Morphology and integrity of surfaces finished by centrifugal force assisted abrasive flow machining

Centrifugal force assisted abrasive flow machining (CFAAFM) process has recently been tried as a hybrid machining process with the aim towards performance improvement of assisted abrasive flow machining (AFM) process by applying centrifugal force on the abrasive-laden media with a rotating centrifugal force generating (CFG) rod introduced in the workpiece passage. In the CFAAFM process, the surfaces are generated by erosion from random attack of abrasive grains. CFAAFMed surfaces are unidirectional but random in nature due to transient media flow conditions. In the present paper, surface morphology, surface micro-hardness, X-ray analysis, and surface compressive residual stress produced in the finished surface layer by CFAAFM process is described. The CFAAFM process was performed under different rotational speeds of CFG rod while keeping other input parameters constant during the experiments. The increase in surface microhardness and compressive residual stress of the workpiece with an increase in the rotational speed of CFG rod is attributed to the work-hardening surface that possibly occurs due to ‘throw’ of abrasive particles upon specimen surface.     

ABRASIVE FLOW MACHINING WITH ADDITIONAL CENTRIFUGAL FORCE APPLIED TO THE MEDIA

Abrasive flow machining (AFM) is one of the important non-traditional metal finishing technologies which was introduced during the late 1960s. The process has found applications in a wide range of fields such as aerospace, defence, surgical and tool manufacturing industries. Recently, an effort has been made towards the performance improvement of this process by applying centrifugal force on the abrasive media with the use of a rotating centrifugal force generating (CFG) rod introduced in the workpiece passage. The results have been encouraging. The present paper discusses the results of changing the parameters like shape and rotational speed of CFG rod, extrusion pressure, number of process cycles and abrasive grit size. The results indicate that all the input variables have significant effect on the response parameters, which for the present study were taken as material removal and surface roughness. An analytical model is proposed for the velocity and the angle at which abrasive particles attack the workpiece surface in the process.     

ABRASIVE FLOW MACHINING WITH ADDITIONAL CENTRIFUGAL FORCE APPLIED TO THE MEDIA

Abrasive flow machining (AFM) is one of the important non-traditional metal finishing technologies which was introduced during the late 1960s. The process has found applications in a wide range of fields such as aerospace, defence, surgical and tool manufacturing industries. Recently, an effort has been made towards the performance improvement of this process by applying centrifugal force on the abrasive media with the use of a rotating centrifugal force generating (CFG) rod introduced in the workpiece passage. The results have been encouraging. The present paper discusses the results of changing the parameters like shape and rotational speed of CFG rod, extrusion pressure, number of process cycles and abrasive grit size. The results indicate that all the input variables have significant effect on the response parameters, which for the present study were taken as material removal and surface roughness. An analytical model is proposed for the velocity and the angle at which abrasive particles attack the workpiece surface in the process.     

Temperature as sensitive monitor for efficiency of work in abrasive flow machining

Work efficiency is considered as most concerned target in abrasive flow machining (AFM). It has many influence factors, such as, temperature, media viscosity, abrasive hardness, particles sharpness and density, workpiece hardness, pressure, piston moving speed, etc. The influence of temperature on work efficiency is most critical. In this investigation, both commercial AFM equipment and test rig are used to carry out AFM experiments. AISI1080, 1045 and A36 steels are used as specimens in the tests. It has been shown from AFM tests that media viscosity decreases continuously with increasing temperature. Media temperature increases with increasing cycles, which means media viscosity decreases with cycles increasing. AFM tests shows that increasing cycles extensively decrease materials removal and surface roughness decreasing efficiency. When media with different viscosity is used media with high viscosity has more effective material removal efficiency. The high viscosity media to surface roughness improvement is also better than the low viscosity media at the initial several cycle numbers. With further increasing cycles the roughness improvement difference among different media with different viscosity is reduced. It is found from Mooney viscosity–temperature relation of media that temperature rising directly results in the decrease of media viscosity. When work cycles are increased the media temperature is quickly increased. The media viscosity is also decreased dramatically. In order to understand the mechanism of decrease of material removal efficiency with temperature, computational fluid dynamics (CFD) approach is applied to predict the abrasive particles movement tendency. A two-dimensional model is constructed for AFM process. The simulation results show that the temperature rising of media results in increasing the rolling tendency of abrasive particles which causes work efficiency deteriorated.     

Forces prediction during material deformation in abrasive flow machining

To study the finishing mechanism of abrasive flow machining (AFM), theoretical model of forces acting on a single grain has been developed. An experimental research has been carried out by measuring the axial force, radial force and active grain density during the AFM process. Results obtained from theoretical model for grain–workpiece interaction during material deformation have been compared with the experimental data of force and active grains obtained during AFM. Scratching experiments have also been carried out to study the mechanism of material removal during the AFM process. The conclusions arrived by the analysis about the presence of rubbing and ploughing is in agreement with the experimental AFM and scratching results.     

