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Minimum quantity lubrication (MQL) is an effective way to reduce the cutting temperature and tool wear. To reveal the effect of MQL on the wear of micro diamond tool, a calculation model for the cutting temperature of micro diamond tool under dry friction condition is established firstly by using the Fourier's law of heat conduction. Regarding the boundary film as a layer of heat-conduction medium, a revised calculation model for the temperature distribution on tool rake face under MQL condition with different cutting fluids is further established. The predicted results indicate that low viscosity is beneficial to the wetting of cutting fluid on tool-chip contact interface, which can relieve the friction. The reduction of friction finally decreases the cutting temperature. Secondly, the cutting temperature–dependent wear volume of micro diamond tool is predicted by using the Usui wear rate model in response to different cutting fluids and different cutting distances. In dry cutting, the graphite wear of micro diamond tool prevails. However, the application of MQL can slow down the graphitization of diamond, so the wear of micro diamond tool visibly decreases. Finally, cutting experiments with different cutting fluids are performed to verify the established models. The experimental observations agree well with the theoretical prediction results. Such satisfactory consistency confirms that the cutting fluid with low viscosity can reduce the cutting temperature and inhibit tool wear effectively. [ABSTRACT FROM AUTHOR]

In diamond turning of polymer bonded explosives (PBXs), a transient temperature monitoring tool is crucial for the processing safety issues. Three design principles are proposed in this work to fulfill the accurate prediction of the temperature distribution on tool cutting edge by using gradient calibration method and heat transfer simulation. Subsequently, the detailed design, microfabrication, and self-calibration test are successfully performed to establish the temperature measuring tool based on a natural diamond cutting tool. A theoretical model is further established to predict the transient temperature of the tool tip in the limit turning experiment and explore the safe cutting factors of typical PBXs. The results show that (1) the unsteady heat transfer model can better describe the self-calibration process of the tool, and it can accurately predict the transient temperature on the tool tip using the error distribution law; (2) finite element method can not only obtain the global temperature distribution field but also analyze the influences of tool structure, material selection, and thermal boundary conditions on prediction errors; and (3) cutting speed, tool tip wear, dry cutting are the key factors that affect the cutting safety of PBXs, and the maximum safe cutting speed vmax ≈ 33.5 m/s. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to reveal the tribochemical reaction mechanism on the nano-cutting interface between HMX crystal and diamond tool. Design/methodology/approach: Molecular dynamics simulation of HMX crystal nano-cutting by the reactive force field is carried out in this paper. The affinity of activated atoms and friction damage at the different interface have been well identified by comparing two cutting systems with diamond tool or indenter. The analyses of reaction kinetics, decomposition products and reaction pathways are performed to reveal the underlying atomistic origins of tribocatalytic reaction on the nano-cutting interface. Findings: The HMX crystals only undergo damage and removal in the indenter cutting, while they appear to accelerate thermal decomposition in the diamond cutting. the C-O affinity is proved to be the intrinsic reason of the tribocatalytic reaction of the HMX-diamond cutting system. The reaction activation energy of the HMX crystals in the diamond cutting system is lower, resulting in a rapid increase in the decomposition degree. The free O atoms can induce the asymmetric ring-opening mode and change the decomposition pathways, which is the underlying atomistic origins of the thermal stability of the HMX-diamond cutting system. Originality/value: This paper describes a method for analyzing the tribochemical behavior of HMX and diamond, which is beneficial to study the thermal stability in the nano-cutting of HMX. [ABSTRACT FROM AUTHOR]

