微细磨料喷射加工仿真与实验研究

利用流体动力学仿真软件CFX对微细磨料喷射加工中,影响加工效果的喷射压力、喷射距离等影响因素进行仿真,模拟出不同参数下磨料微粒的速度、工件表面所受压力的分布规律,并与实验结果进行对比,验证仿真结果的正确性.     

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.     

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。     

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。     

微磨料水射流机床悬臂梁的有限元分析

微磨料水射流切割机床的切割精度与机床数控平台、数控系统精度以及水射流工艺参数直接有关,同时还与安装水射流切割头及其附件的悬臂梁刚度和绕曲变形有关.针对微磨料水射流机床的重要部件悬臂梁进行了Solidworks三维建模,基于ComsWorks进行了静态和模态分析.分析表明,微磨料水射流切割机床悬臂梁固有一阶、二阶、三阶和四阶频率分别为20Hz、31Hz、91Hz和104Hz.为了避免引起共振,负载频率应以一定幅度错开其固有频率.现有悬臂梁结构具有足够的刚度.     

An investigation into superficial embedment in mirror-like machining using abrasive jet polishing

This study performs experimental investigation into the application of abrasive jet polishing (AJP) to the surface finishing of electrical-discharge-machined SKD61 mold steel workpieces. The results indicate that the AJP processing conditions which optimize the surface quality of the SKD61 workpiece when polishing using #2000SiC abrasives are as follows: an abrasive material to additive ratio of 1:2, an impact angle of 30°, a gas pressure of 4 kg/cm² (0.4 MPa), a nozzle-to-workpiece height of 10 mm, a platform rotational velocity of 200 rpm, and a platform travel speed of 150 mm/s. Under these processing conditions, a polishing time of 20 min is sufficient to reduce the surface roughness from an initial value of Ra?=?1.7 μm to a final value of Ra?=?0.27 μm, corresponding to an improvement of 84.12%. The experimental results demonstrate that the maximum attainable improvement in the surface quality of the polished workpiece is limited by a surface-hardening effect caused by the ball-impact phenomenon and the embedment of #2000SiC fragments in the workpiece surface.     

Numerical simulation for abrasive water jet machining based on ALE algorithm

In dealing with fluid impact and large deformation problems by traditional Lagrange grid, calculation failure often happens due to grid distortion. An abrasive water jet machining model is created to simulate the whole stage by software LS-DYNA from the jet into the nozzle to the workpiece material removal process using ALE (Arbitrary Lagrange–Euler) algorithm. The mesh for the abrasive and water is based on the ALE formulation, while the target mesh applies the Lagrange formulation. The effect of jet penetration is implemented by coupling the grids of ALE and Lagrange. The jet traverse speed is achieved by definition of the movement of ALE grid to reduce the mesh domain. The abrasive constitutive equations are also presented in this paper. The uniform mixture for abrasive and water is achieved by definition of volume percentage of the two materials in the initial ALE elements. Simulation results give the relationships between processing parameters and the cutting depth. The good agreement between simulation results and experimental data verifies the correctness of the simulation.     

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.     

Effect of workpiece properties on machinability in abrasive jet machining of ceramic materials

Abrasive jet machining (AJM), a specialized form of shot blasting using fine-grained abrasives, is an attractive micro-machining method for ceramic materials. In this paper, the machinability during the AJM process is compared to that given by the established models of solid particle erosion, in which the material removal is assumed to originate in the ideal crack formation system. However, it was clarified that the erosion models are not necessarily applicable to the AJM test results, because the relative hardness of the abrasive against the target material, which is not taken into account in the models, is critical in the micro-machining process. In contrast to conventional erosion by large-scale particles, no strength degradation occurs for the AJM surface, which is evidence that radial cracks do not propagate downwards as a result of particle impacts.     

Finishing effect of abrasive flow machining on micro slit fabricated by wire-EDM

This experimental research use the method of abrasive flow machining (AFM) to evaluate the characteristics of various levels of roughness and finishing of the complex shaped micro slits fabricated by wire electrical discharge machining (Wire-EDM). An investigative methodology based on the Taguchi experimental method for the micro slits of biomedicine was developed to determine the parameters of AFM, including abrasive particle size, concentration, extrusion pressure and machining time. The parameters that influenced the machining quality of the micro slits were also analyzed. Furthermore, in the shape precision of the micro slit fabricated by wire-EDM and subsequently fine-finished by AFM was also elucidated using a scanning electron microscope (SEM). The significant machining parameters and the optimal combinations of the machining parameters were identified by ANOVA (analysis of variation) and the S/N (-to-noise) ratio response graph. ANOVA was proposed to obtain the surface finishing and the shape precision in this study.     

微磨料水射流切割头装置设计与研究

传统磨料水射流切割头的磨料靠负压吸入,可靠性差、吸入不均匀、流量不能精确控制。采用螺杆泵输送原理,设计了一种新型微磨料水射流切割头装置及控制系统。该装置采用螺杆泵主动送料,螺杆由步进电机驱动,单片机发出的控制脉冲控制步进电机的转速,步进电机的转速与磨料流量一一对应,从而将磨料定量、连续地送到切割头混合腔,实现磨料流量的精确控制。在混合腔的排出通道上设置单向阀门,解决了喷嘴堵塞后高压水直接进入磨料罐引起磨料输送系统失效问题。     

Improvement of abrasive water jet machining accuracy for titanium and TiNb alloy

The International Journal of Advanced Manufacturing Technology - The paper is dealing with abrasive water jet (AWJ) cutting of titanium and titanium–niobium alloy. It contains comparison of...     

A new cutting depth model with rapid calibration in abrasive water jet machining of titanium alloy

Titanium alloys are widely used in the aeronautical and engineering fields as they show an excellent trade-off between the mass and mechanical properties, but as hard materials, they are difficult to machine using cutting tools. The abrasive water jet affords a good solution to produce titanium parts, especially slim ones. To do so, there is a need to adopt a modelling approach for the depth milled. However, a general methodology that takes into account all the parameters leads to complex models based on a large number of experiments. The present article proposes a depth of cut model combined with a rapid calibration method. The case addressed is that of open rectangular pockets on a Ti-6AL-4V titanium alloy. The approach introduces the machine configuration notion considering that a given machine, pressure level and abrasive impose the abrasive flow rate needed in order to obtain an optimal material removal rate. For a chosen configuration, calibration of the model is performed from a series of elementary passes and just three pocket machining passes. The method is rapid and effective as the accuracy of the models obtained over a number of configurations was to within the order of 5%.     

Productivity of abrasive water-jet machining

The productivity in abrasive water-jet machining of titanium alloys and heat-resistant alloys is discussed. Empirical formulas for the rate of metal removal as a function of the machining parameters are presented.     

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.     

Application of Taguchi design for quality characterization of abrasive water jet machining of TRIP sheet steels

In the present paper, the influence of sheet thickness, nozzle diameter, standoff distance, and traverse speed during abrasive water jet machining (AWJM) of transformation-induced plasticity (TRIP) sheet steels on surface quality characteristics (kerf geometry and surface roughness) was investigated. The experiments were designed using Taguchi methodology and carried out by AWJ Machining TRIP 700 CR-FH and TRIP 800 HR-FH steel sheets. As response variables, mean kerf width and average surface roughness were selected. The experimental results were analyzed using analysis of means and analysis of variance methods in order to correlate the AWJM process parameters the response variables. In addition, regression models were obtained using the experimental results and validated with six independent experiments. The reported results indicate that the proposed methodology can satisfactorily analyze the surface roughness and the mean kerf in AWJM; moreover, it can be considered as valuable tools for process planning in workshop.