Development of tool-path generation module for 5-axis control machining of impellers

An impeller is difficult to machine because of severe collision due to the complex shape,overlapping and twisted shape of the impeller blades.So,most computer aided manufacturing(CAM)software companies have developed CAM module for manufacturing impeller according to their CAM software.But these dedicated modules are difficult to use for inexperienced users.The purpose of this work is to develop a tool-path generation module for impellers.For this purpose,it is based on Visual Basic language and used CATIA graphical environment.The result of simulation for generated tool-path by the module is satisfactory.And it has slow processing speed compared to other commercial modules,but it is easy to use.

A Real-time NURBS Surface Interpolator for 5-axis Surface Machining

A real-time non-uniform rational B-spline （NURBS） surface interpolator is proposed and 5-axis machining method with a flat-end cutter is discussed. With the Taylor expansion and the coordinate transformation, the algorithms of NURBS interpolation, cutter effective machining radius, cutter offsetting and.inverse kinematics are deduced and implemented, respectively. Different from the conventional free-form surface machining, the proposed interpolator can real-time generate the motion commands of computer numerical control （CNC） machines with CC feedrate, rather than that of CL. An example part surface is demonstrated and the results of simulation show that the proposed method can be applied in actual 5-axis surface machining.

MOTION ERROR ESTIMATION OF 5-AXIS MACHINING CENTER USING DBB METHOD

In order to estimate the motion errors of 5-axis machine center, the double ball bar （DBB） method is adopted to realize the diagnosis procedure. The motion error sources of rotary axes in 5-axis machining center comprise of the alignment error of rotary axes and the angular error due to various factors, e.g. the inclination of rotary axes. From sensitive viewpoints, each motion error is possible to have a particular sensitive direction in which deviation of DBB error trace arises from only some specific error sources. The model of the DBB error trace is established according to the spatial geometry theory. Accordingly, the sensitive direction of each motion error source is made clear through numerical simulation, which is used as the reference patterns for rotational error estimation. The estimation method is proposed to easily estimate the motion error sources of rotary axes in quantitative manner. To verify the proposed DBB method for rotational error estimation, the experimental tests are carried out on a 5-axis machining center M-400 （MORISEIKI）. The effect of the mismatch of the DBB is also studied to guarantee the estimation accuracy. From the experimental data, it is noted that the proposed estimation method for 5-axis machining center is feasible and effective.

Understanding the hydrogen evolution reaction activity of doped single-atom catalysts on two-dimensional GaPS_(4) by DFT and machine learning

As a zero-carbon fuel,hydrogen can be produced via electrochemical water splitting using clean electric energy by the hydrogen evolution reaction(HER)process.The ultimate goal of HER catalyst is to replace the expensive Pt metal benchmark with a cheap one with equivalent activities.In this work,we investigated the possibility of HER process on single-atom catalysts(SACs)doped on two-dimensional(2D)GaPS_(4)materials,which have a large intrinsic band gap that can be regulated by doping and tensile strain.Based on the machine learning regression analysis,we can expand the prediction of HER performance to more catalysts without expensive DFT calculation.The electron affinity and first ionization energy are the two most important descriptors related to the HER behavior.Furthermore,constrain molecular dynamics with solvation models and constant potentials were applied to understand the dynamics barrier of HER process of Pt SAC on GaPS_(4)materials.These findings not only provide important insights into the catalytic properties of single-atom catalysts on GaPS_(4)2D materials,but also provides theoretical guidance paradigm for exploration of new catalysts.

Development of practical postprocessor for 5-axis machine tool with non-orthogonal rotary axes

In order to develop a practical postprocessor for 5-axis machine tool,the general equations of numerically controlled(NC) data for 5-axis configurations with non-orthogonal rotary axes were exactly expressed by the inverse kinematics,and a windows-based postprocessor written with Visual Basic was developed according to the proposed algorithm.The developed postprocessor is a general system suitable for all kinds of 5-axis machines with orthogonal and non-orthogonal rotary axes.Through implementation of the developed postprocessor and verification by a cutting simulation and machining experiment,the effectiveness of the proposed algorithm is confirmed.Compatibility is improved by allowing exchange of data formats such as rotational total center position(RTCP) controlled NC data,vector post NC data,and program object file(POF) cutter location(CL) data,and convenience is increased by adding the function of work-piece origin offset.Consequently,a practical post-processor for 5-axis machining is developed.

