A novel abrasive blasting process: Abrasive medium classification and CFD simulations

This study concerns the determination of the significant factors for an innovative deburring process: low pressure abrasive water‐jet blasting. The abrasive medium aluminum oxide (Al₂O₃) is classified according to the individual characteristics of different grain sizes. Then, the particle behavior in the air jet is analyzed with an optical measuring method, Particle Image Velocimetry (PIV); the velocity profile and the particle distribution of the dispersed system are obtained. Computational Fluid Dynamics (CFD) simulations were verified by comparing the experimental and numerical results, and the velocity range for the abrasive particles has been specified.     

基于PIV技术的磨料水射流中固体磨料粒子速度分布实验研究

为了解决磨料射流磨料速度测试难问题,本文基于PIV技术,结合图像处理与滤波分析技术,提出了一种测量磨料射流磨料速度的非接触式测试方法。该方法能同时得出磨料速度以及磨料在射流中的位置信息。利用该方法对磨料射流进行磨料速度测试实验,实验结果表明：(1)利用该方法能快速地得到磨料射流中磨料速度;(2)利用该方法得到了磨料在喷嘴出口沿射流方向的速度变化规律,即磨料在喷嘴出口速度先增大后减小,存在速度最大处,意味着磨料射流存在最优靶距;(3)利用该方法得到了磨料沿射流径向的速度变化规律,磨料在射流中心速度最大,其速度从射流中心往射流边界方向逐渐减小,呈现出钟形速度分布。     

磨料水射流对脆性材料的冲蚀研究

磨料水射流技术作为一种特种加工技术，具有无刀具接触、无热影响区和加工范围广等优势，在众多领域得到应用。为了探究磨料水射流对脆性材料的冲蚀效果，构建和设计了磨料水射流外流场冲蚀仿真模型与磨料水射流冲蚀实验。以30 mm×50 mm的喷嘴外流场域为计算域，建立磨料水射流冲蚀仿真模型，并分析射流冲蚀过程中压力分布、水与磨料的速度分布及它们在射流中心线上的衰减规律。通过对氧化铝陶瓷材料的冲蚀实验，分析工艺参数对冲蚀孔径的影响，并结合仿真结果对比分析了射流束宽度与冲蚀孔径的关系。结果表明：水的速度随着喷嘴距离的增大而减小且分布范围变宽，射流宽度呈线性增大，磨料速度随喷嘴距离的增大而减小且分布范围基本不变；射流中心线上水的速度与磨料速度呈三段式衰减，水的第1段速度衰减段长度比磨料的长，但水的第2段速度衰减段长度比磨料的短；射流束能量的有效利用部分逐渐减小，但在15~25 mm的靶距范围内其有效利用部分较稳定，为40%；冲蚀孔径随喷嘴距离增大呈线性增大。研究结果为磨料水射流切割、铣削及抛光加工的参数选择提供实验依据，同时为磨料水射流加工过程仿真提供参考。     

前混合磨料水射流切割HTPB推进剂的可行性研究

针对前混合磨料水射流切割HTPB推进剂的过程安全性和效率，开展了理论分析与试验验证。在理论分析的结果上，分别开展了基于固定和移动两种试验模式下的安全性和效率试验。该切割方式由于有效降低了出口压力，在保证切割能力的前提下其冲击压力远远低于推进剂的冲击感度，导致推进剂内部升温不明显，安全性有足够保证。研究结果表明，在90%的置信水平下，切割的安全可靠度不低于99.52%。而磨料粒子的添加极大地提高了射流的切割效率。试验结果表明，当保持出口压力30 MPa以上、磨料质量分数不低于50%时，磨料水射流约为相同条件下纯水射流切割效率的2倍。由此得出可行性结论:由于前混合磨料水射流具有极强的冷态冲蚀磨削作用，在安全性和效率方面均能够满足对三组元HTPB推进剂的切割作业。     

Measurement of Water Jet Velocity Distribution Using Laser Velocimetry

A laser Doppler velocimetry technique has been implemented in this work to evaluate the water jet velocity distribution in water jet and abrasive water jet cutting applications. Knowledge of the water jet velocity is fundamental to determine the system cutting efficiency; in particular, it allows us to experimentally determine the specific performance of the orifices employed in the cutting process.      

