Simulation and experiment analysis on thermal deformation of tool system in single-point diamond turning of aluminum alloy

The aim of this work is to simulate thermal deformation of tool system and investigate the influence of cutting parameters on it in single-point diamond turning(SPDT) of aluminum alloy. The experiments with various cutting parameters were conducted. Cutting temperature was measured by FLIR A315 infrared thermal imager. Tool wear was measured by scanning electron microscope(SEM). The numerical model of heat flux considering tool wear generated in cutting zone was established. Then two-step finite element method(FEM) simulations matching the experimental conditions were carried out to simulate the thermal deformation. In addition, the tests of deformation of tool system were performed to verify previous simulation results. And then the influence of cutting parameters on thermal deformation was investigated. The results show that the temperature and thermal deformation from simulations agree well with the results from experiments in the same conditions. The maximum thermal deformation of tool reaches to 7 μm. The average flank wear width and cutting speed are the dominant factors affecting thermal deformation, and the effective way to decrease the thermal deformation of tool is to control the tool wear and the cutting speed.     

The Stress Distribution and Thermal Behavior of TiBN and TiBN／TiN Coatings in Milling AISI H13 Work Tool Steel

The FEM model of TiBN ant TiBNI TiN coated cutting tool in milling of H13 steel was developed. Process variables such as temprature and stress in the coating layer as well as in the substrate were analyzed. The efficacy of the present FEM analysis was verified by conducting controlled milling experiments on AISI H13 to collect the relevant tool life and force data. The results show that the stress in a coated tool can significantly be reduced compared to an uncoated cutting tool, possibly due to surface coatings improving the tribolagical properties of cutting tools. Coatings with good thermal properties also help to improve the thermal behavior of cutting tool.     

Characterization of shear stresses in nickel-based superalloy Mar-M247 when orthogonal machining with coatedcarbide tools简

Mar-M247 is a nickel-based alloy which is well known as difficult-to-machine material due to its characteristics of high strength, poor thermal diffusion and work hardening. Calculation of shear stress by an analytical force model to indicate the effect of coating material, cutting speed, feed rate on tool life and surface roughness was conducted experimentally. Cutting tests were performed using round inserts, with cutting speeds ranging from 50 to 300 rn/min, and feed rates from 0.1 to 0.4 mm/tooth, without using cooling liquids. The behavior of the TiN and TiCN layers using various cutting conditions was analyzed with orthogonal machining force model. Cutting results indicate that different coated tools, together with cutting variables, play a significant role in determining the machinability when milling Mar-M247.     

Heat regulating strategy in numerical control end milling for hard metal machining

The trend in die/mold manufacturing at present is towards the hard machining at high speed to replace the electron discharge machining. Failure forms of the A1TiN-coated micro-grain carbide endmill when used for the machining of/IS SKD61 (HRC 53), a widely used material in die/mold manufacturing, are investigated. The endmill shows a characteristic that tool life decreases greatly due to the chipping when overload occurs or the rapid increase of wear when over-heat accumulation in cutting edges. As a consequence of the investigation, a strategy to regulate heat generation in the end milling process is proposed. This is accomplished by controlling the cutting arc length, i.e. the length of each flute engaging workpiece in a cutting cycle. Case studies on the slot end milling and comer rounding are conducted. The results show that the proposed strategy suggests the optimal tool path as well as the optimal pitch between successive tool paths under the cutting time criterion.     

Chip formation in high speed milling of Ti-6Al-4V alloy under nitrogen-oil-mist

High speed milling experiments using nitrogen-oil-mist as the cutting medium were carried out to investigate the characteristics of chip formation for Ti-6Al-4V alloy.Within the range of conditions employed（cutting speed,vc=190-300 m/min;cutting depth of axial,ap=5,7 mm）,saw-tooth chips were produced in these experiments.During the macro and micro analysis of the Ti-6Al-4V chips,an optical microscope and a scanning electron microscope（SEM）were used to study the microstructure and the morphology of the chips,and the X-ray photoelectron spectroscopy（XPS）was employed for chemical analysis.Comparisons were made to study the influence of different cutting media（nitrogen-oil-mist,air-oil-mist and dry cutting condition）on chip formation.Results indicate that cutting media have significant effects on chip formation.Nitrogen-oil-mist is more suitable for improving the contact condition at chip-tool interface and increasing the tool life in high speed milling of Ti-6Al-4V alloy than air-oil-mist and dry cutting.     

A New-type of Cermets Cutter with Nano-TiN Addition： Microstructure, Mechanical and Cutting Properties

The microstructure and mechanical properties of a new-type of cermets cutter （ tool A ） with nano- TiN modification and its cutting properties in cutting gray cast iron are investigated. SEM and TEM observatioas of the microstructure of the above material reveal that nano- TiN modified cermets possess a finer microstructare than conventional cermets. In the cutting tests, for comparison, cemented carbide cutter （ YG8, tool B） was also utilized. The cutting results show that the cutting properties of tool A are superior to those of tool B. It is also Jound that the predominant failare mode of tool A is normal wear and micro-spalling under lower cutting quantities, and that chipping occurs under higher cutting quanthies . SEM analysis reveals that cohesion, oxidation and diffusion wear become very apparent at a higher cutting speed. On the contrary, grain wear also exists but is not apparent.     