In this work, the desensitising effect of water film on the diamond cutting of HMX crystal is studied by using reactive force field (ReaxFF) molecular dynamics simulations. The lubrication behavior, reaction kinetics, decomposition products and reaction pathways are particularly studied to reveal the underlying atomistic origins of desensitisation of wet-cutting system. Simulation results show that a film lubrication and its evolutionary behaviour occur at the nano-cutting interface. And forming a complete water-lubricating film is critical for improving thermal stability of the entire cutting system, which is correlated to tool sharpness, HMX properties and water-lubrication method in the actual cutting process. More interestingly, the mechanism of desensitising effect is confirmed to be that the nano-water film inhibits the C–O affinity between diamond tool and HMX, which makes the relatively stable symmetric cleavage of the main ring dominant in the initial decomposition of HMX. Although the type and evolution trend of the decomposition product is similar to that in dry cutting, the degree of decomposition and the severity of HMX are lower in wet-cutting, and the presence of water-lubricating film causes the transition of main dynamic mechanism function of the HMX from the self-catalysed mode into the random nucleation mode. [ABSTRACT FROM AUTHOR]

An in situ measurement system is established to measure the waviness of rounded cutting edge of diamond tool, into which a capacitive linear variable differential transformer (CLVDT) sensor and a diamond rectangular pyramid probe with an end line length of less than 1.2 μm are integrated. To accurately fit the short-arc cutting edge, a random statistics enhanced least-square circle method is further proposed. Moreover, the rotation error of the air shaft of the planetary lapping machine is measured with consideration of error separation. Finally, in situ measurements are carried out by using the established method to acquire the cutting edge waviness of a newly shaped diamond tool, and off-line measurements are also performed on a surface profiler to verify the in situ acquired data. The results validate that the proposed in situ method is effective to evaluate the cutting edge waviness accurately. [ABSTRACT FROM AUTHOR]

In diamond turning of metal mirrors, the reflectivity heavily relies on the mirror surface roughness, and the vibration of machine tool is one of the crucial factors affecting the mirror surface roughness. Previous articles mostly focused on the vibration of the spindle, but in the process of spherical surface machining, the influence of Z-direction moving parts can not be ignored. In this work, by using the transfer matrix and prediction-correction method, a dynamics model is developed to determine the different order vibration frequencies for Z-direction moving parts. The vibration patterns are further revealed in terms of the state vector of each order component with consideration of the external forces, e.g. dynamic cutting forces and linear motor thrust harmonics. As the machining parameters increase, the vibration tends to become instability, and the bifurcation of vibration frequency appears. The sensitivity analysis results firstly show that the cutting depth and workpiece surface slope are the most important factors influencing the vibration frequency bifurcation phenomenon. The probability density distribution of the vibration frequency bifurcation is firstly established as a function of the workpiece shape by stochastic big data simulations, and an adaptive optimization algorithm of interpolation point position is established. Finally, the correctness of the model is verified by experiments, and the relative error is kept below 10%. Through the new interpolation point planning algorithm, the vibration is reduced by more than 50%. Our findings are of significant importance for improving the spherical/aspherical surface reflectivity of metal mirrors. [ABSTRACT FROM AUTHOR]

Microstructure surface can produce excellent functions or performances. However, many microstructures have not been applied widely because of high production costs on industrial scale. The fabrication of large scale cube corner array is still a challenge because of the time-consuming problem. To reduce the manufacture cost of large scale cube corner array, a modified diamond micro chiseling (DMC) method is proposed in this paper. By using the modified method, a cube corner array with the size of 200 µm is successfully fabricated on a 10 mm × 12 mm Ni-P alloy substrate. Experimental observations show that the machined microstructure array has a good homogeneity, and the surface roughness of three cube facets is less than Sa 10 nm. This modified method employs an optimized tool path and targeted design of diamond cutting tool to reduce the processing time. Three facets of cube corner can be chiseled in one process step. By utilizing the optimization strategies, the processing time is reduced to 40 h without deterioration of machining surface quality, which is far less than that consumed by the conventional method, i.e. 95 h. This work presents a method to reduce the manufacturing cost of microstructure surface, through which the microstructure processing can be more cost-effective and widely applied in the future. [ABSTRACT FROM AUTHOR]

