Effect of cryogenic minimum quantity lubrication on machinability of diamond tool in ultraprecision turning of 3Cr2NiMo steel

This work presents a series of experimental investigations and corresponding theoretical analyses to research on the effect of cryogenic minimum quantity lubrication (MQL) on machinability of diamond tool in ultraprecision turning of typical die steel. The tool wear and machined surface quality were determined as experimental indexes, which were measured using the scanning electron microscope and surface profiler, respectively. Besides, the maximum temperatures of diamond tool surfaces acquired by infrared thermal imager were used to indirectly evaluate the cutting process. The experimental results revealed that cryogenic MQL had obvious advantages in improving diamond tool durability and machined surface quality by comparison with flood cooling, cryogenic gas cooling, and MQL, and its essential function mechanisms were thoroughly understood. On the basis of this, carbon nanofluid was found to achieve optimal tool life in diamond turning compared with polyethylene glycol, castor oil, synthetic ester, and emulsified liquid. Ultimately, the combined machining method of ultrasonic vibration-assisted turning and cryogenic minimal quantity lubrication was proposed in this work. The results showed that this technique could observably improve the machinability of diamond tool and also provide a new direction for exploring a suitable processing method for ultraprecision machining of ferrous materials.     

Study of milling force variation in ultrasonic vibration-assisted end milling

Ultrasonic vibration cutting has been proved to be an effective cutting technology for its excellent cutting performance and has been widely applied in turning and drilling process. However, this kind of technology is rarely tried in milling process. In cutting process, cutting force is an important process parameter, which affects surface finish and tool wear. This paper investigates the milling force variation in ultrasonic vibration-assisted end milling process through a series of slot-milling experiments. The main research contents include two parts, one is the effect of the externally excited vibration on milling force in milling process, and the other is the influence of milling and vibrating parameters matching on milling force value. Experimental results show that ultrasonic vibration can change traditional milling conditions, realize separate-type milling, obtain similar pulse-like profiles of cutting forces, reduce average cutting force value; and the peak value of the feed direction cutting force can also be greatly decreased by adopting reasonable vibration amplitude, an optimal combination of machining parameters is of great benefit to achieving small cutting force. According to the experimental findings, ultrasonic vibration-assisted milling is a prospective technology to achieve precision milling of small part.     

Theoretical and experimental study of the wear factor for a diamond stone-cutting tool

Results are provided for a study of the wear factor in cutting Kursebi deposit teshchenite with a diamond cutter segmented wheel 1250 mm in diameter made of SAM 500/400 diamonds. Analysis shows that diamond consumption varies within considerable limits. For wheels with a diameter of 500–1250 mm, the maximum consumption reaches 0.9–1.5 carat/m². Translated from Izmeritel’naya Tekhnika, No. 3. pp. 45–47, March, 2009.     

Effects of process parameters on periodic impact force exerting on cutting tool in ultrasonic vibration-assisted oblique turning

During ultrasonic vibration-assisted machining, the large impact force induced by tool-workpiece reengagement (TWR) is an important factor that affects tool chipping. However, mechanical analysis into process factors that affect the impact force and their influencing mechanisms are insufficient. Herein, a prediction model for the instantaneous cutting force during both TWR and the stable turning process, which depends on the process parameters and material properties, is firstly proposed based on the kinematic and dynamic analysis of ultrasonic vibration-assisted oblique turning (UVAOT). The results calculated using the developed cutting force model agree well with the experimental results presented in the literature. Next, the linear change law of the instantaneous cutting force with cutting time during the actual TWR is clarified using the proposed model. The effect of the UVAOT process parameters on the average impact force during the periodic TWR process is discussed, and the influence mechanism is analyzed from the perspective of mechanics. A positive linear correlation is discovered between the feed speed and average impact force. The ultrasonic amplitude and cutting speed do not significantly affect the average impact force of the new sharp cutting tools. These findings are consistent with the experimental observations of tool chipping and are applicable to select process parameters for reducing tool chipping during UVAOT.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00398-x     

