For laser cladding a large temperature gradient easily weakened the surface quality by generating cracks and irregular coating surfaces,which in turn affected the bearing capacity and corrosion resistance of coatings ...For laser cladding a large temperature gradient easily weakened the surface quality by generating cracks and irregular coating surfaces,which in turn affected the bearing capacity and corrosion resistance of coatings in the rapid heating and cooling process.The response surface methodology(RSM)was used to predict coating cracks by changing the powder ratio,energy density,and preheating temperature,which obtained the relevant mathematical model.After that,the sensitivity of the crack length to process parameters was analyzed based on the sensitivity analysis method.The effect of Ni60/WC composite powder process parameters on the surface quality was revealed in laser cladding.The crack length first decreased and then increased,and the Smooth decreased with the increased powder ratio.The crack length and Smooth increased with the increased energy density.The crack length decreased and Smooth increased with the increased preheating temperature.Sensitivity analysis showed that the crack length and Smooth were the most sensitive to the powder ratio.Therefore,the process parameters were reasonably selected to control the surface quality.The mathematical model and sensitivity analysis method in the work could improve the surface quality,which provided a theoretical basis for the prediction and control of laser cladding cracks.展开更多
As a substitute for toxic cadmium coatings in the aerospace industry,zinc-nickel coatings have excellent application prospects,and their properties can be improved by adding molybdenum.In this study,laser-assisted ele...As a substitute for toxic cadmium coatings in the aerospace industry,zinc-nickel coatings have excellent application prospects,and their properties can be improved by adding molybdenum.In this study,laser-assisted electrodeposition is used to improve the surface quality and properties of Zn–Ni–Mo coatings,with investigation of how laser energy in the range of 0–21.1μJ affects their element content,surface morphology,crystal phase,microhardness,residual internal stress,and corrosion resistance.The laser irradiation accelerates the electrodeposition,refines the grain size,improves the hydrogen adsorption,and reduces the residual tensile stress,and a laser energy of 15.4μJ gives the highest Ni and Mo contents and the lowest Zn content,as well as the optimum surface morphology,microhardness,residual internal stress,and corrosion resistance of the coating.展开更多
Contour bevel gears have the advantages of high coincidence,low noise and large bearing capacity,which are widely used in automobile manufacturing,shipbuilding and construction machinery.However,when the surface quali...Contour bevel gears have the advantages of high coincidence,low noise and large bearing capacity,which are widely used in automobile manufacturing,shipbuilding and construction machinery.However,when the surface quality is poor,the effective contact area between the gear mating surfaces decreases,affecting the stability of the fit and thus the transmission accuracy,so it is of great significance to optimize the surface quality of the contour bevel gear.This paper firstly analyzes the formation process of machined surface roughness of contour bevel gears on the basis of generating machining method,and dry milling experiments of contour bevel gears are conducted to analyze the effects of cutting speed and feed rate on the machined surface roughness and surface topography of the workpiece.Then,the surface defects on the machined surface of the workpiece are studied by SEM,and the causes of the surface defects are analyzed by EDS.After that,XRD is used to compare the microscopic grains of the machined surface and the substrate material for diffraction peak analysis,and the effect of cutting parameters on the microhardness of the workpiece machined surface is investigated by work hardening experiment.The research results are of great significance for improving the machining accuracy of contour bevel gears,reducing friction losses and improving transmission efficiency.展开更多
Selective laser melting(SLM) is a powerful additive manufacturing(AM) technology, of which the most prominent advantage is the ability to produce components with a complex geometry. The service performances of the SLM...Selective laser melting(SLM) is a powerful additive manufacturing(AM) technology, of which the most prominent advantage is the ability to produce components with a complex geometry. The service performances of the SLM-processed components depend on the microstructure and surface quality. In this work, the microstructures, mechanical properties, and fracture behaviors of SLM-processed Ti-6 Al-4 V alloy under machined and as-built surfaces after annealing treatments and hot isostatic pressing(HIP) were investigated. The microstructures were analyzed by optical microscope(OM), scanning electron microscope(SEM) and transmission electron microscopy(TEM). The mechanical properties were measured by tensile testing at room temperature. The results indicate that the as-deposited microstructures are characterized by columnar grains and fine brittle martensite and the asdeposited properties present high strength, low ductility and obvious anisotropy. After annealing at 800-900°C for 2-4 h and HIP at 920°C/100 MPa for 2 h, the brittle martensite could be transformed into ductile lamellar(α+β) microstructure and the static tensile properties of SLM-processed Ti-6 Al-4 V alloys in the machined condition could be comparable to that of wrought materials. Even after HIP treatment, the as-built surfaces could decrease the ductility and reduction of area of SLM-processed Ti-6 Al-4 V alloys to 9.2% and 20%, respectively. The crack initiation could occur at the columnar grain boundaries or at the as-built surfaces. The lamellar(α+β) microstructures and columnar grains could hinder or distort the crack propagation path during tensile tests.展开更多
The ground surface quality of Cr 2O 3 coatings is investigated in this paper. The influence of some typical grinding parameters on ground surface integrity is discussed in detail. It is found that the ground surface r...The ground surface quality of Cr 2O 3 coatings is investigated in this paper. The influence of some typical grinding parameters on ground surface integrity is discussed in detail. It is found that the ground surface roughness increases with the increase of depth-of-cut. The surface finish is improved as the increase of grinding speed, but too high grinding speed may result in serious vibration of the system. The increase of workpiece speed causes deterioration of surface finish and produces big grinding noise. Experiments on plateau treatment after the rough ground surface were also carried out. The surface profile of the ground surface after plateau treatment becomes much smoother than the former rough surface. Some sharp peaks on the ground surface may be effectively removed by the plateau treatment, which produces a reasonable surface profile and can stand much more load. Surface observations and analyses show that plastic deformation and micro-cracks occur on the ground surface. The material removal process is primarily a serious of localized surface fractures accompanied by multi-plastic deformations. Much more plastic deformation and micro-cracks emerge on the ground surface when the depth-of-cut increases. The increase of workpiece speed may produce more surface micro-cracks, but the relative increase of grinding speed is beneficial to ground surface quality.展开更多
