Search

PurposeThe purpose of this paper is to present a novel method to design and fabricate aeroelastic wing models for wind tunnel tests based on stereolithography (SL). This method can ensure the structural similarity of both external and internal structures between models and prototypes.Design/methodology/approachAn aluminum wing‐box was selected as the prototype, and its natural modes were studied by FEA and scaled down to obtain the desired dynamic behavior data. According to similarity laws, the structurally similar model was designed through a sequential design procedure of dimensional scaling, stiffness optimization and mass optimization. An SL model was then fabricated, and its actual natural modes was tested and compared with the desired data of the prototype.FindingsThe first two natural frequencies of the model presented strong correlation with the desired data of the prototype. Both the external and internal structures of the model matched the prototype closely. The SL‐based method can significantly reduce the total mass and simplify the locating operations of balance‐weights. The cost and time for the fabrication were reduced significantly.Research limitations/implicationsFurther investigation into the material properties of SL resins including stiffness and damping behaviors due to layered process is recommended toward higher prediction accuracy. Wind tunnel tests are needed to study the in situ performance and durability of SL models.Originality/valueAlthough the paper takes a wing‐box as the study object, structurally similar SL models of entire wings can be obtained conveniently, benefiting from the low‐stiffness material properties of SL resins and the fabrication capacity to build complex structures of SL process. This paper enhances the versatility of using SL and other rapid prototyping processes to fabricate models to predict aeroelastic characteristics of aircraft.

The equal-area (EA) method is studied with respect to its applicability to a wide range of phase equilibrium scenarios for pure fluids and binary mixtures. The study covers vapor-liquid equilibrium (VLE), liquid–liquid equilibrium (LLE), solid-liquid equilibrium (SLE) and their crossover transitions. The thermodynamic models studied include equation of state, activity coefficient and solid solubility models and their combinations. The performance of the EA method for chain molecules, at very low temperature and nearby the critical point is also investigated. We conclude that the EA method is very reliable and efficient and has a number of advantages over the conventional method. Finally, we apply the EA method to the regression of the model parameters to demonstrate its attractive application. © 2011 American Institute of Chemical Engineers AIChE J, 2012

PurposeThe purpose of this paper is to investigate the influencing rule of the standoff distance variations between the nozzle outlet and the powder deposition point on forming dimensional accuracy.Design/methodology/approachThe thin‐wall parts were built with three different standoff distances: 1 mm more than the powder focus length, equal to the powder focus length and 1 mm less than the powder focus length. Based on the experimental results, the steady standoff distance can be acquired and the difference between the building height and the ideal height of thin‐wall parts can be compensated automatically in several layers by theoretical calculation.FindingsThe experimental results show that the top surface unevenness of thin‐wall parts can be compensated automatically on the consequent successive layers when the standoff distance is less than the powder focal length from the nozzle outlet to the powder focal point, and the poorer results are obtained when the standoff distance is equal to or more than the powder focal length in the deposition of stainless steel 316L under open‐loop control.Practical implicationsThe shape of parts affects the self‐regulation effect in practical applications, so the self‐regulation effect is useful when the single contour of parts is continuous straight faces and the surface of parts is perpendicular to the build platform, and will be useless for parts with holes.Originality/valueAccording to the requirements under different process conditions in practical applications, one should first find out the relationship between the standoff distance and the building height of single‐trace cladding layer, and then use regression algorithm to obtain the stable standoff distance by simple theoretical calculation. The uniform building height, layer thickness and smooth surface can be obtained at the stable standoff distance under open‐loop control.

To investigate the influencing rule of deposited layer’s shape on coaxial powder feeding flow field in the metal forming process, gas–solid two-phase flow theory is used to analyze effect of deposited layers on powder concentration distribution and variation of focus distance from nozzle outlet to convergence point (the center of the convergent zone). Different height and width parameters of deposited layers were chosen to calculate the powder concentration distribution, consequently, and also their effect on additive height of single-trace cladding layer was studied by experimental investigations. The numerical results are in good agreement with experimental observations. The results indicated that additive height of cladding layer was non-uniform under uneven wall thickness of parts fabrication condition. Consequently, the surface of deposited layers with uneven thickness is not smooth, and hence affects surface forming quality.

In the present study, poly(vinylidene fluoride) (PVDF)/nano-TiO2 electroactive film was prepared by coating a substrate with an acetone/DMF solution, which was evaporated at a high temperature (110 °C). The crystallisation behaviour, dynamic mechanical properties and electroactive properties of this PVDF/nano-TiO2 electroactive film were investigated. The cross-section and surface of the film were observed with a scanning electron microscope (SEM). X-ray diffraction (XRD) results showed that the film containing the PVDF β phase, the desired ferroelectric phase, was obtained by crystallising the mixed solution of nano-TiO2 and PVDF at 110 °C, while the film containing the α phase was obtained from the crystallisation of the pure PVDF solution at the same temperature. It was found that the storage modulus, the room-temperature dielectric constant and the electric breakdown strength of the composite films were much higher than those of a pure PVDF film. TiO2 improved the mechanical properties and electroactive properties of the film. The results indicate that PVDF/nano-TiO2 composite films can be applied to the fabrication of self-sensing actuator devices.

