Microstructure and mechanical properties of WC-Co,WC-Co-Cr_3C_2 and WC-Co-TaC cermets fabricated by spark plasma sintering

Spark plasma sintering was successfully used to produce WC-Co cermets with the addition of Cr3C2and TaC grain growth inhibitors. The spark plasma sintered compacts were investigated by scanning electron microscopy, X-ray diffraction analysis, density measurements, hardness tests, fracture toughness tests and elastic modulus tests. The results were comparedwithan inhibitor-free WC-Co cermet consolidated under the same process parameters. By using Cr3C2and TaC additives, it is possible to improve the hardness and fracture toughness of WC-Co cermets, but Cr3C2has better grain growth inhibition propertythan that of TaC. The best combination of hardness （HV30（2105±38）） and fracture toughness （（8.3±0.2）MPa·m^1/2） was obtained by the WC-5Co-2Cr3C2 cermet.

Mechanical Properties, Microstructure and Surface Quality of Polypropylene Green Composites as a Function of Sunflower Husk Waste Filler Particle Size and Content

Agricultural waste is a still untapped source of materials that can,in case of proper utilization,significantly improve the sustainability of polymers and their composites.In this work,polymer composites based on isotactic polypropylene were produced incorporating ground sunflower husk in the amount of 10 wt%and 20 wt%.The work’s main objective is to evaluate how preliminary fractioning of this agricultural waste filler affects the thermomechanical properties,microstructure and surface topology of polypropylene-based injection molded composites.The composites were analyzed for mechanical properties(tensile,impact strength and hardness),thermomechanical properties(Vicat softening point VST,heat deflection temperature HDT,and dynamic thermomechanical analysis DMTA)with reference to morphological changes evaluated using scanning electron microscopy(SEM).The quality of the produced composites was assessed on the basis of the analysis of the surface topology of the injected composites.It has been shown that the larger particle size of used filler has a direct impact on increasing composite stiffness in the room and elevated temperature.Moreover,a relationship was demonstrated between the size of the filler and the deterioration of the tensile strength in the case of composites with a higher content of filler.The results show that the addition of sunflower husk as a particle-shaped waste filler is an effective method to increase sustainability of polypropylene-based green composites with beneficial thermomechanical properties and to reduce the residue of sunflower husk from industrial oil production.

A New Dynamics Analysis Model for Five-Axis Machining of Curved Surface Based on Dimension Reduction and Mapping

The equipment used in various fields contains an increasing number of parts with curved surfaces of increasing size.Five-axis computer numerical control(CNC)milling is the main parts machining method,while dynamics analysis has always been a research hotspot.The cutting conditions determined by the cutter axis,tool path,and workpiece geometry are complex and changeable,which has made dynamics research a major challenge.For this reason,this paper introduces the innovative idea of applying dimension reduction and mapping to the five-axis machining of curved surfaces,and proposes an efficient dynamics analysis model.To simplify the research object,the cutter position points along the tool path were discretized into inclined plane five-axis machining.The cutter dip angle and feed deflection angle were used to define the spatial position relationship in five-axis machining.These were then taken as the new base variables to construct an abstract two-dimensional space and establish the mapping relationship between the cutter position point and space point sets to further simplify the dimensions of the research object.Based on the in-cut cutting edge solved by the space limitation method,the dynamics of the inclined plane five-axis machining unit were studied,and the results were uniformly stored in the abstract space to produce a database.Finally,the prediction of the milling force and vibration state along the tool path became a data extraction process that significantly improved efficiency.Two experiments were also conducted which proved the accuracy and efficiency of the proposed dynamics analysis model.This study has great potential for the online synchronization of intelligent machining of large surfaces.

Stress-Induced Deformation of Thin Copper Substrate in Double-Sided Lapping

Double-sided lapping is an precision machining method capable of obtaining high-precision surface.However,during the lapping process of thin pure copper substrate,the workpiece will be warped due to the influence of residual stress,including the machining stress and initial residual stress,which will deteriorate the flatness of the workpiece and ultimately affect the performance of components.In this study,finite element method(FEM)was adopted to study the effect of residual stress-related on the deformation of pure copper substrate during double-sided lapping.Considering the initial residual stress of the workpiece,the stress caused by the lapping and their distribution characteristics,a prediction model was proposed for simulating workpiece machining deformation in lapping process by measuring the material removal rate of the upper and lower surfaces of the workpiece under the corresponding parameters.The results showed that the primary cause of the warping deformation of the workpiece in the doublesided lapping is the redistribution of initial residual stress caused by uneven material removal on the both surfaces.The finite element simulation results were in good agreement with the experimental results.