In conventional grinding theory, the chief removed mode of ceramic coprocessor by diamond tools was brittle removal. In order to perform the plastic removal or ductility processing of engineering ceramics the high deg...In conventional grinding theory, the chief removed mode of ceramic coprocessor by diamond tools was brittle removal. In order to perform the plastic removal or ductility processing of engineering ceramics the high degree of accuracy and high rigidity grinner must be using micro grain size diamond grinding wheel to direct the processing of micron below rank depth to prevent form the occurring of the brittle processing zone. This will resulted in the high expense of grinding. The expense of grinding could even reach the 80% of the total manufacture cost of the ceramic part. Ultra-precision grinding for advanced ceramics has been achieved by the unsteady-state grinding technique. In this paper, we mainly deals with observing and analyzing the surface quality of the silicon nitride ground by pink fused alumina wheel in different grinding parameters. To optimize the grinding parameters in the process of the unsteady-state grinding, the experiments of X-ray diffraction, energy spectrum analysis, SEM observation and roughness measurement were performed. The results show that: 1. In the process of unsteady state grinding, high line speed (rotational speed) of the grind wheel can improve the roughness of the silicon nitride apparently. It was also evident that the larger the grain mesh size, the better the surface quality. 2. There exists an optimum combination of grinding conditions such as grinding wheel speed, rotational speed of the workpiece, feed rate between the grinding wheel and the workpiece, grinding times and cutting coolant. The surface quality of the silicon nitride can be up to the standard of mirror finishing. 3. By analyzing the finished surface with X-ray diffraction and energy spectrum, the existence of some new phases including titanium and alumina was proved. 4. By utilizing the unsteady state grinding technique, the surface roughness of Ra ≤ 0.030 μm can be achieved by grinding the silicon nitride with the pink fused alumina wheel in low cost. Based on the unsteady-state grinding technique, this paper put forward a new processing method which by utilizing aluminum oxide grinding wheel to perform burnishing process and impudent the low surface roughness processing of engineering ceramic, the Ra is about 0.01 μm. Furthermore, the working efficiency of this method is high, and the process cost is low, so it is a prospective processing method.展开更多
As a natural and environmentally friendly renewable material,Northeast China ash wood(NCAW)(Fraxinus mandshurica Rupr.)was cut by water-jet assisted CO_(2) laser(WACL),the surface quality was evaluated by surface roug...As a natural and environmentally friendly renewable material,Northeast China ash wood(NCAW)(Fraxinus mandshurica Rupr.)was cut by water-jet assisted CO_(2) laser(WACL),the surface quality was evaluated by surface roughness of cut section.The surface roughness was measured by three-dimensional(3D)profilometry.Furthermore,the micromorphology of machined surface was observed by scanning electronic microscopy(SEM).Carbon content changes of machined surface were measured by energy dispersive spectrometer(EDS).A relationship between surface roughness and cutting parameters was established using response surface methodology(RSM).It is concluded that the cutting speed,laser power and water pressure played an important role in surface roughness of cut section.The surface roughness increased as an increase in laser power.It decreased caused by increasing of cutting speed and water pressure.Measurements revealed that the surface quality of NCAW part was improved using the optimized combination of cutting parameters.The established quadratic mathematical model of a good prediction is helpful for matching suitable cutting parameters to obtain expected surface quality.展开更多
Three different punches are designed for the hydropiercing experiments and finite element simulations are conducted by finite element program ABAQUS-3D to investigate the influence of punch shape on the fracture surfa...Three different punches are designed for the hydropiercing experiments and finite element simulations are conducted by finite element program ABAQUS-3D to investigate the influence of punch shape on the fracture surface quality of hydropiercing holes. The results show the fracture burrs are not obvious punched by all the three punches. The collapse punched by the round punch is a little larger than the others. The fracture surface quality punched by the round punch is good with larger smooth zone and the interface between smooth zone and tear zone is even with large gradient. The size of the smooth zone is larger and the interface between smooth zone and tear zone is uneven with large gradient punched by the flat punch. The size of the smooth zone is smaller and the size of the tear zone increases from the first fractured to the last fractured punched by the inclined punch.展开更多
This article is try to explain or analyze the key technologies of controlling the surface quality of low carbon steel as cast strip through investigation of interface heat transfer between solidified shell and liquid ...This article is try to explain or analyze the key technologies of controlling the surface quality of low carbon steel as cast strip through investigation of interface heat transfer between solidified shell and liquid steel.The one of the key technologies of controlling surface quality of low carbon steel as cast strip is through the casting roll surface texture in order to achieve the homogeneous solidification on the casting roll.Another is through forming a thin film on the casting roll surface in order to achieve a balance between rapid solidification and homogeneous solidification.This film formed between the twin roll and the molten steel can be controlled by adjusting the chemical composition and inclusion in liquid steel through controlling the amount of all[O]and free[O].展开更多
Electrochemical machining(ECM)has emerged as an important option for manufacturing the blisk.The inter-electrode gap(IEG)distribution is an essential parameter for the blisk precise shap-ing process in ECM,as it affec...Electrochemical machining(ECM)has emerged as an important option for manufacturing the blisk.The inter-electrode gap(IEG)distribution is an essential parameter for the blisk precise shap-ing process in ECM,as it affects the process stability,profile accuracy and surface quality.Larger IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of blisk.To achieve micro-IEG(<50 lm)blisk finishing machining,this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse duration.The modelling and simulation of the blisk micro-IEG machining have been carried out.Exploratory experiments of variable-parameters blisk ECM were car-ried out.The results illustrated that the IEG width reduced with the progress of variable parameter pro-cess.The IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 lm and 21 lm,respectively.The profile deviation for the blade’s concave surface and convex surface are 49 lm and 35 lm,while the surface roughness reaches R_(a)=0.149 lm and R_(a)=0.196 lm,respectively.The profile accuracy of the blisk leading/trailing edges was limited to within 91 lm.Com-pared with the currently-established process,the profile accuracy of the blade’s concave and convex profiles was improved by 50.5%and 53.3%,respectively.The surface quality was improved by 53.2%and 50.9%,respectively.Additionally,the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective dissolution.Some electrolytic products were dispersed on the machined surface,and their components were mainly composed of the carbide and oxide products of Ti and Nb elements.The results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM,which can be used in engineering practice.展开更多
