A study on the use of single mesh size abrasives in abrasive waterjet machining

This paper details the studies on the use of single mesh size garnet abrasives in abrasive waterjet machining for cutting aluminum. The influence of three different single mesh size abrasives, pressure, traverse rate, and abrasive flow rate; on depth of cut, top kerf width, bottom kerf width, kerf taper, and surface roughness are investigated. Experiments designed using standard L9 orthogonal array and the analysis of variance helped in the determination of highly significant, significant and weakly significant cutting parameters. Single mesh size abrasives are found to yield decreased surface roughness than multi mesh size abrasives. Based on these studies, response equations are developed to predict the target parameters. Using single mesh abrasives, a practitioner not only can cut faster but also achieve reduced surface roughness.     

Hermite五坐标数控加工刀位算法研究

复杂自由曲面五坐标刀位优化问题一直是数控加工领域的一个热点问题，该问题的解决对于显著提高国防和民用工业中重要零件的加工质量和加工效率具有重要意义。Hermite27位算法和MPM算法是国际上最近提出的2种最先进的五坐标27位优化算法。作者给出了2种算法的完整数学模型，将Hermite算法与MPM算法进行了比较研究，从理论上对2种算法解的一致性进行了证明，对2种算法求解过程的重要差别进行了比较，对Hermite算法的求解过程进行了改进，并通过2个实例验证了所提出的改进算法的可行性。     

Optimization of abrasive waterjet machining using multi-objective cuckoo search algorithm

Abrasive waterjet (AWJ) machining is widely applied in the fields of civil and mechanical engineering. In this study, a general and theoretical analysis procedure was presented before computing application. It mainly focused on the kinetic energy model and wear rate model in machining process. Then, the multi-objective cuckoo algorithm was employed for optimization design of AWJ cutting head model, making sure to maximize the output energy and minimize the nozzle erosion rate while keeping the other factors constant. To demonstrate the effectiveness of the above strategy, a practical AWJ machining system was selected for investigation purpose. The proposed model was compared with experimental data for investigating the difference between the initial design and the optimized model. The results showed that the multi-objective cuckoo algorithm has great ability in prediction of outlet power and wear rate. Meanwhile, the optimized parameters were also superior to the original design, compared with experimental test data. The developed model can be used as a systematic approach for prediction in an advanced manufacturing process.     

Inertia effect in squeeze film air contact

The analysis presented in this paper explores the effect of air inertia on the squeeze film air contact operation and assesses the contribution of air inertia to the mechanism of squeeze film formation. Derivation of the Reynolds equation containing inertia term for squeeze film air contact is outlined. An average inertia concept is used in dealing with inertia force across the squeeze film thickness. Numerical iteration is used in solving for the non-linear inertia term in the modified Reynolds equation. Results are compared with the performance of the squeeze film air contact without inertia.     

Material removal in abrasive waterjet machining of metals Surface integrity and texture

An experimental study was conducted to determine the influence of material properties on the surface integrity and texture that results from abrasive waterjet (AWJ) machining of metals. A microstructure analysis, microhardness measurements, and profilometry were used in determining the depth of plastic deformation and surface texture that result from material removal. Models now available for dry abrasive erosion were adopted and found useful in understanding the influence of material properties on the hydrodynamic erosion process. It was found that the depth of subsurface plastic deformation is inversely proportional to a metals strength coefficient and extends the greatest depth near jet entry in the initial damage region (IDR). Furthermore, surface skewness in AWJ machining of metals increases with ductility and the corresponding critical strain for lip formation.     

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.     

ANFIS modeling of surface roughness in abrasive waterjet machining of carbon fiber reinforced plastics

Journal of Mechanical Science and Technology - This study discusses the development of an Adaptive neuro–fuzzy inference system (ANFIS) model for determining the surface roughness (Ra) during...     

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.     

磨料水射流加工技术的应用展望

磨料水射流（AWJ）加工技术作为一门新兴的特种加工技术与其他加工技术相比具有很多优点。这里论述了通过有关加工机理模型的建立和设备的改进以及合理的操作方法,能使磨料水射流技术的优点充分发挥出来的方法。     

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.     

Particle movement patterns and their prediction in abrasive flow machining

Abrasive particle movement pattern is an important factor in estimating the wear rate of materials, especially, as it is closely related to the burring, buffing and polishing efficiency of the abrasive flow machining (AFM) process. There are generally two kinds of particle movement patterns in the AFM process, i.e. sliding–rubbing and rolling. In mechanism, AFM grain–workpiece interaction is taking place in any one or a combination of the possible modes: elastic/plastic deformation by sliding–rubbing grain movement; elastic/plastic deformation by rolling grain movement; chip formation (micro‐cutting) by rubbing grain movement; ridges formation by rubbing and rolling grain movement; and low‐cycle fatigue wear. Therefore, the machining efficiency of a machine part is predominantly dependent upon the particle movement patterns. In this paper, normal load, particle size and hardness of machine parts were investigated to understand the involved parameters of particle movement patterns and propose a computer statistic prediction of particle movement patterns. It has been found that there are two cases. In case of large‐size particles, the ratio of rolling particles is increased with increasing normal load. For small‐size particles, the ratio of grooving particles is increased with increasing normal load and vice versa. When normal load is light, the particle size cannot usually give an effect on movement patterns. That influence will be predominant under heavy normal load. Most of the particles will tend to groove when the particle size is below a certain value. Hardness of the material and their hardness difference for tribological pairs are other important monitors in predicting particle movement patterns. In this research, increasing hardness of materials results in more rolling particles, which results in much less cutting particles. Copyright © 2007 John Wiley & Sons, Ltd.     

