Radial-mode abrasive waterjet turning of short carbon–fiber-reinforced plastics

An experimental study is carried out for single-pass radial-mode abrasive waterjet (AWJ) turning of a short carbon–fiber-reinforced polyetheretherketone (PEEK) specimen to understand the machining process and the effects of major process variables (feed speed, water pressure, abrasive mass flow rate, nozzle tilt angle, and rotational surface speed) on the major machining performance measures, that is, the depth of cut, material removal rate (MRR) and surface roughness. It is found that high water pressure, normal nozzle impact angle and high rotational speed with suitably selected feed speed and abrasive flow rate may be selected to achieve a high MRR without significantly compromising the surface roughness. Mathematical models for the three cutting performance measures are then developed for use in process control.     

磨料水射流对金属材料去除力和去除模型的研究

磨料水射流抛光技术作为一种新型技术,广泛应用于表面抛光加工作业中,利用含有细小磨料粒子的抛光液在高压作用下,与工件表面发生冲击、冲蚀而去除材料,以达到抛光目的。采用单颗粒磨料粒子使材料产生塑性变形模型来研究磨料水射流对金属材料的去除力,通过对纯水射流冲击材料的作用力和射流中磨料射流对材料的作用力以及接触应力的理论推导,得出磨料射流中轴线上磨料颗粒去除金属材料最大打击力和最大剪应力以及最大拉应力;通过建立伯努利方程,得到射流压力与金属材料的剪切力和拉应力的直接关系,为工程上磨料水射流抛光喷嘴设计和泵压选择提供了理论参考依据。     

An investigation of the hole machining processes on woven carbon-fiber reinforced polymers (CFRPs) using abrasive waterjets

An investigation of the hole cutting and drilling processes on woven carbon-fiber reinforced polymer sheets using abrasive waterjet (AWJ) is presented. The drilling process uses a stationary AWJ to impinge a target material to make a hole, while the cutting process requires an AWJ to penetrate the workpiece before moving in a circular path to cut a hole. It is found that the holes machined by both the processes exhibit similar geometrical features, where the diameter at the top is greater than at the bottom. It is further found that the holes from the drilling process have a better roundness than those from cutting process primarily due to the jet instability during cutting movement. Plausible trends of the hole characteristics (e.g., diameter and wall inclination) and defects (e.g., delamination) with respect to the process parameters are discussed. It is shown that water pressure is the major parameter affecting hole defects. The hole drilling process yields more severe defects than the cutting process because of the initial impact of the jet. Predictive models for machined hole diameter in both processes are developed. The model predictions are in good agreement with the experimental data under the corresponding conditions.     

Monitoring of abrasive water jet (AWJ) cutting using sound detection

Our main objective in the present work is to develop a methodology and create a system for the abrasive water jet (AWJ) machining process control. In the case of AWJ cutting, besides the cutting head traverse rate, the distance between the mixing tube and the workpiece, designated as the stand-off distance, has a predominant influence on the workpiece quality. The control of the traverse rate is performed by the machine controller. The stand off-distance control during the machining represents a problem because no effective on-line in real-time stand-off distance detection system has been developed yet. The detection of the stand-off distance during cutting enables better AWJ machining process control. order to monitor the stand-off distance, we measure the emitted sound generated during the AWJ straight cut operation and analyse its characteristic attributes. In order to verify the proposed stand-off distance monitoring methods, a set of experiments was carried out. The signal analysis was performed in both time and frequency domain. The obtained results show an evident influence of the stand-off distance on sound emission. Thus, efficient control of the AWJ cutting process through sound detection appears to be viable.     

Parametric Effects on Particle Deposition in Abrasive Waterjet Surface Treatments

The abrasive waterjet (AWJ) has primarily been used for net-shape sectioning of engineering materials. In this study an AWJ was adopted for the surface treatment of commercially pure titanium (cpTi) and the contribution of treatment parameters to material removal and the deposition of particles within the substrate were examined. The surface texture and material removal rate were analyzed using conventional techniques whereas the quantity of abrasive particles embedded within the cpTi surfaces was determined using energy dispersive X-ray analysis (EDXA). Parametric effects related to particle hardness were distinguished from a comparison of surfaces treated with Aluminum oxide, garnet, and crushed glass abrasives. According to an analysis of variance (ANOVA), treatment responses were found to be primarily dependent on the abrasive size, abrasive hardness, angle of incidence, and jet pressure. The minimum and maximum concentration of particles embedded in the AWJ treated cpTi (in percent surface area covered) was 2.5 and 21.6%, respectively. Particle concentration and mean particle size in the cpTi increased with abrasive size, angle of incidence and jet pressure; the particle concentration reached saturation at an angle of incidence near 80°. Although abrasive hardness was important to the treatment responses, an increase in hardness beyond 800 on the Rosiwal scale resulted in minimal changes in material removal or other features of the process.     