Creep feed profile grinding of the fir-tree blade root forms of single crystal nickel-based superalloy was conducted using microcrystalline alumina abrasive wheels in the present study. The grinding force and the surf...Creep feed profile grinding of the fir-tree blade root forms of single crystal nickel-based superalloy was conducted using microcrystalline alumina abrasive wheels in the present study. The grinding force and the surface quality in terms of surface topography, subsurface microstructure,microhardness and residual stress obtained under different grinding conditions were evaluated comparatively. Experimental results indicated that the grinding force was influenced significantly by the competing predominance between the grinding parameters and the cross-sectional root workpiece profile. In addition, the root workpiece surface, including the root peak and valley regions, was produced with the large difference in surface quality due to the nonuniform grinding loads along the root workpiece profile in normal section. Detailed results showed that the surface roughness, subsurface plastic deformation and work hardening level of the root valley region were higher by up to25%, 20% and 7% in average than those obtained in the root peak region, respectively, in the current investigation. Finally, the superior parameters were recommended in the creep feed profile grinding of the fir-tree blade root forms. This study is helpful to provide industry guidance to optimize the machining process for the high-valued parts with complicated profiles.展开更多
In this study,the machined surface quality of powder metallurgy nickel-based superalloy FGH96(similar to Rene88DT)and the grinding characteristics of brown alumina(BA)and microcrystalline alumina(MA)abrasive wheels we...In this study,the machined surface quality of powder metallurgy nickel-based superalloy FGH96(similar to Rene88DT)and the grinding characteristics of brown alumina(BA)and microcrystalline alumina(MA)abrasive wheels were comparatively analyzed during creep feed grinding.The infuences of the grinding parameters(abrasive wheel speed,workpiece infeed speed,and depth of cut)on the grinding force,grinding temperature,surface roughness,surface morphology,tool wear,and grinding ratio were analyzed comprehensively.The experimental results showed that there was no significant difference in terms of the machined surface quality and grinding characteristics of FGH96 during grinding with the two types of abrasive wheels.This was mainly because the grinding advantages of the MA wheel were weakened for the difficult-to-cut FGH96 material.Moreover,both the BA and MA abrasive wheeIs exhibited severe tool wear in the form of wheel clogging and workpiece material adhesion.Finally,an analytical model for prediction of the grinding ratio was established by combining the tool wear volume,grinding force,and grinding length.The acceptable errors between the predicted and experimental grinding ratios(ranging from 0.6 to 1.8)were 7.56%and 6.31%for the BA and MA abrasive wheels,respectively.This model can be used to evaluate quantitatively the grinding performance of an alumina abrasive wheel,and is therefore helpful for optimizing the grinding parameters in the creep feed grinding process.展开更多
The unsatisfied surface quality seriously impedes the wide application of incremental sheet forming(ISF)in industrial field.As a novel approach,the interpolator method is a promising strategy to enhance the surface qu...The unsatisfied surface quality seriously impedes the wide application of incremental sheet forming(ISF)in industrial field.As a novel approach,the interpolator method is a promising strategy to enhance the surface quality in ISF.However,the mechanism for the improvement of surface quality and the influence of interpolator properties on surface roughness are not well understood.In this paper,the influences of process variables(i.e.tool diameter,step size and thickness of interpolators)on the forming process(e.g.surface roughness,forming force and geometric error)are investigated through a systematic experimental approach of central composite design(CCD)in two-point incremental sheet forming(TPIF).It is obtained that the increase in thickness of interpolators decreases the surface roughness in direction vertical to the tool path while increases the surface roughness in direction horizontal to the tool path.Nevertheless,the combined influence between thickness of interpolators and process parameters(tool diameter and step size)is limited.Meanwhile,the placement of interpolator has little influence on the effective forming force of blank.In addition,the geometric error enlarges with the increase of step size and thickness of interpolator while decreases firstly and then increase with an increase in tool diameter.Finally,the influencing mechanism of the interpolator method on surface quality can be attributed to the decrease of thecontact pressure due to the increase of contact area with the unchanged contact force.Meanwhile,the interpolator method eliminates the sliding friction on the surface of blank due to the stable relative position between the blank and the interpolator.展开更多
Bearings are one of the most important components in modern industry.Rolling contact fatigue(RCF)initiating from surface and subsurface is the major failure mode.In this paper,a typical high speed thrust angular conta...Bearings are one of the most important components in modern industry.Rolling contact fatigue(RCF)initiating from surface and subsurface is the major failure mode.In this paper,a typical high speed thrust angular contact ball bearing was selected,and the machined surface quality and near-surface microstructure of the race-way and rolling ball were systematically characterized by using of a probe surface profiler,white light interferometer,optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM)combined with focused ion beam(FIB).Two kinds of precursor,probably resulting in pitting or spalling during the following rolling contact,were detected.One is the defects on the surface of either the race-way or the rolling ball,such as heavy machining marks,scratches and slag-hole.The other is nano-crystalline layer due to machining,in the outermost layer around the surface of race-way.The results may well lay foundation for our further research on RCF with the real part of such typical rolling bearings.展开更多
Electrochemical milling is eminently suitable for machining aerospace parts(which usually have complex structures) because of its great flexibility. However,titanium alloys are particularly sensitive to changes in the...Electrochemical milling is eminently suitable for machining aerospace parts(which usually have complex structures) because of its great flexibility. However,titanium alloys are particularly sensitive to changes in the flow field,which often cause severe pitting corrosion of the machined surface. Although electrochemical sinking and milling(ESM) can restrict the flow of electrolyte and reduce pitting corrosion,the quality of the machined surface is not ideal because the latter are susceptible to stray corrosion. To reduce such corrosion and improve the surface quality,the internal flow channel of the tool electrode and the cutting depth were investigated thoroughly. Extensive experiments revealed that stray corrosion could be reduced significantly and surface quality improved by controlling the electrolyte flow direction in the machining area,which was achieved by changing the style of the internal flow channel of the tool electrode. These reductions in corrosion and surface roughness were achieved using a tool electrode with a triangular internal flow channel. In addition,the main components and micro-hardness of the machined surface were close to that of the TB6 titanium alloy substrate,which helped to maintain the inherent high strength of the titanium alloy. The surface of the workpiece changed from being hydrophilic to being hydrophobic,which reduced the flow resistance.展开更多
