modification for tools and machine parts. Through sliding experiment against an aluminum alloy without lubrication, it was shown on a wear map that there are two domains depending on sliding conditions: the wear domain and the transfer domain. In this study, focusing on the improvement in the tribological properties of the duplex coating in terms of the wear domain, the effects of film characteristics on film resistance to erosion wear and film life were investigated. Two kinds of duplex coatings with different film characteristics were prepared by hollow cathode discharge ion plating: a newly developed TiN film with a strong (1 1 1) orientation and an ordinary TiN film with (1 1 1) and (2 0 0) orientations. The erosion wear rate of duplex coating was evaluated by a micro slurry jet erosion test. Film life was evaluated by a sliding test against an aluminum alloy as in previous experiments. It was revealed that the duplex coating with the newly developed TiN film (N-coating) shows higher erosion resistance than previously reported duplex coating (C-coating). From the sliding test, it was also revealed that the N-coating whose XRD intensity ratio of (1 1 1) to (2 0 0) is over 100 shows a wear mode with only chipping, with no scratching, which shortens film life. The film life of N-coating increases about twice as long as C-coating, which has shown higher performance than a conventional duplex coating. Possible mechanisms of the improvement in the tribological properties with N-coating are discussed.     

Analysis of computational EELS modelling results for MgO-based systems

The ab-initio density functional theory (DFT) code CASTEP was used to model oxygen K edges in various magnesium oxide systems. Firstly, for the bulk material the process of geometry optimisation was carried out. Predicted oxygen K edges were found for a single cell with experimental lattice parameters, and parameters obtained after geometry optimisation, both with single electron core-holes in place. After geometry optimisation, a different predicted result was obtained, although it was qualitatively similar to the result for experimental lattice parameters in some respects. For example, approximately the same sets of peaks are observed, though in different energy positions, and with different relative peak intensities within those sets. Ultimately for the single cell results the experimental lattice parameters generated the predicted result that was in the closest agreement with experiment. It was further observed that a large supercell result (based on the experimental lattice parameters, utilising a core-hole) led to a slightly improved comparison with experiment as compared to the corresponding single cell result, although the latter result, and indeed a ground state calculation also give reasonable agreement with experiment. To rationalise these observations it was necessary to investigate the density of states (DOS) for the MgO cell and its constituent atoms, and it was observed that the conduction bands were of predominantly magnesium character. Furthermore, the core-hole’s introduction had relatively little overall effect on the p DOS prediction for oxygen, though there is a significant localised change close to the Fermi level. This work also considers interface and surface results. The principal aim of the study was to explore the interface of Fe (0 0 1)/MgO (0 0 1), crucial in certain classes of magnetic tunnel junctions (MTJs), which have significant technological applications. An initial step was to consider a MgO (0 0 1) surface. It was verified that a surface could be constructed such that within that surface a theoretical result could be found that matched the bulk result. It was then valid to use this surface as part of an interface with iron. Theoretical results obtained at that interface compare well with experimental results from an epitaxially grown MTJ, and various conclusions are drawn with regard to the nature of the interface.     

Distinguishing crystallographic misorientations of lanthanum zirconate epilayers on nickel substrates by electron backscatter diffraction

Electron backscatter diffraction (EBSD) was used for distinguishing crystallographic orientations and local lattice misfits of a La₂Zr₂O₇ (LZO) buffer layer epitaxially grown on a cube textured Ni-5.%W (Ni-W) substrate for a YBCO superconductor film. Orientation data were obtained from the LZO epilayer using low energy primary electrons (5 keV) and from the Ni-W substrate by increasing the voltage to 15 keV. In-plane and out-of-plane orientations of the LZO epilayer were revealed with respect to its Ni-W substrate. A strong {1 0 0} 〈0 1 1〉 rotated-cube texture in the LZO epilayer was formed on the {1 0 0} 〈0 0 1〉 cube-textured Ni-W substrates. LZO and Ni in-plane crystallographic axes are related by an expected 45° rotation. The step-misorientations and the local misfit strains between the LZO epilayer and the substrate were also analyzed.     