To discuss the influence of thin-walled blade’s curvature change and accumulating layer number on the temperature field distribution in laser direct metal deposition and obtain a uniform thickness of a thin-walled blade, the temperature field distribution was calculated by numerical simulation. The thin-walled blade’s curvature change and accumulating layer number can be studied, respectively. The effect of accumulating layer number on temperature field distribution was studied by thin wall; the effect of curvature change on temperature distribution was investigated by thin-walled rings with different curvatures. The numerical results show that the molten pool temperature of the thin wall increases with the layer number, and the molten pool temperature of thin-walled ring increases with the its curvature. The rules of laser power changing with the layer number and curvature in the processing of the thin-walled blade can be obtained by simulation when keeping molten pool temperature stable. According to the numerical results, the thin-walled blades were fabricated by experiments. The experimental results show that the laser power should be changed with the layer number and curvature if a uniform thickness of the blade can be obtained, which is in agreement with the numerical simulation.

A novel control algorithm, namely subsection adaptive hill climbing method (SSAHC), for seeking the maximum power point (MPP) of a photovoltaic (PV) panel for any temperature and solar radiation level is proposed. The algorithm is thus a combination of the subsection and adaptive hill climbing methods. In this algorithm, the characteristic curve of power-voltage of PV panel was divided into three subsections, namely large step approximation section, adaptive hill climbing section and maximum power section. Using this method, the MPP tracker (MPPT) can tune adaptively the step to track the MPP of PV system. The main advantage of the MPPT controlled by this new algorithm, when is compared with others, is that it can draw more power at a certain weather condition, especially, in case solar radiation changes rapidly at higher radiation.

To balance the hydraulic and anti-clogging performances for labyrinth-channel emitters, a multi-objective optimization was performed to improve the structure of trapezoidal labyrinth channels. Two variables, pressure loss coefficient (PLC) and passage rate of particles (PRP), were proposed to evaluate the hydraulic and anti-clogging performances, respectively. The Pareto fronts of PLC and PRP were calculated using the elitist non-dominated sorting genetic algorithm version II (NSGA-II). The results show that the optimal fronts are obtained through 100 generations evolution. The associated key parameters D/W and H/D are constant, while S/H and α are different for each front. In addition, the approach to obtain a trade-off solution from these fronts was developed by arranging different weights for the two variables. This approach is very suitable for structural optimization of labyrinth channels with the same shape but different dimensions.

A UV-curable glass fiber-reinforced composites was investigated in order to develop a cost-effective fabrication approach for manufacturing polymer—matrix composites. The effects of glass fiber-treating process and UV exposure power on the tensile strength were studied through scanning electron microscopy, contact angle determination, and curing degree test. The experimental results showed 11.5% increase in tensile strength for the UV-cured composite reinforced with heat-treated glass fiber, and 51.4% increase with glass fiber treated by coupling agent. The optimal exposure power was 0.94 J/mm2 to obtain the optimized mechanical properties. However, overexposure could seriously result in the loss of tensile strength. The maximum tensile strength and shear strength of composite cured by UV approach in this study were 902.09 and 25.04 MPa, respectively.

The anti-clogging performance of emitters with labyrinth channels is a key factor affecting their long-term service. Considering the limitation of evaluation on emitter's anti-clogging performance at present, a new method using passage rate of particles as the evaluation index was proposed based on stochastic trajectory model in a Lagrangian reference frame. Using orthogonal design, the passage rates of particles of 16 trapezoidal labyrinth channels with various geometries were calculated, where 4 dimensionless parameters were taken as the factors. The results obtained from analysis of range and variance showed that the influence degree on passage rate of particles ranks as follows: @a>D/W>S/H>H/D. A mathematic model was established between the particle passage rate and 4 key parameters according to the multivariable regression method, which can be used to predict and compare the anti-clogging performance of trapezoidal labyrinth channels with different geometries.

An improved direct correlation function is proposed and applied to construct an accurate free energy functional. The theoretical method is extended to analyze the pore size distributions (PSDs) of both slit- and cylindrical-shaped carbonaceous materials. With the same parameters for the fluid and material as in the simulation, the model is much more advantageous than the known density functional methods for calculating the adsorption isotherms in individual pores. The overall PSDs for two model carbons are evaluated for CH4, CF4, and SF6 absorbates, and good results are obtained. The results are reliable because the two model carbons have structures that are exactly known. Encouraged by the success with slit pores, we further extend the model to the internal cylindrical space of a single-walled carbon nanohorn. The PSDs of the carbon nanohorn are evaluated, and satisfactory results are again obtained.

Injection moulding is accepted as one of the most important methods for shaping complex ceramic cores, which are used to form intricate internal cooling passages of gas turbine blades. But the relatively long lead time and high costs involved in the fabrication of hard tooling render it uneconomical for new products development and low-volume production. In the study, a rapid prototyping process is developed to fabricate complex-shaped alumina-based ceramic core by combining stereolithography (SL) with gelcasting. SL is utilized to fabricate an integral sacrificial resin mold, and gelcasting is utilized to form a wet ceramic core green body through polymerization of aqueous ceramic slurry. The freeze-drying process is adopted to treat the wet green body surrounded by the resin mold, the drying shrinkage is decreased, and the generation of crack can be prevented. The sintering shrinkage of ceramic core is controlled by adding magnesium oxide power and developing a novel sintering process. After the resin mold is burnt out, the complex-shaped alumina-based ceramic core is obtained.

