基于数据库的耐磨材料选材专家系统

基于数据库技术和模块化设计方法,采用产生式规则知识表示方式,将耐磨材料的大量相关数据、专家经验知识和选材准则构成知识库,设计了耐磨材料选材专家系统整体框架。实现了对耐磨材料的信息存储、快速查询等功能。运用现代选材方法,通过简单判断、典型零件选材、综合选材和目标选材进行定性、定量选材并作出评价,对耐磨材料的使用及生产工艺的制定、新材料的开发等方面提供依据和指导。     

Assessment of PM-EDM cycle factors influence on machining responses and surface properties of biomaterials: A comprehensive review

Powder mixed-electro discharge machining (PM-EDM) is recently evolving machining technique which can simultaneously remove and modify the machined surface through thermo-electrical process. It is a modified form of EDM in which the conductive powder elements are added in the dielectric liquid to enhance machined surface characteristics and machining responses. The commonly used biomaterials such as 316L stainless steel, Ti-based alloy, Ni–Ti, Mg alloy, and Co–Mo–Cr alloy have excellent mechanical characteristics while the biofunction of these materials are not in satisfactory level. Due to higher hardness, brittleness, and heat resistant natures of the biomaterials, it is very challenging to machine them with conventional machining. Both the system efficiency and modified surface properties depend on the associated electrical and non-electrical factors of PM-EDM cycle. This review focuses on the influence of process factors such as current, pulse duration, tool-polarity, duty cycle, potential voltage, types of liquid, and added powder concentration on performance outputs including material removal and tool wear rate, coating thickness, coarseness, microhardness, coating adhesion bonding, biocompatibility, and resistant to corrosion. This study also discusses influence of various powders on machining and modified surface characteristics of biomaterials. The future research scopes and challenges of PM-EDM process are included in this study thoroughly.     

MACHINING OF FIBER-REINFORCED COMPOSITES

Abstract

Since the introduction of glass fiber-reinforced polymer composites in the early 1940s, composite materials development was driven by the needs of space, defense, and aircraft industries where performance rather than cost was the prime consideration. At the beginning, conventional machining techniques were adopted to machine glass fiber-reinforced composites for convenience as well as to keep the capital costs down. This was followed by significant advancements in tool materials and tooling design. With the development of new and more challenging metal-matrix and ceramic-matrix composites, conventional manufacturing processes proved to be inadequate or even inappropriate to process them. Need and opportunity, therefore, exists for alternate nontraditional machining operations, such as laser machining, water jet (WJ) and abrasive water jet (AWJ) cutting, electrical discharge machining, ultrasonic-assisted machining, and electrochemical spark machining. When composites become more popular and are used in large volume in the civilian sector, such as auto and other consumer industries, material and processing costs will be the driving factors. A high degree of automation for the mass manufacturing of composite parts will be required to bring the costs down and compete with other materials. Advancements in the nontraditional machining processes offer an opportunity to process these materials economically, thus realizing the full potential of the composite materials. This paper gives a broad overview on the various issues involved in machining (conventional and nonconventional) of fiber-reinforced composites. The field of composites, in general, and machining of composites, in particular, are so broad that it would not be possible to do justice by discussing each aspect of composite material machining without ending up with a voluminous document. This review, therefore has to be limited to a few aspects of composite materials and their machining techniques. It may also be pointed out that in this review certain areas are dealt more in-depth than others. Personal preferences and availability of material in the open literature are some of the reasons for this nonuniformity in coverage. Also, some areas are more actively pursued than others. An attempt is made to highlight some of the issues and opportunities in the area of machining of composites.     

Study of surface quality in high speed turning of Inconel 718 with uncoated and coated CBN tools

Inconel 718 is known to be among the most difficult-to-machine materials due to its special properties which cause the short tool life and severe surface damages. The properties, which are responsible for poor machinability, include rapid work hardening during machining; tendency to weld with the tool material at high temperature generated during machining; the tendency to form a built-up edge during machining; and the presence of hard carbides, such as titanium carbide and niobium carbide, in their microstructure. Conventional method of machining Inconel 718 with cemented carbide tool restricts the cutting speed to a maximum 30?m/min due to the lower hot hardness of carbide tool, high temperature strength and low thermal conductivity of Inconel 718. The introduction of new coated carbide tools has increased cutting speed to 100?m/min; nevertheless, the time required to machine this alloy is still considerably high. High speed machining using advanced tool material, such as CBN, is one possible alternative for improving the productivity of this material due to its higher hot hardness in comparison with carbide tool. This paper specifically deals with surface quality generated under high speed finishing turning conditions on age-hardened Inconel 718 with focus on surface roughness, metallographic analysis of surface layer and surface damages produced by machining. Both coated and uncoated CBN tools were used in the tests, and a comparison between surfaces generated by both tools was also discussed.     