Burnishing is a profitable process of surface finishing due to its ability to be automated,which makes burnishing method more desirable than other finishing methods.To obtain high surface finish,non-stop operation is ...Burnishing is a profitable process of surface finishing due to its ability to be automated,which makes burnishing method more desirable than other finishing methods.To obtain high surface finish,non-stop operation is required for CNC machine and we can attain that by choosing a suitable trajectory of the finishing tool.In other words,burnishing paths should be multidirectional rather than monotonic,in order to cover uniformly the surface.Indeed,the burnishing force is also a key parameter of the burnishing process because it determines the degree of plastic deformation,and that makes determining the optimum burnishing force an essential step of the burnishing process a success.Therefore,we consider the strategy of ball burnishing path and the burnishing force as variable parameters in this study.In this paper,we propose a new strategy of burnishing tool path with trochoid cycles that achieves a multidirectional burnishing of the surface according to various patterns.Taking into consideration the optimum burnishing force,to improve flat surface finish of AL6061-O samples by reducing the surface roughness parameter(Rz).Experiments carried out on 3-axis milling machine show that the proposed trochoidal path is more effective than the conventional one.展开更多
Fused deposition modeling is one of the most adaptable additive production method as a result of the value-effectiveness and environment-friendly nature.However,FDM technique nevertheless possesses primary problems in...Fused deposition modeling is one of the most adaptable additive production method as a result of the value-effectiveness and environment-friendly nature.However,FDM technique nevertheless possesses primary problems in phrases of negative surface best due to including layer by using layer production method for the prototypes.It is acceptable to explore an efficient method for FDM elements to enhance the bad surface first-rate and dimensions precision.In the present research paper,an effort has been made to decorate the surface better and optimize the vital processing parameter of FDM based benchmark the use of vapor smoothing procedure(VSP).A comparative experimental take a look at has been completed by layout of experiments,Taguchi technique to analyse impact of input layout parameters at the floor finish of benchmark FDM parts.The outcomes of prevailing research display that VSP treatment improves the surface excellent of FDM components to micro stage with negligible dimensional variation.It is observed that improved floor excellent is observed in the 1,2,-Dichloroethane chemical at 90°component construct orientation,0.25 mm layer thickness,10%fill density and 90 sec Exposure times.展开更多
The surface water in the southern of Hanoi capital is researched by identifying δ<sup>2</sup>H and δ<sup>18</sup>O stable isotopes together with EC, DO, BOD<sub>5</sub>, COD, TSS....The surface water in the southern of Hanoi capital is researched by identifying δ<sup>2</sup>H and δ<sup>18</sup>O stable isotopes together with EC, DO, BOD<sub>5</sub>, COD, TSS. Surface water samples for studying include the Red river, Nhue river and Kim Nguu river, Thanh Nhan lake, Yen So lake and Van Quan lake were collected in the dry season (April) and the rainy season (August) in 2015. The stable isotope analysis results showed that the δ<sup>18</sup>O values is a range from -42.53‰ to -64.05‰ and, the δ<sup>2</sup>H values is the range from -5.09‰ to -8.79‰ under global meteoric waterline (in the water vapor region). The δ<sup>2</sup>H results of the rivers and lakes in the dry season are more negative than the rainy season with a small difference. The δ<sup>18</sup>O results of lakes in the dry season are more negative than the rainy season, but the δ<sup>18</sup>O results of river in the dry season are more positive than the rainy season. The results of the EC, BOD, COD, DO, TSS analysis showed that surface water environment has changed clearly in the two seasons and the contamination level in the dry season is usually higher than the rainy season. The lakes and rivers strongly influenced by human activities led to seriously pollution are Van Quan lake and Yen So lake, Nhue river and Kim Nguu river.展开更多
Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing ineffici...Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing inefficiency,serious wear,poor workpiece face quality,etc.Aiming at the above problems,this paper carried out a comparative experimental study on titanium alloy milling based on the CAMCand BEMC.The variation law of cutting force and wear morphology of the two tools were obtained,and the wear mechanism and the effect of wear on machining quality were analyzed.The conclusion is that in contrast with BEMC,under the action of cutting thickness thinning mechanism,the force of CAMC was less,and its fluctuation was more stable.The flank wear was uniform and near the cutting edge,and the wear rate was slower.In the early period,the wear mechanism of CAMC was mainly adhesion.Gradually,oxidative wear also occurred with milling.Furthermore,the surface residual height of CAMC was lower.There is no obvious peak and trough accompanied by fewer surface defects.展开更多
With the increasing use of difficult-to-machine materials in aerospace applications,machining requirements are becoming ever more rigorous.However,traditional single-point diamond turning(SPDT)can cause surface damage...With the increasing use of difficult-to-machine materials in aerospace applications,machining requirements are becoming ever more rigorous.However,traditional single-point diamond turning(SPDT)can cause surface damage and tool wear.Thus,it is difficult for SPDT to meet the processing requirements,and it has significant limitations.Research indicates that supplementing SPDT with unconventional techniques can,importantly,solve problems due to the high cutting forces and poor surface quality for difficult-to-machine materials.This paper first introduces SPDT and reviews research into unconventional techniques for use with SPDT.The machining mechanism is discussed,and the main advantages and disadvantages of various methods are investigated.Second,hybrid SPDT is briefly described,which encompasses ultrasonic-vibration magnetic-field SPDT,ultrasonic-vibration laser SPDT,and ultrasonic-vibration cold-plasma SPDT.Compared with the traditional SPDT method,hybrid SPDT produces a better optical surface quality.The current status of research into unconventional techniques to supplement SPDT is then summarized.Finally,future development trends and the application prospects of unconventional assisted SPDT are discussed.展开更多
基金supported by Science and Technology Major Project of Fujian Province(Grant No.2020HZ03018).