磨料水射流切割防暴弹的试验研究

针对前混合式磨料水射流切割防暴弹的过程,分析磨料水射流对装药的切割安全性,探讨射流参数的选取及工程化处废的可行性。根据弹性力学的固体接触理论,建立磨料水射流冲击弹体时的数学模型,从而选取射流出口压力等工艺参数。依据射流的冲击理论和装药的热感度及撞击感度,结合射流作用时的升温试验,分析证实在该射流参数下的冲击安全性。结果表明,以手投催泪(或发烟)弹、枪射催泪(或发烟)弹为代表的4种防暴弹,其试验结果与实例计算相吻合,切割安全可靠度不低于98.57%。该研究可为防暴弹的工程化处废提供理论依据和技术支持。     

An Analytical Model for Material Removal in Abrasive Jet Machining for Brittle Materials

Optical microscopy has indicated that the abrasive particles used in abrasive jet machining have sharp edges with the shapes similar to cone or pyramid. Moreover, microscopic examination of cross section of work samples eroded by AJM shows that, for brittle materials, material removal is due to intersection and propagation of cracks produced by adjacent impacting particles on target surface. An analytical model has been developed based on the above observations for predicting the material removal in abrasive jet machining process. The model also suggests the critical value of mass flow rate which has been substantiated experimentally. In addition, the influence of velocity and mass flow rate of abrasive particles on material removal rate is briefly described.     

前混合磨料水射流对HTPB推进剂的切割 工艺参数优化研究

利用前混合磨料水射流，对高、低两种燃速的HTPB推进剂开展切割试验，着重研究不同切割条件下工艺参数对切割效率的影响，进而为工艺参数优化提供理论依据。选取切割速度（v）、出口压力（p）、磨料浓度比（T）和靶距（L）4个工艺参数为主要影响因素，以最大切割深度（H）作为切割效率的衡量指标，分别通过单因素试验和正交试验进行分析，进而完成工艺参数的优化。试验结果表明，最大切割深度随切割速度的增加而减小，且单位时间内的切割面积存在最佳值；随着出口压力的增加，最大切割深度在特定范围内近似线性增加，并逐渐趋于平缓；磨料浓度比与靶距和最大切割深度均存在最佳对应关系。正交试验结果表明，切割速度对指标影响较为显著，靶距等3个工艺参数的影响相对较小。该研究可为前混合磨料水射流作为HTPB推进剂的工程化处废技术提供理论支持。     

Machinability of Nickel-Based Superalloy by Abrasive Water Jet Machining

This paper deals with the machinability of nickel-based superalloys using abrasive water jet machining process. The machining studies were carried out with three different parameters such as water jet pressure, traverse speed of jet nozzle, and standoff distance at three different levels. The performances of the process parameters are evaluated by measuring difference in kerf width, kerf wall inclination, and material removal rate (MRR). Further, the surface morphology and material removal mechanisms are analyzed through scanning electron microscope (SEM) images. It is found that water jet pressure is the most influencing factor related to surface morphology and surface quality.     

Multiresponse Optimization of Abrasive Water Jet Cutting Process Parameters Using TOPSIS Approach

This paper describes how optimization studies were carried out on an abrasive water jet (AWJ) cutting process with multiresponse characteristics based on Multi Criteria Decision Making Methodology (MCDM) using the Technique for Order Preference by Similarity Ideal Solution (TOPSIS) approach. The process parameters water jet pressure, traverse rate, abrasive flow rate, and standoff distance are optimized with multiresponse characteristics, including the depth of penetration (DOP), cutting rate (CR), surface roughness (R_a), taper cut ratio (TCR), and top kerf width (TKW). The optimized results obtained from this approach indicate that higher DOP and CR and lower R_a, TCR, and TKW were achieved with combinations of the AWJ cutting process parameters, such as water jet pressure of 300 MPa, traverse rate of 120 mm/min, abrasive flow rate of 360 g/min, and standoff distance of 1 mm. The experimental results indicate that the multiresponse characteristics of the AA5083-H32 unit used during the AWJ cutting process can be enhanced through the TOPSIS method. Analysis of variance was carried out to determine the significant factors for the AWJ cutting process.     