Finite element prediction of material removal rate due to traveling wire electrochemical spark machining

Manufacturing engineers are facing new challenges during machining of electrically nonconducting or partially conducting materials such as glass, quartz, ceramics, and composites. Traveling wire electrochemical spark machining (TW-ECSM), a largely unknown technology, has been applied successfully for cutting these types of materials. However, hardly any theoretical work has been reported related to machining performance of TW-ECSM process. The present work is an attempt in this direction. In the present work, a 3-D finite element transient thermal model has been developed to estimate the temperature field and material removal rate (MRR) due to Gaussian distributed input heat flux of a spark during TW-ECSM. First, the developed code calculates the temperature field in the workpiece and then MRR is calculated using this temperature field. The calculated MRR has been compared with the experimental MRR for verifying the approach. Computational experiments have been performed for the determination of energy partition and spark radius of a single spark. The effects of various process parameters such as energy partition, duty factor, spark radius, and ejection efficiency on MRR have been reported. It has been found that MRR increases with increase in energy partition, duty factor, and ejection efficiency but decreases with increase in spark radius.     

可转位刀具在汽封弧段强力铣削中应用

采用不同结构、精度的数控铣床,用两种结构铣刀加工汽封弧段,用可转位刀片加工试验,总结出相应材料应该采用刀具的几何参数、材质及机械加工切削参数。有利于在此类零件的加工中,为工艺编制、工人操作提供方便,加工参数更加规范,可以大大降低刀具使用成本,提高加工效率,更好地保证产品质量。     

A new rapid manufacturing process for multi-face high-speed machining

High-speed machining is known as one of the most effective rapid prototyping and/or manufacturing (RPM) processes that provides the various machining materials with excellent quality and dimensional accuracy. However, the high-speed machining process is not suitable for the rapid realization of 3D-shaped product because a considerable amount of time is required for the work piece fixturing process. High-speed rapid prototyping (HisRP), a new type of RPM technology, will be presented in this paper. The proposed HisRP has been developed using a combination of a multi-face high-speed machining process and a flexible fixturing technique. Low melting point metal alloys are used to hold the work piece during multi-face machining. An automatic set-up device, mounted and fixed to the work table, has also been developed to guarantee positional accuracy during a series of multi-face machining operations. This set-up device is expected to be beneficial for successive multi-face high-speed machining of working materials, for example for two-face or four-face machining. The proposed HisRP process has been shown to be a useful method for manufacturing 3D metal products with reduced lead time.     

A comparative experimental investigation of deep-hole micro-EDM drilling capability for cemented carbide (WC-Co) against austenitic stainless steel (SUS 304)

Microelectro-discharge machining (micro-EDM) has become a widely accepted non-traditional material removal process for machining difficult-to-cut but conductive materials effectively and economically. The present study aims to investigate the feasibility of machining deep microholes in two difficult-to-cut materials: cemented carbide (WC-Co) and austenitic stainless steel (SUS 304) using the micro-EDM drilling. The effect of discharge energy and electro-thermal material properties on the performance of the two work materials during the micro-EDM drilling has also been investigated. The micro-EDM drilling performance of two materials has been assessed based on the quality and accuracy of the produced microholes, machining stability, material removal rate (MRR), and electrode wear ratio. The results show that deep-hole micro-EDM drilling is technically more feasible in WC-Co as it offers microholes with smooth and burr-free surfaces at the rim in addition to improved circularity and lower overcut than those provided by SUS 304. Moreover, WC-Co exhibits better machinability during the deep-hole micro-EDM drilling, providing relatively higher MRR and stable machining.     

A Taylor-based plasticity model for orthogonal machining of single-crystal FCC materials including frictional effects

The purpose of this study is to explain the experimentally observed variations in cutting parameters during the machining of single-crystal materials. Fundamental relationships between crystal plasticity and machining are developed. The workpiece anisotropy stem from crystallographic differences are explained with a rate-insensitive Taylor plasticity model. A brief discussion of the applicability of Schmid-based models to machining processes is also presented. The periodic variations with changing crystal orientations observed in experimental studies are explained with the results of the proposed model for machining. The friction between the rake face of the tool and the material is introduced to the existing model. The applicability of concepts like Texture Softening Factor and Effective Taylor Factor in previous works are discussed. The specific energy of cutting is related to Taylor factor for better understanding of crystallographic effects.     