An access detection and machine cycle tracking system for machine safety

Abrasive water jet (AWJ) machining is characterized by its versatility, i.e., it can be applied to a wide variety of materials. Currently, one important application is for manufacturing gem artifacts, especially agate, which is the largest gemological material produced in the state of Rio Grande do Sul. However, one of the main obstacles to its popularization is the cost associated with the process, due to the high abrasive consumption required for a good quality surface finish. In this sense, this research paper presents a study of the influence of the main process parameters (traverse speed and abrasive mass flow rate) on the surface finish of agates machined by AWJ. The experimental procedure used three different traverse speeds, four abrasive mass flow rate in two different thicknesses of agate’s plates. Surface roughness and angle of striation marks were observed for different depths from the jet entrance surface. Results were analyzed using analysis of variance (ANOVA). Through the study, it was found that the machined surface finish varies according to the depth from the entrance surface of the abrasive jet. Also, it was concluded that the surface finish of the machined surface by AWJ (surface roughness and striation marks) of the agate’s plates machined by AWJ exhibits similar results for both thicknesses tested. ANOVA showed that the traverse speed is more significant than abrasive mass flow rate for the material studied with respect to the surface finish. Thus, for a small material thickness, it is possible to use high traverse speed and low abrasive mass flow rate which makes the process more economical.     

高压水磨料射流切割机制的实验研究

根据工业性切割的需要，对磨料水射流（ＡＷＪ）切割机制进行实验研究。通过射流与材料之间的相互作用过程，建立和验证了ＡＷＪ切割过程模型，ＡＷＪ切割过程主要是通过磨粒对材料的周期性切割磨削和变形磨削完成；验证分析了典型材料的切割特征（切割深度、切口宽度、冲蚀量）与切割变量（水压、靶距、切速等）的关系，以及磨料、材质两大因素的影响。实验研究结果对ＡＷＪ切割技术的开发与应用具有指导意义和实用价值。     

Analytical modeling of grinding wheel loading phenomena

Wheel surface condition plays an important role in the grinding operation. Grinding wheel loading, meaning chip accumulation in the space between grains, leads to deteriorating wheel cutting ability and causes excessive force and temperature. This paper presents an analytical model of wheel loading phenomena as a function of cutting parameters, wheel structure, and material properties. The model is based on the adhesion of workpiece material to abrasive grain surface. It is validated by experimental results from grinding nickel-based superalloy with cubic boron nitride vitrified wheel. This model considers wheel specifications including abrasive grains size and the number of cutting edges. Cutting parameters and process temperature are the other determinant factors. On the basis of this model and empirical results, the effects of the various process parameters are presented.     

基于人工神经网络的磨料水射流切割加工模型

作为一种冷态加工新工艺 ,磨料水射流 (AWJ)以其独特的优点得到广泛应用 ,但由于高速液固两相流本身的特性 ,AWJ切割加工是一个受多参数影响的复杂随机过程 ,很难建立一个适当的机理模型。基于人工神经网络理论 ,本文建立了切割厚度与主要工艺参数间的AWJ切割加工预测模型 ,模型预测结果与实验值及Zeng的经验模型进行了比较 ,该网络模型能可靠、准确地映射出AWJ的加工规律 ,可应用于AWJ切割加工过程的参数优化选择、加工规律计算机仿真及智能化控制中。     

A finite element-based model for pure waterjet process simulation

The utilization of abrasive waterjet (AWJ) cutting/drilling, and in particular its application into hard-to-cut materials, is growing. However, the mechanics of AWJ cutting is complex; the material removal process is not fully understood and, consequently, it has not been accurately modeled. In the current study, work was undertaken to mesh in a first stage the waterflow into the waterjet nozzle in order to use the finite element (FE) method to simulate the pure waterjet flow. The main objective is to investigate and analyze in detail the workpiece material behavior under waterjet impingement; a non-linear FE model (using LS-DYNA 3D code) has been developed, which simulates the erosion of the target material caused by the high-pressure waterjet flow. A combination of Eulerian–Langrangian elements is used for the waterjet and the target material, respectively, in order to handle their interaction. Damaged zones can be localized on impinged materials. Elements’ failure is handled by introducing a threshold strain after which Langrangian elements are removed. The results obtained from this numerical simulation (velocity profile, stress, erosion stages) show a good agreement with the results from previous experimental work that is available in bibliography. The next step of the research will be focused on the simulation of the whole procedure using various abrasives.     

磨料水射流的切割机制

研究了100MPa～400MPa高水压下磨料水射流（AWJ）的切割机制。根据射流与材料之间的相互作用过程,建立和验证了AWJ切割过程模型。揭示了典型材料的切割特征（切割深度、切口宽度和冲蚀量）与切割变量（水压、靶距和切割速度等）的相关规律,以及磨料、材质两大因素的影响。获得了结果对AWJ切割技术的开发和应用具有指导意义和实用价值。     

磨料水射流切割工艺参数的实验研究

磨料水射流切割中影响切割深度的因素很多,各工艺参数的选择和合理搭配对切割结果有很大影响,并且难以用精确的数学模型来描述.以磨料水射流切割混凝土为例,考察了射流压力、进给速度、靶距、磨料流量、磨料粒径和材料性能等工艺参数对最大切割深度的影响.结果表明:(1)切割深度与射流压力呈线性增长关系;(2)在一定范围内切割深度随磨料流量增加而增加,但当磨料流量达到一定值后,切割深度随流量增加反而下降;(3)切割深度随磨料粒径的增加呈先增加后减小的规律,存在一极值点;(4)切割深度随切割速度的增加呈指数衰减;(5)存在一最佳靶距,超过这个界限值时,随着靶距的增大,切割深度急剧减小;(6)混凝土试件抗压强度的抗压强度越大,切割深度越小.     