Constitutive Modeling for Ti-6Al-4V Alloy Machining Based on the SHPB Tests and Simulation

A constitutive model is critical for the prediction accuracy of a metal cutting simulation. The highest strain rate involved in the cutting process can be in the range of 104-106 s 1. Flow stresses at high strain rates are close to that of cutting are difficult to test via experiments. Split Hopkinson compression bar （SHPB） technology is used to study the deformation behavior of Ti-6Al-4V alloy at strain rates of 10 -4-10 4s- 1. The Johnson Cook （JC） model was applied to characterize the flow stresses of the SHPB tests at various conditions. The parameters of the JC model are optimized by using a genetic algorithm technology. The JC plastic model and the energy density-based ductile failure criteria are adopted in the proposed SHPB finite element simulation model. The simulated flow stresses and the failure characteristics, such as the cracks along the adiabatic shear bands agree well with the experimental results. Afterwards, the SHPB simulation is used to simulate higher strain rate（approximately 3 × 10 4 s -1） conditions by minimizing the size of the specimen. The JC model parameters covering higher strain rate conditions which are close to the deformation condition in cutting were calculated based on the flow stresses obtained by using the SHPB tests （10 -4 - 10 4 s- 1） and simulation （up to 3 × 10 4 s - 1）. The cutting simulation using the constitutive parameters is validated by the measured forces and chip morphology. The constitutive model and parameters for high strain rate conditions that are identical to those of cutting were obtained based on the SHPB tests and simulation.

Micro electrical discharge machining of small hole in TC4 alloy

Aiming at machining deeply small holes in TC4 alloy,a series of experiments were carried out on a self-developed multi-axis micro electrical discharge machining(micro-EDM)machine tool.To improve machining efficiency and decrease relative wear of electrode in machining deeply small hole in TC4 alloy,many factors in micro-EDM,such as polarity,electrical parameters and supplying ways of working fluid were studied.Experimental results show that positive polarity machining is far superior to negative polarity machining;it is more optimal when open-circuit voltage,pulse width and pulse interval are 130 V,5μs and 15μs respectively on the self developed multi-axis micro-EDM machine tool;when flushing method is applied in micro-EDM,the machining efficiency is higher and relative wear of electrode is smaller.

Machine learning and bioinformatics to identify biomarkers in response to Burkholderia pseudomallei infection in mice

Objective:In the realm of Class I pathogens,Burkholderia pseudomallei(BP)stands out for its propensity to induce severe pathogenicity.Investigating the intricate interactions between BP and host cells is imperative for comprehending the dynamics of BP infection and discerning biomarkers indicative of the host cell response process.Methods:mRNA extraction from BP-infected mouse macrophages constituted the initial step of our study.Employing gene expression arrays,the extracted RNA underwent conversion into digital signals.The percentile shift method facilitated data processing,with the identification of genes manifesting significant differences accomplished through the application of the t-test.Subsequently,a comprehensive analysis involving Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway was conducted on the differentially expressed genes(DEGs).Leveraging the ESTIMATE algorithm,gene signatures were utilized to compute risk scores for gene expression data.Support vector machine analysis and gene enrichment scores were instrumental in establishing correlations between biomarkers and macrophages,followed by an evaluation of the predictive power of the identified biomarkers.Results:The functional and pathway associations of the DEGs predominantly centered around G protein-coupled receptors.A noteworthy positive correlation emerged between the blue module,consisting of 416 genes,and the StromaScore.FZD4,identified through support vector machine analysis among intersecting genes,indicated a robust interaction with macrophages,suggesting its potential as a robust biomarker.FZD4 exhibited commendable predictive efficacy,with BP infection inducing its expression in both macrophages and mouse lung tissue.Western blotting in macrophages confirmed a significant upregulation of FZD4 expression from 0.5 to 24 h post-infection.In mouse lung tissue,FZD4 manifested higher expression in the cytoplasm of pulmonary epithelial cells in BP-infected lungs than in the control group.Conclusion:Thesefindings underscore the upregulation of FZD4 expression by BP in both macrophages and lung tissue,pointing to its prospective role as a biomarker in the pathogenesis of BP infection.

B_(4)C陶瓷电火花工艺温度场仿真及试验研究

B_(4)C陶瓷具有硬度高、密度低等特性,在军工装甲等领域应用前景广阔,但由于硬度高、脆性大,传统加工方法难以胜任孔、槽等加工。考虑半导电特性,拟采用电火花方法对其进行孔加工技术研究。利用ANSYS软件对电火花放电过程中的单脉冲温度场进行仿真建模,输出凹坑半径、深度及温度场数值,并引入锥角物理量进行仿真和试验比对。结果表明:凹坑半径、深度随峰值电流、脉冲宽度增加而增加,温度场特点满足高斯热源正态分布;随着峰值电流、脉冲宽度的增加,仿真锥角和试验锥角数值更贴合。

Realization Methodology of a 5-axis Spline Interpolator in an Open CNC System

By making use of the advantages of non-uniform rational B-spline （NURBS） curves to represent spatial curves, an instruction format with double NURBS curves suitable for 5-axis coordinated real-time interpolation is presented to replace the current 5-axis coordinated linear interpolation method defective in low-speed, low-accuracy and enormous numerical control （NC） files in sculptured surface machining. A generation procedure of the NC files with the presented format is introduced and the method to realize the interpolation in an open computer numerical control （CNC） system is developed by ourselves. These illustrated the feasibility of the proposed method and its capability of avoiding all the shortages of 5-axis linear interpolation method.

