特种加工技术及其应用研究

本文简述了特种加工技术的概念、分类,重点阐述了其领域的实际应用与研究发展方向。     

医械专业《特种加工》课程介绍及教学方法探索

针对我院开设的精密医疗器械专业《特种加工》课程,介绍了医学领域中常用的几种特种加工方法以及它们的典型应用。并根据《特种加工》课程学习中存在的问题,结合作者的实践经验,从多方面对如何改进教学方法进行了探索。     

虚拟现实技术在特种加工教学中的应用研究

根据特种加工实践教学的要求，以激光切割加工为例介绍了利用VRML进行加工模拟的步骤和方法。详细阐述了用VRML表现加工过程各种变化时用到的实时交互控制、信息处理和动态显示等技术，并给出了相应的程序代码，实现了激光切割的虚拟加工试验。采用基于网络的三维动态虚拟加工模拟，为特种加工的实践教学提供了理想的工具。     

基于SPH-FEM耦合算法的后混合磨料水射流冲击破岩数值模拟研究

采用SPH-FEM (smoothed particle hydrodynamics with finite element method)模拟了后混合磨料水射流在喷嘴中的混合过程,并研究了射流速度、磨料浓度以及岩石围压等因素对后混合磨料水射流破岩效果的影响规律.研究结果表明:在柱塞推动下,水与磨料在喷嘴的混合段、收敛...     

磨料水射流切割深度的数学模型

磨料水射流切割加工是一个受多参数影响的复杂过程，很难建立一个有效的理论切割深度模型，而现有经验模型由于工作参数的差异很难可靠应用。本文在实验基础上，对ZengJ的模型进行了修正。修正后的模型可用于工程实际。     

超硬材料的特种加工技术

超硬材料具有高硬度、高耐磨性等特点，使用传统的机械方法成型加工非常困难，特种加工技术具有以柔克刚、精密微细、仿形逼真等优点，是超硬材料或半导体新材料的有效加工方法。[编按]     

特种加工与机械制造工艺技术变革探讨

特种加工作为先进制造技术中的重要组成部分,对制造业的作用日益重要。特种加工方法就是将电、磁、声、光、化学等能量或其组合施加在工件的被加工部位上,从而实现材料被去除、变形、改变性能或被镀覆等的加工方法。特种加工具有区别于传统机械加工方法的一些特点：特种加工有多种加工方法：特种加工对机械制造及结构工艺性具有重大影响。     

Study the parametric effect of abrasive water jet machining on surface roughness of Inconel 718 using RSM-BBD techniques

This paper presents an experimental investigation to ascertain the parametric impact of abrasive water jet machining on the surface quality of Inconel 718 material. Experiments were designed according to response surface methodology-box Behnken design by maintaining three levels of four process parameters—abrasive flow rate, water pressure, stand-off distance and traverse speed. The surface irregularity is measured during machining. The design expert software was used to establish an optimized mathematical model of process parameters for achieving the required surface roughness. Desirability function has also been used to optimize the process parameters. The confirmation experiments validate the reliability and capability of the developed model. Further, the surface characteristics were analyzed through scanning electron microscope images and energy-dispersive X-ray spectroscopy.     

Multi-performance optimization of abrasive water jet machining of Inconel 617 using WPCA

Inconel 617 is a hard-to-machine material used for various high-temperature components like headers, pipes and turbine blades in ultra-supercritical power plants. This material necessitates nontraditional machining methods. The processing of these alloys using abrasive water jet machining (AWJM) needs attention. This paper details the multi-response optimization in the AWJM of Inconel 617 using weighted principal components analysis (WPCA). The significant process parameters are water pressure, abrasive flow volume, standoff distance and table feed. The performance characteristics are material removal rate (MRR), circularity, cylindricity, perpendicularity and parallelism. Multi-performance optimization is performed using the weighted principal component analysis method. Mean response tables are developed and plotted and the optimal factor levels for the best values of the objectives are reported. The developed technique shows flexibility as different responses with different weightages based on the product application could be tested and established.     

