Effect of process parameter on the kerf geometry in abrasive water jet milling

This research work introduces a model to predict the kerf profile in abrasive water jet slot milling in aluminium 7075-T651. The experimentation allowed modelling the maximum cutting depth and the width at the half of maximum depth in terms of four process parameters: pressure, abrasive mass flow rate, stand-off distance, and traverse feed rate. It is shown that the introduction of the maximum depth and the width at the half of maximum depth in a Gaussian function is suitable to describe the kerf profile. The definition of an equivalent traverse feed rate at every instant along the jet trajectory introduces the effect of the jet acceleration in the model. Thus, the model is capable of predicting the kerf profile at constant traverse feed rate and at variable traverse feed rate due to direction changing trajectories. The variations of cutting depth along a slot are also studied in order to avoid the cutting parameters combinations which lead to low repetitiveness conditions and then irregular milling surfaces.     

淹没磨料水射流中磨料破碎状况分析

磨料水射流中的磨料在冲蚀破碎后,颗粒的分布在一定范围内表现出自相似的分形特征.对颗粒分布进行测定并分析,得出磨料水射流中磨料颗粒在喷嘴内有破碎发生,且颗粒愈大破碎愈强烈,分析得出颗粒的分形维度可作为磨料破碎状态的一个重要指标,应用于对颗粒破碎程度的评定.     

Parameter estimation for abrasive water jet machining process using neural networks

The abrasive water jet machining process, a material removal process, uses a high velocity jet of water and an abrasive particle mixture. The estimation of appropriate values of the process parameters is an essential step toward an effective process performance. This has led to the development of numerous mathematical and empirical models. However, the complexity of the process confines the use of these models for limited operating conditions; e.g., some of these models are valid for special material combinations while others are based on the selection of only the most critical variables such as pump pressure, traverse rate, abrasive mass flow rate and others that affect the process. Furthermore, these models may not be generalized to other operating conditions. In this respect, a neural network approach has been proposed in this paper. Two neural network approaches, backpropagation and radial basis function networks, are proposed. The results from these two neural network approaches are compared with that from the linear and non-linear regression models. The neural networks provide a better estimation of the parameters for the abrasive water jet machining process.     

淹没磨料水射流与非淹没磨料水射流冲蚀破岩效果比对分析

磨料水射流的冲蚀能力主要依赖于磨料颗粒所获得的能量,对非淹没磨料水射流和淹没磨料水射流的冲蚀实验结果进行比对,从能量角度和磨料颗粒速度变化角度分析了造成非淹没磨料水射流和淹没磨料水射流的冲蚀效果差异的原因。     

Study and evaluation of abrasive water jet cutting performance on AA5083-H32 aluminum alloy by varying the jet impingement angles with different abrasive mesh sizes

This article describes the experimental investigation of abrasive water jet (AWJ) cutting on AA5083-H32 aluminum alloy. In this study, the influence of varying the jet impingement angles and abrasive mesh sizes with different water jet pressures, on the output parameters for the AWJ cutting of the aluminum alloy, was analyzed. The experimental results found that the output parameters, namely, the depth of penetration, top kerf width, kerf taper ratio, surface roughness, and abrasive contaminations, were strongly influenced by the combined effect of oblique jet impingement angles and abrasive mesh sizes on AWJ. Also, it is noticed that oblique jet impingement angles have more influence on the output cutting responses than the normal jet impingement angle, and consequently, each abrasive mesh size has an influence on the different output responses for the AWJ cutting of AA5083-H32. Scanning electron microscope and microhardness tester were used to examine the different cutting regions of the kerf wall surfaces. The Energy-dispersive X-ray spectroscopy analysis was used to confirm the amount of silicon particles embedded in the AWJ cut surfaces. The adequacy checking of the experimental data for the AWJ cutting performance models has been analyzed through the residual plots using the statistical software.     

磨料水射流除锈技术仿真研究

针对钢材的锈蚀广泛存在于工业生产中并造成了很大的经济损失这一问题,从磨料水射流除锈技术角度出发,采用ANSYS/LS-DYNA有限元软件,建立了多粒子侵蚀靶板模型,对多粒子连续冲击靶板过程进行了仿真模拟,分析研究了靶板材料去除机理.为磨料水射流除锈工艺提供了一定的理论基础.通过对各种不同算例进行仿真模拟,得到了不同冲击速度、冲击角度等情况下粒子对目标靶板侵蚀情况,通过对结果进行分析比较,研究了粒子冲击参数对冲蚀过程的影响.研究结果表明,材料侵蚀率随着冲击次数的增加而增加,但是经过一定次数冲击后,目标靶板去除量达到了一种相对稳定的状态.随着冲击角度的增加,侵蚀深度增加但是侵蚀面积减小.随着磨粒直径的增加,侵蚀深度及侵蚀体积均逐渐增加.     

磨料浆体射流切割中添加剂的性能及试验研究

结合高聚物添加剂的特性,讨论其在磨料射流切割中的作用。研究了使用高聚物添加剂后的切割效果、特点,首次分析了磨料浆体射流中比能耗的变化趋势,并进行了相关试验结果的机理分析。     

声悬浮抛光磨粒微流场研究

为了解决纳米试样超光滑表面的制备问题,将能提供稳定声压场的声悬浮抛光技术应用到流体抛光中,开展了声压场和磨粒流场之间关系的分析.利用Matlab/PDE工具箱对抛光装置内部声压仿真的方法,对比不同反射端对抛光槽声压场的影响,优化了适合抛光的反射端形状尺寸和发射端与反射端之间的距离.利用PIV测试分析了磨粒流场与声压场的相关性,建立了声压场和磨粒流场之间的关系.试验结果表明,磨粒的运动方向与声压等势线大致相同,而且磨粒的最大速度与声压大小成正比.     