Analysis of magnetorheological abrasive flow finishing (MRAFF) process

A new precision finishing process called magnetorheological abrasive flow finishing (MRAFF), which is basically a combination of abrasive flow machining (AFM) and magnetorheological finishing (MRF), has been developed for nano-finishing of parts even with complicated geometry for a wide range of industrial applications. In this paper microstructure of the mixture of magnetic and abrasive particles in magnetorheological polishing fluid (MRPF) has been proposed, and normal force on the abrasive particles is calculated from the applied magnetic field. A model for the prediction of material removal and surface roughness achieved has also been presented. And, finally theoretical results are compared with the experimental data available in the literature, and they are found to agree well.     

Simulation of abrasive flow machining process for 2D and 3D mixture models

Improvement of surface finish and material removal has been quite a challenge in a finishing operation such as abrasive flow machining (AFM). Factors that affect the surface finish and material removal are media viscosity, extrusion pressure, piston velocity, and particle size in abrasive flow machining process. Performing experiments for all the parameters and accurately obtaining an optimized parameter in a short time are difficult to accomplish because the operation requires a precise finish. Computational fluid dynamics (CFD) simulation was employed to accurately determine optimum parameters. In the current work, a 2D model was designed, and the flow analysis, force calculation, and material removal prediction were performed and compared with the available experimental data. Another 3D model for a swaging die finishing using AFM was simulated at different viscosities of the media to study the effects on the controlling parameters. A CFD simulation was performed by using commercially available ANSYS FLUENT. Two phases were considered for the flow analysis, and multiphase mixture model was taken into account. The fluid was considered to be a Newtonian fluid and the flow laminar with no wall slip.     

Study of the rheological properties and the finishing behavior of abrasive gels in abrasive flow machining

Abrasive flow machining (AFM) is an effective method to finish the smooth surface in the complex holes. Abrasive media are key elements which dominate the polished results in AFM. But it is hard to develop the machining model of these abrasive gels because of its complicated mechanism. In this research, a non-Newtonian flow is used to set up the abrasive mechanism of the abrasive media in AFM. Power law is a main equation of the non-Newtonian flow to describe the motion of the abrasive media. Viscosities vs. shear rates of different abrasive gels are used to establish the power law in CFD-ACE⁺ software first. And the working parameters of AFM were applied as input to study the properties of the abrasive gels in AFM. Finally, the relationships between the simulations and the experiments were found. And the abrasive mechanism of the abrasive gels was set up in AFM. The simulated results show that the abrasive gel with high viscosity can entirely deform in the complex hole than the abrasive gel with low viscosity. And the abrasive gel with high viscosity generates a larger shear force than the abrasive gel with low viscosity in the same area. Moreover, the strain rate is seriously changed when the abrasive gel cross over the narrow cross-section of the complex hole. It also means that abrasive gel will produce large finish force in that area. And these results indeed consist with the experiments in AFM.     

Modeling of abrasive flow rotary machining process by artificial neural network

Abrasive flow machining (AFM) is one of the non-traditional machining processes applicable to finishing, deburring, rounding of edges, and removing defective layers from workpiece surface. Abrasive material, used as a mixture of a polymer with abrasive material powder, has reciprocal motion on workpiece surface under pressure during the process. In the following study, a new method of AFM process called henceforth abrasive flow rotary machining (AFRM) will be proposed, in which by elimination of reciprocal motion of abrasive material and the mere use of its stirring and rotation of workpiece, the amount of used material would be optimized. Furthermore, AFRM is executable by simpler tools and machines. In order to investigate performance of the method, experimental tests were designed by the Taguchi method. Then, the tests were carried out and the influence of candidate effective parameters was determined and modeled by artificial neural network (ANN) method. To evaluate the ANN results, they were compared with reported results of AFM. An agreement between our ANN results on predictions of AFRM material removal value and surface roughness was observed with AFM data. The results showed through AFRM, in addition to saving of abrasive material, surface finish is achievable same as AFM’s.     