Influence of niobium and molybdenum addition on microstructure and wear behavior of laser-borided layers produced on Nimonic 80A-alloy

Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy.For laser surface modification,three types of pre-coated pastes were applied:with amorphous boron,with amorphous boron and molybdenum as well as with amorphous boron and niobium.The microstructure,hardness and wear resistance of produced layers were studied in details.The presence of different types of borides in re-melted zone depended on the paste composition and caused an increase in hardness up to about HV 1000.The wear resistance was evaluated by calculation of mass wear intensity factor Imw and relative mass loss of specimen and counter-specimen.The wear behavior of the tested frictional pairs was determined by 3D interference microscopy,scanning electron microscopy equipped with EDS microanalyzer.The significant increase in abrasive wear resistance was observed in comparison to untreated Nimonic 80A-alloy.The lowest mass loss intensity factor was characteristic of laser-alloyed Nimonic 80A-alloy with boron and niobium(Imw=1.234 mg/(cm2?h)).Laser alloyed-layers indicated abrasive wear mechanism with clearly visible grooves.Laser alloying with boron and niobium resulted in the additional oxidative wear mechanism.In this case,EDS patterns revealed presence of oxygen on the worn surface of specimen.

Optimal design considering structural efficiency of compressed natural gas fuel storage vessels for automobiles

The shape and thickness of the dome were investigated with the aim of optimizing the type II CNG storage vessels by using a finite element analysis technique. The thickness of the liners and reinforcing materials was optimized based on the requirement of the cylinder and dome parts. In addition, the shape of the dome, which is most suitable for type lI CNG storage vessels, was proposed by a process of review and analysis of various existing shapes, and the minimum thickness was established in this sequence： metal liners, composite materials and dome parts. Therefore, the new proposed shape products give a mass reduction of 4.8 kg（5.1%）

Integrated Design of D.D.I., Filament Winding and Curing Processes for Manufacturing the High Pressure Vessel(Type Ⅱ)

As energy crisis and environment pollution all around the world threaten the widespread use of fossil fuels,compressed natural gas(CNG)vehicles are explored as an alternative to the conventional gasoline powered vehicles.Because of the limited space available for the car,the composite pressure vessel(TypeⅡ)has been applied to the CNG vehicles to reach large capacity and weight lightening vehicles.High pressure vessel(TypeⅡ)is composed of a composite layer and a metal liner.The metal liner is formed by the deep drawing and ironing(D.D.I.)process,which is a complex process of deep drawing and ironing.The cylinder part is reinforced by composite layer wrapped through the filament winding process and is bonded to the liner by the curing process.In this study,an integrated design method was presented by establishing the techniques for FE analysis of entire processes(D.D.I.,filament winding and curing processes)to manufacture the CNG composite pressure vessel(TypeⅡ).Dimensions of the dies and the punches of the 1 st(cup drawing),2 nd(redrawing-ironing 1-ironing 2)and 3 rd(redrawing-ironing)stages were calculated theoretically,and shape of tractrix die to be satisfied with the minimum forming load was suggested for life improvement and manufacturing costs in the D.D.I.process.Thickness of the composite material was determined in the filament winding process,finally,conditions of the curing process(number of heating stage,curing temperature,heating rate and time)were proposed to reinforce adhesive strength between the composite layers.

Crack Localization Using Transmissibility of Operational Deflection Shape and Its Application in Cantilever Beam

Due to the nonlinearity of breathing crack, cracked structure under excitation of a single frequency always generates higher harmonic components. In this paper, operational deflection shape (ODS) at excitation frequency and its higher harmonic components are used to map the deflection pattern of cracked structure. While ODS is sensitive to local variation of structure in nature, a new concept named transmissibility of operational deflection shape (TODS) has been defined for crack localization using beam-like structure. The transmissibility indicates the energy transfer from basic frequency to higher frequency. Then, Teager energy operator (TEO) is employed as a singularity detector to reveal and characterize the features of TODS. Numerical and experimental analysis in cantilever beam show that TODS has strong sensitivity to crack and can locate the crack correctly.