Risk-based maintenance (RBM) strategy can be used in developing a cost-effective maintenance plan to make financial and safety improvements in a petrochemical system. Most maintenance is imperfect in process industries. Previous works on RBM did not consider imperfect maintenance and thus could hardly meet the engineering requirements of process industries. An improved RBM approach based on the proportional age reduction model is proposed in this paper. The parameters of the failure distribution and maintenance effect of equipment are estimated by maximum likelihood estimation. The financial risk for each subsystem is estimated and compared with the risk criteria. Under the risk constraints, the proper interval of periodic preventive maintenance is determined for the equipment in high-risk subsystems. The case of a reforming reaction system in a petrochemical plant is studied using the improved RBM approach. The results show most equipment in this system is imperfectly repaired. The imperfect nature of the periodic preventive maintenance means it needs to be carried out more frequently.

The friction and wear properties of short carbon fibers (SCFs) reinforced aluminum matrix composite were studied. The influences of the fiber volume fraction, load applied, rotating speed, and wear mechanism were discussed. The results indicated that SCFs/Al composite had better tribological properties than Al alloy. The friction coefficient and wear mass loss decreased with the fiber volume fraction increased, but increased as the load and rotating speed increased, respectively. SCF reduced direct contact between the matrix and counterpart and improved the wear resistance of SCFs/Al composite greatly. The wear displayed a linear evolution in all the range of load. Surfaces before and after wear tests were characterized using scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX) spectroscopy.

Trivalent cerium actived yttrium aluminum garnet (YAG: Ce) phosphor was prepared using the Pechini method. Phase transition during calcination was investigated through Fourier transform infrared spectroscopy and X-ray diffraction. The results show that the powders directly transform into the pure YAG phase at 80°C. The dimension of phosphor calcined at 1200°C is micro-scale, which consists of nanometer scale primary particles. The effect of Ce doping content and calcination temperature on the luminescence properties is also discussed. The maximum emission is obtained for about 1 at.% Ce additions. The concentration quench effect is observed when Ce content increases beyond this limit. With the increment of calcination temperature, the emission intensity and lifetime increase.

In UV nanoimprint lithography (NIL) with elastic mould, a novel multi-step loading and demoulding process, called distortion reduction by pressure releasing (DRPR) and two-step curing method for demoulding, is developed. This novel imprint process is continuous, the pressure releasing method, used to optimize the loading process, can reduce the distortions of imprint mould and wafer stage, while obtain better cavity filling and thin and uniform residual layer; through two-step curing method instead of traditional simple demoulding, the curing degree of resist can be controlled, which is helpful to decrease the demoulding force and avoid residual layer pulled-up while ensure replicated protrusions not collapse. It is a novel and robust process with high fidelity of pattern replication in micro/nano structures fabrication, and the replication error caused by distortions and ''blind'' demoulding can be reduced effectively.

This paper describes an investigation on an improvement of the interface between Al and short carbon fibers (SCFs) with α-Al 2 O 3 coating by sol–gel technology. The composites of Al/uncoated SCFs and Al/α-Al 2 O 3 -**coated SCFs were fabricated successfully by vacuum press infiltration. The formation of α-Al 2 O 3 coating during calcination was analysed by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Scanning electron microscopy (SEM), energy-dispersive analysis of X-ray (EDAX) and transmission electron microscope (TEM) were used to observe the coated SCFs and the interface of composites. The results showed that the average thickness of the α-Al 2 O 3 coating was about 200–250 nm and the formation of Al 4 C 3 at the interface between Al matrix and SCFs was controlled by the α-Al 2 O 3 coatings.

Aluminum alloy matrix samples reinforced with short carbon fibers or hybrid SiCp composites were prepared, and friction and wear tests were carried out on a wear test machine using a rotation ring on a stationary disk at high load. Optical microscopy, scanning electron microscopy and energy-dispersive analysis of X-rays were used to investigate the composites, worn surface, wear debris and composition changes after wear. By comparison with Al alloy, Al/SCF and Al/SCF/SiCp, the results indicate that the incorporation of SCF into Al alloys improves the wear resistance significantly, the combination of a mechanically mixed layer formed on the worn surface and hard SiCp are responsible for the good tribological properties of the hybrid Al/SCF/SiCp composites at high load. During sliding, an obvious decrease in the temperature rise with SCF addition is attributed to the good anti-friction of SCF.

The friction and wear properties of the copper matrix composites reinforced with short carbon fibers (CFs) were studied. The influence of short CFs contents, load and rotating speed on tribological behavior of composites was discussed. The results indicate that the wear resistance improve with the increasing of fiber volume fraction. Both friction coefficient and wear mass loss increase with the increase in load and rotating speed, respectively. The wear mechanism is transferred from adhesive wear for pure Cu to delamination wear for Cu/short CFs composites. A graphite film forms on the worn surface of the composite and acts as a solid lubricant.