Enhancing AFM process productivity through improved fixturing

Abrasive flow machining (AFM) is a non-conventional finishing process that deburrs and polishes by forcing an abrasive laden media across the workpiece surface. The process embraces a wide range of applications from critical aerospace and medical components to high-production volumes of parts. One serious limitation of this process is its low productivity in terms of rate of improvement in surface roughness. Limited efforts have hitherto been directed towards enhancing the productivity of this process with regard to better quality of workpiece surface. This paper discusses improved fixturing as a technique for productivity enhancement in terms of surface roughness (R _a). A rotating centrifugal-force-generating (CFG) rod is used inside the cylindrical workpiece which provides the centrifugal force to the abrasive particles normal to the axis of workpiece. The effect of the key parameters on the performance of process has been studied. The results shows that for a given improvement in R _a value, the processing time can be reduced by as much as 70–80%. It is seen that the significant process parameters are revolutions per minute of CFG rod, extrusion pressure and abrasive mesh size.     

Effects of finishing in abrasive fluid machining on microholes fabricated by EDM

This research investigated the effects of the fine-finishing process on microholes in abrasive fluid machining (AFM). Microholes on stainless steel (SUS 304) and titanium alloy (Ti-6Al-4V) plates were fabricated using a deep drilling machine of electrical discharge machining (EDM) prior to AFM. In the experiment, the Taguchi method was adopted to explore the effects of the machining parameters associated with AFM on the experimentally observed values, such as the material removal rate (MRR) and differences between the dimensions of the entrance and the exit of the microhole. Furthermore, the improvement in the shape precision of the microhole fabricated by EDM and subsequently fine-finished by AFM was also elucidated by using a scanning electron microscope (SEM). The significant machining parameters and the optimal combination levels of the machining parameters were identified by analysis of variance (ANOVA) and the S/N (signal-to-noise) ratio response graph obtained from the analysis of the experimental data.     

ON THE PERFORMANCE ANALYSIS OF FLEXIBLE MAGNETIC ABRASIVE BRUSH

ABSTRACT

Magnetic abrasive finishing (MAF) of alloy steel workpiece with unbounded magnetic abrasive particles (UMAPs) indicates that the surface finish in the range of nanometer can be achieved. Important controllable four process parameters have been identified which are as current to the electromagnet, machining gap, abrasive size (mesh number), and number of cycles. Experiments have been planned using design of experiments technique. Based upon the results of response surface methodology and analysis of variance (ANOVA), it is concluded that magnetic flux density that depends on current to the electromagnet and machining gap, is most influencing parameter followed by grain size and number of cycles. The surface roughness profile generated during the MAF process has been discussed. To understand the cutting mechanism of magnetic abrasive finishing process, scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the machined surfaces have been carried out. The correlation between surface finish and material removal has also been established.     

Modelling the erosion rate in micro abrasive air jet machining of glasses

Micro abrasive jet machining (MAJM) is an economical and efficient technology for micro-machining of brittle material like glasses. The erosion of brittle materials by solid micro-particles is a complex process in which material is removed from the target surface by brittle fractures. The rate of material removal is one of the most important quantities for a machining process. Predictive mathematical models for the erosion rates in micro-hole drilling and micro-channel cutting on glasses with an abrasive air jet are developed. A dimensional analysis technique is used to formulate the models as functions of the particle impact parameters, target material properties and the major process parameters that are known to affect the erosion process of brittle materials. The predictive capability of the models is assessed and verified by an experimental investigation covering a range of the common process parameters such as air pressure, abrasive mass flow rate, stand-off distance and machining time (for hole machining) or traverse speed (for channel machining). It shows that model predictions are in good agreement with the experimental results.     

EVALUATION OF RHEOLOGICAL PROPERTIES OF MEDIUM FOR AFM PROCESS

Abrasive Flow Machining (AFM) is a new non-traditional machining process used to deburr, radius, polish, and remove recast layer of components used in a wide range of applications. Material removal in AFM takes place by flowing medium (i.e. carrier/or putty mixed with abrasive particles), across the surface to be machined. The medium is the key element in the process because of its ability to precisely abrade the selected areas along its flow path. From the literature review, it is found that there is a need to study how to evaluate rheological properties of the medium in general, and viscosity in particular. Viscosity of the medium has significant effects on the AFM process performance.

In the present work, effects of concentration and mesh size of abrasive particles, and temperature of medium on the medium viscosity have been studied. To determine the viscosity of the abrasive medium, a viscometer has been designed and fabricated based on the principle of capillary viscometry. Experiments have been conducted at different abrasive concentrations and mesh sizes, and medium temperatures. It is observed from the experiments that the viscosity of the medium increases with the abrasive concentration and decreases with the abrasive mesh size and medium temperature. Theoretical values obtained from mathematical model, and experimental results are compared. The results of viscosity are correlated with the process performance parameters, i.e. material removal and surface roughness. It is observed that there is an increase in material removal and decrease in surface roughness value as viscosity of the medium increases.     