Investigation of multiple process parameters in abrasive water jet machining of tiles

This paper discusses the optimization of an abrasive water jet machining process with multiple characteristics, using the Taguchi orthogonal array and grey relational analysis (GRA). The machining process variables, such as mesh size, nozzle diameter, abrasive flow rate, water pressure, stand-off distance, and feed rate, were optimized with respect to multiple performance characteristics, namely, the surface roughness and the kerf angle. Experiments were performed using an L₁₈ orthogonal array, and the optimum machining process variables were determined, using GRA. Analysis of variance was used to identify the most significant factor in the machining performance. A confirmatory test was performed to verify the improvement of the performance characteristics. The microstructure of the machined surfaces was also examined by scanning electron microscopy and atomic force microscopy. The results showed that the surface roughness and kerf angle were minimized under optimal machining conditions.     

Investigation on performance of abrasive water jet in machining hybrid composites

For machining of composites, abrasive water jet machining is widely employed. For assembly of the machine tool structure, production of slots is essential. In this paper, abrasive water jet machining of composite laminates was experimentally investigated for various cutting parameters in terms of average surface roughness (R_a) and kerf taper (K_t). By generating a response surface model, the experimental values obtained for quality characteristics (R_a and K_t) were empirically related to cutting parameters. The effects of cutting parameters on quality characteristics were analyzed by utilizing empirical models and also optimized within the tested range based on desirability approach. The optimum parameter levels were also validated by confirmation test. From this investigation, it is evident that for obtaining a minimum kerf taper, traverse speed, water pressure, and abrasive mass flow rate are significant parameters and for obtaining less surface roughness traverse speed is the significant parameter.     

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.     

An investigation on cutting quality by adding polymer in abrasive water jet

ABSTRACT

An experimental investigation is presented to improve the cutting quality in abrasive water jet (AWJ) cutting of marble by an addition of polyacrylamide (PAM). Considering experimental data, the kerf widths have a remarkable change when the PAM concentration approaches to 400 ppm. The deviation between top and bottom kerf width reaches the minimal value when PAM concentration is equal to about 600 ppm. In addition, the surface topography analyses illustrate that an addition of PAM can broaden the cutting wear zone and make the cutting quality better. Furthermore, the effects of PAM on the surface roughness are assessed by a profilometer. It is eventually found that the surface roughness decreases initially and then increases greatly with the increase of the depth of cut. Additionally, the minimum surface roughness occurs when the PAM concentration is 600 ppm, which agrees well with the experimental result of kerf width. An increasing stand-off distance or traverse speed produces a higher surface roughness.     

Surface texturing on SiC by multiphase jet machining with microdiamond abrasives

The multiphase microabrasive jet machining is a new type of surface texturing technique using compressed air to accelerate the mixtures of abrasive and water to remove material. It is effective for surface texturing on different materials, and can also reduce the pollution and cost by recycling the microabrasive particles easily. Basing on this technique and using the micro synthetic diamond as the abrasive, a multiphase jet technique is developed for machining on silicon carbide (SiC) surfaces. The processing results are compared to other abrasives, and influences of the processing parameters such as jet distance, jet pressure, abrasive concentration, particle size, and jet angle are investigated experimentally. The improvement on machining quality and efficiency are confirmed.     

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。     

45CrNiMoVA高速切削条件下本构关系建模技术研究

为建立连续介质材料高速切削的材料本构关系模型,以45Cr Ni Mo VA材料为研究对象,通过准静态扭转试验和直角自由切削试验相结合的方法,建立了满足高速切削仿真要求的45Cr Ni Mo VA材料的Johnson-Cook本构模型.采用建立的Johnson-Cook本构模型参数,利用ABAQUS有限元分析软件建立了直角自由切削的有限元模型,对切削过程中的切屑厚度、主切削力、进给抗力进行了仿真,并将仿真预测值同试验测量值进行了对比.结果表明:由于切削仿真过程中刀具不存在磨损,进给抗力的仿真误差较大;主切削力和切屑厚度的仿真预测值与试验测量值的误差在10%之内,模型的准确度较好.最后,利用VB和C语言,开发了Johnson-Cook材料本构集成建模系统,并验证了其使用效果的实用性.     

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.