文摘For laser cladding a large temperature gradient easily weakened the surface quality by generating cracks and irregular coating surfaces,which in turn affected the bearing capacity and corrosion resistance of coatings in the rapid heating and cooling process.The response surface methodology(RSM)was used to predict coating cracks by changing the powder ratio,energy density,and preheating temperature,which obtained the relevant mathematical model.After that,the sensitivity of the crack length to process parameters was analyzed based on the sensitivity analysis method.The effect of Ni60/WC composite powder process parameters on the surface quality was revealed in laser cladding.The crack length first decreased and then increased,and the Smooth decreased with the increased powder ratio.The crack length and Smooth increased with the increased energy density.The crack length decreased and Smooth increased with the increased preheating temperature.Sensitivity analysis showed that the crack length and Smooth were the most sensitive to the powder ratio.Therefore,the process parameters were reasonably selected to control the surface quality.The mathematical model and sensitivity analysis method in the work could improve the surface quality,which provided a theoretical basis for the prediction and control of laser cladding cracks.
基金supported by the National Natural Science Foundation of China(Grant Nos.51905226,52075227,and 52105449)the Natural Science Foundation of Jiangsu Province(Grant No.BK20210755)the Postdoctoral Foundation of Jiangsu Province(Grant No.2021K264B).
文摘As a substitute for toxic cadmium coatings in the aerospace industry,zinc-nickel coatings have excellent application prospects,and their properties can be improved by adding molybdenum.In this study,laser-assisted electrodeposition is used to improve the surface quality and properties of Zn–Ni–Mo coatings,with investigation of how laser energy in the range of 0–21.1μJ affects their element content,surface morphology,crystal phase,microhardness,residual internal stress,and corrosion resistance.The laser irradiation accelerates the electrodeposition,refines the grain size,improves the hydrogen adsorption,and reduces the residual tensile stress,and a laser energy of 15.4μJ gives the highest Ni and Mo contents and the lowest Zn content,as well as the optimum surface morphology,microhardness,residual internal stress,and corrosion resistance of the coating.
基金National Key R&D Program of China(Grant No.2019YFE0121300)Yancheng Hali Power Transmission and Intelligent Equipment Industrial Research Institute Project。
文摘Contour bevel gears have the advantages of high coincidence,low noise and large bearing capacity,which are widely used in automobile manufacturing,shipbuilding and construction machinery.However,when the surface quality is poor,the effective contact area between the gear mating surfaces decreases,affecting the stability of the fit and thus the transmission accuracy,so it is of great significance to optimize the surface quality of the contour bevel gear.This paper firstly analyzes the formation process of machined surface roughness of contour bevel gears on the basis of generating machining method,and dry milling experiments of contour bevel gears are conducted to analyze the effects of cutting speed and feed rate on the machined surface roughness and surface topography of the workpiece.Then,the surface defects on the machined surface of the workpiece are studied by SEM,and the causes of the surface defects are analyzed by EDS.After that,XRD is used to compare the microscopic grains of the machined surface and the substrate material for diffraction peak analysis,and the effect of cutting parameters on the microhardness of the workpiece machined surface is investigated by work hardening experiment.The research results are of great significance for improving the machining accuracy of contour bevel gears,reducing friction losses and improving transmission efficiency.
基金financially supported by the National Program on Key Basic Research Project of China(973 Program)under Grant(No.613281)the National Natural Science Foundation of China(No.51505451)+3 种基金the Natural Science Foundation of Beijing(No.3172042)supported by EMUSIC which is part of an EU-China collaborationthe European Union’s Horizon 2020 research and innovation programme under Grant Agreement No.690725MIIT under the programme number MJ-2015-H-G-104
文摘Selective laser melting(SLM) is a powerful additive manufacturing(AM) technology, of which the most prominent advantage is the ability to produce components with a complex geometry. The service performances of the SLM-processed components depend on the microstructure and surface quality. In this work, the microstructures, mechanical properties, and fracture behaviors of SLM-processed Ti-6 Al-4 V alloy under machined and as-built surfaces after annealing treatments and hot isostatic pressing(HIP) were investigated. The microstructures were analyzed by optical microscope(OM), scanning electron microscope(SEM) and transmission electron microscopy(TEM). The mechanical properties were measured by tensile testing at room temperature. The results indicate that the as-deposited microstructures are characterized by columnar grains and fine brittle martensite and the asdeposited properties present high strength, low ductility and obvious anisotropy. After annealing at 800-900°C for 2-4 h and HIP at 920°C/100 MPa for 2 h, the brittle martensite could be transformed into ductile lamellar(α+β) microstructure and the static tensile properties of SLM-processed Ti-6 Al-4 V alloys in the machined condition could be comparable to that of wrought materials. Even after HIP treatment, the as-built surfaces could decrease the ductility and reduction of area of SLM-processed Ti-6 Al-4 V alloys to 9.2% and 20%, respectively. The crack initiation could occur at the columnar grain boundaries or at the as-built surfaces. The lamellar(α+β) microstructures and columnar grains could hinder or distort the crack propagation path during tensile tests.
文摘The ground surface quality of Cr 2O 3 coatings is investigated in this paper. The influence of some typical grinding parameters on ground surface integrity is discussed in detail. It is found that the ground surface roughness increases with the increase of depth-of-cut. The surface finish is improved as the increase of grinding speed, but too high grinding speed may result in serious vibration of the system. The increase of workpiece speed causes deterioration of surface finish and produces big grinding noise. Experiments on plateau treatment after the rough ground surface were also carried out. The surface profile of the ground surface after plateau treatment becomes much smoother than the former rough surface. Some sharp peaks on the ground surface may be effectively removed by the plateau treatment, which produces a reasonable surface profile and can stand much more load. Surface observations and analyses show that plastic deformation and micro-cracks occur on the ground surface. The material removal process is primarily a serious of localized surface fractures accompanied by multi-plastic deformations. Much more plastic deformation and micro-cracks emerge on the ground surface when the depth-of-cut increases. The increase of workpiece speed may produce more surface micro-cracks, but the relative increase of grinding speed is beneficial to ground surface quality.