Dry face milling of titanium alloys

In machining titanium alloys, cutting tools generally wear out very rapidly because of the high cutting temperature resulted from the low thermal conductivity and density of the work material. In order to increase the tool life, it is necessary to suppress the cutting heat as much as possible by applying an abundant amount of coolant, but this will entail serious techno-environmental and biological problems. To study the performance and avoid these limitations, a PVD-coated insert was used to the dry face mill of (α β) titanium alloys. As a result it was found that the inserts exhibit an excellent cutting performance at low cutting speeds and feed rates, and there is no significant difference in the dominant insert failure mode between the wet and dry cutting in discontinuous cutting.     

Multi-objective Optimization in the Milling of Titanium Alloys Using the MQL Technique

The process for face milling of (α β) titaniwn alloy while using minimum quarttity librication (MQL) as the cooling technique was optimized by using of the Taguehi method to improve characteristics. The cutting speed, feed rate, and depth of cut were optimized with consideration of multiple performance characteristics including tool life, volume removed and surface roughness. The experimental results show that the nudtiple performance characteristics can be simultaneously improved through this approach, and the feed rate is the most influential cutting parameter in the face milling of titanium alloys.     

State Dependent Regenerative Delay Model for High-Speed Milling Processes

A 2 DOF dynamic model of regenerative chatter model with state-dependent time delay is developed in milling processes. Regenerative effects, "ploughing" or "rubbing" effects between the flank of the cutting edge and the machined surface, and feed effects are considered. It is shown that the regenerative delay is determined by the combination of the cutter rotation and the tool vibrations resulting in a state-dependent time delay. The governing equation is a delay-differential equation with state-dependent delay (SD-DDE), as opposed to the standard models with constant time delay. Based on Frechet derivative theory, the linearization of periodic state-dependent delay differential equation is also investigated. For a system with practical milling parameters, the incorporation of the state-dependent delay into the model does not essentially affect the linear stability properties of the system.     

Investigation of Surface Roughness in High-Speed Milling of Aeronautical Aluminum Alloy

An approach is presented to optimize the surface roughness in high-speed finish milling of 7050-T7451 aeronautical aluminum alloy. In view of this, the multi-linear regression model for surface roughness has been developed in terms of slenderness ratio, cutting speed, radial depth-of-cut and feed per tooth by means of orthogonal experimental design. Variance analyses were applied to check the adequacy of the predictive model and the significances of the independent input parameters. Response contours of surface roughness were generated by using response surface methodology (RSM). From these contours, it was possible to select an optimum combination of cutting parameters that improves machining efficiency without increasing the surface roughness.     

航空铝合金高速铣削加工的三维数值模拟

针对当前高速切削加工中模拟直角和斜角的有限元模型将变厚度切削层、螺旋形刀刃分别简化为等厚度切削层和直线形刀刃的不足,采用更接近实际的三维螺旋齿铣刀模型和变厚度切削层模型,对航空铝合金7050 T7451进行了高速铣削加工数值模拟,得到了铣削过程的切削力、切削温度及切屑形状.通过高速铣削实验测得了切削力,在相同的切削条件下模拟结果与实验结果比较吻合,切削温度及切屑形状也与实际相符.研究表明,三维螺旋齿铣刀模型和变厚度切削层模型可以准确模拟高速铣削加工过程,能够进一步用于研究切削参数与切削力、切削热之间的关系,进行切削参数及刀具寿命优化.     

刀具几何角度对高速铣削性能影响的仿真分析

切削力和切削温度是影响刀具耐用度及被加工表面质量的重要因素,其中刀具几何角度在金属切削加工过程中对切屑的形成、切削力的大小以及散热条件等影响很大。因此,合理地选择刀具几何角度对提高刀具使用寿命和生产效率、降低生产成本具有重要意义。以铝合金7075-T651高速铣削为研究对象,借助金属切削工艺软件AdvantEdge对铣削加工进行模拟仿真,得到加工过程中切削力和温度随时间的变化关系,并结合单因素法,分析了不同刀具角度的选择对切削力和切削温度的影响。该结果为高速铣削刀具几何角度的选择提供参考。     

聚晶金刚石刀具高速铣削钛合金切削温度分析

为了研究聚晶金刚石高速铣削钛合金时的切削温度的影响因素,揭示切削温度的变化规律,进行了切削温度试验．采用2^k因子试验设计,找出对切削温度有重要影响的主影响因素及交互影响因素;利用均匀设计试验,分析主影响因素及交互影响因素对切削温度的影响规律;建立切削用量与切削温度之间的非线性数学模型．试验结果表明：聚晶金刚石刀具高速...     