In this work, the influences of sliding velocity and contact pressure on the wear rate of diamond substrate in mechanical polishing are investigated experimentally and theoretically. The experimental observations indicate that the wearing process only consists of the wear-in and stable wear periods. The removal thickness of diamond crystal first increases nonlinearly in the wear-in stage, but then linearly in the subsequent stable wear stage. A diamond carbon amorphization-dependent model is established to calculate the linear variations of removal thickness, which gives a satisfactory prediction accuracy as compared to the experimental data. Although the experiment results demonstrate that the higher sliding velocity or contact pressure will cause a higher wear rate of diamond substrate, the action laws are thoroughly different according to the theoretical prediction. A greater sliding velocity increases the amorphization rate of diamond carbons and the scratching frequency of diamond grits. However, a higher contact pressure produces a larger contact area, which forces more diamond grits to scratch on the surface of diamond substrate. [ABSTRACT FROM AUTHOR]

In mechanical lapping, diamond exhibits a highly anisotropic tribological behavior. The dependency of wear rate on crystal orientation has long been noticed by diamond polishers. However, in the diamond manufacturing, the surface quality is another side in need of attention. In this paper, the relationship between surface morphology and crystallographic orientation under a certain lapping condition was examined. It is found that a fine surface can still be obtained at the directions that deviate a lot from the 'soft' directions (near <001> crystal direction for {110} surface). But, with respect to the 'hard' directions (near <110> crystal direction for {110} surface), a bad surface finish with a fracture appears. This result comes down to two aspects. First, on {110} surface, as the lapping direction from the <001> (soft direction) approaches <110> (hard direction) the phase change of diamond carbon atoms gets more difficult, which causes the depth of the amorphization layer becomes thinner. Second, the energy required by diamond amorphization is lower than that by surface fracture around the soft direction, while near the hard direction, the contrary is the case. Our work provides a further understanding of the diamond tribological properties. [ABSTRACT FROM AUTHOR]

In this work, molecular dynamic (MD) simulation is employed to investigate the formation and evolution of amorphous carbons in the surface layer of diamond crystal as the frictional sliding is performed on diamond (1 0 0) plane. Simulation results reveal that the formation of amorphous carbons at the sliding interface is inevitable due to the friction. In this case, transformation from diamond sp 3 hybridized carbons to sp 2 hybridization structures is dominant. More interestingly, most of the sp hybridized carbons appear on the topmost surface of the amorphous layer. Amorphization rate in sliding along the [1 0 0] direction is greater than that along the [1 1 0] direction due to the smaller resistance forces. In the light of the velocity variation of carbon atoms, the amorphous layer is divided into two layers, i.e. the coherent layer and transition layer. Moreover, a density transition region appears with the formation of amorphous carbons, and the thickness of transition region can be used to characterize the amorphization degree. [ABSTRACT FROM AUTHOR]

According to the Hencky stress theorem and J-C constitutive equation, a cutting force model is established for the diamond turning process when using micro diamond tool, through which the stress distributions on tool rake face and flank face are calculated. A stress model is further developed to calculate the stress distribution on the cutting edge region by using the stress intensity factor theory of fracture mechanics, into which the influences of crystal orientation of rake and flank faces are integrated. With consideration of elastic modulus and defect density of diamond crystal, the critical stress for graphitization of diamond tool is also deduced in response to different crystal orientations and types of diamond material. Finally, cutting experiments are performed to validate the theoretical predictions. Results show that the experimental observations agree well with the theoretical predictions. Such satisfactory consistency confirms that the natural cape Ia diamond as tool material and the (100) crystal plane as tool faces can effectively inhibit the graphitization wear of micro diamond tool. [Display omitted] • According to the Hencky stress theorem and J-C constitutive equation, the stress distributions on tool rake face and flank face are calculated. • A stress model is further developed to calculate the stress distribution on the cutting edge region by using the stress intensity factor theory of fracture mechanics. • With consideration of elastic modulus and defect density of diamond crystal, the critical stress for graphitization of diamond tool is also deduced in response to different crystal orientations and types of diamond material. • The natural cape Ia diamond as tool material and the (100) crystal plane as tool faces can effectively inhibit the graphitization wear of micro diamond tool. [ABSTRACT FROM AUTHOR]

