Thermomechanical finite element simulations of ultrasonically assisted turning

Ultrasonically assisted turning (UAT) is studied with finite element (FE) simulations and compared with conventional turning (CT) using both computational results and infrared thermography experiments. The two-dimensional thermomechanically coupled FE model of both UAT and CT utilizes MSC MARC general FE code and incorporates temperature dependent material properties, strain rate effects, heat generated due to plastic flow, contact interaction and friction at the cutter/workpiece interface. Material separation in front of a cutting edge and automatic remeshing of distorted elements are implemented in the developed computational scheme. Influence of friction on resultant temperatures and chip shapes in turning for both UAT and CT is discussed. Temperature fields in the cutting region and in the cutting tool for CT and UAT are studied and compared with the experimental data. A role of various heat transfer parameters on thermal processes in UAT and CT is investigated.     

Tool wear mechanisms in axial ultrasonic vibration assisted milling in-situ TiB2/7050Al metal matrix composites

The in-situ TiB₂ particle reinforced aluminum matrix composites are materials that are difficult to machine, owing to hard ceramic particles in the matrix. In the milling process, the polycrystalline diamond (PCD) tools are used for machining these materials instead of carbide cutting tools, which significantly increase the machining cost. In this study, ultrasonic vibration method was applied for milling in-situ TiB₂/7050Al metal matrix composites using a TiAlN coated carbide end milling tool. To completely understand the tool wear mechanism in ultrasonic-vibration assisted milling (UAM), the relative motion of the cutting tool and interaction of workpiecetool-chip contact interface was analyzed in detail. Additionally, a comparative experimental study with and without ultrasonic vibration was carried out to investigate the influences of ultrasonic vibration and cutting parameters on the cutting force, tool life and tool wear mechanism. The results show that the motion of the cutting tool relative to the chip changes periodically in the helical direction and the separation of tool and chip occurs in the transverse direction in one vibration period, in ultrasonic vibration assisted cutting. Large instantaneous acceleration can be obtained in axial ultrasonic vibration milling. The cutting force in axial direction is significantly reduced by 42%-57%, 40%-57% and 44%-54%, at different cutting speeds, feed rates and cutting depths, respectively, compared with that in conventional milling. Additionally, the tool life is prolonged approximately 2-5 times when the ultrasonic vibration method is applied. The tool wear pattern microcracks are only found in UAM. These might be of great importance for future research in order to understand the cutting mechanisms in UAM of in-situ TiB₂/7050Al metal matrix composites.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00294-2     

Vibration-Assisted Precision Machining of Steel with PCD Tools

This article presents experimental results of precision machining of steel alloys with polycrystalline diamond tools. Ultrasonic vibration-assisted cutting was tried out for expanding the application of diamond tools for high-precision and high-quality machining of ferrous materials. The experimental results show that compared with conventional turning, the cutting performance, in terms of cutting force, surface finish, and tool life, was improved by applying ultrasonic vibration to the cutting tool. The cutting forces and tool wear measured in vibration cutting are much lower than those in conventional cutting. The tool wear mechanism was discussed on the basis of the observation of wear zone.     

Fundamental Turning Characteristics of Inconel 718 by Applying Ultrasonic Elliptical Vibration on the Base Plane

Inconel 718, a nickel-based superalloy, exhibits desirable properties over a wide temperature range, and it is widely used in industry. However, Inconel 718 is typically difficult to cut because of its strong work hardening, high temperature tensile strength, and shear strength. To improve the machinability of Inconel 718, this study proposes ultrasonic turning by applying elliptical vibration to the base plane. The principle and features of the ultrasonic elliptical vibration are discussed in detail. Experiments were conducted on a commercial ultrasonic cutting unit installed onto a commercial numerical control (NC) lathe; the cutting forces were found to be lower in the new method than in conventional turning (CT). Microchip particles were observed on both chip and work surface in CT but were almost absent on the surfaces prepared by ultrasonic elliptical vibration assisted turning (UEVT). Furthermore, the cutting tool used in CT developed built-up edge (BUE), and its flank wear became heavier; in contrast, negligible BUE and less flank wear were found on the cutting tool used in UEVT. The theoretical surface roughness of UEVT was calculated and it agreed much well with the measured surface roughness.     