磨料射流切割钻杆的喷嘴设计

在高含硫油气田中,为避免剪切闸板发生硫化物应力腐蚀开裂,采用前混合磨料射流替代剪切闸板切割钻杆.将S135钻杆51/2″作为研究对象,选取圆锥带圆柱段型喷嘴.通过分析磨料粒子在喷嘴内的加速过程,对喷嘴的结构参数进行了系统研究,得出啧嘴的加速性能和收敛性能达到最佳时的具体结构尺寸.并且计算出磨料颗粒与钻杆材料接触时的最大剪应力,校核了设定参数在理论上的可行性.     

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.     

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.     

磨料喷射加工加工特性研究

磨料喷射加工是利用微细磨料与高压空气或其它气体混合而成的高速喷射流，依靠磨料的高速冲击，冲蚀作用而去处或修饰材料的一种特种加工方法，适用于零件的微细加工和零件的表面处理。主要分析了磨料喷射加工的原理，通过对自行设计的试验装置进行一系列试验结果的分析，研究了其加工特性。     

Cryogenic abrasive jet machining of polydimethylsiloxane at different temperatures

The temperature dependence of the solid particle erosion of polydimethylsiloxane (PDMS) using aluminum oxide particles was investigated between the temperatures of ?178 and 17 °C for a variety of angles of attack using a novel cryogenic abrasive jet machining apparatus. It was found that the most efficient machining of PDMS (volume removed per kinetic energy of erodent) occurred at approximately ?178 °C, at angles of attack between 30° and 60° from the surface. A previously developed surface evolution model was used to predict the size and shape of unmasked channels at various temperatures. A good agreement between the predicted and measured channel profiles was obtained when the average blasting temperature was between approximately ?127 and ?178 °C. At ?82 °C, the fit was poorer, probably because of an increase in particle embedding. Although it was demonstrated that PDMS could be machined at temperatures above its glass transition, the erosion rate increased by a factor of more than 10 when the machining temperature was below this point.     

磨料水射流仿真分析与试验研究

为有效保持油田的稳产增产,磨料水射流技术逐渐被应用于油田生产.磨料水射流切割利用高速混砂液体的射流来完成切割作业,具有安全、多能、环保、便捷、高效的特点.本文对前混式磨料水射流切割的喷嘴结构进行了优化设计计算,采用计算流体力学的方法,利用CFD仿真软件,对不同喷嘴类型﹑喷嘴长度和不同锥角角度的喷头的工作情况进行数值模拟...     

Effect of helium atmospheres on abrasive suspension water jets

The coherence of cutting pure water jets can be enhanced by shooting them into low-density atmospheres. To answer the question about the possibility to also improve the coherence of abrasive water suspension jets (AWSJ), experiments were performed surrounding AWSJs with a parallel stream of helium. Although in some cases a change on the structure of the jets was recognized, the studied jets shot into helium atmospheres did not show appreciable improvements on their cutting and kerfing performance.     

The effects of blast lag in abrasive jet machined micro-channel intersections

Abrasive jet micro-machining (AJM) uses compressed air carrying abrasive solid particles to micro-machine a variety of features into surfaces. If the feature sizes are less than the size of the abrasive jet footprint, then a patterned erosion-resistant mask is used to protect the substrate material, leaving exposed areas to define the features. Previous investigations have revealed a ‘blast lag’ phenomenon in which, for the same dose of abrasive particles, narrower mask openings lead to channels that are shallower than wider ones. Blast lag occurs when using AJM on brittle substrates because of the natural tendency to rapidly form a V-shaped cross-sectional profile which inhibits abrasive particle strikes on the narrow vertex at the feature centerline. In this paper, the blast lag phenomenon is studied when using AJM to machine a network of microfluidic channels. It is found that, in some cases, differences in blast lag occurring at channel intersections and within the channels themselves, can lead to channel networks of nonuniform depth. A previously developed surface evolution model is adapted to allow prediction of the onset of blast lag in the channels and intersections and thus explain these differences. Finally, methods to eliminate the differences are discussed.     

Development of an algorithm for optimum control process to compensate the nozzle wear effect in cutting the hard and tough material using abrasive water jet cutting process

In the process of abrasive water jet cutting, the change of nozzle diameter, due to nozzle wearing throughout cutting process, causes a decrease in surface quality and an increase in kerf width. In this paper, a series of experiments have been done to determine the effect of process parameters and the results show that traverse speed and nozzle diameter are significant parameters on the kerf quality and geometry, and a control program algorithm is suggested to compensate the effect of nozzle diameter increase on cut surface quality and kerf width and the control program creates an offset with required amount in nozzle path.     

An exploration of an abrasive water jet cutting front profile

Abrasive water jet (AWJ) now is used as a precision cutting tool. With this tool, dimension tolerance less than 0.1 mm is expected in the cutting process. This dimension tolerance is enough for some applications. However, higher precision is necessary in order to use AWJ in some other applications. To get higher precision in an AWJ cutting process, controlling AWJ beam more accurately is needed, and this further leads to understanding AWJ cutting front more accurately. This paper compared the current cutting front profile exploration methods and then provided a new method to collect AWJ cutting front information accurately. With this new method, a better understanding of the cutting front profile is possible, which further leads to higher precision cutting of AWJ. This paper also demonstrated that the AWJ cutting front profile could be fitted by parabolic curves accurately.