Micro diamond tools are indispensable for machining microstructured arrays. The cutting edge durability and consistency of micro diamond tools are the determinants of the microstructure quality and accuracy, in addition to the motion accuracy of the machine tool. A strength distribution model of the working area including the cutting edge and rake and flank faces was established considering diamond anisotropy and chip flow direction. Comprehensive wear resistances of micro diamond tools with different crystal orientation combinations were analyzed based on the model, and the wear prone areas of different tools were successfully predicted. The evolution processes of the sharpness and wear topography were monitored for every micro diamond tool in the micromachining experiments. The morphologies, profile errors and topological characteristic of the microstructures machined with different micro diamond tools with increasing cutting distance were analyzed. Finally, a conclusion was drawn that the wear resistances of the micro diamond tools in ascending order are A γ {100} A α {100}, A γ {100} A α {110}, A γ {110} A α {100}, and A γ {110} A α {110}. The three working areas of the A γ {100} A α {100} tool are prone to wear; in contrast, those of the A γ {110} A α {110}tool are resistant to wear. The tool wear of A γ {100} A α {110}is caused by flank face wear, and that of A γ {110} A α {100} is caused by rake face wear. [Display omitted] • A 3D spatial strength model of micro diamond tool nose is developed for the micromachining. • Relative wear resistance and wear location of micro diamond tools are successfully predicted. • A wear resistant design scheme for the micro diamond tools is indicated to prolong tool life. • Dependence of the machined quality on the crystal orientation of micro diamond tool was revealed. [ABSTRACT FROM AUTHOR]

In the present work, we propose a novel thermo-chemical post-processing method for refining the mechanically polished surface of natural diamond crystal. The deformation mechanisms of diamond crystal during mechanical polishing are elucidated by Raman Spectroscopy corroborated by molecular dynamics simulations. Moreover, the surface mechanical properties of diamond crystal are qualitatively characterized by nanoindentation tests. Our results reveal that under mechanical polishing there are phase transformations from diamond carbons to layered graphite, amorphous sp 3 and sp 2 hybrided structures occurred in the topmost surface layer, which consequently deteriorates the intrinsic surface strength of diamond crystal. In the following thermo-chemical refinement, the polishing-induced amorphous carbons, layered graphite and internal stress are largely removed through the weak oxidation reaction. It is found that the formation of considerable graphene structures in the topmost surface layer results in an ultra-hard diamond crystal surface with dramatically enhanced hardness and Young's modulus. Our findings shed light on the preparation of natural diamond crystal surface with superior mechanical properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • A whole cutting edge dynamic strength distribution model of micro diamond tool is established. • Relationships between the dynamic strength and cutting edge waviness and sharpness are disclosed. • Design criteria of micro diamond tools are proposed according to different applications. Micro diamond tool has been developed as an essential cutting tool to fabricate the functional microstructure arrays, and its waviness and sharpness directly influence the accuracy and quality of the microstructures. The dependency of waviness and sharpness on the cutting edge dynamic strength is discussed in present work. To fulfill this objective, firstly, an analytical model of cutting edge dynamic strength is established to predict the spatial distribution of dynamic strength on the whole cutting edge. Secondly, the influence mechanism of dynamic strength on the waviness and sharpness is revealed, and two comprehensive parameters are further defined to evaluate the influences of cutting edge dynamic strength on the waviness and sharpness. Finally, according to the different machining demands, two criteria are proposed for designing micro diamond tools in light of the analytical model and comprehensive parameters. [ABSTRACT FROM AUTHOR]

The implications of the end effect for flux linkage and thrust ripple in a slot-less long-stator permanent magnet linear synchronous motor (LSPMLSM), are analyzed in this paper. Since it is affected by the end effect, the air-gap magnetic field density under the end permanent magnet is different from that under the non-end permanent magnet, leading to asymmetry in the thrust ripple. For this reason, we establish a dynamic permanent magnet flux linkage model, which proves that the end effect leads to sub-harmonics in the permanent magnet flux linkage. The motor's magnetic field distribution in the left and right parts is symmetrical. A thrust model taking into account the flux linkage sub-harmonics is established, from which the amplitude and period of the thrust ripple caused by the end effect can be calculated. There is no detent force for the slot-less LSPMLSM, and the end effect is the primary origin of the motor thrust ripple. In order to suppress the end effect, a method of increasing the end iron length is proposed, as a result of which the sub-harmonics in the flux linkage and the motor thrust ripple are effectively suppressed. Experimental and simulation results verify the results of this paper. [ABSTRACT FROM AUTHOR]

