A note of hybrid GR-SVM for prediction of surface roughness in abrasive water jet machining: a response

This paper is the responses for a note submitted by Dr. Antoni Wibowo based on the article entitle “Hybrid GR-SVM for prediction of surface roughness in abrasive water jet (AWJ) machining”. The author of the note pointed out some problems in the original paper. The paper presented a proposed hybridization approach of grey relational analysis and support vector machine in predicting surface roughness (Ra) in AWJ machining. We deny all the claims given by Dr. Wibowo based on the justifications stated in this paper.     

Hybrid GR-SVM for prediction of surface roughness in abrasive water jet machining

This paper presents a hybridization model of support vector machine (SVM) and grey relational analysis (GRA) in predicting surface roughness value of abrasive water jet (AWJ) machining process. The influential factors of five process parameters in AWJ, namely traverse speed, water jet pressure, standoff distance, abrasive grit size and abrasive flow rate, need to be analyzed using GRA approach. Then, the irrelevance factors of process parameters are eliminated. There is a need of determining the influential factors of process parameters to the surface roughness as to develop a robust prediction model. GRA acts as feature selection method in preprocessing process of hybrid grey relational-support vector machine (GR-SVM) prediction model. Efficiency of the proposed model is demonstrated. GR-SVM presents more accurate result than conventional SVM as it removes the redundant features and irrelevant element from the experimental datasets.     

珩磨缸套表面粗糙度预测及多目标优化研究

为了对粗珩阶段缸套内孔表面粗糙度Rk粗糙度集中的Rk、Rpk和Rvk进行预测,进而对粗珩加工参数进行优化,以珩磨压力(P)、珩磨头旋转速度(VR)和往复速度(VRe)为决定因素,Rk粗糙度集为目标响应,进行多目标优化.建立基于广义回归神经网络(Generalized regression neural network, GRNN)与响应曲面法(Response surface methodology,RSM)的粗糙度预测模型,并采用三因素三水平的全因子珩磨试验进行验证,结果表明所建立模型的预测结果与试验结果具有很好的一致性. GRNN预测模型决定系数R²的均值为0.959,RSM多元回归预测模型决定系数R²的均值为0.963,与RSM所建立的多元回归预测模型相比,GRNN预测模型在预测Rk和Rpk时,预测精度更高,预测误差更小,R²分别提高了0.025和0.020,在预测Rvk时RSM多元回归模型更优,R²提高了0.057.进一步结合响应曲面法分析了3个决定因素对粗糙度的影响显著性并进行了排序,对于...     

Investigation of displacement fields in an abrasive waterjet drilling process: Part 1. Experimental measurements

The transient state of displacement fields in the machining zone of a target material during abrasive waterjet impinging and drilling was investigated. A moiré interferometry experimental setup for recording displacement fields and a dynamometer for measuring the reaction force were developed. Whole fields of surface displacement fields and the reaction force of the ceramic and polycarbonate target materials were successfully recorded when the specimen was being pierced by high-pressure abrasive waterjet (AWJ). This paper demonstrates that bothu andv displacement fields of a workpiece during AWJ drilling can be recorded in real time and simultaneously by the moiré interferometry experimentation. The measured surface displacement distributions and the machining forces will be used to drive a finite element model in the second part of this investigation, in which the authors study the stress and strain state for the target material associated with the jet-materials interaction during the jet penetration process.     

Investigation of displacement fields in an abrasive waterjet drilling process: Part 2. Numerical analysis

In this paper, the displacement fields associated with the abrasive waterjet (AWJ) drilling process were simulated using the finite element method. A threedimensional finite element model was established, and justifiable pressure loads were used in the numerical model to simulate the AWJ drilling process. It was assumed that the pressure load in the AWJ could be resolved into three components, such as impact jet pressure, shear and normal pressure. The effect of these three pressure loads and their magnitudes on the surface displacement were investigated as a function of the jet penetration depth through numerical modeling. Using the hybrid experimental-numerical stress analysis approach, the transient state of stress and strain associated with the notch crest of the jet-induced hole at the impingement zone of the target material during AWJ piercing can be modeled numerically. It was found that the shear contributed the most in shaping the displacement contour patterns and that the jet pressure did not play a dominant role in determining theu field displacement. The jet pressure and shear had the most effect on thev field displacement contour pattern. It was demonstrated that the principal stresses at the bottom of the cavity increase as the depth of the hole increases.     