Deburring of burrs in spring collets by abrasive flow machining

Micro burrs occurring inside the small and large diameters adversely affect the properties of products. Manual deburring of micro burrs in particular damages the processed surface and reduces production efficiency. In this study, spring collets made of chrome-molybdenum are used to test the deburring of the surface of collets including crossed micro grooves by abrasive flow machining. This revised version was published online in October 2004 with a correction to the issue number.     

磨粒流精密光整加工的微切削机理

利用磨粒流的流变特性,通过对应力张量的分析,研究了磨粒流加工中的微切削力。提出了磨粒流加工是兼挤压与微去除方式为一体的复合加工,微切削动力主要来自于磨粒挤压力、磨粒的犁削力及磨料介质的剪切力。建立了磨粒流动力学模型,通过改变磨粒流流道的加工条件和测试加工过程的接触区压力、去除量及表面粗糙度等参数,用量化的方式揭示了磨粒流加工中抽象微切削力的变化规律。最后,结合COMSOL Multiphysics软件的CFD模块数值仿真了剪切力。结果显示:基于加模芯的方法有效地提高了磨粒流加工的微切削力,滑块4经15次循环后表面粗糙度由加工前的2.918μm下降为1.027μm,而去除量下降了0.09g。实验表明,磨粒流加工中去除量确有变化,但随着加工次数增加去除作用迅速削弱,而表面粗糙度在挤压力的作用下仍有所降低。     

Prediction of surface roughness in abrasive waterjet machining of particle reinforced MMCs using genetic expression programming

Machining of particle-reinforced metal matrix composites has been considerably difficult due to the extremely abrasive nature of the reinforcements that causes rapid tool wear and high machining cost. Abrasive water jet (AWJ) machining has proven to be a viable technique to machine such materials compared to conventional machining processes. The present study is focused on the surface roughness of AWJ cut surfaces and genetic expression programming (GEP) was proposed to predict surface roughness in AWJ machining of 7075 Al alloy composites reinforced with Al₂O₃ particles. In the development predictive models, characteristics of materials such as size and weight fraction of reinforcement particles, and depth of cut were considered as model variables. The training and testing data sets were obtained from the well-established machining test results. The weight fraction of particle, size of particle, and depth of cut were used as independent input variables, while arithmetic mean of surface roughness, maximum roughness of profile height, and mean spacing of profile irregularity as dependent output variables. Different models for the output variables were predicted on the basis of training data set using GEP and accuracy of the best model was proved with testing data set. The test results showed that output variables increased with increasing input variables. The predicted results were compared with experimental results and found to be in good agreement with the experimentally observed ones.     

模具结构化表面SAF精密光整技术

针对模具结构化表面难以采用传统抛光工具实现精密光整加工的问题,提出了一种基于软性磨粒流(SAF)的模具结构化表面无工具精密加工新技术.该技术通过约束模块与结构化表面组合构成特定形状的磨粒流流道,利用SAF在流道中的湍流流动使磨粒对结构化表面进行微力微量切削,进而实现光整加工.介绍了SAF加工技术原理、SAF流体力学特征...     

Effects of process parameters on surface roughness in abrasive waterjet cutting of aluminium

Abrasive waterjet cutting is a novel machining process capable of processing wide range of hard-to-cut materials. Surface roughness of machined parts is one of the major machining characteristics that play an important role in determining the quality of engineering components. This paper shows the influence of process parameters on surface roughness (R_a) which is an important cutting performance measure in abrasive waterjet cutting of aluminium. Taguchi’s design of experiments was carried out in order to collect surface roughness values. Experiments were conducted in varying water pressure, nozzle traverse speed, abrasive mass flow rate and standoff distance for cutting aluminium using abrasive waterjet cutting process. The effects of these parameters on surface roughness have been studied based on the experimental results.     

Optimization of machining parameters in the abrasive waterjet turning of alumina ceramic based on the response surface methodology

A study on the radial-mode abrasive waterjet turning (AWJT) of 96 % alumina ceramic is presented and discussed. An experimental investigation is carried out to explore the influence of process parameters (including water pressure, jet feed speed, abrasive mass flow rate, surface speed, and nozzle tilted angle) on the material removal rate (MRR) when turning 96 % alumina ceramic. The experiments are conducted on the basis of response surface methodology (RSM) and sequential approach using face-centered central composite design. The quadratic model of RSM associated with the sequential approximation optimization (SAO) method is used to find optimum values of process parameters in terms of surface roughness and MRR. The results show that the MRR is influenced principally by the water pressure P and the next is abrasive mass flow rate m _a . The optimization results show that the MRR can be improved without increasing the surface roughness when machining 96 % alumina ceramic in the radial-mode abrasive waterjet turning process.     

圆环面刀具五坐标数控加工复杂曲面刀位算法分析

对圆环面刀具五坐标数控加工复杂曲面编程方法进行了综述 ,指出大多数算法仍采用仅适用于点接触加工的以局部微分几何为基础的刀位算法。本文证明了这些算法的缺陷 ,提出了一种针对圆环面刀具的五坐标数控宽行加工复杂曲面的刀位计算的思想。     

基于oldroyd-B本构模型的磨料流加工壁面滑移仿真分析

基于oldroyd-B粘弹性本构模型,应用POLYFLOW软件对流体磨料在圆管中的壁面滑移状态进行了模拟仿真。将得到的圆管中流体磨料的压力值与磨料流加工机床上测试点的压力值进行比较,得到二者的相对误差不超过5%,验证了模拟仿真的可行性。通过仿真可知,流体磨料在工件壁面上的滑移存在速度临界点。通过比较不同管道入口流量、流体磨料黏度和壁面滑移系数对壁面滑移速度的影响可知,当管道入口流量越大、流体磨料的黏度越高,以及壁面滑移系数越小时,加工过程中的壁面滑移速度越大。