• A FE-SPH hybrid model is used to simulate the oblique cutting of KDP crystal. • Hydrostatic pressure reflects the susceptibility of surface to cracks formation. • Chip flow angle in oblique diamond cutting follows the Stabler's chip-flow rule. • Phenomena of chip tearing and interference zone are relieved in oblique cutting. • Surface roughness depends on the competition of multiple influencing factors. Due to the soft and brittle characteristic, the potassium dihydrogen phosphate (KDP) crystal undergoes a complex process in diamond cutting, which makes the material removal mechanism is still a subject of controversy. In this paper, based on the machining model of oblique diamond cutting of KDP crystal, the effect of tool inclination angles in machining is numerically investigated by constructing a FE-SPH hybrid model, which combines the finite element (FE) method and smoothed particle hydrodynamics (SPH). Subsequently, oblique fly-cutting experiments with the same tool geometries and cutting parameters are performed, and the topographies of uncut shoulder and finally machined surface are measured by the atomic force microscope (AFM). Results show that the distribution of hydrostatic pressure clearly reflects the susceptibility of the processed surface to the cracks formation. With the consideration of hydrostatic pressure, the simulated results of cracks on the uncut shoulder and finally machined surface present a good consistency with the measured results in experiments. Moreover, the chip flow angle in simulation approximately follows the Stabler's chip-flow rule. As tool inclination angle increases, the width of interference zone decreases and the phenomenon of chip tearing is gradually relieved. Finally, the simulation results and experimental observations confirm that the roughness of finally machined surface is influenced by the average slope of uncut shoulder, the width of interference zone and the distribution of cracks. [Display omitted] [ABSTRACT FROM AUTHOR]

• The dependency of diamond phase transition on the frictional force is explained. • An origin of directional graphitization in mechanical polishing of diamond is revealed. • Mechanisms of anisotropic material removal rate of diamond are disclosed in a new light. Molecular dynamics simulation is employed to represent the mechanical polishing of diamond crystal, in which two diamond substrates with free surface of {1 0 0} and {1 1 0} faces are established. Firstly, the polishing direction related to variations of friction force on the both substrates are analyzed, and the non-diamond carbon atoms produced due to the phase transformation, mainly sp2 and amorphous sp3 hybridizations, in the surface layer are further extracted. Then, the distribution planes of ordered sp2 hybridizations are fitted, on which the length and angles of C–C bonds are also calculated. Finally, dependence of the length of dislocation lines and the distribution area of localized von Mises shear strain in the polishing direction are discussed. The results suggest that friction force decreases gradually when the polishing direction transiting from the 'soft' direction to the 'hard' direction, and the same variation tendency is also observed on the phase transformation, length of dislocation lines as well as distribution area of localized shear strain. More interestingly, the appearance of ordered sp2 structures, which can be considered as graphitization of diamond, has an obvious directionality. It always generates on the {1 0 0} crystal planes, regardless of polishing on the {1 0 0} and {1 1 0} faces. [ABSTRACT FROM AUTHOR]

The friction coefficient, an important parameter to evaluate the dynamic properties of friction pairs, has been widely used in macro engineering fields. However, it is probably inappropriate to characterize the tribological properties at the nanoscale due to the strong size effect, and the conventional formula cannot reveal its determinants owing to its oversimple form. Therefore, in the present work, a new formula is deduced to overcome these shortcomings. The established formula for the friction coefficient considers the adhesion and discloses the relationship between the friction coefficient and the material properties of diamond. It effectively suppresses the dependency of the friction coefficient on the load, although such a dependency cannot be eliminated completely. Therefore, another new formula, independent of the loading force, is derived. Interestingly, the results indicate that the size effect is invariably observed in the friction coefficients derived from the three formulas due to different accumulation effects of debris atoms, which is verified by molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