薄膜多层滚压的表面粗糙度晶体学分析

提出了晶体学模型来研究多层薄膜滚压的表面粗糙度。研究了单层滚压模型,提出滚压的三维模型和二维模型（平面应变）,讨论了晶粒大小和应力状态的影响。把单个单层滚压和多层滚压模型、三维模型和平面应变模型进行了比较,发现对于所涉及的二维和三维模型来说,单层滚压和多层滚压模型并无明显的差别。因此在这些情况下,可以用单个单层滚压模型来代替多层滚压模型从而节省CPU时间。     

表面粗糙度对TC4钛合金柱壳剪切带形成的影响

剪切带是材料在高应变率加载条件下特有的变形和损伤形式之一,关于影响金属材料中剪切带形成的敏感性因素及其机理的研究,一直是科学研究和工程设计中关注的重点问题. 在柱壳高速坍塌过程中,剪切带优先在内表面形核, 其形核及扩展行为受内表面介观状态的影响显著.本文采用爆轰加载厚壁圆筒坍塌实验技术,结合材料表面处理技术、微结构表征技术和剪切带理论模型分析,研究了内表面粗糙度变化对TC4钛合金柱壳剪切带形成影响的细观动力学规律.结果表明, 在爆炸加载形成的高应变率条件下,表面粗糙度对TC4钛合金柱壳中剪切带形成具有明显影响. 在相同的变形条件下,随着试样内表面粗糙度的增大, 剪切带数量、长度和形核速率均增大;表面粗糙度越大, 部分剪切带扩展速率越快, 剪切带长度差异越大,剪切带的屏蔽效应增强. 分析表明,实验获得的剪切带间距与W-O模型和M模型预测结果基本吻合,具体数值受试样内表面粗糙度影响, 随着表面粗糙度的增大,实验结果逐渐小于预测数值.      

Frictional pressure drop during vapour–liquid flow in minichannels: Modelling and experimental evaluation

Condensation in minichannels is widely used in air-cooled condensers for the automotive and air-conditioning industry, in heat pipes and other applications for system thermal control. The knowledge of pressure drops in such small channels is important in order to optimize heat transfer surfaces. This paper presents a model for calculation of the frictional pressure gradient during condensation or adiabatic liquid–gas flow inside minichannels with different surface roughness. In order to account for the effects of surface roughness, new experimental frictional pressure gradient data associated to single-phase flow and adiabatic two-phase flow of R134a inside a single horizontal mini tube with rough wall has been used in the modelling. It is a Friedel (1979) [Friedel, L., 1979. Improved friction pressure drop correlations for horizontal and vertical two-phase pipe flow. In: Proceedings of the European Two-Phase Flow Group Meeting, Ispra, Paper E2] based model and it takes into account mass velocity, vapor quality, fluid properties, reduced pressure, tube diameter, entrainment ratio and surface roughness. With respect to the flow pattern prediction capability, it has been built for shear dominated flow regimes inside pipes, thus, annular, annular-mist and mist flow are here predicted. However, the suggested procedure is extended to the intermittent flow in minichannels and it is also applied with success to horizontal macro tubes.     

Optimization of cutting conditions for end milling of Ti6Al4V Alloy by using a Gravitational Search Algorithm (GSA)

Surface roughness is commonly used to indicate the quality of machine parts. Optimizing cutting parameters throughout the machining process is an important aspect for manufacturers, as it allows them to achieve a minimum surface value. During this study, a new optimization technique known as the gravitational search algorithm (GSA) was employed in order to achieve minimum surface roughness when end milling a Ti6Al4V alloy under dry cutting conditions, with both PVD coated and uncoated cutting tools. Regression models have been created based on the results of real experimental data. Through use of SPSS software, it was possible to formulate the objective (fitness) functions which were used in the GSA optimization for each cutting tool. A MATLAB code was then created to instigate the optimization process. The results indicated that high cutting speed and low feed rate and depth of cut could result in a minimum surface roughness value of (0.6255 μm), based on the objective function for the PVD cutting tool. Alternatively, surface roughness of around (0.4165 μm) could be achieved by using an uncoated tool on a lower feed rate, depth of cut and cutting speed. The same GSA technique was used in another case study optimized by Genetic algorithm (GA). The GSA achieved the same results, and proved that it is faster than GA: GSA could reach the optimum solution in the third iteration; GA could only reach it in the 67th.     

