Modeling of cutting force under the tool flank wear effect in end milling Ti6Al4V with solid carbide tool

This paper presented a study of the relationship between cutting force and tool flank wear of solid carbide tool during the wet end milling Ti6Al4V. The modeling of 3D cutting force in end milling considering tool flank wear was discussed, which showed that for the given cutting conditions, tool geometries, and workpiece material, cutting force under the tool flank wear effect can be predicted easily and conveniently. In addition, the experimental work of end milling Ti6Al4V with solid carbide tool was developed to investigate the relationship between cutting force and tool flank wear, and comparison between experimental results and predicted results was discussed. The results showed that the proposed mathematical model can help to predict 3D cutting force under the tool flank wear effect with high accuracy.     

Influence of cutting speed on cutting force,flank temperature,and tool wear in end milling of Ti-6Al-4V alloy

Tool wear is one of the most important problems in cutting titanium alloys due to the high-cutting temperature and strong adhesion. Recently, the high-speed machining process has become a topic of great interest for titanium alloys, not only because it increases material removal rates, but also because it can positively influence the properties of finished workpiece. However, the process may result in the increase of cutting force and cutting temperature which will accelerate tool wear. In this paper, end milling experiments of Ti-6Al-4V alloy were conducted at high speeds using both uncoated and coated carbide tools. The obtained results show that the cutting force increases significantly at higher cutting speed whether the cutter is uncoated carbide or TiN/TiAlN physical vapor deposition (PVD)-coated carbide. For uncoated carbide tools, the mean flank temperature is almost constant at higher cutting speed, and no obvious abrasion wear or fatigue can be observed. However, for TiN/TiAlN PVD-coated carbide tools, the mean flank temperature always increases as the increase of cutting speed, and serious abrasion wear can be observed. In conclusion, the cutting performance of uncoated inserts is relatively better than TiN/TiAlN PVD-coated inserts at a higher cutting speed.     

Balancing the transverse cutting force during inclined milling and effect on tool wear: application to Ti6Al4V

The present article studies the effect on cutter wear of balancing transverse cutting forces during inclined milling applied to a titanium alloy (Ti6Al4V). Indeed, this method is advantageous as it helps reduce vibrations as also the amplitude of such forces thanks to balancing. These observations provide the means to enhance cutting conditions and thus boost productivity when roughing. The method was first validated on Ti6Al4V titanium alloy. A model was then proposed to estimate the maximum axial cutting force at angular positions 0 and p. A wear test was then conducted and notching, flaking and flank types of wear were observed as being most representative. Roughness measurements were made throughout the wear test as also measurements of cutting forces with a new cutter and the worn cutter to provide a comparison. The cutting forces remained acceptable and the roughness values measured remained below the criteria generally retained for roughing. The improvements obtained in terms of extended tool life when using this method were extremely significant since under the same cutting conditions flat milling gave a lifetime of 2.03 min while when machining with balancing of the transverse cutting forces this was extended to 23.6 min.     

3D FEM simulation of milling process for titanium alloy Ti6Al4V

Milling is used as one of the most important tools with the complex tool geometry in industry. However, the complex milling process cannot be simulated by 2D finite element method. Therefore, a more real 3D finite element model (FEM) for the complex milling process of titanium alloy Ti6Al4V is firstly developed using the finite element software ABAQUS. This model takes into account the dynamic effects, thermomechanical coupling, material damage law, and contact criterion. Firstly, the Johnson–Cook material constitutive equation was proposed, considering the effects of strain, strain rate, and temperature on material properties. Secondly, the damage constitutive law was adopted as the chip separation criterion. Then, the simulation for the milling process of Ti6Al4V was conducted through ABAQUS based on the established 3D FEM. Finally, chip formation, stress distribution, cutting force, and milling temperature were obtained. Further, a series of milling experiments of Ti6Al4V were carried out to validate the simulation results. It confirms the capability and advantage of 3D FEM simulation in the complex milling process of titanium alloy.     

Influence of micro-textured parameters on cutting performance and chip formation of milling Ti6Al4V

Journal of Mechanical Science and Technology - In view of the lack of researches on the influence of micro textures on the cutting performance of milling cutters, this paper studies the cutting...     

钛合金铣削刀具磨损对表面完整性影响研究

为了掌握钛合金TC4铣削过程中刀具磨损对表面完整性的影响规律,通过对不同刀具后刀面磨损量下铣削钛合金工件的表面完整性测试,得出了刀具磨损对表面完整性的影响规律,并对其影响机理进行了分析.结果表明,在刀具处于初期磨损和正常磨损阶段,刀具的挤光效应引起的压应力占主导地位,而在刀具剧烈磨损阶段,加工过程中的热塑性变形引起的拉应力占主导地位;随着刀具后刀面磨损量的增加,刀具正常磨损阶段粗糙度值缓慢增加,剧烈磨损阶段粗糙度值迅速增加;随着刀具后刀面磨损量的增加,已加工表面的显微硬度值和表面层的硬化深度都随之增大.     