镍基粉末高温合金的铣削加工

为了研究镍基粉末高温合金的切削加工性,用整体硬质合金TiC涂层和未涂层立铣刀对镍基粉末高温合金FGH95进行铣削试验.通过研究铣削力、铣削温度与铣削用量之间的关系,分析硬质合金刀具的磨损、破损机理,观察其切屑形态,得出了镍基粉末高温合金FGH95的铣削力和铣削温度经验公式.试验表明：硬质合金涂层刀具加工镍基粉末高温合金FGH95的性能要明显优于未涂层刀具,未涂层刀具的崩刃现象严重,涂层刀具最佳铣削速度为40m/min,铣削速度对铣削温度的影响最大,并且随着铣削速度的提高形成了锯齿状切屑.     

CVD复合涂层刀具在天然大理石切削中的磨损特性

目的分析CVD复合涂层刀具在天然石材加工中的磨损特性,探讨涂层刀具在石材加工中参数选择的合理性．方法使用CVD复合涂层刀具对天然大理石进行了高速铣削试验,利用测力仪测量出不同加工参数下的切削力,分析不同参数对切削力的影响,利用扫描电子显微镜观察刀具磨损形貌,通过能谱分析刀具组成．结果CVD复合涂层刀具切削天然大理石过程中,切削力随切削深度和进给速度的增大而增大,随主轴转速的增大而减小,切削深度对切削力的影响程度最大．刀具磨损量随主轴转速的增大而减小,与切削深度和进给速度之间为非线性关系,进给速度高于2000mm／min时出现整体磨损,磨损量不随进给速度的增大而变化．结论CVD复合涂层刀具铣削天然大理石时的磨损机理是：涂层和刀具基体的机械损耗去除（剥落和崩刃）、高温下的氧化磨损和粘结磨损．由于工件和刀具表面存在摩擦产生热量,刀具涂层发生粘结磨损,在周期性冲击力作用下造成后刀面涂层和基体的机械损耗去除,裸露的刀具基体与空气中的氧发生氧化磨损,其中机械损耗去除磨损和粘结磨损伴随整个刀具磨损过程．     

高速铣削Ti6Al4V刀具磨损的试验研究

针对钛合金Ti6Al4V加工过程中产生的切削热导致刀具的快速磨损这一工艺难题,进行了不同冷却条件下的铣削加工实验。借助扫描电镜分析(SEM)、能谱分析(EDS)等分析手段,研究了刀具的磨损形态及磨损机理。研究表明,粘结磨损是加工钛合金过程中刀具的主要磨损形式,切削液的使用并不一定提高刀具寿命,而机床的稳定性能对刀具磨损有较大影响。     

滚切端铣刀的切削力试验研究

本文研究滚切端铣刀的切削力变化规律。针对滚切端铣刀的加工特点,改变刃倾角、刀片直径及切削用量,分别测量切削力,并给出切削力的变化规律。试验研究结果表明,铣削深度对切削力的影响较大,进给量的影响次之,刀片直径、刃倾角及铣削速度对切削力也有影响。本课题的研究结果,将有助于滚切端铣刀具的应用和推广。     

刀具前角对螺纹铣刀铣削性能影响的仿真分析

为合理选择刀具前角,提高刀具使用寿命和螺纹加工效率,对某可转位螺纹铣刀铣削加工45号钢进行研究。借助金属切削工艺有限元软件AdvantEdge对铣削加工进行模拟仿真,得到加工过程中切削力和温度随时间的变化关系,对比分析了不同刀具前角对切削力和切削温度的影响,进而优化选择合理的铣刀前角,为实际螺纹铣削加工刀具前角的选择提供参考。     

球头刀高速铣削模具钢热力分布3D模拟

为了获得球头刀高速铣削模具钢在切削过程中的热力分布状态,为已加工表面的热力形成机制研究提供基础数据,利用基于拉格朗日算法的有限元工艺仿真系统DEFORM,对汽车覆盖件模具钢Cr12Mo V的高速铣削过程进行了3D有限元建模仿真.模型模拟了球头刀在倾角为15°时的切屑形成过程,预测的进给方向、跨距方向以及轴向方向的切削力与实验数据相符,在剪切面处模拟所得切削平均温度偏差在10%以内.模具表面切削区轮廓形状与高速铣削产生切屑形貌基本吻合,证明建立的3D模型能够较好地反应切削过程中的热力分布情况.     

考虑过程阻尼的圆弧刃铣削淬硬钢极限切深

为了研究圆弧刃铣刀动态铣削过程中的过程阻尼情况,通过分析刀具结构的几何参数和工艺参数,对现有的模型进行整合优化,建立了圆弧刃铣刀过程阻尼的动态铣削数学模型.基于改进的数学模型,计算出后刀面侵入体积,并进行大量切削稳定极限实验,得到了高速下的极限切深.同时,应用Matlab和ANSYS软件解算得到铣削模态方程的过程阻尼系数,结合能量平衡方程,给出了淬硬钢耕犁力系数,进而预测极限切深.仿真结果表明,刀具后角和刃口半径对过程阻尼影响显著,预测极限切深与实验结果一致.