Processing capabilities of micro ultrasonic machining for hard and brittle materials: SPH analysis and experimental verification

Micro ultrasonic machining (micro-USM) is an unconventional micromachining technology that has capability to fabricate high aspect ratio micro-holes, intricate shapes and features on various hard and brittle materials. The material removal in USM is based on brittle fracture of work materials. The mechanical properties and fracture behaviour are different for varied hard and brittle materials, which would make a big difference in the processing capability of micro-USM. To study the processing capability of USM and exploit its potential, the material removal of work materials, wear of abrasive particles and wear of machining tools in USM of three typical hard and brittle materials including float glass, alumina, and silicon carbide were investigated in this work. Both smoothed particle hydrodynamics (SPH) simulations and verification experiments were conducted. The material removal rate is found to decrease in the order of glass, alumina, and silicon carbide, which can be well explained by the simulation results that cracking of glass is faster and larger compared to the other materials. Correspondingly, the tool wear rate also dropped significantly thanks to the faster material removal, and a formation of concavity on the tool tip center due to intensive wear was prevented. The SPH model is proved useful for studying USM of different hard and brittle materials, and capable of predicting the machining performance.     

Investigations into machining of composites

Fibre reinforced plastics (FRP) have an important place in the field of engineering materials. Initially, the main emphasis in research was on the development of materials. Currently, however, more attention is being paid to the industrial production of FRP products. Normally, conventional methods for machining of these materials are used, but reports have indicated poor performance of these conventional types of cutting tools during machining of FRP. In this paper, a new approach using electrochemical spark machining (ECSM) for cutting and drilling holes in composites is proposed.

The feasibility of using ECSM for machining FRP was first ascertained. Then a parametric study of the process was performed by planning the experiments using a ‘design of experiments’ concept as well as a ‘one variable at a time’ approach. Kevlar-fibre-epoxy and glass-fibre-epoxy composites as work materials, copper as the tool material and an aqueous solution of NaCl as electrolyte were used.

It is concluded that ECSM is a viable solution for cutting FRP. However, for achieving the desired accuracy, surface finish and economics of the process, the machining parameters need to be optimized.     

ELECTROCHEMICAL SPARK TREPANNING OF ALUMINA AND QUARTZ

Alumina and quartz (brittle, electrically non-conducting, and inert in nature) are popular materials in advanced engineering industries, but their shaping by die conventional machining processes is not possible; even ECM and EDM can't be employed to shape them because of their electrically nonconducting nature. However, an attempt has been made to find out the capabilities of a new process called electro-chemical spark machining (ECSM), in machining these electrically non-conducting, hard, brittle, and high temperature resistant materials. In this work, eccentrically rotating tools have been used. This tool configuration has made it possible to relax the limited depth constraint, and it has been possible to drill 2.35 mm deep through holes in quartz samples and 1.35 mm deep holes in alumina.

Through an experimental parametric study, it was found that beyond a certain value of electrolyte temperature, the ECSM process performance starts deteriorating. SEM photographs reveal that the combined action of melting and chemical etching seems to be the probable mechanism of material removal.     

Machining optimization using swarm intelligence in titanium (6Al 4V) alloy

The process of titanium machining in the aerospace industry today is by personal experience, producing non-efficient results. Assignment of the correct parameter for machining is hard to determine because the material has a high chemical reaction with other materials and has low thermal conductivity. These are the reasons why researchers are developing new prediction models to optimize such parameters. In this paper, particle swarm optimization (PSO) is used to optimize machining parameters in high-speed milling processes where multiple conflicting objectives are presented. The relationships between machining parameters and the performance measures of interest are obtained by using experimental data and a hybrid system using a PSO and a neural network. Results showed that particle swarm optimization is an effective method for solving multi-objective optimization problems and also that an integrated system of neural networks and swarm intelligence can be used to solve complex machining optimization problems.     

High-Speed Machining of Malleable Cast Iron by Various Cutting Tools Coated by Physical Vapor Deposition

The coating material of a tool directly affects the efficiency and cost of machining malleable cast iron.However,the machining adaptability of various coating materials to malleable cast iron has been insufficiently researched.In this paper,turning tests were conducted on cemented carbide tools with different coatings(a thick TiN/TiAlN coating,a thin TiN/TiAlN coating,and a nanocomposite(nc)TiAlSiN coating).All coatings were applied by physical vapor deposi-tion.In a comparative study of chip morphology,cutting force,cutting temperature,specific cutting energy,tool wear,and surface roughness,this study analyzed the cutting characteristics of the tools coated with various materials,and established the relationship between the cutting parameters and machining objectives.The results showed that in malleable cast iron machining,the coating material significantly affects the cutting performance of the tool.Among the three tools,the nc-TiAlSiN-coated carbide tool achieved the minimum cutting force,the lowest cutting tempera-ture,least tool wear,longest tool life,and best surface quality.Moreover,in comparisons between cemented-carbide and compacted-graphite cast iron machined under the same conditions,the wear mechanism of the coated tools was found to depend on the cast iron being machined.Therefore,the performance requirements of a tool depend on multiple factors,and selecting an appropriately coated tool for a particular cast iron material is essential.     