Study of deformation zone effects of low,conventional, high and very high speed machining

The paper deals with cutting speed in range 3 m?min^‐1 up to 2200 m?min^‐1 and its complex impact mainly on chip macroscopic shape, chip microstructure, chip compression, tool wear, tool life and machined surface quality and interprets and compares the effects regarding low, conventional, high and very high speed machining based on the dry turning of carbon steel by sintered carbide coated by titanium nitride and ceramic cutting inserts. The deformation zone response for different cutting speeds at the tool‐chip‐workpiece interfaces and their effect on tool wear were studied. The extensive (so called complete) experiments within wide range of values and large number of measurements were carried out. The formation of secondary chip occurring in high speed turning is reported. Moreover, the paper analyses the total machining time involving tool replacement time in terms of high speed machining regarding the obtained experimental results.     

基于ALE方法的钛合金超声振动车削仿真

采用ALE方法建立了钛合金超声振动车削有限元仿真模型。预测了超声振动车削过程中切削力变化规律,并将模拟获得的切削力平均值与相同条件实验获得的切削力平均值比较,验证了有限元模型的正确性。将超声振动主切削力模拟平均值与普通切削主切削力实验平均值比较,结果表明,采用超声振动辅助手段可以明显降低切削力平均值。预测了超声振动车削一个周期内工件及刀尖温度变化规律,结果表明,刀具切入阶段,工件及刀尖温度迅速升高,当刀具到达运动轨迹最大位移时,工件及刀尖温度达到最大值,随后进入分离阶段,工件及刀尖温度迅速降低。研究了超声振动振幅、频率对切削力及刀尖温度的影响规律,结果表明,随着超声振动振幅及频率的增大切削力有较明显的降低,刀尖温度有小幅降低。     

Deformation behaviour of different types of inclusion during chip formation in turning of quenched and tempered steels

Abstract

The deformation behaviour of different types of inclusion in the secondary shear zone of the chip and at the tool/chip interface has been studied during turning of quenched and tempered steel SS 2541 (En 24, SAE 4337) using coated carbide inserts. Inclusion types typical for both untreated and calcium treated steel were analysed. The analysis of inclusions in the secondary shear zone was based on semiautomatic image analysis in a scanning electron microscope. The influence on tool wear and on the formation of protective layers on the tool surface are discussed for the different types of inclusion. Examples are given of worn cutting inserts after machining steels of different inclusion content.

MST/937     

Investigation on diamond tool wear in ultrasonic vibration-assisted turning die steels

This paper presents comprehensive theoretical analyses and experimental investigations for evaluating the ultrasonic vibration-assisted turning (UVAT) of die steels with single-crystal diamond tools. The diamond tool wear was found to rely heavily on the feed rate and the cutting speed while being insensitive to the depth of cut and the tool relief angle under the cutting conditions used in the tests. The tool wear characteristics were further studied based on the observation of wear zone using Raman spectral analysis and energy-dispersive X-ray (EDX) analysis. The detection results of the tool worn topography, the phase transformation and the carbon diffusion of diamond crystals revealed that tool wear mainly occurred on the tool flank face due to the graphitization and the diffusion of the diamond tool. Analytical results of the function mechanisms of the ultrasonic turning indicated that the friction force between the tool flank face and the machined surface, which depended mainly on the ratio of the cutting speed and the vibration speed, could be effectively reduced in ultrasonic turning process. The analytical and experimental results indicated that compared with conventional turning (CT), the cutting performance, in terms of the tool life, was markedly improved by applying ultrasonic vibration to the cutting tool.     