As a low-cost and high-efficiency alternative to conventional photolithography, imprint lithography has been paid serious attention for it can realize the pattern transfer easily and repeatedly. Even so, there is still a long way to go before this technique can be used to manufacture ICs since the layer-to-layer alignment is a main obstacle. In this paper, the pattern distortion and position shift induced by loading force and friction force are investigated and an optimized process is proposed to realize high precision overlay, in which an optimal loading force and a load release and an alignment error pre-compensation (LRAEPC) method are adopted. The optimal loading force is acquired by comparing the variety trends of the residual layer and position shift with the loading force. Using the optimal loading force, transferred patterns with proper resist thickness and the minimal distortion are achieved. In LRAEPC method, load release is used to correct the pattern distortion and to alleviate the position shift. To avoid subsequent position adjustment in the fluid after load release, the pre-compensation alignment is performed before the mold is in contact with the wafer. This process does not locate correct alignment position and there is an alignment compensation value determined by the statistical data of alignment position shift after load release. Using this pre-compensation alignment method, the correct alignment can be obtained after load release.

Short carbon fibers (SCFs) reinforced copper matrix composites have been produced by a new electrodeposition plus cold press and sintering technique. SCFs were copperized directly by the new method, and the electrodeposit had a loose porous structure. The coating thickness is uniform, and can be controlled by appropriate parameters. A model representing the growth process of these electrodeposits was presented. SCFs were distributed homogeneously, and no defects were found in the Cu/SCFs composites. The effects of SCFs volume fraction on mechanical, physical, thermal, and tribological properties of the composites were discussed.

PurposeThe paper aims to summarize the design theory for labyrinth channels of water saving emitters.Design/methodology/approachOn the basis of extracting the structural parameters of labyrinth channels in water saving emitters, the hydraulic performance experiments on the integral emitters fabricated with higher resolution rapid prototyping technology are performed. Then, using multivariable linear regression, formulas of pressure versus flow rate and regression plots for different emitters are induced.FindingsThe formulas of flow rate versus structural parameters are summarized based on the trapezoid‐type channel unit, and verified through experiments. The relationships between flow rate, pressure and structural parameters of channels are established.Research limitations/implicationsThe effect of emitter fabrication error on the flow rate is analyzed, which provides a basis for parameterized structural design and accuracy control in the fabrication of future emitters.Practical implicationsThe Q‐H‐n relationship equations are used to design emitters which have flow‐rate errors under both high‐ and low‐water pressure of less than 4 percent. So the Q‐H‐n relationship equation of the emitter is well proven and accurate which can guide the design for the structure of emitters with trapezoid labyrinth channels.Originality/valueIn this paper, a new stereolithography system has been used to fabricate accurately a drip irrigation emitter with a complex microstructure, which cannot be obtained with conventional RP or other manufacturing processes. Compared to other manufacturing process, this new technique has higher manufacturing accuracy and can reduce the manufacturing cost and time. Furthermore, a design theory for labyrinth channels of water saving emitters is established.

In this paper, a new method to prepare Al–8.5Fe–1.3V–1.7Si (FVS0812) alloy by spray co-deposition with added its over-sprayed powders was studied. Two kinds of powders which are different in particle size (≤43, 43–74 μm) were used in the new process. Under the same experimental conditions, the alloys were produced by spray deposition without powders and the spray co-deposition. The deposited alloys were subsequently hot extruded with an extrusion ratio of 16:1 at 450 °C. The results showed that the addition of over-sprayed powders refined the microstructure and improved the mechanical properties, and the effect of the fine over-sprayed powders was more evident than that of the coarse powders. The ultimate tensile strength was enhanced from 360.5 MPa (without powders) to 433.3 MPa (≤43 μm) and 392.4 MPa (43–74 μm). The mechanical properties increase is mainly due to the over-sprayed powders pulverizing melt effectively, absorbing heat greatly and increasing the number of heterogeneous nuclei in matrix, which result in the enhancement of cooling rate and the refinement of microstructure.

PurposeThe purpose of this paper is to adopt rapid prototyping (RP) technology to fabricate self‐hardening calcium phosphate composite (CPC) scaffolds with a controlled internal channel network to facilitate nutrient supplying and cell growth using RP technique and investigate their in vitro performance.Design/methodology/approachPorous scaffolds should possess branched channels to ensure uniform cell feeding and even flow of culture medium to promote uniform cell attachment and growth. A new three dimensional (3D) flow channel structure has been designed based on conversation of energy and flow. The CPC scaffold possessing such a channel network was made by indirect solid free form fabrication. Negative model of scaffold was designed by Pro/E software and its epoxy resin mold was fabricated on a sterolithography apparatus and the CPC slurry was filled in these molds. After CPC was self hardened, the mold was baked. The mold was removed by pyrolysis and then the designed scaffold was obtained.FindingsThe sizes of the fabricated scaffolds were consistent with the designed. The average compressive strength of the scaffold is approximately 6.0 MPa. Computational fluid dynamics and perfusion culture results showed that such a 3D flow channel arrangement would lead to a more uniform distribution of flow and cells and good transportation of nutrients.Research limitations/implicationsThe size errors of fabricated scaffolds could not escape and perfusion methods were difficult to control.Originality/valueThe basic design concept presented showed great promise for use in bone tissue engineering and fabrication method enhanced the versatility of scaffold fabrication. The designed scaffold structure made it possible to keep integrality of the scaffold when direct observation cells inside the channel by scanning electron microscopy (SEM).