文摘In conventional grinding theory, the chief removed mode of ceramic coprocessor by diamond tools was brittle removal. In order to perform the plastic removal or ductility processing of engineering ceramics the high degree of accuracy and high rigidity grinner must be using micro grain size diamond grinding wheel to direct the processing of micron below rank depth to prevent form the occurring of the brittle processing zone. This will resulted in the high expense of grinding. The expense of grinding could even reach the 80% of the total manufacture cost of the ceramic part. Ultra-precision grinding for advanced ceramics has been achieved by the unsteady-state grinding technique. In this paper, we mainly deals with observing and analyzing the surface quality of the silicon nitride ground by pink fused alumina wheel in different grinding parameters. To optimize the grinding parameters in the process of the unsteady-state grinding, the experiments of X-ray diffraction, energy spectrum analysis, SEM observation and roughness measurement were performed. The results show that: 1. In the process of unsteady state grinding, high line speed (rotational speed) of the grind wheel can improve the roughness of the silicon nitride apparently. It was also evident that the larger the grain mesh size, the better the surface quality. 2. There exists an optimum combination of grinding conditions such as grinding wheel speed, rotational speed of the workpiece, feed rate between the grinding wheel and the workpiece, grinding times and cutting coolant. The surface quality of the silicon nitride can be up to the standard of mirror finishing. 3. By analyzing the finished surface with X-ray diffraction and energy spectrum, the existence of some new phases including titanium and alumina was proved. 4. By utilizing the unsteady state grinding technique, the surface roughness of Ra ≤ 0.030 μm can be achieved by grinding the silicon nitride with the pink fused alumina wheel in low cost. Based on the unsteady-state grinding technique, this paper put forward a new processing method which by utilizing aluminum oxide grinding wheel to perform burnishing process and impudent the low surface roughness processing of engineering ceramic, the Ra is about 0.01 μm. Furthermore, the working efficiency of this method is high, and the process cost is low, so it is a prospective processing method.
基金This research was supported by the Applied Technology Research and Development Project in Heilongjiang Province of China(GA19A402)Fundamental Research Funds for the Central Universities(2572018CG06).
文摘As a natural and environmentally friendly renewable material,Northeast China ash wood(NCAW)(Fraxinus mandshurica Rupr.)was cut by water-jet assisted CO_(2) laser(WACL),the surface quality was evaluated by surface roughness of cut section.The surface roughness was measured by three-dimensional(3D)profilometry.Furthermore,the micromorphology of machined surface was observed by scanning electronic microscopy(SEM).Carbon content changes of machined surface were measured by energy dispersive spectrometer(EDS).A relationship between surface roughness and cutting parameters was established using response surface methodology(RSM).It is concluded that the cutting speed,laser power and water pressure played an important role in surface roughness of cut section.The surface roughness increased as an increase in laser power.It decreased caused by increasing of cutting speed and water pressure.Measurements revealed that the surface quality of NCAW part was improved using the optimized combination of cutting parameters.The established quadratic mathematical model of a good prediction is helpful for matching suitable cutting parameters to obtain expected surface quality.
基金Sponsored by the High-End CNC Machine Tools and Basic Manufacturing Equipment Technology Major Project(Grant No.2011ZX04001-011)partly supported by Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT1229)
文摘Three different punches are designed for the hydropiercing experiments and finite element simulations are conducted by finite element program ABAQUS-3D to investigate the influence of punch shape on the fracture surface quality of hydropiercing holes. The results show the fracture burrs are not obvious punched by all the three punches. The collapse punched by the round punch is a little larger than the others. The fracture surface quality punched by the round punch is good with larger smooth zone and the interface between smooth zone and tear zone is even with large gradient. The size of the smooth zone is larger and the interface between smooth zone and tear zone is uneven with large gradient punched by the flat punch. The size of the smooth zone is smaller and the size of the tear zone increases from the first fractured to the last fractured punched by the inclined punch.
文摘This article is try to explain or analyze the key technologies of controlling the surface quality of low carbon steel as cast strip through investigation of interface heat transfer between solidified shell and liquid steel.The one of the key technologies of controlling surface quality of low carbon steel as cast strip is through the casting roll surface texture in order to achieve the homogeneous solidification on the casting roll.Another is through forming a thin film on the casting roll surface in order to achieve a balance between rapid solidification and homogeneous solidification.This film formed between the twin roll and the molten steel can be controlled by adjusting the chemical composition and inclusion in liquid steel through controlling the amount of all[O]and free[O].
基金sponsored by the National Science and Tech-nology Major Project(Grant No.2017-VII-0004-0097)National Natural Science Foundation of China for Creative Research Groups(Grant No.51921003)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX21_0191).
文摘Electrochemical machining(ECM)has emerged as an important option for manufacturing the blisk.The inter-electrode gap(IEG)distribution is an essential parameter for the blisk precise shap-ing process in ECM,as it affects the process stability,profile accuracy and surface quality.Larger IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of blisk.To achieve micro-IEG(<50 lm)blisk finishing machining,this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse duration.The modelling and simulation of the blisk micro-IEG machining have been carried out.Exploratory experiments of variable-parameters blisk ECM were car-ried out.The results illustrated that the IEG width reduced with the progress of variable parameter pro-cess.The IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 lm and 21 lm,respectively.The profile deviation for the blade’s concave surface and convex surface are 49 lm and 35 lm,while the surface roughness reaches R_(a)=0.149 lm and R_(a)=0.196 lm,respectively.The profile accuracy of the blisk leading/trailing edges was limited to within 91 lm.Com-pared with the currently-established process,the profile accuracy of the blade’s concave and convex profiles was improved by 50.5%and 53.3%,respectively.The surface quality was improved by 53.2%and 50.9%,respectively.Additionally,the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective dissolution.Some electrolytic products were dispersed on the machined surface,and their components were mainly composed of the carbide and oxide products of Ti and Nb elements.The results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM,which can be used in engineering practice.