Modelling the orthogonal machining process using coated carbide cutting tools

In this paper finite element methods were used to determine the influence of various coated and uncoated tungsten carbide cutting tools on the machining of a nickel-based super alloy Inconel 718. Disposable coated and uncoated carbide inserts were used both experimentally and as FEA models to study how the stress distribution within different coatings and carbide grades compared to each other, under a range of cutting conditions. Simulation of an orthogonal metal cutting process was performed using FORGE2, an elasto-visco plastic FEA code. All FE models were assumed to be plane strain. The results include the stress and temperature distributions through the primary shear zone, the chip/tool contact region and the coating/substrate boundaries. The tool wear and stress results from the FE modelling agree favourably with those obtained from experimental work.     

钛合金超声振动辅助切削研究进展

超声振动辅助切削（UVAM）作为一种新颖而有效的加工技术,可有效提高工件的切削加工性能,被广泛应用于钛合金切削加工领域。主要综述了钛合金超声振动辅助切削技术的国内外研究进展,主要集中于降低钛合金切削的切削力、切削温度、刀具磨损和提高工件表面质量等方面,可以较好地提高钛合金的切削性能,进而阐述新技术结合应用研究的新进展。最后,展望了该研究领域未来的主要研究方向和发展前景。对工程应用可行性、微观组织演变规律和专用设备的开发等的研究,仍然是当下和未来的研究热点。     

Influence of wire-EDM textured conventional tungsten carbide inserts in machining of aerospace materials (Ti–6Al–4V alloy)

Importance of this present investigation is to identify the influence of modified tool (tool with texturing) on the process of orthogonal turning of Ti–6Al–4V work material. To achieve the enhanced turning conditions, four different types of textures (plain conventional, cross, perpendicularly textured and parallel textured tool to the chip flow direction) were fabricated on the rake face of the tool insert and the lubricant used during the machining process is molybdenum disulfide (MoS₂). Machining forces (the force of cutting and feed), angle of shear, chip morphology, temperature distribution between tool and chip were measured. Shear strain and strain rate were also computed and compared with all type of cutting tools. Experimental results revealed that the cross-textured cutting tool exhibit an effective reduction in cutting force, friction, shear strain and strain rate. The favorable metal removal condition of curling chip with low diameter was achieved through cross-textured tool.     

Experimental investigations on cryogenic cooling by liquid nitrogen in the end milling of hardened steel

Milling of hardened steel generates excessive heat during the chip formation process, which increases the temperature of cutting tool and accelerates tool wear. Application of conventional cutting fluid in milling process may not effectively control the heat generation also it has inherent health and environmental problems. To minimize health hazard and environmental problems caused by using conventional cutting fluid, a cryogenic cooling set up is developed to cool tool–chip interface using liquid nitrogen (LN₂). This paper presents results on the effect of LN₂ as a coolant on machinability of hardened AISI H13 tool steel for varying cutting speed in the range of 75–125 m/min during end milling with PVD TiAlN coated carbide inserts at a constant feed rate. The results show that machining with LN₂ lowers cutting temperature, tool flank wear, surface roughness and cutting forces as compared with dry and wet machining. With LN₂ cooling, it has been found that the cutting temperature was reduced by 57–60% and 37–42%; the tool flank wear was reduced by 29–34% and 10–12%; the surface roughness was decreased by 33–40% and 25–29% compared to dry and wet machining. The cutting forces also decreased moderately compared to dry and wet machining. This can be attributed to the fact that LN₂ machining provides better cooling and lubrication through substantial reduction in the cutting zone temperature.     

Experimental studies on the cryogenic machining of biodegradable ZK60 Mg alloy using micro-textured tools

Reducing the contact area between the cutting tool rake surface and chip promotes the machining performance of the work material and increases the tool life. Magnesium alloys are ductile-lightweight materials that form continuous chips during machining. The present investigation discusses the orthogonal turning of ZK60 magnesium alloy with linearly textured cutting inserts under both dry and liquid nitrogen (LN₂) cooling conditions. Linear grooves that are parallel and perpendicular to chip flow direction were created using Nd-YAG laser on the tungsten carbide cutting inserts. The effect of texturing combined with the application of LN₂ cooling is studied by evaluating the machining temperature and forces, microhardness, surface roughness and tool wear. Textured tools considerably minimize the liaison area of the chip with the rake plane compared to non-textured tools, which resulted in favorable effects in machinability. In case of cryogenic machining, textured tools substantially minimize the friction by the coupled effect of micro-pool lubrication and the formation of thin-film lubrication between the tool–chip/tool–work interfaces. Parallel-textured tools aided with cryogenic cooling exhibit superior performance during machining among the different types of tools employed in the present investigation.     