Analysis of hydraulic characteristics for hollow semi-circular weirs using artificial neural networks

Weirs are small overflow dams used to alter and raise water flow upstream and regulate or spill water downstream watercourses and rivers. This paper presents the application of artificial neural network (ANN) to determine the discharge coefficient (Cd) for a hollow semi-circular crested weirs. Eighty five experiments were performed in a horizontal rectangular channel of 10 m length, 0.3 m width and 0.45 m depth for a wide range of discharge. The results of examination for discharge coefficient were yielded by using multiple regression equation based on dimensional analysis. Then, the results obtained were also compared using ANN techniques. A multilayer perceptron MLP algorithm FFBP network was developed. The optimal configuration of ANN was [2,10,1] which gave mean square error (MSE) and correlation coefficient (R) of 0.0011 and 0.91, respectively. Performances of ANN model reveal that the Cd could be better estimated by the ANN technique in comparison with Cd obtained using statistical approach.     

A microstructure evolution model for numerical prediction of austenite grain size distribution

In this study, a mathematical model has been developed to predict austenite grain size (AGS) of hot rolled steel. Using the compression test, the static (SRX) and metadynamic (MDRX) recrystallization characteristics of medium carbon steel were studied. Compression tests were carried out at various temperatures in the range 900-1100 °C with strain rates ranging from 0.1 to 10 s⁻¹. The time required for 50% recrystallization for the SRX and MDRX was determined by carrying out double compression tests, respectively. Grain growth equation after full recrystallization was also derived by compression tests with various interpass times. The currently determined microstructure model has been integrated with a three-dimensional non-isothermal finite element program. The predicted results based on the model proposed in the present investigation for hot bar rolling processes were compared with the experimental data available in the literature. It was found that the proposed model was beneficial to understand the effect of recrystallization behavior and control the microstructure evolution during the hot bar rolling.     

FEA calculation of pressure distortion coefficients of gas-operated pressure balances – EURAMET project 1039

Finite element analysis methods were developed and applied to gas piston–cylinder units (PCUs) of piston- and cylinder-floating configuration (2, 5, 10 and 20) cm² nominal effective area, operated in gauge and absolute mode at pressures (0.06–7.5) MPa to determine their zero pressure and pressure-dependent effective areas, as well as pressure distortion coefficients (λ) with associated uncertainties. Real dimensional properties of the PCUs were used. λ were found to be independent of gas (ideal, N₂, He) within the viscous flow model, but strongly dependent on the gap shape, operation mode and elastic properties. Results demonstrate good agreement for λ, with its uncertainty for different PCUs varying between (0.03 and 0.21) × 10⁻⁶ MPa⁻¹ corresponding to maximum relative uncertainties in pressure of (0.07–0.34) × 10⁻⁶.     

Monte Carlo simulation of 10 MV photon beams and beam profile validations

In radiation therapy, various radiation energies have been used according to the size and depth of tumor for therapeutic purpose. The electron energies are used for superficial treatments, whereas photon energies such as 6 MV, 10 MV and 18 MV energy levels are utilized for the treatment of deeper tumors. The suitability of energy levels for treatment has been determined by dose distributions in water phantom. In this study, beam profiles of clinical linear accelerators for 10 MV photon beams in water phantom were obtained by using Monte Carlo simulation program (MCSP) developed. MCSP was carried out taking into account the interactions of photons with matter in MATLAB (The Mathworks, Inc.). Monte Carlo simulation results were calculated for 5 × 5, 10 × 10 and 20 × 20 cm² field sizes at 5, 10 and 20 cm depths for the dose profiles. In order to validate the beam profiles, Monte Carlo results were compared with experimental results for 1 cm and 10 cm depths at all the field sizes. MCSP results have shown a good agreement with experimental results.     

Solid particle erosion of unidirectional fibre reinforced thermoplastic composites

In the present study, the solid particle erosion behaviour of neat PEEK matrix and unidirectional glass fibre (GF) and carbon fibre (CF) reinforced polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) composites has been studied. The erosion experiments have been carried out by using silica sand particles (200 ± 50 μm) as an erodent. Steady state erosion rates of these composites have been evaluated at different impact angles and impact velocities. The neat PEEK exhibited peak erosion rate at 30° impingement angle whereas the composites exhibited a semi-ductile behaviour with peak erosion rate at 60° impact angle. The erosion rate of the glass fibre reinforced composites was higher than that of the carbon fibre reinforced composites. The results show that the fibre orientation has a significant influence on erosion rate only at lower impact angles. The erosion rate of the composites was higher when the particles impact perpendicular to the fibre direction than parallel to the fibres. The morphology of eroded surfaces was observed under scanning electron microscope and damage mechanisms were discussed.