FORMING PRINCIPLE OF TWO SIDE-DIRECTION BURR AND IT'S PREDICTION IN METAL CUTTING

The burr is one of the common phenomena occurring i n metal cutting operations The mathematical mechanical model of two side dir ection burr formation and transformation is established with plane stress strain theory,based on the orthogonal cutting The main laws of formation and change of the burr are revealed,and it is confirmed by experiment result,which first realizes prediction of the forming and changing of the two side direction burr in metal cutting operation.

Finite Element Analysis and OADs Optimization of the Temperature in the Plane-strain Orthogonal Metal Cutting Process

In order to analyze the influences of the different tool’s shape and surface conditions (such as different coated and material) and their interaction on the cutting temperature, a coupled thermo-mechanical finite element analysis (FEA) model of plane-strain orthogonal metal cutting process is constructed, and 16 simulation cases with 16 different types of tools, which cover 4 rake angles, -10°, 0°, 10°, 20°, and 4 friction coefficient values, 0, 0.1, 0.2, 0.3 in the same cutting condition (cutting depth and cutting speed) have been performed. Finally the simulation results are analyzed according to the variance analysis method (VAM) of orthogonal array designs (OADs), the relationships between the rake angle, tool-workpiece interface’s friction coefficient and their interact effect to the maximum temperature value and the temperature field of the chip are obtained. This result has some instructive meaning to analyze the causes of the cutting temperature and to control the maximum temperature value and the overall temperature field in the metal cutting process.

Conventional and micro scale finite element modeling for metal cutting process:A review

The metal cutting process is accompanied by complex stress field,strain field,temperature field.The comprehensive effects of process parameters on chip morphology,cutting force,tool wear and residual stress are complex and inter-connected.Finite element method(FEM)is considered as an effective method to predict process variables and reveal microscopic physical phenomena in the cutting process.Therefore,the finite element(FE)simulation is used to research the conventional and micro scale cutting process,and the differences in the establishment of process variable FE simulation models are distinguished,thereby improving the accuracy of FE simulation.The reliability and effectiveness of FE simulation model largely depend on the accuracy of the simulation method,constitutive model,friction model,damage model in describing mesh element,the dynamic mechanical behavior of materials,the tool-chip-workpiece contact process and the chip formation mechanism.In this paper,the FE models of conventional and micro process variables are comprehensively and up-to-date reviewed for different materials and machining methods.The purpose is to establish a FE model that is more in line with the real cutting conditions,and to provide the possibility for optimizing the cutting process variables.The development direction of FE simulation of metal cutting process is discussed,which provides guidance for future cutting process modeling.

An adaptive smoothed particle hydrodynamics for metal cutting simulation

Normally large amounts of particles are required to accurately simulate the metal cutting process,which consumes a lot of computing time and storage.Adaptive techniques can help decrease the number of particles,hence reducing the runtime.This paper presents a novel adaptive smoothed particle hydrodynamics(SPH)method for the metal cutting simulation.The spatial resolution changes adaptively according to the distance to the tool tip by the particle splitting and merging.More particles are selected in the region where the workpiece and the tool are in contact.Since the contact region constantly changes during the cutting process,two quadrilateral frames are adopted in the adaptive algorithm to dynamically change the distribution of particles.One frame for the refinement,the other for the coarsening.These frames move at the same speed as the tool.To test the computational efficiency,the metal cutting process is simulated by using SPH with three different adaptive approaches.Numerical results show that the proposed adaptive algorithm with dynamic refinement and coarsening can significantly optimize the runtime.

Experimental technique to analyze the influence of cutting conditions on specific energy consumption during abrasive metal cutting with thin discs

Specific energy consumption is an important indicatorfora better understanding of the machinability of materials.The present study aims to estimate the specific energy consumption for abrasive metal cutting with ultrathin discs at comparatively low and medium feed rates.Using an experimental technique,the cutting power was measured at four predefined feed rates for S235JR,intermetallic Fe-Al(40%),and C45K with different thermal treatments.The variation in the specific energy consumption with the material removal rate was analyzed through an empirical model,which enabled us to distinguish three phenomena of energy dissipation during material removal.The thermal treatment and mechanical properties of materials have a significant impact on the energy consumption pattern,its corresponding components,and cutting power.Ductile materials consume more specific cutting energy than brttle materials.The specific cutting energy is the minimum energy required to remove the material,and plowing energy is found to be the most significant phenomenon of energy dissipation.