Molecular dynamics simulation model for the quantitative assessment of tool wear during single point diamond turning of cubic silicon carbide

Silicon carbide (SiC) is a material of great technological interest for engineering applications concerning hostile environments where silicon-based components cannot work (beyond 623 K). Single point diamond turning (SPDT) has remained a superior and viable method to harness process efficiency and freeform shapes on this harder material. However, it is extremely difficult to machine this ceramic consistently in the ductile regime due to sudden and rapid tool wear. It thus becomes non trivial to develop an accurate understanding of tool wear mechanism during SPDT of SiC in order to identify measures to suppress wear to minimize operational cost.In this paper, molecular dynamics (MD) simulation has been deployed with a realistic analytical bond order potential (ABOP) formalism based potential energy function to understand tool wear mechanism during single point diamond turning of SiC. The most significant result was obtained using the radial distribution function which suggests graphitization of diamond tool during the machining process. This phenomenon occurs due to the abrasive processes between these two ultra hard materials. The abrasive action results in locally high temperature which compounds with the massive cutting forces leading to sp³-sp² order-disorder transition of diamond tool. This represents the root cause of tool wear during SPDT operation of cubic SiC. Further testing led to the development of a novel method for quantitative assessment of the progression of diamond tool wear from MD simulations.     

Microstructure and mechanical properties of Cr12MoV by ultrasonic vibration-assisted laser surface melting

The effects of laser surface melting assisted by ultrasonic vibration on the microstructure and mechanical properties of Cr12MoV were investigated. Results indicated that the original coarse columnar dendrite can be converted into a fine dendritic and equiaxed. The average microhardness increase from 389HV_0.2 to 427HV_0.2 resulted from the effect of grain refinement. The friction coefficient was lower than the melted layer without ultrasonic vibration and substrate. Under the same experimental conditions, the width and depth of wear scar were decreased by 19% and 25% than that of without ultrasonic vibration, respectively. The wear mechanism from severe adhesive wear into slight abrasive wear under the action of ultrasonic vibration. Experimental results revealed that melted layer fabricated by ultrasonic vibration exhibit finer and more uniform microstructure as well as superior tribological properties.     

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     

旋转摩擦挤压加温法制备金刚石表面Ti涂层

为了实现金刚石表面金属化,提出了一种旋转摩擦挤压加温法在人造单晶金刚石表面制备Ti涂层.利用SEM和XRD,分析了Ti涂层内表面的微观形貌和界面间的物相组成,并采用能谱仪进行了元素分析,研究了扩散退火温度和保温时间对Ti涂层内表面物相组成的影响,并分析了金刚石/Ti涂层的界面形成机制.研究结果表明:经过旋转摩擦挤压涂覆...     

基于LuGre摩擦模型的轮胎多边形磨损机理分析

多边形磨损是汽车轮胎磨损研究中的一个新课题,具有重要的理论价值和研究意义。考虑轮胎接地磨擦的非线性特性,建立了基于LuGre摩擦模型的轮胎多边形磨损的动力学模型。通过仿真给出了能够引起自激振动的车速和轮胎初始前束角范围。这些结果为减小或消除轮胎的自激振动提供了理论依据。     

超声振动对单晶硅锯切比能的影响

超声振动能很好地改善硬脆性材料的加工性能,为了探索超声振动锯切比能对单晶硅的影响,本文采用薄金刚石锯片,在有无超声振动的条件下对单晶硅进行锯切实验.实验结果表明:超声振动使锯切材料过程中的比能大幅度降低;2种锯切方式下锯切比能都随着单颗磨粒最大锯切厚度的增大而降低,但普通锯切方式下锯切比能呈幂指数递减趋势,而在超声振动的作用下比能变化趋势转变为良好的线性递减;并且单晶硅材料的去除方式由普通锯切中塑性去除为主导转变为脆性断裂去除,其破碎方式属于微破碎,趋于粉末状破碎,由此在不会对工件表面产生严重损伤的同时使材料去除所消耗的能量得到了有效降低.同时,超声振动使得锯片上的磨粒对单晶硅表面的高速冲击作用,使单晶硅产生大量微裂纹,对单晶硅的微小剥离起到很大作用.因此,超声振动在单晶硅材料的加工中有着很大的发展前景.     