微磨削与超声振动复合加工技术研究现状与展望

微细切削技术是传统加工工艺向微观尺度的延伸,在微加工领域具有重要的作用,尤其适用于三维零件及微结构的加工。与其他微细切削技术相比,微细磨削技术具有加工零件棱边精度高、适于硬脆性材料加工等优势,但其存在加工效率低、磨削热量大、微砂轮易磨损等缺陷。已有研究表明,于机械加工辅加超声振动的复合加工技术可有效降低切削力、切削温度,增大脆性材料脆-塑转变临界切削深度,改善加工表面质量等。因而超声振动辅助微磨削技术被认为是一种可有效解决微磨削加工现存缺陷的技术。主要从微磨削技术研究现状、尺寸效应机理研究、脆性材料塑性域去除机理研究、超声振动切削实验研究、超声振动切削断续切削机理研究及微磨削动态有效磨刃密度建模研究六个方面,对微磨削技术及超声振动辅助切削技术相关领域研究进行综述,并探讨超声振动辅助微细磨削技术加工机理研究及未来发展需注重解决的问题。     

Turning of Microgrooves Both With and Without Aid of Ultrasonic Elliptical Vibration

Microgroove, as a form of surface texturing, has a wide array of industrial applications. However, the use of conventional methods to machine microgrooves leads to a number of problems including large burrs, high cutting forces, and poor machining quality. In this paper, ultrasonic elliptical vibration cutting is used to assist microgrooves turning on cylindrical workpiece surfaces. The elliptical locus in the cutting process is generated by a newly designed 2D resonant ultrasonic vibrator. A series of microgrooves cutting experiments without and with the ultrasonic elliptical vibration-assistance is performed to verify the effects of the ultrasonic elliptical vibrations as compared to the ordinary cutting method. The generated cutting forces, burr suppression action, and microgroove surface quality are compared for the two classes of processes. Comparison results show the effectiveness of elliptical vibration-assisted microgroove cutting in reducing cutting forces and improving microgrooves machining quality for difficult-to-cut materials. The results also show that ultrasonic elliptical vibration-assisted cutting improves the microgroove turning process with respect to cutting forces, microgroove surface roughness, and burr formation for difficult-to-cut materials.     

Effect of machining parameters on turning of VAT32® superalloy with ceramic tool

The objective of this research was to study the machining of superalloy VAT32® using alumina-based ceramic tool without cutting fluid, applying different machining parameters to evaluate the surface finish of parts, vibration and main wear of tools. For this, a turning process with a linear trajectory of 30 mm was performed, in which were collected data vibration and surface roughness of the stretch, as well as wear and damage in the tools. The turning tests were performed utilizing cutting speeds of 270, 280 and 300 m/min, a feed of 0.10, 0.18 and 0.25 m/rev and a cutting depth of 0.50 mm. With results, it was identified that the feed influenced significantly both the vibration and the system, since the cutting speed influenced only the vibration. Being that the best results happened for the smaller feed and greater cutting speed. It concludes that the machining of superalloy VAT32® with ceramic tool introduced herself promising.     