基金financial support for this work by the National Natural Science Foundation of China (No. 51775275)the Funding of Jiangsu Innovation Program for Graduate Education of China (KYCX170245)+2 种基金the Funding for Outstanding Doctoral Dissertation in NUAA of China (BCXJ17-04)the Fundamental Research Funds for the Central University of China (No. NP2018110)the National Science and Technology Major Project and the Six Talents Summit Project in Jiangsu Province of China (No.JXQC-002)。
文摘Creep feed profile grinding of the fir-tree blade root forms of single crystal nickel-based superalloy was conducted using microcrystalline alumina abrasive wheels in the present study. The grinding force and the surface quality in terms of surface topography, subsurface microstructure,microhardness and residual stress obtained under different grinding conditions were evaluated comparatively. Experimental results indicated that the grinding force was influenced significantly by the competing predominance between the grinding parameters and the cross-sectional root workpiece profile. In addition, the root workpiece surface, including the root peak and valley regions, was produced with the large difference in surface quality due to the nonuniform grinding loads along the root workpiece profile in normal section. Detailed results showed that the surface roughness, subsurface plastic deformation and work hardening level of the root valley region were higher by up to25%, 20% and 7% in average than those obtained in the root peak region, respectively, in the current investigation. Finally, the superior parameters were recommended in the creep feed profile grinding of the fir-tree blade root forms. This study is helpful to provide industry guidance to optimize the machining process for the high-valued parts with complicated profiles.
基金supported by the National Natural Science Foundation of China(Grant Nos.51775275 and 51921003)National Major Science and Technology Project(Grant No.2017-Ⅶ-0002-0095)+2 种基金Funding for Outstanding Doctoral Dissertation in NUAA(Grant No.BCXJ19-06)the Six Talents Summit Project in Jiangsu Province(Grant No.JXQC-002)Fundamental Research Funds for the Central Universities(Grant No.NP2018110).
文摘In this study,the machined surface quality of powder metallurgy nickel-based superalloy FGH96(similar to Rene88DT)and the grinding characteristics of brown alumina(BA)and microcrystalline alumina(MA)abrasive wheels were comparatively analyzed during creep feed grinding.The infuences of the grinding parameters(abrasive wheel speed,workpiece infeed speed,and depth of cut)on the grinding force,grinding temperature,surface roughness,surface morphology,tool wear,and grinding ratio were analyzed comprehensively.The experimental results showed that there was no significant difference in terms of the machined surface quality and grinding characteristics of FGH96 during grinding with the two types of abrasive wheels.This was mainly because the grinding advantages of the MA wheel were weakened for the difficult-to-cut FGH96 material.Moreover,both the BA and MA abrasive wheeIs exhibited severe tool wear in the form of wheel clogging and workpiece material adhesion.Finally,an analytical model for prediction of the grinding ratio was established by combining the tool wear volume,grinding force,and grinding length.The acceptable errors between the predicted and experimental grinding ratios(ranging from 0.6 to 1.8)were 7.56%and 6.31%for the BA and MA abrasive wheels,respectively.This model can be used to evaluate quantitatively the grinding performance of an alumina abrasive wheel,and is therefore helpful for optimizing the grinding parameters in the creep feed grinding process.
基金support from the National Natural Science Foundation of China(51575028)National Natural Science Foundation of China(51605258)the Fundamental Research Funds for the Central Universities of China(YWF-18-BJ-J-75)。
文摘The unsatisfied surface quality seriously impedes the wide application of incremental sheet forming(ISF)in industrial field.As a novel approach,the interpolator method is a promising strategy to enhance the surface quality in ISF.However,the mechanism for the improvement of surface quality and the influence of interpolator properties on surface roughness are not well understood.In this paper,the influences of process variables(i.e.tool diameter,step size and thickness of interpolators)on the forming process(e.g.surface roughness,forming force and geometric error)are investigated through a systematic experimental approach of central composite design(CCD)in two-point incremental sheet forming(TPIF).It is obtained that the increase in thickness of interpolators decreases the surface roughness in direction vertical to the tool path while increases the surface roughness in direction horizontal to the tool path.Nevertheless,the combined influence between thickness of interpolators and process parameters(tool diameter and step size)is limited.Meanwhile,the placement of interpolator has little influence on the effective forming force of blank.In addition,the geometric error enlarges with the increase of step size and thickness of interpolator while decreases firstly and then increase with an increase in tool diameter.Finally,the influencing mechanism of the interpolator method on surface quality can be attributed to the decrease of thecontact pressure due to the increase of contact area with the unchanged contact force.Meanwhile,the interpolator method eliminates the sliding friction on the surface of blank due to the stable relative position between the blank and the interpolator.
基金funded by the Strategic Priority Research Program of the Chinese Academy of Sciences,China through Projects No.XDC04030400。
文摘Bearings are one of the most important components in modern industry.Rolling contact fatigue(RCF)initiating from surface and subsurface is the major failure mode.In this paper,a typical high speed thrust angular contact ball bearing was selected,and the machined surface quality and near-surface microstructure of the race-way and rolling ball were systematically characterized by using of a probe surface profiler,white light interferometer,optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM)combined with focused ion beam(FIB).Two kinds of precursor,probably resulting in pitting or spalling during the following rolling contact,were detected.One is the defects on the surface of either the race-way or the rolling ball,such as heavy machining marks,scratches and slag-hole.The other is nano-crystalline layer due to machining,in the outermost layer around the surface of race-way.The results may well lay foundation for our further research on RCF with the real part of such typical rolling bearings.