含磨粒润滑条件下3Cr13涂层加速磨损机理研究

提出3Cr13涂层加速磨损失效新的实验方法.采用该方法在MM200摩擦磨损试验机上,对高速电弧喷涂3Cr13涂层在含SiO_2磨粒的润滑条件下磨损失效开展了加速磨损试验,通过对比分析扫描电镜照片筛选合适的磨粒颗粒,并分析SiO_2磨粒加速涂层磨损可能的机理.结果表明:适合3Cr13涂层的加速磨损试验的磨粒粒度为微米级,通过磨损表面照片得出了磨粒在润滑条件下对涂层加速磨损作用主要表现为:微观切削、挤压和磨粒的聚集.     

Three Dimensional Nanoscale Abrasive Cutting Simulation and Analysis for Single-Crystal Silicon Workpiece

The paper establishes a new three-dimensional quasi-steady molecular statics nanoscale abrasive cutting model to investigate the abrasive cutting behavior in the downpressing and abrasive cutting process of a workpiece in chemical mechanical polishing (CMP) process. The downpressing and abrasive cutting process is a continuous process. The abrasive cutting process is done after the single abrasive particle has downpressed and penetrated a workpiece to a certain depth of a workpiece. The paper analyzes the effects of the abrasive particles with different diameters on action force. It also analyzes the action force change of abrasive particles with different diameters on the projected area of unit contact face between abrasive particle and workpiece. The distribution of nanoscale equivalent stress and equivalent strain of the midsection of workpiece in abrasive cutting process are also analyzed. Furthermore, the special phenomena those are found in this paper, the one is the diameter of abrasive particle is greater, the action force on the projected area of its unit contact face is smaller and the other one is particular prominent regional action force in nanoscale abrasive cutting process. Besides, adopting the new molecular statics abrasive cutting model developed by the paper, the paper undergoes the simulation of same parameter conditions, and compares the simulation results with the related literature of using molecular dynamics method in order to prove that the new model developed by the paper is reasonable.     

Investigation of process parameters influence in abrasive water jet cutting of D2 steel

In the present experimental study, abrasive water jet (AWJ) cutting tests were conducted on D2 steel by different jet impingement angles and abrasive mesh sizes. The experimental data was statistically analyzed using the simos–grey relational method and ANOVA test. In addition, the outcome of influencing cutting parameters, namely jet pressure, jet impingement angle, and abrasive mesh size on the different response parameters, namely, the jet penetration, material removal rate, taper ratio, roughness, and topography, were studied. Micro-hardness test and surface morphology analysis were employed to examine the D2 cut surfaces at different AWJ cutting conditions. The chemical element study was performed to determine the abrasive particle contamination in the AWJ kerf wall cut surfaces. The ANOVA test result indicated the jet pressure and jet impingement angle as the influencing process parameters affecting the various performance characteristics of AWJ cutting. The overall AWJ cutting performance of the D2 steel has been improved through proper identification of the optimal process parameter settings, namely jet pressure 225?MPa, abrasive mesh size #100, and jet impingement angle 70° by the simos–grey relational analysis.     

Parametric optimization of abrasive water-jet machining processes using grey wolf optimizer

Abrasive water-jet machining (AWJM) is a hybrid advanced machining process, which can be economically applied to machine almost any kind of material. It employs a high velocity waterjet to propel abrasive particles through a nozzle on the workpiece surface for material removal. The machining performance of AWJM process naturally depends on its several control (input) parameters, like water pressure, nozzle diameter, jet velocity, abrasive concentration, nozzle tip distance etc., which have also predominant effects on its responses, i.e., material removal rate, surface roughness, overcut, taper etc. In this paper, a new evolutionary algorithm, i.e., grey wolf optimizer (GWO), a technique based on the hunting behavior of grey wolves, is applied for finding out the optimal parametric combinations of AWJM processes. The main advantage of this algorithm is that it does not accumulate towards some local optima, and the presence of a social hierarchy helps it in storing the best possible solutions obtained so far. The derived results using GWO exhibit a significant improvement in the response values as compared to the previous attempts for parametric optimization of AWJM processes while applying other algorithms.     