Application of MBAM Neural Network in CNC Machine Fault Diagnosis

In order to improve the bidirectional associative memory(BAM) performance, a modified BAM model(MBAM) is used to enhance neural network(NN)’s memory capacity and error correction capability, theoretical analysis and experiment results illuminate that MBAM performs much better than the original BAM. The MBAM is used in computer numeric control(CNC) machine fault diagnosis, it not only can complete fault diagnosis correctly but also have fairly high error correction capability for disturbed Input Information sequence.Moreover MBAM model is a more convenient and effective method of solving the problem of CNC electric system fault diagnosis.

Effect of N-Doping on Absorption and Luminescence of Anatase TiO_(2) Films

Anatase TiO_(2) films are deposited on glass substrates at different oxygen partial pressures of 0.8-1.6 Pa.Room temperature N ion implantation is conducted in the films at ion fluences up to 5 × 10^(17) ions/cm^(2).UV-visible absorption and photoluminescence (PL) are investigated.With the increase of N ion fluences,the band gap of TiO_(2) decreases and the absorbance increases.X-ray photoelectron spectroscopy (XPS) confirms the formation of O-Ti-N nitride after implantation,resulting in the red shift of the band gap.The PL intensity of the deposited films increases with the increasing oxygen partial pressure and decreases remarkably due to the irradiation defects induced by ion implantation.

Chemical-mechanical dispersing behavior of a nanoceria abrasive

The authors studied dispersing behavior of a nanoceria abrasive under joint actions of mechanical ultra-sonication and chemical dispersants,to explore effective approaches and methods for dispersing it and manifesting its functions of nanometric scale.It was found that mechanical ultra-sonication solely could not disperse the nanoceria abrasive effectively,while dispersants such as sodium hexametaphosphate(SHP) and sodium dodecylbenzenesulfonate(SDBS) could help to disperse the nanoceria abrasive.SHP and SDBS were found to increase value of zeta potential of the nanoceria abrasive markedly and decrease level of apparent viscosity of its slurry observably.It was deduced by analysis that the dispersants increased inter-particles mutual repulsive force by forming steric hindrance between particles and augmenting zeta potential of particle surfaces,which could overcome van der Waals attracting force to some extent,reduce agglomeration and flocculation of the nanoceria particles,thus improve dispersibility and stability of the nanoceria particles in slurries.

Elliptical vibration cutting of large-size thin-walled curved surface parts of pure iron by using diamond tool with active cutting edge shift

Large-size thin-walled curved surface parts of pure iron are crucial in aerospace,national defense,energy and precision physical experiments.However,the high machining accuracy and surface quality are difficult to achieve due to the serious tool wear and deformation when machining the parts with conventional cutting tools.In this paper,an elliptical vibration cutting(EVC)with active cutting edge shift(ACES)based on a long arbor vibration device is proposed for ultraprecision machining the pure iron parts by using diamond tool.Compared with cutting at a fixed cutting edge,the influence of ACES on the EVC was analyzed.Experiments in EVC of pure iron with ACES were conducted.The evolutions of the surface roughness,surface topography,and chip morphology with tool wear in EVC with ACES are revealed.The reasonable parameters of ultraprecision machining the pure iron parts by EVC with ACES were determined.It shows that the ACES has a slight influence on the machined surface roughness and surface topography.The diamond tool life can be significantly prolonged in EVC of pure iron with ACES than that with a fixed cutting edge,so that high profile accuracy and surface quality could be obtained even at higher nominal cutting speed.A typical thin-walled curved surface pure iron part with diameter φ240 mm,height 122 mm,and wall thickness 2 mm was fabricated by the presented method,and its profile error and surface roughness achieved PV 2.2μm and Ra less than 50 nm,respectively.

Recent advances in gecko adhesion and friction mechanisms and development of gecko-inspired dry adhesive surfaces

The remarkable ability of geckos to climb and run rapidly on walls and ceilings has recently received considerable interest from many researchers.Significant progress has been made in understanding the attachment and detachment mechanisms and the fabrication of articulated gecko-inspired adhesives and structured surfaces.This article reviews the direct experiments that have investigated the properties of gecko hierarchical structures,i.e.,the feet,toes,setae,and spatulae,and the corresponding models to ascertain the mechanical principles involved.Included in this review are reports on gecko-inspired surfaces and structures with strong adhesion forces,high ratios of adhesion and friction forces,anisotropic hierarchical structures that give rise to directional adhesion and friction,and“intelligent”attachment and detachment motions.