Tool wear prediction of machining hydrogenated titanium alloy Ti6Al4V with uncoated carbide tools

Tool wear is a problem in the turning of titanium alloy, and it is thus of great importance to understand and quantitatively predict tool wear and tool life. In this paper, a combined tool wear model including abrasive, adhesion, and diffusion wear has been implemented in a commercial finite element (FE) code to predict tool wear. Many key problems in tool wear simulation are presented and discussed such as temperature distribution, the updating of tool geometry, and the smoothing of wear boundary. Subsequently, a finite element method wear prediction model is built, and the results are compared with the experimental value; a good agreement was found. Simulated results showed that cutting force will decrease first and then increase with the increase of the concentration of hydrogen, while tool life varies in the opposite way; therefore, the optimum value of hydrogen content is about 0.3 %. The addition of 0.3 % hydrogen could improve tool life greatly, and its tool life is more than three times that of the as-received material. The hydrogenation process's favorable effect is limited by cutting parameters and cooling conditions. According to the numerical results, an appropriate machining speed and higher feed is the selection criterion for high-efficiency machining of hydrogenated titanium alloy. Furthermore, a reasonable range of cutting parameters is found; the cutting speed is in the range of 50–100 m/min, and the feed is in 0.15–0.25 mm/rev.     

An experimental investigation of the influence of cutting parameters on cutting temperature in milling Ti6Al4V by applying semi-artificial thermocouple

An investigation was reported on the cutting temperature in milling Ti6Al4V by applying semi-artificial thermocouple. ANOVA was conducted on the experimental results, and regression models were obtained. Analysis results showed that the tool temperature and workpiece temperature performed a similar rising trend with the increase of cutting parameters, including cutting speed, feed rate, radial feed, and axial feed. And their influence degrees decreased successively. The cutting force with different cutting parameters was also measured, and the relationship between cutting temperature and cutting force was discussed. It was found that cutting temperature and cutting force obtained in the experiment had the same fluctuation feature. Therefore, the cutting force and cutting temperature could complement each other for monitoring and analysis of the cutting process.     

The effect of particle hardness and shape when abrasive water jet milling titanium alloy Ti6Al4V

Legislative restriction on effluent disposal has resulted in an increase in the environmental costs of chemical milling and replacement methods are being sought. Abrasive water jet cutting (AWJ) is a mature process that is employed to through cut materials that are difficult to process by more conventional methods and the process is also being developed for controlled depth milling (CDM) to produce three-dimensional features which in the past might have been produced by chemical or etching processes. A major problem to be solved when using AWJ as a CDM technique is that of tolerance on depth, surface waviness and surface roughness of the milled area. In the current work, the effects of milling parameters on the surface characteristics are investigated when milling a titanium alloy (Ti6Al4V) with different abrasives, namely white and brown aluminium oxide, garnet, glass beads and steel shot. It has been demonstrated that the ratio between the hardness of the workpiece and the abrasive is more important than particle shape. Material removal rate and surface roughness increased when particle hardness is increased. Shape factor and particle hardness have no significant effect on surface waviness. For the abrasives investigated; traverse speed is shown to govern the operative mechanism of material removal and thus the material removal rate. It is also shown that the surface waviness can be reduced as the traverse speed is increased whilst, the surface roughness is not strongly dependent on traverse speed.     

A method for identification of geometrical tool changes during machining of titanium alloy Ti6Al4V

There exists an increasing demand for cost and time-efficient cutting tests for describing the performance of different combinations of cutting tools and workpiece materials in the cutting process both in industry and academia. Cutting tools are expected to withstand the heat and the pressure developed during the machining of difficult-to-machine materials such as Ti6Al4V. This article introduces a new test method which may be used in order to analyze both the machinability of a workpiece material as well as the cutting tool behavior. The experiments were performed by using a predefined sequence of feeds, a so-called Stepwise Increased Feed Test. A gradually increased load on the cutting edge was thus applied up to the point where plastic deformation of the cutting edge was obtained. The limit for the initial change in tool geometry was identified through analysis of measured cutting forces.     

Effect of microstructure and cutting speed on machining behavior of Ti6Al4V alloy

Machining of aerospace and biomedical grade titanium alloys has always been a challenge because of their low conductivity and elastic modulus. Different machining methods and parameters have been adopted for high precision machining of titanium alloys. Machining of titanium alloys can be improved by microstructure optimization. The present study focuses on the effect of microstructure on machinability of Ti6Al4V alloys at different cutting speeds. Samples were subjected to different annealing conditions resulting in different grain sizes and local micro-strains (misorientation). Cutting forces were significantly reduced after annealing; consequently, sub-surface residual stresses were reduced. Deformation twinning was also observed on samples annealed at a higher temperature due to larger grain size. Initial strain free grains and deformation twinning during machining reduces the cutting force at higher cutting speed.     

Several plasma diffusion processes for improving wear properties of Ti6Al4V alloy

Different kinds of diffusion processes, plasma nitriding, oxidizing and oxynitriding as of a combination of other two, have been applied to Ti6Al4V alloy to evaluate the effect of treatment times (1 and 4 h) and temperatures (650 and 750 °C) on wear properties of the alloy. It was observed that a hard modified layer was produced on the surface of the alloy after each diffusion process. While TiN and Ti₂N phases form in the modified layer with plasma nitriding, mainly TiO₂ phase forms after plasma oxidizing treatment. The wear tests performed at different normal loads showed that all treated samples, except for nitrided and oxidized at 650 °C for 1 h, exhibited higher wear resistance than untreated Ti6Al4V alloy. The plasma nitrided samples showed adhesive wear. On the other hand, while the plasma oxidizing samples displayed adhesive wear at lower loads, wear mechanism changed to abrasive wear as the load increased because the oxide film which covers the surface was broken during the sliding at higher loads.