An integral 3D numerical model based on the structural characteristics of the emitter with arc labyrinth channels was constructed to simulate the relationship between flow rates and pressure heads as well as the flow field distribution in the small channels by computational fluid dynamics (CFD). Meanwhile, the emitter prototypes fabricated by stereolithography technology were used in the flow rate experiments. The calculation results obtained revealed turbulence model can supply a better agreement with the experimental data than laminar flow model under pressure ranges of 40-160kPa. Most pressure losses are occurred in labyrinth channels and the losses within each arc unit are constants under different inlet conditions. In addition, laser-Doppler velocimetry (LDV) was employed to measure the flow fields of the magnified model with a magnifying scale of 15:1 according to the channel structure of the emitter, and the measured velocity distribution in the cross-section is in good agreement with calculation results. It was found that reversed flow happened near the upper fringe of the flow path, and that in the longitudinal symmetric plane mainstream velocity regions and low velocity regions could be observed clearly. The vortexes of different sizes were developed in low velocity regions, which may be one of the reasons leading to channel clogging.

A new method of electrodeposition to prepare Ni/short carbon fibers (CFs) composites with network and sheet structures is described. The key point of the electrodeposition process is to obtain a sheet like preform floating on the electrolyte surface by froth flotation. The preform was composed of short homogeneous CFs. During the electrodeposition process, the preform was uniformly coated by nickel and the coating gradually grew from cathode to anode. The electrodeposits retained the network and sheet structures. The coating thickness can be controlled by appropriate electroplating conditions. The composites of epoxy resin reinforced by the electrodeposits were prepared successfully, and its electrical resistivity and electromagnetic shielding properties are reported.

Electrodeposited nickel was prepared from a sulphamate bath at different current densities ranging from 0.01 A cm− 2 to 0.1 A cm− 2. Based on the analysis of the microstructure, the corrosion behavior of the electrodeposited nickel in 3.5%NaCl solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). All the electrodeposits display active–passive–transpassive behavior in potentiodynamic polarization process. The electrodeposits with the best corrosion resistance are obtained at 0.05 A cm− 2. As for other electrodeposits, the corrosion potential and breakdown potential decrease with increasing current density used to prepare electrodeposits. However, the variation of both corrosion current density and passive current density is opposite to that of the corrosion potential. The changes in the charge-transfer resistance determined from the impedance spectra are consistent with the results determined from potentiodynamic measurements.

In this paper, we present a method to evaluate and optimize traffic patrol based on the generalized maximal covering model. We first build a criterion to evaluate how well a traffic patrol deployment is, and then we formulate an optimization problem for selecting optimal patrol centers from candidates. We show that the optimal patrol centers can be found by an algorithm derived from the method of Lagrange relaxation. Experiments over the datasets of the downtown of Hangzhou demonstrate that the proposed algorithm is effective and useful in the practical situations.

To ensure the safety and serviceability of underground pipeline, it is essential to inspect and assess its structural and functional condition. Underground pipe inner-surface defect inspection is constrained by space accessibility. Thus, in this work we propose a comprehensive in-pipe inspection method based on active stereo omnidirectional vision. In our system, a crawling robot equipped with an active stereo omnidirectional vision sensor travels along the pipeline, taking panoramic images of the internal surface and laser streaks projected from an omnidirectional laser in real time. Afterwards, the internal surface panoramic images are disposed as follows: unwrapping, pre-processing and geometrical features extraction of the defect region, ultimately we classify the defects' category and degree. On the other hand, image sequences with laser streaks are used to extract 3D point cloud data of the inner-surface and calculate the deformation rate of the pipe, this part is not included in this paper. Experimental results show that our system is capable to achieve a qualitative and quantitative analysis of the in-pipe defects such as crack and corrosion, and provide a new approach for inspection of the in-pipe internal surface defects.

A new approach is introduced to measure tunnel deformation by active panorama vision technology aiming at the long-distance tunnel, long maintenance intervals, limited repairing time, a little of deformation change of the tunnel. In order to monitor the tunnel deformation information, Firstly, the panoramic scanning image of tunnel section can be directly received when the Active Stereo Omni-Directional Vision Sensors (ASODVS) in the tunnel detection device is going through the tunnel to make a panoramic scanning, then the geometry information of target surface can be analyzed through extracting the reflected laser image from the picture captured, after that, the tunnel is reconstructed using spatial point cloud data, finally, the refactoring tunnel model precision is analyzed. The experimental research shows that the system has the advantages of high speed acquisition, more real-time, more detailed data, high visualization. It can meet the needs of the rapid qualitative and quantitative analysis.