刀具磨损声发射信号小波分析中小波基的选取

针对在用小波理论分析刀具磨损声发射（AE）信号时选取不同的小波基对分析结果有重要影响的问题,通过对小波基性质和刀具磨损AE信号特点的研究,从理论上分析了小波分析中刀具磨损AE信号处理中小波基选取的方法。在试验验证过程中,根据信号在小波包分解前后遵循能量守恒的原理,用四种小波基对刀具磨损AE信号进行三层小波包分解。以经小波包分解后AE信号各频带上的频带能量为特征参数,比较四种情况下特征参数的变化,验证了理论分析的正确性。     

The study of wear of cutting tools of cBN-based composite material and the influence of tool wear on cutting forces in turning hardened steels

The paper presents some findings of the investigation of finish turning of KhVG hardened steel using a cutting tool with an insert made of a cubic boron nitride based composite (cBN-Si₃N₄ system). The behavior of tool wear throughout the machining time as well as the influence of the tool wear on cutting force components and resulting cutting force have been clarified.     

Investigation on tool wear process of milling wave-transmitting Si3N4 ceramics

Due to the low fracture toughness of wave-transmitting Si₃N₄ ceramics, the special material removal mechanism causes the tool wear to be different. The paper presents the tool wear forms and mechanism under different milling depth. The effect of tool wear on cutting force and machined surface morphology is discussed. Tests have been performed under typical conditions of cutting depth of 0.3 mm (in plastic-domain processing) and 0.4 mm (in brittle-domain processing). The results show that the abrasive wear caused by the chips is the main mechanism of the cutting edge wear and the flank wear, the increase of the side edge rear angle with tool wear is the main cause of the chipping phenomenon. The cutting depth is a significant influence parameter to the wear characteristics, and two types have been distinguished. As the material removal volume ascending, the cutting edge wear and the flank face wear has a stable period, and the root-mean-square deviation of processing surface increases to 1.6 μm, while that increase with the material removal volume continuously, and the processing surface decreases to 1.4 μm. It has been proved that the cutting force tends to increase first and then decrease as the material removal volume is about 4320 mm³.     

TC4钛合金微弧氧化复合陶瓷膜制备及耐磨性能研究

采用微弧氧化技术,通过向电解液中分别添加不同的陶瓷颗粒(SiC、SiO2),在TC4钛合金表面制备复合陶瓷膜。采用扫描电镜(SEM)、X射线衍射仪(XRD),MMA-1万能摩擦磨损实验机研究了不同的陶瓷颗粒对膜层微观组织结构、元素分布特征、相组成和耐磨性能的影响。结果表明,在电解液中添加陶瓷颗粒都能使膜层表面变得致密平整且膜层的厚度增加。陶瓷颗粒能够进入氧化层中,但并不发生相变反应。SiC和SiO2颗粒能显著提高膜层耐磨性能。     

旋转超声磨削Si3 N4陶瓷用金刚石磨具磨损行为研究

热压烧结Si₃N₄陶瓷材料常应用于航天飞行器中关键耐高温零部件,但由于高硬度和低断裂韧性,其加工效率和加工表面质量难以满足制造需求。为了提高热压烧结Si₃N₄陶瓷旋转超声磨削加工质量,减小由于金刚石磨具磨损带来的加工误差,开展了磨具磨损行为研究。基于热压烧结Si₃N₄陶瓷旋转超声磨削加工实验,分析了金刚石磨具磨损形式;基于回归分析建立了金刚石磨具磨损量数学模型,揭示了加工参数及磨具参数与金刚石磨具磨损量间映射关系;并研究了磨损形式与磨具磨损量及加工表面粗糙度影响规律。结果表明：磨粒磨耗是旋转超声磨削Si₃N₄陶瓷用金刚石磨具最主要磨损形式,比例超过50%;主轴转速和磨粒粒度对磨具磨损量影响最为显著;且磨损量较小时,加工表面粗糙度值反而增加。以上研究可为提高旋转超声磨削Si₃N₄陶瓷加工精度和加工质量提供指导。     