System Identification Modeling of Ship Manoeuvring Motion in 4 Degrees of Freedom Based on Support Vector Machines

Based on support vector machines, three modeling methods, i.e., white-box modeling, grey-box modeling and black-box modeling of ship manoeuvring motion in 4 degrees of freedom are investigated. With the whole-ship mathematical model for ship manoeuvring motion, in which the hydrodynamic coefficients are obtained from roll planar motion mechanism test, some zigzag tests and turning circle manoeuvres are simulated. In the white-box modeling and grey-box modeling, the training data taken every 5 s from the simulated 20°/20° zigzag test are used, while in the black-box modeling, the training data taken every 5 s from the simulated 15°/15°, 20°/20° zigzag tests and 15°, 25° turning manoeuvres are used; and the trained support vector machines are used to predict the whole 20°/20° zigzag test. Comparisons between the simulated and predicted 20°/20° zigzag tests show good predictive ability of the proposed methods. Besides, all mathematical models obtained by the proposed modeling methods are used to predict the 10°/10° zigzag test and 35° turning circle manoeuvre, and the predicted results are compared with those of simulation tests to demonstrate the good generalization performance of the mathematical models. Finally, the proposed modeling methods are analyzed and compared with each other in aspects of application conditions, prediction accuracy and computation speed. The appropriate modeling method can be chosen according to the intended use of the mathematical models and the available data needed for system identification.

EQUIVALENT NORMAL CURVATURE APPROACH MILLING MODEL OF MACHINING FREEFORM SURFACES

A new milling methodology with the equivalent normal curvature milling model machining freeform surfaces is proposed based on the normal curvature theorems on differential geometry. Moreover, a specialized whirlwind milling tool and a 5-axis CNC horizontal milling machine are introduced. This new milling model can efficiently enlarge the material removal volume at the tip of the whirlwind milling tool and improve the producing capacity. The machining strategy of this model is to regulate the orientation of the whirlwind milling tool relatively to the principal directions of the workpiece surface at the point of contact, so as to create a full match with collision avoidance between the workpiece surface and the symmetric rotational surface of the milling tool. The practical results show that this new milling model is an effective method in machining complex three- dimensional surfaces. This model has a good improvement on finishing machining time and scallop height in machining the freeform surfaces over other milling processes. Some actual examples for manufacturing the freeform surfaces with this new model are given.

Support-Vector-Machine-based Adaptive Scheduling in Mode 4 Communication

Vehicular ad-hoc networks(VANETs)are mobile networks that use and transfer data with vehicles as the network nodes.Thus,VANETs are essentially mobile ad-hoc networks(MANETs).They allow all the nodes to communicate and connect with one another.One of the main requirements in a VANET is to provide self-decision capability to the vehicles.Cognitive memory,which stores all the previous routes,is used by the vehicles to choose the optimal route.In networks,communication is crucial.In cellular-based vehicle-to-everything(CV2X)communication,vital information is shared using the cooperative awareness message(CAM)that is broadcast by each vehicle.Resources are allocated in a distributed manner,which is known as Mode 4 communication.The support vector machine(SVM)algorithm is used in the SVM-CV2X-M4 system proposed in this study.The k-fold model with different values of k is used to evaluate the accuracy of the SVM-CV2XM4 system.The results show that the proposed system achieves an accuracy of 99.6%.Thus,the proposed system allows vehicles to choose the optimal route and is highly convenient for users.

Sintering and Machinability of Monazite-Type CePO_4 Ceramics

The sintering and machinability of monazite-type CePO_4 ceramics were investigated. Relative density ≥98% and apparent porosity <2% were achieved when the monazite-type CePO_4 were sintered at 1500 ℃/1 h in air,and the maximal bending strength value (184 MPa) was achieved at this temperature. CePO_4 ceramics has a multilayer structure and an exciting 'ductility',so it can be drilled and cut with WC cutter with a small machining damage.