ON THE PERFORMANCE ANALYSIS OF FLEXIBLE MAGNETIC ABRASIVE BRUSH

Magnetic abrasive finishing (MAF) of alloy steel workpiece with unbounded magnetic abrasive particles (UMAPs) indicates that the surface finish in the range of nanometer can be achieved. Important controllable four process parameters have been identified which are as current to the electromagnet, machining gap, abrasive size (mesh number), and number of cycles. Experiments have been planned using design of experiments technique. Based upon the results of response surface methodology and analysis of variance (ANOVA), it is concluded that magnetic flux density that depends on current to the electromagnet and machining gap, is most influencing parameter followed by grain size and number of cycles. The surface roughness profile generated during the MAF process has been discussed. To understand the cutting mechanism of magnetic abrasive finishing process, scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the machined surfaces have been carried out. The correlation between surface finish and material removal has also been established.     

EVALUATION OF RHEOLOGICAL PROPERTIES OF MEDIUM FOR AFM PROCESS

Abrasive Flow Machining (AFM) is a new non-traditional machining process used to deburr, radius, polish, and remove recast layer of components used in a wide range of applications. Material removal in AFM takes place by flowing medium (i.e. carrier/or putty mixed with abrasive particles), across the surface to be machined. The medium is the key element in the process because of its ability to precisely abrade the selected areas along its flow path. From the literature review, it is found that there is a need to study how to evaluate rheological properties of the medium in general, and viscosity in particular. Viscosity of the medium has significant effects on the AFM process performance.

In the present work, effects of concentration and mesh size of abrasive particles, and temperature of medium on the medium viscosity have been studied. To determine the viscosity of the abrasive medium, a viscometer has been designed and fabricated based on the principle of capillary viscometry. Experiments have been conducted at different abrasive concentrations and mesh sizes, and medium temperatures. It is observed from the experiments that the viscosity of the medium increases with the abrasive concentration and decreases with the abrasive mesh size and medium temperature. Theoretical values obtained from mathematical model, and experimental results are compared. The results of viscosity are correlated with the process performance parameters, i.e. material removal and surface roughness. It is observed that there is an increase in material removal and decrease in surface roughness value as viscosity of the medium increases.     

On the modelling of abrasive waterjet cutting

Abrasive waterjet cutting operates by the impingement of a high-velocity abrasive-laden waterjet against the workpiece. The jet is formed by mixing abrasive particles with high-velocity water in mixing tubes and is forced through a tiny sapphire orifice. The accelerated jet exiting the nozzle travels at more than twice the speed of sound and cuts as it passes through the workpiece.This cutting process is being developed as a net-shape and near-net-shape machining process for cutting many metals and hard-to-machine materials. The narrow kerf produced by the stream results in neither delimitation nor stresses along the cutting path. This new technology offers significant advantages over traditional processes for its ability to cut through most sections of dense or hard materials without the need for secondary machining, to produce contours, and to be integrated into computer-controlled systems.The abrasive waterjet cutting process involves a large number of process and material parameters which are related to the waterjet, the abrasive particles, and workpiece material. Those parameters are expected to effect the material removal rates and the depth of cut. The purpose of the present work is to propose a model which is capable of predicting the maximum depth of cut for different types of materials using different process parameters. A comparison of the results of the proposed model and the models reported in the literature is introduced along with a discussion of the limitations of those models.On leave from: Mechanical Engineering Department, Suez Canal University, Egypt.On leave from: Industrial Production Engineering Department, Mansoura University, Egypt.On leave from: Mechanical Power Engineering Department, Alexandria University, Egypt.     

Prediction of surface roughness during abrasive flow machining

An analytical model is proposed to simulate and predict the surface roughness for different machining conditions in abrasive flow machining (AFM). The kinematic analysis is used to model the interaction between grain and workpiece. Fundamental AFM parameters, such as the grain size, grain concentration, active grain density, grain spacing, forces on the grain, initial topography, and initial surface finish (R _a value) of the workpiece are used to describe the grain-workpiece interaction. The AFM process is studied under a systematic variation of grain size, grain concentration and extrusion pressure with initial surface finish of the workpiece. Simulation results show that the proposed model gives results that are consistent with experimental results.     

利用摩擦学系统理论对磨粒流加工过程的分析

简介当前磨粒流加工技术的现状,得到了磨粒流和工件表面的摩擦以及导致的材料去除是该加工过程的核心问题.利用摩擦学系统理论,构建了针对磨粒流-工件表面的摩擦学系统框架,得到了系统的主要结构元素、元素的特性和相互之间的关系.归纳了磨粒流加工过程中材料去除的摩擦学机理,并讨论摩擦学机理与该摩擦学系统的关系,对从摩擦学角度认识磨...