超声波加工参数的实验研究

超声波加工己被证明是陶瓷、金刚石、半导体等硬脆性材料加工的有效方法,但其加工效率不高制约着它的广泛应用。因此根据超声波加工材料去除率模型,对磨料粒度、静载荷等加工参数进行探讨,可得出各加工参数对材料去除率的影响。     

适应高速切削的数控刀具材料

高速切削因其加工质量好、生产效率高等优点得到广泛应用。数控刀具材料是实现高速数控加工的关键技术之一,它直接影响加工工件的质量和性能。为了适应高速数控加工技术的需要,对数控刀具材料提出了比传统的加工用刀具材料更高的要求。本文对高速切削的数控刀具材料的特点、使用范围进行了研究,并指出了数控加工刀具材料的发展趋势。     

State of the art in powder mixed dielectric for EDM applications

Electrical discharge machining (EDM) is a non-conventional machining technique for removing material based on the thermal impact of a series of repetitive sparks occurring between the tool and workpiece in the presence of dielectric fluid. Since the machining characteristics are highly dependent on the dielectric’s performance, significant attention has been directed to modifying the hydrocarbon oil properties or introducing alternative dielectrics to achieve higher productivity. This article provides a review of dielectric modifications through adding powder to dielectric. Utilizing powder mixed dielectric in the process is called powder mixed EDM (PMEDM). In order to select an appropriate host dielectric for enhancing machining characteristics by adding powder, a brief background is initially provided on the performance of pure dielectrics and their selection criteria for PMEDM application follow by powder mixed dielectric thoroughly review. Research shows that PMEDM facilitates producing parts with predominantly high surface quality. Additionally, some studies indicate that appropriate powder selection increases machining efficiency in terms of material removal rate. Therefore, the role of powder addition in the discharge characteristics and its influence on machining output parameters are explained in detail. Furthermore, by considering the influence of the main thermo-physical properties and concentration of powder particles, the performance of various powder materials is discussed extensively. Since suitable powder selection depends on many factors, such as variations in EDM, machining scale and electrical and non-electrical parameter settings, a thorough comparative review of powder materials is presented to facilitate a deeper insight into powder selection parameters for future studies. Finally, PMEDM research trends, findings, gaps and industrialization difficulties are discussed extensively.     

Developments in microultrasonic machining (MUSM) at FEMTO-ST

The aim of the article is to present new developments in microultrasonic machining concerning design and manufacture of a complete acoustic system optimized for ultraprecise processing on 2-in. wafer and examples of microstructures produced at FEMTO-ST institute, particularly in piezoelectric materials. The potentialities and the limitations of the ultrasonic machining technique are discussed. The choice and the dimensions of the material for the acoustic transducer were defined through finite element modeling. Other parameters affecting the machining process such as static load of the tool, vibration amplitude, grain material and size of the abrasive slurry, and workpiece characteristics were hierarchized experimentally in order to increase machining quality (surface state, precision) and minimize tool wear.     

Characterisation of friction properties between a laminated carbon fibres reinforced polymer and a monocrystalline diamond under dry or lubricated conditions

The machining of carbon fibre reinforced polymer (CFRP) is a hot topic for the aircraft industry. Such materials are considered as difficult to cut materials due to their heterogeneity and presence of hard fibres. In this context, a lot of finite element models have been developed in order to understand their material removal mechanisms. Among the scientific issues faced by these works, the identification of friction coefficients between CFRP and cutting tool materials remains unanswered. So, this paper aims to characterize the friction properties between composite and cutting tool materials. For instance, the paper focuses on the context of a laminated CFRP machined with a monocrystalline diamond tool under dry or under lubricated conditions. The specific tribological conditions during machining of such heterogeneous materials are discussed in the paper, especially the configuration of the tribosystem (‘opened tribosystem’) and the orientation of laminates and fibres during sliding. The great lack of friction coefficient is mainly due to the absence of relevant tribometers simulating the tribological conditions occurring in cutting. This paper presents the development of a new tribometer designed to simulate conditions corresponding to machining of CFRP materials. It provides quantitative values of friction coefficient depending on several key parameters. A range of sliding velocities and contact pressures has been tested. The influence of layers orientation and cutting fluids has also been investigated. It has been shown that friction coefficients are very low (∼0.06) in dry regime. Friction coefficient is not sensitive to contact pressure nor to sliding velocity. Additionally this works has revealed that a cutting fluid leads to a significant decrease in friction coefficients (∼0.02), which corresponds to a friction less situation.