A theoretical model that integrates the comprehensive effects of surface roughness, plastic deformation, adhesion, material strength and crystal orientation is established to quantitatively calculate the frictional force of diamond sliding on diamond. The effectiveness and accuracy of the model are verified by various nanofrictional experiments using an atomic force microscopy tip and molecular dynamics simulations sliding along the different orientations on the {100} and {110} crystal planes. Moreover, the internal reasons why the frictional force of diamond sliding on diamond is anisotropic are analyzed to be caused by the amorphous defects, dislocations and von Mises shear strain occurring on the rubbed surface. Image 1 • An accurate model was established to predict anisotropic friction force of diamond. • The amorphous defects influence the value of frictional force of diamond. • The anisotropy of diamond friction is related to the dislocation and shear strain. [ABSTRACT FROM AUTHOR]

• A surface roughness model is developed for oblique cutting of KDP crystal. • Hydrostatic pressure is considered in modeling relative length of crack (RLC). • Roughness component of cracks effect R c is modeled based on RLC. • R c is a non-negligible factor in predicting surface roughness. KDP crystal is a typical soft-brittle material, and the challenge of predicting its surface roughness at a wide range of feed rates in oblique cutting invokes the comprehensive consideration of various factors, e.g. the plastic behavior in ductile mode and the cracks effect in brittle mode. In this work, a novel theoretical roughness model, into which the components of kinematics, plastic side flow, materials elastic recovery and cracks effect are integrated, is proposed to reveal the underlying mechanisms of surface roughness variation in oblique diamond turning of KDP crystal. In modeling, the duplication effect of the active cutting edge contour is successfully used to calculate the component of kinematics, and an empirical expression with consideration of equivalent cutting edge radius in oblique cutting is reconstructed to estimate the materials elastic recovery. For the component of plastic side flow, the effect of the volume of unremoved materials and the scale coefficient of plastic side flow determined by feed rate and tool inclination angle are taken into account. Moreover, the component of cracks effect is quantified based on the relative length of crack (RLC) model that considers the material properties, tool geometries, process parameters and the suppression of hydrostatic pressure in the cutting area. In experiments, a method of oblique fly-cutting is employed to reduce the impact of material anisotropy on surface roughness. The results show that the RLC model can well predict the distribution of cracks, and the surface roughness model considering these four components has a satisfactory prediction accuracy. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The adsorption processes of four butanol isomers (n-butanol, tert-butanol, sec-butanol and isobutanol) on the BaTiO 3 (0 0 1) surface were calculated based on the first-principles. From the geometrically optimized configuration, it is found that the adsorption occurs more easily when the H atom (H m) in the O-H bond of the butanol molecules is close to the adsorption site on the BaTiO 3 (0 0 1) surface. The adsorption process is characterized by the dissociation of H m atom from the butanol molecules and the formation of covalent bonds with the O atom on the surface of BaTiO 3. Among the four isomers, the sec-butanol has the largest adsorption energy of -1.422 eV, while the adsorption energy of the n-butanol is the smallest of -1.098 eV. Therefore, it is inferred that the adsorption process is chemisorption. Bader charge analysis indicates that the butanol isomer molecules act as electron acceptors to receive the charge from the BaTiO 3 surface. In addition, the analysis on density of states shows that the C atom and H atom of butanol isomer molecules have obvious electronic orbital interaction with O atom on BaTiO 3 surface. The charge transfer and O-H bond breaking and generation during the adsorption process are further confirmed by the charge density difference and electron localization function. • The adsorption of butanol isomers on BaTiO 3 surface was studied systematically. • The BaTiO 3 (0 0 1) surface shows different sensitivities to butanol isomers. • Butanol isomers have similar adsorption performance. • Butanol isomers are electron acceptors in the adsorption process. [ABSTRACT FROM AUTHOR]