FEM and Experimental Investigation of Cutting Force During UAT Using Multicoated Inserts

This paper presents finite-element modeling and experimental study of the main cutting force in ultrasonic assisted turning (UAT) of Aerospace Aluminum using multicoated carbide inserts. At first, mathematical models were developed to investigate the effects of tool coating, rake angle, cutting speed, and feed rate on the friction coefficient. Then, with respect to the kinematics of the process, the cutting velocity model is presented. This velocity model is used in combination with mathematical models to define the friction coefficient during UAT. The mentioned frictional model is used to write a user subroutine to incorporate the effect of friction coefficient as a function of cutting parameters in the finite-element software Abaqus. Then, 2D finite-element modeling (FEM) models are developed for simulation of conventional turning (CT) and UAT with multilayer cutting tools. The models are used to investigate the effect of vibration amplitude, work velocity, feed rate, rake angle, and multicoated tool on the main cutting force during both CT and UAT. Finally, the results of FEM are compared with experimental measurements of the main cutting force. The results show that UAT is able to lower the main cutting force, by about 29%, in low feed rates (≈0.14 mm/rev), with vibration amplitude of ≈10 µm and work velocity of ≈0.5 m/s.     

基于CVD厚膜金刚石刀具的超声振动切削模具钢实验

采用化学气相沉积（chemicalvapordeposition,CVD）厚膜金刚石刀具进行模具钢超声振动切削实验．首先阐述刀具的材质特点,观测其刀尖微观形貌和切削刃截面轮廓．然后搭建了适应精密／超精密加工需求的超声振动切削实验装置,其中激振机构可稳定实现频率42．0kHz、振幅峰峰值8～9μm的振动输出．通过切削无氧铜实验证明该超声振动切削装置工作有效、稳定后,选用AISI420模具钢进行切削实验,研究切削工艺条件及切削用量对加工质量的影响,得到适用于CVD厚膜金刚石刀具的切削用量选取范围,对比研究发现超声振动切削在提升加工表面质量、减少金刚石刀具磨损方面均优于常规切削．本研究可使切削模具钢时的金刚石刀具磨损VBmax由500～600μm减少至40μm,模具铜表面粗糙度Ra由0．93μm改善至0．09μm．本研究为金刚石刀具超声振动切削模具钢的实用化积累工艺经验,并探索提供可行的技术实现途径．     

Investigation on Some Machinability Aspects of Inconel 825 During Dry Turning

In the current study, attempt has been made to investigate the influence of cutting speed (Vc) (51, 84, and 124 m/min) on various machining characteristics like chip morphology, chip thickness ratio, tool wear, surface, and sub-surface integrity during dry turning of Inconel 825. Comparable study was carried out using uncoated and commercially available chemical vapor deposition multilayer coated (TiN/TiCN/Al₂O₃/ZrCN) cemented carbide (ISO P30 grade) insert. Chip morphology consists of chip forms obtained at different cutting conditions. Serrated chips were observed when machining Inconel 825 with both types of tool with more serration in case of uncoated insert. The chip thickness ratio increased as cutting speed was increased. Use of multilayer coated tool also resulted in increase in chip thickness ratio. Rake and flank surfaces were examined with scanning electron microscope and optical microscope. Abrasion, adhesion, and diffusion wears were found to be dominating tool wear mechanism during dry machining of Inconel 825. The beneficial effect of coated tool over its uncoated counterpart was most prominent during machining at high cutting speed (Vc = 124 m/min). The surface and sub-surface integrity obtained with coated tool were superior to that while machining Inconel 825 with uncoated tool.     

钛合金超声椭圆振动辅助车削实验研究

设计钛合金超声椭圆振动辅助车削实验,获得不同超声波电源电压下刀具近似椭圆运动轨迹。分析超声椭圆振动辅助车削切削力变化规律,与普通车削相比超声椭圆振动辅助车削能在较大程度上降低切削力。研究超声椭圆振动辅助车削工件表面粗糙度变化规律,与普通车削相比超声椭圆振动辅助车削工件表面粗度Ra值略增大,Rz值明显降低。分析进给速度对切削力的影响规律,随进给速度增大,普通车削及超声椭圆振动辅助车削切削力均升高。对同一进给速度,与普通车削相比超声椭圆振动辅助车削切削力均降低,且随进给速度增加其降低幅度减小。对比超声椭圆振动辅助车削与普通车削工件表面形貌发现,施加超声椭圆振动后工件表面沿切削速度方向形成有规律振纹。