In this work, Cu-graphite composites were prepared by electroforming technology in an acidic copper sulfate bath with graphite particles in suspension. The factors affecting the codeposition of graphite particles with copper were studied. At a particle concentration of 20 g l –1, a current density of 3 A dm– 2 and a stirring rate of 100 min–1 graphite content in the composites was 21.7 vol.%.Microhardness and friction coefficient of the composites decreased with increasing graphite content. However, wear mass-loss decreased, but increased with graphite content above 21.7 vol.%. The wear mechanisms of pure Cu and Cu-graphite composites were adhesive wear and delaminating wear, respectively.

First-order mean spherical approximation (FMSA) equation of state (EOS) with two parameters for Lennard-Jones (L-J) fluid proposed by Tang has been studied in this article. This equation was used to predict the vapor-liquid phase coexisting diagrams, saturated vapor pressure profiles, and PVT properties of real fluids. The results of prediction were compared with literature data and those from three-parameter FMSA EOS. The two parameters of L-J potential model were determined with vapor-liquid phase coexistence data of the corresponding fluid at the reduced temperature T r

A creative robot wrist consisting of link mechanisms and a novel robot motion control method based on the cross-sectional vector contours of an STL-formatted model was proposed. By using the wrist and the control method, an industrial robot with five degrees of freedom for rapid tooling using metal arc spraying and electric brush plating techniques was developed. The wrist of the robot including a specially designed link mechanism can maintain the position of the spraying point on the surface of the master pattern whatever the orientation of the gun. Therefore, the kinematic nonlinear coupling between the position mechanism and orientation mechanism in a traditional robot can be avoided. The only input of the control system is the STL-formatted 3D CAD model of the pattern. Without the need of any manual programming, the metal arc spraying and brush plating (if necessary) processes can be performed automatically and efficiently after receiving the 3D CAD data of the pattern. Using this robot system in new car development and trial production, the cost and lead-time can be reduced substantially as compared with the conventional tool making method.

PurposeTo fabricate fully dense components with low costs, a rapid prototyping (RP) system based on micro‐plasma arc welding (MPAW) was developed. The appropriate process parameters were investigated to build the parts with good mechanical properties and surface smoothness.Design/methodology/approachA simplified overlapping model between deposited tracks was established to investigate the relationships among the overlapping parameters, such as the ratio of width to height of the deposited track cross‐section (λ), scan spacing and overlapping ratio. Some ER308L stainless steel parts were built by different overlapping parameters, and the surface smoothness, tensile strength and elongation of the parts were tested.FindingsThe overlapped surface smoothness, tensile strength and elongation of the parts built with larger λ were better than those built with smaller λ. The longitudinal tensile strength and elongation of the parts were better than the transverse data.Research limitations/implicationsThe scanning direction obviously affected the tensile strength and elongation of the parts, so the multi‐directional scanning mode should be used to get isotropic parts.Originality/valueThis MPAW‐based RP system provides a solution to build fully dense metal parts with relatively lower costs. The appropriate process parameters can be obtained with the developed overlapping model.

A high-resolution stereolithography (SL) system for fabricating small objects with complex microstructures has been developed. This novel SL system consists of a single mode He-Cd laser, an improved optical scanning system, a novel recoating system and a control system. A laser light spot with the diameter of 12.89 μm on the focal plane is obtained with the improved optical scanning system, and resin layers with the thickness of 20 μm can be built with the novel recoating system. Experimental studies were carried out to investigate the influences of the build parameters on the cured line width and depth with this novel SL system. The experimental results showed that the cured depth and width increase with the increasing ratio of laser power to scanning speed. And it is found that the cured line built using the high-resolution SL system is smaller in width and deeper in depth compared with the cured line fabricated in conventional SL system under the same scanning conditions. Based on the cured line width and depth obtained in the experiment, empirical equations predicting the cured line width and depth according to the ratio of laser power to scanning speed are established using a least-square fitting. The cured line width and depth predicted by the empirical equations provide a foundation to set up accurate line width compensation and appropriate layer thickness in the high-resolution SL system. Some small objects with microstructures have been fabricated with the new SL system.

In order to reduce the process uncertainty and the labor intensity in manual metal arc spraying for rapid tooling, this paper presents a robot wrist design and a robot motion control method based on the cross-sectional contours and related surface normal vectors extracted from STL model, a de facto standard for representing a 3D part geometry in rapid prototyping (RP) industry. A computer controlled five-axis robot for the rapid tooling was built by using the wrist, which drives the spraying gun. The wrist comprises a linkage that can maintain the working position of the gun while changing its spraying orientation freely. Such a design ensures that adjusting the gun along the normal of the master surface to satisfy the process requirement will not result in any position change of the spraying point. A kinematic analysis on the wrist indicates this kinematic decoupling between the positioning mechanism and the orientating mechanism. The working trajectory of the gun is generated off-line by slicing the STL model of the master pattern. To bypass the need for any teaching or NC programming, the arc-spraying robot can carry out the tooling process automatically and efficiently fully based on the sliced data of the master pattern. In addition, a case study on the production of automobile body panel dies using this robotic tooling system is introduced.