An Experimental Study of Cutting Performance of Ti(C, N) Based Cermet Cutting Tool

Through systematic cutting experiments, characteristics of the cutting performance of Ti(C, N) based cermets is identified. The experiments were designed to study their resistance,toughness, cutting force, tool-chip friction coefficient and machining quality by comparing them with those of WC based cemented carbides. The cutting data and the regressed empirical formulae would be useful to promote proper application of cermet cutting tool materials.

CUTTING-DIRECTION BURR FORMATION IN ORTHOGONAL PRECISION CUTTING

The cutting burr is one of the common phenomena occurring in metal cutting.In this paper,the forming processes,main effect factors and change law of the cutting direction burr in orthogonal cutting have been studied and related theories are analyzed based on the cutting experiments.The result shows that:(1)the forming processes of cutting direction burr consist of normal cutting,flexure deformation of end surface of workpiece,plastic effect,continuous cutting and shear break separating in orthogonal cutting;(2)a new phenomenon is found that cutting direction burr is formed with the shear break separation of the chip and workpiece machined surfaces;(3)the size of cutting direction burr varies with workpiece materials,cutting parameters and geometric parameters of the cutting tool.

Modeling of Transient Thermal Conditions in Cutting

The thermal conditions like the temperature distribution and the heat fluxes during metal cutting have a major influence on the machinability, the tool lifetime, the metallurgical structure and thus the functionality of the work piece. This in particular applies for manufacturing processes like milling, drilling and turning for high-value turbomachinery components like impellers, combustion engines and compressors of the aerospace and automotive industry as well as energy generation, which play a major role in modern societies. However, numerous analytical and experimental efforts have been conducted in order to understand the thermal conditions in metal cutting, yet many questions still prevail. Most models are based on a stationary point of view and do not include time dependent effects like in intensity and distribution varying heat sources, varying engagement conditions and progressive tool wear. In order to cover such transient physics an analytical approach based on Green＇s functions for the solution of the partial differential equations of unsteady heat conduction in solids is used to model entire transient temperature fields. The validation of the model is carried out in orthogonal cutting experiments not only punctually but also for entire temperature fields. For these experiments an integrated measurement of prevailing cutting force and temperature fields in the tool and the chip by means of high-speed thermography were applied. The thermal images were analyzed with regard to thermodynamic energy balancing in order to derive the heat partition between tool, chips and workpiece. The thus calculated heat flow into the tool was subsequently used in order to analytically model the transient volumetric temperature fields in the tool. The described methodology enables the modeling of the transient thermal state in the cutting zone and particular in the tool, which is directly linked to phenomena like tool wear and workpiece surface modifications.

Experimental Investigation and Numerical Simulation on Interfacial Carbon Diffusion of Diamond Tool and Ferrous Metals

We numerically simulated and experimentally studied the interfacialcarbon diffusion between diamond tooland workpiece materials.A diffusion modelwith respect to carbon atoms of diamond toolpenetrating into chips and machined surface was established.The numericalsimulation results of the diffusion process revealthat the distribution laws of carbon atoms concentration have a close relationship with the diffusion distance,the diffusion time,and the originalcarbon concentration of the work material.In addition,diamond face cutting tests of die steels with different carbon content are conducted at different depth of cuts and feed rates to verify the previous simulation results.The micro-morphology of the chips is detected by scanning electron microscopy.Energy dispersive X-ray analysis was proposed to investigate the change in carbon content of the chips surface.The experimentalresults of this work are of benefit to a better understanding on the diffusion wear mechanism in single crystaldiamond cutting of ferrous metals.Moreover,the experimentalresults show that the diffusion wear of diamond could be reduced markedly by applying ultrasonic vibration to the cutting toolcompared with conventionalturning.

CHIP FORMATION MODEL OF TITANIUM ALLOYS

The chip deformation of titanium alloys is typical shear localization from low cutting speed, which is general phenomenon in machining of difficult to cut material at high cutting speed. This paper investigates the chip formation process in machining titanium alloys, and puts forward a three stage model describing formation process of shear localized chip. This model explains how the shear localized chip segments initiate, become trapezoid and form serrated chips.