基于立式圆台磨削的Si_(3)N_(4)套圈磨削机理与工艺研究

轴承套圈端面形位公差直接影响轴承的精度,为提高氮化硅套圈的加工精度,对套圈端面的宽度变动量进行研究。在立式圆台磨削方式下,采用正交试验,确定各因素对套圈宽度变动量影响的主次顺序,优化获得套圈端面的最佳加工工艺参数;后通过单因素试验,探究单一磨削参数对宽度变动量的影响规律。主轴进给速度对氮化硅套圈宽度变动量影响最为显著,砂轮转速次之,工件转速影响最小;氮化硅套圈宽度变动量随进给速度的增大而增大,随工件转速和砂轮转速的增大先减小后增大;降低进给速度,有利于减小裂纹及凹坑缺陷的产生,提高套圈端面表面质量。在最佳加工工艺参数砂轮转速为800 r/min、进给速度为5μm/min、工件转速为55 r/min下,可获得氮化硅套圈宽度变动量≤6μm,实现氮化硅轴承套圈高效精密加工。

Design of novel transition-metal-doped C_(4)N_(4) as highly effective electrocatalysts for nitrogen fixation with a new intrinsic descriptor

Electrocatalytic nitrogen reduction reaction(NRR) is an efficient and green way to produce ammonia,which offers an alternative option to the conventional Haber-Bosch process.Unfortunately,the large-scale industrial application of NRR processes is still hindered by poor Faraday efficiency and high overpotential,which need to be overcome urgently.Herein,combined with density functional theory and particle swarm optimization algorithm for the nitrogen carbide monolayer structural search(C_mN_(8-m),m=1-7),the surprising discovery is that single transition metal-atom-doped C_(4)N_(4) monolayers(TM@C_(4)N_(4)) could effectively accelerate nitrogen reduction reaction.TM@C_(4)N_(4)(TM=29 transition metals) as single-atom catalysts are evaluated via traditional multi-step screening method,and their structures,NRR activity,selectivity and solvation effect are investigated to evaluate their NRR performance,Through the screening steps,W@C_(4)N_(4) possesses the highest activity for NRR with a very low limiting potential of-0.29 V.Moreover,an intrinsic descriptor φ is proposed with machine learning,which shortens the screening process and provides a new idea for finding efficient SACs.This work not only offers promising catalysts W@C_(4)N_(4) for NRR process but also offers a new intrinsic and universal descriptor φ.

基于UG和VERICUT槽轮类4轴加工的仿真分析

槽轮是4轴加工工艺的典型代表,对槽轮类零件进行铣削加工时,其加工工艺直接影响工件的残余量和过切量,是加工制造中急需研究和提高的环节。该文使用UG和VERICUT对槽轮进行模拟加工,通过对加工参数的合理设置仿真模拟验证了零件的加工程序,分析了零件的加工余量和过切现象。结果表明:VERICUT仿真能够直观地模拟数控加工的全过程,缩短试件和样件的加工时间,仿真中的控制残留余量为±0.1 mm,过切和残留为±0.1 mm,有效地降低了铣削之后抛光的工艺量,提高了首次加工的安全性,增加了中小企业的经济效益。

Dual Drive Curve Tool Path Planning Method for 5-axis NC Machining of Sculptured Surfaces

The problem of finished surface being not first-order continuous commonly exists in machining sculptured surfaces with a torus cutter and some other types of cutters. To solve this problem, a dual drive curve tool path planning method is proposed in this article. First, the maximum machining strip width of a whole tool path can be obtained through optimizing each tool position with multi-point machining （MPM） method. Second, two drive curves are then determined according to the obtained maximum machining strip width. Finally, the tool is positioned once more along the dual drive curve under the condition of tool path smoothness. A computer simulation and cutting experiments are carried out to testify the performance of the new method. The machined surface is measured with a coordinate measuring machine （CMM） to examine the machining quality. The results obtained show that this method can effectively eliminate sharp scallops between adjacent tool paths, keep tool paths smooth, and improve the surface machining quality as well as machining efficiency.

铝青铜QAl9-4的性能分析

铝青铜具有许多优良的性能,在机械行业中起着重要的作用。尤其含铝量约10%时机械强度最高,且能通过热处理进一步强化,故QAl9-4可得到较高的强度、硬度、耐磨性、冲击无火花等优良性能。该材料已在抽油井光杆密封装置和阀门上得到了广泛应用,结果表明,QAl9-4耐磨、耐腐蚀,且对光杆及其密封填料、阀杆等具有良好的保护作用,提高了产品的使用寿命。

弱结合、可加工Ce-ZrO_2/CePO_4陶瓷材料设计

对含有弱结合界面的可加工Ce-ZrO2 /CePO4陶瓷材料的设计进行了研究。结果表明 ,在Ce -ZrO2 中引入CePO4后可形成强弱界面共存的情况 ,弱界面处易形成微裂纹 ,并发生裂纹桥联等形式 ,改善了材料的加工性能。但Ce -ZrO2 /CePO4材料的强度等力学性能受温度等工艺因素影响较大 ,在 15 5 0℃× 2h下颗粒尺寸与发生裂纹桥联等形式相适应 ,耗散了主裂纹扩展的能量 ,增加了材料的断裂功 ,从而使得Ce -ZrO2 /CePO4陶瓷材料具有可加工性的同时仍可维持一定的力学性能 ,且加工损伤变小 。