基金This work was supported by the National Natural Science Foundation of China(Grant No.91860208)the National Natural Science Foundation of China for Creative Research Groups(Grant No.51921003)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX19_0160)。
文摘Electrochemical milling is eminently suitable for machining aerospace parts(which usually have complex structures) because of its great flexibility. However,titanium alloys are particularly sensitive to changes in the flow field,which often cause severe pitting corrosion of the machined surface. Although electrochemical sinking and milling(ESM) can restrict the flow of electrolyte and reduce pitting corrosion,the quality of the machined surface is not ideal because the latter are susceptible to stray corrosion. To reduce such corrosion and improve the surface quality,the internal flow channel of the tool electrode and the cutting depth were investigated thoroughly. Extensive experiments revealed that stray corrosion could be reduced significantly and surface quality improved by controlling the electrolyte flow direction in the machining area,which was achieved by changing the style of the internal flow channel of the tool electrode. These reductions in corrosion and surface roughness were achieved using a tool electrode with a triangular internal flow channel. In addition,the main components and micro-hardness of the machined surface were close to that of the TB6 titanium alloy substrate,which helped to maintain the inherent high strength of the titanium alloy. The surface of the workpiece changed from being hydrophilic to being hydrophobic,which reduced the flow resistance.
文摘Burnishing is a profitable process of surface finishing due to its ability to be automated,which makes burnishing method more desirable than other finishing methods.To obtain high surface finish,non-stop operation is required for CNC machine and we can attain that by choosing a suitable trajectory of the finishing tool.In other words,burnishing paths should be multidirectional rather than monotonic,in order to cover uniformly the surface.Indeed,the burnishing force is also a key parameter of the burnishing process because it determines the degree of plastic deformation,and that makes determining the optimum burnishing force an essential step of the burnishing process a success.Therefore,we consider the strategy of ball burnishing path and the burnishing force as variable parameters in this study.In this paper,we propose a new strategy of burnishing tool path with trochoid cycles that achieves a multidirectional burnishing of the surface according to various patterns.Taking into consideration the optimum burnishing force,to improve flat surface finish of AL6061-O samples by reducing the surface roughness parameter(Rz).Experiments carried out on 3-axis milling machine show that the proposed trochoidal path is more effective than the conventional one.
基金The authors would like to thank the CIPET:IPT Ahmedabad for the grant to provide a facility in which to carry out this study.
文摘Fused deposition modeling is one of the most adaptable additive production method as a result of the value-effectiveness and environment-friendly nature.However,FDM technique nevertheless possesses primary problems in phrases of negative surface best due to including layer by using layer production method for the prototypes.It is acceptable to explore an efficient method for FDM elements to enhance the bad surface first-rate and dimensions precision.In the present research paper,an effort has been made to decorate the surface better and optimize the vital processing parameter of FDM based benchmark the use of vapor smoothing procedure(VSP).A comparative experimental take a look at has been completed by layout of experiments,Taguchi technique to analyse impact of input layout parameters at the floor finish of benchmark FDM parts.The outcomes of prevailing research display that VSP treatment improves the surface excellent of FDM components to micro stage with negligible dimensional variation.It is observed that improved floor excellent is observed in the 1,2,-Dichloroethane chemical at 90°component construct orientation,0.25 mm layer thickness,10%fill density and 90 sec Exposure times.
文摘The surface water in the southern of Hanoi capital is researched by identifying δ<sup>2</sup>H and δ<sup>18</sup>O stable isotopes together with EC, DO, BOD<sub>5</sub>, COD, TSS. Surface water samples for studying include the Red river, Nhue river and Kim Nguu river, Thanh Nhan lake, Yen So lake and Van Quan lake were collected in the dry season (April) and the rainy season (August) in 2015. The stable isotope analysis results showed that the δ<sup>18</sup>O values is a range from -42.53‰ to -64.05‰ and, the δ<sup>2</sup>H values is the range from -5.09‰ to -8.79‰ under global meteoric waterline (in the water vapor region). The δ<sup>2</sup>H results of the rivers and lakes in the dry season are more negative than the rainy season with a small difference. The δ<sup>18</sup>O results of lakes in the dry season are more negative than the rainy season, but the δ<sup>18</sup>O results of river in the dry season are more positive than the rainy season. The results of the EC, BOD, COD, DO, TSS analysis showed that surface water environment has changed clearly in the two seasons and the contamination level in the dry season is usually higher than the rainy season. The lakes and rivers strongly influenced by human activities led to seriously pollution are Van Quan lake and Yen So lake, Nhue river and Kim Nguu river.
基金Supported by National Natural Science Foundation of China(Grant No.51975168).
文摘Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing inefficiency,serious wear,poor workpiece face quality,etc.Aiming at the above problems,this paper carried out a comparative experimental study on titanium alloy milling based on the CAMCand BEMC.The variation law of cutting force and wear morphology of the two tools were obtained,and the wear mechanism and the effect of wear on machining quality were analyzed.The conclusion is that in contrast with BEMC,under the action of cutting thickness thinning mechanism,the force of CAMC was less,and its fluctuation was more stable.The flank wear was uniform and near the cutting edge,and the wear rate was slower.In the early period,the wear mechanism of CAMC was mainly adhesion.Gradually,oxidative wear also occurred with milling.Furthermore,the surface residual height of CAMC was lower.There is no obvious peak and trough accompanied by fewer surface defects.
基金supported by the National Natural Science Foundation of China(Grant No.52175431)the Natural Science Foundation of Tianjin of China(Grant No.22JCZDJC00730)the Scientific Research Project of Tianjin Municipal Education Commission(Grant No.2022ZD021).
文摘With the increasing use of difficult-to-machine materials in aerospace applications,machining requirements are becoming ever more rigorous.However,traditional single-point diamond turning(SPDT)can cause surface damage and tool wear.Thus,it is difficult for SPDT to meet the processing requirements,and it has significant limitations.Research indicates that supplementing SPDT with unconventional techniques can,importantly,solve problems due to the high cutting forces and poor surface quality for difficult-to-machine materials.This paper first introduces SPDT and reviews research into unconventional techniques for use with SPDT.The machining mechanism is discussed,and the main advantages and disadvantages of various methods are investigated.Second,hybrid SPDT is briefly described,which encompasses ultrasonic-vibration magnetic-field SPDT,ultrasonic-vibration laser SPDT,and ultrasonic-vibration cold-plasma SPDT.Compared with the traditional SPDT method,hybrid SPDT produces a better optical surface quality.The current status of research into unconventional techniques to supplement SPDT is then summarized.Finally,future development trends and the application prospects of unconventional assisted SPDT are discussed.