Due to the light source limitation and prohibitive cost inherent in conventional photolithography, various nontraditional patterning technologies, such as imprint lithography, electron beam or X-ray lithography have been attempted over the past 10 years. In this paper, a UV imprint lithography process is introduced for patterning sub-micrometer structures by using a soft PDMS mould, and an imprint experimental device with a loading mechanism driven by PZT for generating a time-variant load is described. As shown experimentally, an increased pressing load will reduce the thickness of the resist layer, leading to a reliable etching-through of the resist. It is found, however, that the mechanical pressing can generate geometrical distortion on the patterned resist mainly due to the elasticity. Incorporated with the use of a low viscosity photo-curable resist, a loading process with a load release step is proposed to reduce the geometrical distortion on the resist patterns. In the loading process, the loading force is partially released after the press peak but before the resist curing. Such a loading process can reduce the elastic distortion while attaining a thin remained resist layer. It is shown that this loading process, called Distortion Reduction by Load Release or DRLR simply can be combined with an imprint process for different patterning areas and feature sizes.

This paper presents a simple and reliable imprint template fabrication process for MEMS based on glass wet etching using a single-layer photoresist as the etching mask. In this work a novel vapour deposition process is adopted to cover a thin layer of silane coupler on the glass surface to improve the adhesion strength of the resist and hence attenuate the undercutting phenomenon, which reduces the extra undercut ratio to 0.6 and improves the sharpness of the etched pattern edges. Since the air bubbles in the photoresist and the particle contamination on the glass surface will cause some defects on the etched surface, the authors adopted a thick layer of resist to eliminate defects and reduce the stringent requirement for clean-room conditions. A smooth template surface is obtained by using hydrochloric acid as an etching agent additive, which can facilitate the template separation in the imprint lithography process. Imprint templates with a pattern feature size of 100 µm have been fabricated using the developed process and the imprint results are demonstrated.

PurposeTo satisfy the demands for rapid prototyped small‐size objects with intricate microstructures, a high‐resolution stereolithography (SL) system is developed.Design/methodology/approachThis novel SL system consists of a single mode He‐Cd laser, an improved optical scanning system, a novel recoating system and a control system. The improved optical system consists of a beam expander, an acoustic‐optic modulator, a galvanometric scanner and an F‐θ lens; the recoating system consists of roller pump, resins vat with an integrated high‐resolution translation stage and part building platform and a scraper. Experimental studies were performed to investigate the influences of building parameters on the cured line width and depth.FindingsWith the SL system, a laser light spot with a diameter of 12.89 μm on the focal plane and resin layers with a thickness of 20 μm have been obtained. The experimental results indicate that cured depth and width increase with the ratio of laser power to scanning speed, and cured line with a width of 12 μm and a depth of 28 μm was built, which showed the capability building microstructures with this new SL system.Research limitations/implicationsThe building area limited to 65 × 65 mm, is smaller than that of current SL system.Practical implicationsSmall objects with intricate microstructures can be fabricated with the SL system.Originality/valueThe high‐resolution SL system provides a solution to the problem that has hampered the progress of SL process into a high resolution ranges below 75 μm.

Because of the increasing interest in studying the phenomenon exhibited by charge-stabilized colloidal suspensions in confining geometry, we present a density functional theory (DFT) for a hard-core multi-Yukawa fluid. The excess Helmholtz free-energy functional is constructed by using the modified fundamental measure theory and Rosenfeld's perturbative method, in which the bulk direct correlation function is obtained from the first-order mean spherical approximation. To validate the established theory, grand canonical ensemble Monte Carlo (GCMC) simulations are carried out to determine the density profiles and surface excesses of multi-Yukawa fluid in a slitlike pore. Comparisons of the theoretical results with the GCMC data suggest that the present DFT gives very accurate density profiles and surface excesses of multi-Yukawa fluid in the slitlike pore as well as the radial distribution functions of the bulk fluid. Both the DFT and the GCMC simulations predict the depletion of the multi-Yukawa fluid near a nonattractive wall, while the mean-field theory fails to describe this depletion in some cases. Because the simple form of the direct correlation function is used, the present DFT is computationally as efficient as the mean-field theory, but reproduces the simulation data much better than the mean-field theory.

PurposeTo fabricate the self‐hardening calcium phosphate composite scaffolds with controlled internal pore architectures using rapid prototyping (RP) techniques and investigate their in vitro bone tissue engineering responses.Design/methodology/approachThe three‐dimensionally interconnected pores in scaffolds can facilitate sufficient supply of blood, oxygen and nutrients for the ingrowth of bone cells, tissue regeneration, and vascularization. It is essential for bone tissue engineering to provide an accurate control over the scaffolds material, porosity, and internal pore architectures. Negative image of scaffold was designed and epoxy resin molds were fabricated on sterolithography apparatus. Calcium phosphate cement slurry was cast in these molds. After self‐hardening, the molds were removed by pyrolysis and the resulting scaffolds were obtained.FindingsEight scaffolds with 54.45 percent porosity were tested on an Instron machine. The average compressive strength measured was 5.8±0.8 Mpa. Cytotoxicity and cell proliferation studies were conducted with rabbit osteoblast. Results showed that these scaffolds were non‐toxic and displayed excellent cell growth during the 2 weeks of in vitro culture.Research limitations/implicationsThe resulting scaffolds inherited errors and defects from the molds, such as cracks and dimensional changes.Originality/valueThe present method enhances the versatility of scaffold fabrication by RP. It is capable of reproducibly fabricating scaffolds from a variety of biomaterials.