Surface-roughness measurement using dry friction noise

A new technique for determining surface roughness is introduced. It is based upon measuring the generated noise due to dry friction of a metallic blade which travels over the surface under consideration. If the frictional force is made small enough to excite the blade, and not the entire system, then the noise will be proportional to surface roughness, and independent of the measured specimen size and material. A prototype acoustic device was designed and constructed and then used to substantiate the technique. Several specimens were machined by different machining processes to obtain a wide range of roughnesses. The specimen surface roughness was measured by a widely used commercial instrument (Talysurf 10), and the prototype transducer. A straight line correlation (on a logarithmic graph) between sound pressure levels (SPL), obtained from the transducer, and roughnesses, obtained from the Talysurf instrument, was found over the range from 0.025 to 100 m. The coefficient of correlation between the measured values of SPL and roughness was as high/as 98 percent. Therefore, the technique could be adopted for measuring roughness and the prototype may thus be considered as a new roughness measuring device.The prototype device has the advantages of being sensitive, accurate and compact. It also has the capability of measuring the roughness of almost any type of surface regardless of its shape, material and complexity. Hence it is considered adequate for most engineering applications.     

淹没磨料射流研究进展及冲击特性试验研究

本文简要回顾了非淹没磨料射流技术与人工淹没环境条件理论的发展与应用，认为将磨料射流引入水下加工领域是一种新的尝试，通过介绍国内外的一些相关研究，充分显示了淹没磨料射流的潜在优势，在此基础上，提出一套淹没磨料射流的模拟装置，实现了在实验室进行模拟大水深环境的淹没磨料射流性能试验。     

Al2O3陶瓷引弧微爆炸加工温度场模拟

建立了Al2O3陶瓷引弧微爆炸加工(micro-detonationofstrikingarcmachining,MDSAM)过程的 传热模型,基于有限元理论,利用ANSYS软件对加工过程中的温度场分布进行了模拟。结合材料性质,对模 拟和实验得到的蚀坑尺寸进行了比较,并分析了加工参数对温度场的影响。模拟结果表明,Al2O3陶瓷引弧 微爆炸加工时在给定的加工参数下的最高温度可达13435℃,且高温影响区范围很小,加工实验与模拟结果 符合较好。随着脉冲宽度和工作电流的增加,加工区域的温度以及蚀坑的半径和深度增大;随着喷嘴半径的 增大,加工区域的温度降低而蚀坑的径深比增大。模拟结果可为Al2O3 陶瓷引弧微爆炸加工过程中表面形 貌的预测、材料去除机理的揭示以及加工参数的选择等提供参考。     

一套预测冰面上汽车牵引力的模型

根据传热学中的热平衡原理及冰的摩擦经理论，建立了冰面汽车牵引力的预测模型。研究表明：所建立的理论模型比已有的模型更接近实际，从摩擦学角度系统分析了汽车工作条件和环境因素以及表面粗糙度等对牵引力的影响，提出了今后研究中有待解决的几个问题。     

Passive vibration absorber effect on the machining surface quality of a flexible workpiece

This paper presents a study of the vibratory behaviour of a flexible workpiece subject to a milling end operation. Indeed, this vibratory behaviour is critical, especially when the excitation frequency is near to the resonance. For this reason, passive vibration suppression is considered in order to attenuate the dynamic response of the milled workpiece and decrease the dynamic effect on the resulting machined surface roughness and flatness. In order to confirm the efficiency of the passive vibration suppression, the vibratory behaviour and the quality (roughness and flatness) of a machined surface are studied without and with passive absorber (TMD) using a finite-element model.     

Heat transfer in pool boiling of binary and ternary non-azeotropic mixtures

Heat transfer coefficients in nucleate pool boiling of binary and ternary non-azeotropic hydrocarbon mixtures were obtained experimentally using a vertical electrically heated cylindrical carbon steel surface at atmospheric pressure with several surface roughness. The fluids used were Methanol/1-Pentanol and Methanol/1-Pentanol/1,2-Propandiol at constant 1,2-Propandiol mole fraction of 30%. Heat fluxes were varied in the range 25–235 kW/m². The cylindrical heater surface was polished to an average surface roughness of 0.2 μm, and sandblasted yielding surface roughness of 2.98 and 4.35 μm, respectively. The experimental results were compared to available prediction correlations, indicating that the correlations based on the boiling range are in better qualitative agreement than correlations based on the phase envelope. Increasing surface roughness resulted in an increase in the heat transfer coefficient, and the effect was observed to be dependent on the heat flux and fluid composition.     