高速轮轨钢超声振动辅助激光熔覆涂层的滚动摩擦磨损性能

目前有关高速轮轨钢超声振动辅助下的激光熔覆研究鲜有报道。在高速轮轨钢表面施加超声振动辅助激光熔覆制备了铁钴基复合涂层来改善其耐磨性能,借助扫描电镜(SEM)、X射线衍射仪(XRD)、能量色散谱仪(EDS)等手段分析熔覆层的微观结构、物相成分和元素分布,采用GPM-30轮轨滚动接触疲劳试验机对比研究轮轨钢超声振动辅助作用下激光熔覆前后涂层的滚动摩擦磨损性能。结果表明:熔覆层主要由Fe-Cr的马氏体组织、Co-Cr的γ相固溶体、Fe-Ni固溶体以及弥散析出的含MxCy(M=Cr、W)的碳化物、硼化物、硅化物等硬质相组成;超声激光熔覆强化处理后,轮轨表面的平均显微硬度分别为539 HV3 N和582 HV3 N,磨损速率分别降低59.1%,37.3%,轮轨试环熔覆层的抗磨损性能大幅提高,磨损机制由剥落磨损和严重的疲劳磨损转变为轻微的磨粒磨损和疲劳磨损。     

Cutting force behavior during a cutting tool entering and exiting a workpiece in turning silumins using tools with round polycrystalline diamond inserts

The pattern of variation of the cutting force components, resultant cutting force, and cut layer area at the stages of a tool entering and exiting a workpiece during the turning of silumins using round poly-crystalline diamond cutting inserts.     

The study of the influence of wear of a cutting tool of cBN-based composite material on the tool fracture probability in the finish turning of hardened steels

The authors have experimentally clarified the influence of the tool wear on the tool fracture probability in the finish turning of hardened steels of various hardness values using a tool with a round cutting insert of cBN/Si₃N₄ composite. The maximum stresses and fracture probability have been determined for the tool face and flank. Recommendations regarding the use of cBN/Si₃N₄-inserted cutting tools are provided.     

Investigation of die radius arc profile on wear behaviour in sheet metal processing of advanced high strength steels

Advanced high strength steels (AHSS) are increasingly used in sheet metal stamping in the automotive industry. In comparison with conventional steels, AHSS stampings produce higher contact pressures at the interface between draw die and sheet metal blank, resulting in more severe wear conditions, particularly at the draw die radius. Developing the ability to accurately predict and reduce the potential tool wear during the tool design stage is vital for shortening lead times and reducing production cost. This paper investigates the effects of draw die geometry on the sheet metal tool wear distribution over the draw die radius using numerical and experimental methods. A numerical tool wear model is introduced and applied using the commercial software package Abaqus. Channel bend tests are carried out using an Erichsen sheet metal tester to verify the numerical model. Various geometries of radius arc profiles, including standard circular profiles, high elliptical profiles, and flat elliptical profiles, are numerically investigated, and the wear volume and contact pressure distribution along the radii are determined. The results show that the profile of the draw die radius has a significant effect on the wear distribution, and that a low contact pressure distribution can be achieved by using a combination of circular and high elliptical curved geometries.     

The study of the influence of wear of the cutting tool with an insert of cBN-based composite material on the tool vibrations in finish turning of hardened steels

It has been found out that wear of a cutting tool with an insert of cBN-based composite material has an effect on the tool vibrations in finish turning of hardened steels with various hardness values. The influence of the tool vibrations on the machined surface roughness has been studied.