Traditional processes for machining mould cavities are lengthy and costly. Electro-discharge machining (EDM) is the most commonly used technique to obtain complex mould cavities. However, some electrodes are difficult to fabricate because of the complexity. Applying rapid prototyping (RP) technology to fabricate an abrading tool which is used to abrade graphite EDM electrodes, the cost and cycle-time can greatly be reduced. The paper describes the work being conducted in this area by the authors. This technique will find widespread applications in rapid steel mould manufacturing.

The recently proposed renormalization group (RG) theory is reformulated within the context of density functional theory and applied to predicting global vapor–liquid equilibria (VLE) of Lennard–Jones chain pure fluids and fluid mixtures. An accurate equation based on the solution of the first-order mean-sphere approximation (FMSA) is adopted outside the critical region. Inside the critical region, the direct correlation function of FMSA is incorporated into the new RG transformation to describe the long-range fluctuation, which is conformal to general inhomogeneous studies. The new RG theory is applied to correcting real mixture phase envelopes, as well as corresponding phase diagrams of pure compounds for the critical region. The calculated results are in substantial agreement with those from experiment and molecular simulation both inside and outside the critical region. The new method is highly predictive because no adjustable parameters and no mixing rule are needed for both model and real fluid mixtures. © 2005 American Institute of Chemical Engineers AIChE J, 2006

A new technique based on rapid prototyping (RP) is proposed to fabricate the mould of artificial bone composed of a nontoxic soluble material. The mould has both an external structure that exactly coincides with the replaced natural bone and an internal 3D scaffolds simulating the bone microtubule structure. By injecting self‐setting calcium phosphate cement (CPC) with bone morphogenetic protein (BMP, a kind of bone growth factors) into the cavities of the mould, the CPC solidified and the micropores can be formed after the internal 3D scaffolds is dissolved, finally the artificial bioactive bone can be produced. This approach is better than the traditional fabrication process, which the latter method cannot fabricate an artificial bone with inter‐connective micropores so as to realize the osteo‐induction for lack of bioactivity. Through animal experiments, it shows that the simulated inter‐structure could provide artificial bone with proper voids for the growth of the bone tissue and the quick activation, and hence effectively speed up the bone growth by means of activating osteo‐conduction and osteo‐induction. So, the new method of fabricating artificial bone with biological behaviors is justified.

On the basis of White's theory, an improved renormalization group (RG) theory is developed for chain bonding fluids inside the critical region. Outside the critical region, the statistical associating fluid theory based on the first-order mean sphere approximation [Fluid Phase Equilibria 171, 27 (2000)] is adopted and all the microscopic parameters are taken directly from its earlier application of real fluids. Inside the critical region, the RG transformation for long-range density fluctuation is derived in the k space, which illustrates explicitly the contributions from the mean-field term, the local density fluctuation, and the nonlocal density fluctuation. The RG theory is applied to describe physical behavior of ten n alkanes (C1-C10) both near to and far from the critical point. With no additional parameters for chain bonding fluids, good results are obtained for critical specific heat and phase coexistence curves and the resulting critical exponents are in good agreement with the reported nonclassic values.

Paper lamination rapid prototyping technology has an advantage of its low overall cost due to the building materials and the processing principle. To reduce the system and its operating cost further, a cutter-based paper lamination rapid prototyping system is proposed. The cutter set employed is cheap and the cutter can turn its cutting direction automatically so as to simplify the system control. In this paper, the cutting mechanism of the cutter was studied. According to its kinetic characteristics, the motion of the cutter nose was described by a tractrix model, and its trace error can be eliminated by modifying the cutter path. Experimental study on the cutting notch was carried out, and the notch specimens were measured through a high-power microscope VH-8000. According to the analysis of the experimental results, the dimension error caused by the cutting notch was within 3 μm and the roughness average (Ra) was less than 6 μm. Two physical parts have been fabricated on the developed experimental machine, which indicates the proposed system has use value.

This paper describes the rapid development process for emitter which is the key part in water‐saving irrigation device. The design of labyrinth‐channel in emitters, the generation of process‐oriented structural CAD model, the building of emitter prototype and its integrative experimental model based on RP are introduced in detail. The emitter prototypes can be directly applied to irrigation experiments and production practice, and hence the rapid development of drip irrigation emitters can be realized.

The general solution of the Ornstein–Zernike equation presented by Tang and Lu [J. Chem. Phys. 99, 9828 (1993)] is further discussed. By applying the Hilbert transform, the first-order factorization and direct correlation functions (DCF) are generally and analytically obtained, with emphasis on the mean spherical approximation (MSA) for Yukawa fluids. These analytical results are employed to produce a new DCF for hard spheres through integrating with the previous generalized mean spherical approximation [J. Chem. Phys. 103, 7463 (1995)]. The new DCF is of simple analytical form and remedies the deficiencies of its Percus–Yevick version at high densities. Comparisons between the first-order and full MSA solutions are also made. It is shown that the two solutions give very close results for thermodynamic properties in the phase stable region and phase coexistence curves away from the critical point. At unstable states, the first-order MSA looks more advantageous when applications go beyond homogeneous.