The effects of surface roughness geometry of flow undergoing Poiseuille flow by molecular dynamics simulation

Numerical simulation of Poiseuille flow of liquid Argon in a rough nano-channel using the non-equilibrium molecular dynamics simulation is performed. Density and velocity profiles across the channel are investigated in which roughness is implemented only on the lower wall. The Lennard–Jones potential is used to model the interactions between all particles. The effects of surface roughness geometry, gap between roughness elements (or roughness periodicity), surface roughness height and surface attraction energy on the behavior of the flow undergoing Poiseuille flow are presented. Results show that surface shape and roughness height have a decisive role on the flow behaviors. In fact, by increasing the roughness ratio (height to base ratio), the slip velocity and the maximum velocity in the channel cross section are reduced, and the density fluctuations near the wall increases. Results also show that the maximum density near the wall for a rough surface is less than a smooth wall. Moreover, the simulation results show that the effect of triangle roughness surface on the flow behavior is more than the cylindrical ones.     

接触表面不平度对摩擦尖叫噪声的影响

针对摩擦尖叫的间歇性特点,建立了考虑摩擦接触表面不平度的3自由度摩擦自激振动机理模型.应用数值方法分析了接触表面不平度倾角对系统稳定性及瞬态动力学特性的影响,并进行了基于销-盘装置的摩擦尖叫噪声试验研究.结果表明:系统的稳定性主要取决于系统自身的耦合特性,但也与摩擦特性和接触表面不平度倾角的综合作用有关.当接触表面不平度倾角增大时,系统趋向不稳定,会激发尖叫噪声.     

高温发汗润滑膜覆盖率预测模型的研究

本文基于高温发汗自润滑材料的特征,建立了其润滑膜的覆盖率模型.利用广义W-M函数产生的粗糙表面,讨论了摩擦表面粗糙度、环境温度及材料参数等因素对发汗润滑膜覆盖率的影响.研究表明:通过降低摩擦表面粗糙度、提高基体材料孔隙率,固体润滑剂熔浸深度和环境温度可以增加摩擦表面边界润滑膜覆盖率,改善摩擦副的摩擦学性能.研究为高温发汗自润滑材料润滑控制及其摩擦副的设计提供理论依据.     

Complex microtopography analysis in sliding friction of steel-ferodo material pair

The tribological behaviour—friction, wear and lubrication—of machine elements highly depends on the operating state and also on the original topography of the working pair. Wear tests and 3D surface roughness measurements were carried out to analyse the effect of surface topography in friction and wear between ground steel specimens of various machining directions and different surface quality levels and a ferodo sliding pair. Three different techniques were used for surface topography evaluation: a parameter-based technique, a slicing method, and power spectral density analysis. Several parameters were found to be sensitive to surface wear phenomena; their changes indicate, among other things, surface platoing or the appearance of dominant scratches. The peak angle and height of asperities convey important information on numerous tribological changes. Power spectral density (PSD) analysis shows that the result of changes in the topography is an ‘equilibrium’ surface.     

润滑条件下铜锌合金表面粗糙度对磨损率的影响

采用基于原位全息显微技术和放射性核素技术的试验装置对润滑条件下的Cu Zn36和100Cr6进行了摩擦磨损试验,分析了Cu Zn36在试验过程中的摩擦磨损特性,以及摩擦系数、磨痕表面粗糙度和实时磨损率之间的关系,进而建立了关于表面粗糙度的磨损模型,并通过拟合优度方法对磨损模型进行了评价.结果表明:在试验磨合的初始阶段,Cu Zn36表面平整性被迅速破坏而产生了较高的磨损率,随着试验的进行,磨痕表面的强化层逐渐形成,表面粗糙度和实时磨损率逐渐降低并趋于稳定.磨损模型的拟合优度R2的计算结果为90.23%,说明建立的磨损模型能够对给定工况下的实时磨损率进行较为准确的预测.