Modeling and simulation of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, which produces a high level of surface quality and is primarily controlled by a magnetic field. In MAF, the workpiece is kept between the two poles of a magnet. The working gap between the workpiece and the magnet is filled with magnetic abrasive particles. A magnetic abrasive flexible brush (MAFB) is formed, acting as a multipoint cutting tool, due to the effect of the magnetic field in the working gap. This paper deals with the theoretical investigations of the MAF process. A finite element model of the process is developed to evaluate the distribution of magnetic forces on the workpiece surface. The MAF process removes a very small amount of material by indentation and rotation of magnetic abrasive particles in the circular tracks. A theoretical model for material removal and surface roughness is also proposed accounting for microcutting by considering a uniform surface profile without statistical distribution. Numerical experiments are carried out by providing different routes of intermittent motion to the tool. The simulation results are verified by comparing them with the experimental results available in the literature.     

Modeling and simulation of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, which produces a high level of surface quality and is primarily controlled by a magnetic field. In MAF, the workpiece is kept between the two poles of a magnet. The working gap between the workpiece and the magnet is filled with magnetic abrasive particles. A magnetic abrasive flexible brush (MAFB) is formed, acting as a multipoint cutting tool, due to the effect of the magnetic field in the working gap. This paper deals with the theoretical investigations of the MAF process. A finite element model of the process is developed to evaluate the distribution of magnetic forces on the workpiece surface. The MAF process removes a very small amount of material by indentation and rotation of magnetic abrasive particles in the circular tracks. A theoretical model for material removal and surface roughness is also proposed accounting for microcutting by considering a uniform surface profile without statistical distribution. Numerical experiments are carried out by providing different routes of intermittent motion to the tool. The simulation results are verified by comparing them with the experimental results available in the literature.     

A study on the application of newly developed magneto-elastic abrasive to improving the surface roughness of the bore

Spiral polishing mechanism refers to the technology of applying a high-speed turning screw rod in the process of workpiece surface polishing. For the purpose of increasing the machining effect, a powerful ring magnet was installed around the workpiece. In this study, the new self-developed magneto-elastic abrasive would be used to polish the inner wall of the bore, the so-called workpiece surface, under the attraction of the surrounding magnet and the drive of the turning rod. The new magneto-elastic abrasive not only eased the polishing force by its flexibility but also avoided deep scratches on the workpiece surface. The control of machining parameters on surface roughness and material removal were discussed to look for the best combination of the parameters; at the same time, the effects of each parameter on the workpiece surface topography after the polishing were also examined. The results of the experiment indicated that magnetic flux density and magneto-elastic abrasive concentration affected the surface roughness the most. In addition, the newly developed magneto-elastic abrasive significantly improved the polishing effect of the workpiece surface, at the rate of 94 %.     

非一致曲率表面下的气压砂轮磨粒剪胀及加工试验研究#br#

针对软固结磨粒气压砂轮在加工异形曲面时,工件所受的切削力以及接触区内磨粒速度因工件曲率发生变化,导致工件不同曲率处材料去除量不均匀的问题, 基于修正的Rowe剪胀理论建立砂轮切削力模型,提出了非一致曲率表面下修正的气压砂轮材料去除模型。通过EDEM软件建立了软固结磨粒气压砂轮模型,分析了砂轮下压量为1.5 mm时工件曲率对接触力以及接触区内磨粒速度的影响。搭建气压砂轮加工试验平台,通过光整加工试验验证修正的材料去除模型。研究结果表明：修正的材料去除模型平均绝对值误差为0.095,而原始的材料去除模型平均绝对值误差为0.291,说明修正的材料去除模型可以用于气压砂轮抛光过程中的定量分析,且工件加工表面划痕明显减少。     

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.     

An Experimental Study to Enhance the Cutting Performance in Abrasive Waterjet Machining

An experimental study to enhance the cutting performance in abrasive waterjet (AWJ) machining is presented. The study uses the techniques of jet forward impact angles and multipass operations both individually and concurrently when cutting an alumina ceramic and a polymer matrix composite. A brief report on the effect of jet impact angle in single pass cutting is made first, which shows that the optimum jet impact angle for both the ceramics and polymer matrix composite is about 80°. It is found that the multipass cutting technique can increase the cutting capability and application domain of AWJ cutting. It can also improve the major cutting performance such as the depth of cut as compared to single pass cutting within the same total cutting time. The benefit of using multipass cutting operations is further enhanced when it is combined with a jet forward angle of 80° in cutting alumina ceramics.