Correlation between Single Factor Material Constitutive Model Parameters and Temperature for Ti6Al4V Alloy

Accurate material constitutive model is considered highly necessary to perform finite element simulation and analysis.However,it is difficult to establish the material constitutive model because of uncertainty of mathematical relationship and constraint of existing experimental condition.At present,there exists considerable gap between finite element simulation result and actual cutting process.Particular emphases were put on investigating the correlation between ＂single factor＂ material constitutive model parameters and temperature for Ti6Al4V alloy,and also establishment of material constitutive model for this kind of material.Theoretical analyses based on dislocation theory and material functional relations showed that material model was deeply affected by variation temperature.By the least squares best fit to the available quasi-static and high-speed impact compression experiment data,material parameters at various temperatures were found.Experimental curves analyses and material parameters comparison showed that the ＂single factor＂ material constitutive model parameters were temperature dependent.Using the mathematical mapping between material parameters and temperature,＂single factor＂ material constitutive model of Ti6Al4V alloy was established,which was proven to be right by comparing with experimental measurements.This work makes clear that the ＂single factor＂ material constitutive model parameters of Ti6Al4V alloy are temperature dependent.At the same time,an accurate material constitutive model is established,which helps to optimize cutting process and control machining distortion for Ti6Al4V alloy aerospace parts.

NOTCH WEAR OF MACHINING NICKEL BASED ALLOYS WITH CERAMIC TOOLS

The performances of mixed ceramic and sialon ceramic tools in machining nickel based alloy are tested.The negative cutting edge inclination and small tool lead angle are recommended for reducing ceramic tool failure. So called“notching at depth of cut”is not actually at the depth of cutting line, but out of cutting area。 The real reason of notching is caused by shocking of “sawtooth”on sawtooth- shaped burr and fin- shaped edges of chip

Structure Design of the Mobile Cutting Machine Tool Based on Pro / Engineer

In order to solve the existing problems of current metal cutting equipment,combined with the development situation of metal cutting industry in China,on this basis,a design can realize multi-shaped metal cutting machine tool. Introduces the working principle of the machine tool,the structure and parameters of the main component,and the establishment of the model by using the 3D modeling software Pro / Engineer（ Pro / E）;through listing the advantages of the mobile machine,shown that the metal machine tool has the structural characteristics of mobile,semi automated,can improve the cutting precision,increase cutting efficiency,and the utility market has certain value. It has guiding significance for the further study and the potential applications of the mobile cutting machine tool.

Finite element modeling of chip separation in machining cellular metals

Cellular metals and metal foams belong to a young material group. Although it is desired to manufac- ture near-net-shape parts of cellular metals by primary shaping processes, additional secondary machining opera- tions are often unavoidable to obtain the required geome- tries and quality demands. Nevertheless, conventional machining of cellular metals leads to undesirable surface damage and poor precision. Furthermore, the chip forma- tion and the mechanism description of the surface damage are still unclear. A mesoscopic finite element model was developed to simulate the chip formation process in machining cellular metals. Experimental data of orthogonal machining tests were used to validate the finite element model. The cutting and thrust forces, as well as the images of the chip formation process of both experiments and simulations were compared and analysed. The model enabled the analysis of the chip formation and the surface defect mechanisms. The rake angle and cutting conditions affected the chip formation process, but the cell arrange- ment was detected as a decisive factor in the chip forma- tion and the resulting surface damage.

Technological lubricating means： Evolution of materials and ideas

The main stages of technological lubricating material development from ancient times to date are described. How the chemical composition of these products changed with time, how new ideas revealing the physical and chemical basics of external media that influence the mechanical processing of materials appeared, how these ideas explained the differences between traditional tribology and specific technology of metal processing are discussed. The question of the possible realization of Rehbinder＇s adsorption effect in contact zone is also stated. The description of a very captivating problem is related to the explanation of the mechanism of lubricant penetration into the contact zone between the material being processed and the tool. The birth and development of the hypothesis of microcapillary penetra- tion of the lubricant into the dynamically changed intersurface clearance that has finally led to formulating the ＂necessary kinetic condition of the lubricating activity＂ is relayed.

Tool Materials Rapid Selection Based on Initial Wear

Based on a large amount of literature about tool wear research,873 tool wear curves are taken as samples,and statistical analysis is carried out to select the most suitable tool from all the tool materials suggested by the tool manufacturers. Statistical relationships between the initial wear and uniform wear periods are obtained. The results show that there is qualitative relationship between wear rate during initial wear period （WRIWP） and wear rate in uniform wear period （WRUWP） to certain extent. On this basis,a tool material rapid selection method based on the initial wear is put forward,and suitable tool materials for machining titanium alloy are selected. The experimental results indicate that this method is effective and useful. The new tool materials rapid selection can be used to select suitable cutting tool materials quickly before carrying out systematic machinability tests with the most suitable tool materials. The technology can be applied to doing the initial selection of cutting tool materials in either the machinability research or the workshop production.