Numerical optimization of hole making in GFRP composite using abrasive water jet machining process

Machining of composite materials for the production of bolt holes is essential in the assembly of the structural frames in many industrial applications of glass fiber-reinforced plastic (GFRP). Abrasive water jet cutting technology has been used in industry for such purposes. This technology has procured many overlapping applications and as the life of the joint in the assembled structure can be critically affected by the quality of the holes, so it is important for the industry to understand the application of the abrasive water jet cutting process on GFRP composite materials. The aim of the present work is to assess the influence of abrasive water jet machining parameters on the hole making process of woven-laminated GFRP material and to find the optimum values of the process parameters. Statistical approach was used to understand the effects of the predicted variables on the response variables. Analysis of variance was performed to isolate the effects of the parameters affecting the hole making in abrasive water jet cutting. The results show that the optimum values of cutting feed, fiber density, water jet pressure, standoff distance, and abrasive flow rate upon the response variables are 0.3 m/min, 0.82 g/cm³, 150 MPa, 2 mm, and 100 g/min, respectively.     

喷磨法测定铝合金阳极氧化膜耐磨性的影响因素

铝合金阳极氧化膜的耐磨性反映了膜层对摩擦作用的抵抗能力,是氧化膜的一个重要质量指标,可通过喷磨试验来进行测试。考察了测试压力、测试角度、测试距离等对喷磨试验结果的影响。结果表明:喷磨时间随着测试角度的增大而减少,随着测试压力的增大而减小,随着测试距离的变化出现先减少后增加的趋势。对于不同的试样,应选择合适的试验参数来进行检测。     

Investigation on the cutting quality characteristics of abrasive water jet machining of AA6061-B4C-hBN hybrid metal matrix composites

Aluminum metal matrix composites (AMMCs) explicitly show better physical and mechanical properties as compared to aluminum alloys and results in a more preferred material for a wide range of applications. The addition of reinforcements embargo AMMCs employment to industry requirements by increasing order of machining complexity. However, it can be machined with a high order of surface integrity by nonconventional approaches like abrasive water jet machining. Hybrid aluminum alloy composites were reinforced by B₄C (5–15?vol%) and solid lubricant hBN (15?vol%) particles and fabricated using a liquid metallurgy route. This research article deals with the experimental investigation on the effect of process parameters such as mesh size, abrasive flow rate, water pressure and work traverse speed of abrasive water jet machining on hybrid AA6061-B₄C-hBN composites. Water jet pressure and traverse speed have been proved to be the most significant parameters which influenced the responses like kerf taper angle and surface roughness. Increase in reinforcement particles affects both the kerf taper angle and surface roughness. SEM images of the machined surface show that cutting wear mechanism was largely operating in material removal.     

Water jet and abrasive water jet cutting of unidirectional graphite/epoxy composite

Unidirectional graphite/epoxy composite material has been machined by water jet and abrasive water jet cutting processes. Topography and morphology of the machined surfaces were evaluated with surface profilometry and scanning electron microscopy. The surface characteristics in terms of roughness and the micromechanisms of material removal for both processes were analysed and compared. Abrasive water jet surface characteristics of graphite/epoxy were found to be significantly different from those of the water jet cutting process and micromechanical behaviour of material removal was strongly dependent on the fibre orientation.     

微磨料浆体射流形成过程的能量传输

为了研究微磨料浆体射流形成的能量传输与转换,用碳化硅磨料对40CrMnMo7钢进行冲击,建立数学模型描述冲击力与射流压力、喷嘴效率、射流流量、水力功率等参数的相互影响,通过测量射冲击力、射流流量来预测射流系统的单位水力功率的出力状况。结果表明,该数学模型可以预测射流冲击力与水力功率之比,由系统压力模型计算的冲击力比实验结果小20%;在射流的滞止区内,压力与冲击力不呈线性关系,在相同压力下,磨料粒子具有更大的动能,微磨料浆体射流冲击力比纯水射流的大20%,单位水力功率提供的射流冲击力随着射流压力的增大而减小;射流冲击力随着喷嘴直径、射流压力的增大而增大,在靶距较小的情况下,冲击力随着靶距的增大而增大,当靶距达到一定值时,冲击力随着靶距的增大而减小。     

Computer simulation of the jet of rarefied plasma outflowing from a nozzle of a plasma thruster

Physical, mathematical and numerical models for the problem of the outflow of a jet of rarefied plasma from the nozzle of a plasma thruster of the cylindrical and rectangular shape have been considered. The main results of computation experiments have been presented: distribution functions of charged particles in the plasma flow, velocity and concentration fields of charged particles, and isolines of the potential of the self-consistent electric field.