Real-time Bezier interpolation satisfying chord error constraint for CNC tool path

G01 code generated by a computer-aided manufacture （CAM） system is the most common form of tool trajeclory in computer numerical control （CNC） machining. A tool path composed of short line segments has discontinuous tangenc t and curvature, generating large fluctuations of feedrate and acceleration, which in turn produces vibration in a machine tool. To obtain a smooth tool path, many methods on tool-path smoothing have been developed. However, the shortcomings i：1 these methods exist when they are employed in a CNC system. It is difficult to simultaneously to guarantee the following requirements of CNC machining： （1） chord error should be rigidly constrained; （2） G01 points should be interpolated; （3） cur,,ature should be continuous （G2）; （4） machining should be applicable to spatial cases; （5） real-time performance of computaEion is required.Based on these various requirements, this study proposes an interpolation scheme using CUDlC t^ezler curves anu mciuucb illl adjustment strategy to eliminate deficiencies in the tool path. The tool path generated is G2, chord-elror-constrained, G01-point-interpolated, loop-free, and optimized for both stretch and jerk energy. The method is applicable ：o 3D cases and involves only simple algebraic computations. Thus, the algorithm can be applied to real-time CNC machining. A simulation is conducted to validate the efficiency of the algorithm. In addition, an experiment reveals its advantage over Hermite interpola- tion in surface quality and machining efficiency.

A novel method for workpiece deformation prediction by amending initial residual stress based on SVR-GA

High-precision manufactured thin-walled pure copper components are widely adopted in precision physics experiments,which require workpieces with extremely high machining accuracy.Double-sided lapping is an ultraprecision machining method for obtaining high-precision surfaces.However,during double-sided lapping,the residual stress of the components tends to cause deformation,which affects the machining accuracy of the workpiece.Therefore,a model to predict workpiece deformation derived from residual stress in actual manufacturing should be established.To improve the accuracy of the prediction model,a novel method for predicting workpiece deformation by amending the initial residual stress slightly based on the support vector regression(SVR)and genetic algorithm(GA)is proposed.Firstly,a finite element method model is established for double-sided lapping to understand the deformation process.Subsequently,the SVR model is utilized to construct the relationship between residual stress and deformation.Next,the GA is used to determine the best residual stress adjustment value based on the actual deformation of the workpiece.Finally,the method is validated via double-sided lapping experiments.

Spectroscopic study on the interaction between[Hg(SCN)_4]^(2-) and hemoglobin

The interaction between [Hg（SCN）4]^2- and hemoglobin （Hb） under conditions that simulate a physiological environment was investigated by UV-vis spectroscopy, fluorescence spectroscopy, resonance Rayleigh scattering （RRS） spectroscopy and circular dichroism （CD） spectroscopy. The results obtained from the change of UV-vis and CD spectra, the quenching of Hb fluorescence and the enhancement of RRS intensity proved that a 10：1 type complex was formed between [Hg（SCN）4]^2- and Hb. The possible mechanism suggested for the interaction was that ten Hg（SCN）4]^2- anions entered the four subunits of a Hb molecule to react with some residues to form an adduct by coordination and electrostatic forces. The coordination of [Hg（SCN）4]^2- with Trp was the major cause of the fluorescence quenching of Hb.

Carbon-Doped Titanium Oxide Films by DC Reactive Magnetron Sputtering Using CO_2 and O_2 as Reactive Gas

CO2 and O2 were employed as reactive gases to fabricate carbon-doped titanium oxide films using DC reactive magnetron sputtering. Microstructure, composition and optical band gap of the films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and UV-visible spectrophotometer, respectively. The results showed that carbon-doped titanium monoxide films （C-TiO） with a carbon concentration of 5.8 at.% were obtained in an AffCO2 mixed atmosphere. However, carbon-doped futile and anatase （C-TiO2） with a carbon concentration of about 1.4 at.% were obtained in an Ar/CO2/O2 mixed atmosphere. The optical band gaps of C-TiO and C-TiO2 were about 2.6 and 2.9 eV, respectively. Both of them were narrower than that of pure TiO2 films. Films with narrowed optical band gap energy are promising in promoting their photo-catalytic activity.