Multi-axis ultra-precision milling is a powerful technology which enables the manufacturing of various complicated curved surfaces. However, in the fabrication of an undetermined and random micro-structured surface, the conventional manufacturing mode from a given geometry model to the final surface machining is no longer applicable. Therefore, this work presents an integrative numerical control (NC) code generation method for fabricating randomly distributed V grooves on the great circles of a spherical surface firstly, in which the tool path generation is integrated into the geometry design process. The randomness of the V grooves refers to the geometric feature that the normal vectors of all the planes of the great circles are randomly generated, which are uniformly distributed towards the corresponding points on a unit sphere. Besides, the singular movements in five-axis milling of the randomly distributed V grooves on the great circles are analyzed. It is revealed that there are two distinct mechanisms of the singularity problem. One is the singular configuration of the machine tool, and the other is the discretization of the generated tool path. Subsequently, a general post-processing algorithm is contributed to solve the singularity problem, which enables the generation of NC code with error control. Furthermore, in five-axis milling of the randomly distributed V grooves on the great circles, the position error of tool virtual center can also significantly influence the machining accuracy. Therefore, a two-point calibration method is proposed to accurately determine the position of tool virtual center. Finally, a high-precision random V groove-structured sphere is machined by using the proposed NC code generation method and the tool virtual center calibration method. The maximum depth error of the V grooves is controlled less than 3.3 μm. The proposed methods in this work enable five-axis milling of high-precision random micro-structures on a spherical surface. [Display omitted] • A method is proposed for tool path generation of random V grooves on a sphere. • Two mechanisms of singularity problem in five-axis milling are revealed. • A novel method with error control is developed to solve the singularity problem. • High precision random V grooves are successfully machined on a spherical surface. [ABSTRACT FROM AUTHOR]

Single crystal diamond is widely used in the manufacturing of diamond cutting tools. In this work, the diamond (100) plane which is always orientated as the rake face of diamond cutting tools is polished by using a polishing pad covered with nano silica and nickel powder. The results show that the polishing with nano nickel powder can achieved the satisfactory surface quality in a defined polishing time of 140 min, in which the surface roughness of the polished diamond (100) plane reaches to 0.25 nm Ra and 2.30 nm PV in a scanning area of 50 × 50 μm2. Raman spectra analysis further reveals that graphitization or amorphization occurs on the diamond surface during polishing with nickel powder. Finally, based on the polishing method with nano nickel powder, the influence of the polishing parameters on the achieved surface quality is investigated so as to optimize the polishing parameters. 3D surface topography of the diamond (100) plane polished by the polyurethane pad coated with nano nickel (scanning area: 50 × 50 μm2). Unlabelled Image • A polishing method by using nano silica and nano nickel powders is established. • Surface roughness of the polished diamond (100) plane reaches to 0.25 nm Ra. • Grinding induced micro grooves on diamond surface are effectively removed. • This polishing method can be employed as a passivation solution for diamond tool. [ABSTRACT FROM AUTHOR]

In this work, the ion implantation effect of focused ion beam (FIB) is employed to modify the single crystal diamond tools, and the cutting performances of the irradiated and unirradiated tools are further evaluated. Firstly, the characteristics of the irradiated rake face are measured to determine the impact of the implanted ions. The results show that the surface energy of the rake face irradiated by FIB decreases significantly. Secondly, cutting experiments are carried out on the Al6061 alloy substrates. The results demonstrate that the ion implantation improves the self-cleaning of rake face and the wear resistance of cutting edge, which is conducive to reduce the cutting force and cutting temperature, resulting in an improvement of the manchined surface quality. All the experimental observations confirm that the FIB implantation process is an effective method to improve the cutting performance of single crystal diamond tool. [Display omitted] • The surface energy of the irradiated rake face is reduced. • The self-cleaning of rake face is improved by ion implantation. • The cutting force and cutting temperature is reduced. • The wear resistance of the irradiated tool is increasing. [ABSTRACT FROM AUTHOR]

Diamond ball-end milling is an enabling technology to fabricate complex curved surfaces with a nanometer level roughness. However, limited by the errors of tool manufacturing and installation, the cutting edge profile of a single-bladed diamond milling tool cannot form an ideal sphere crown in rotation, which will significantly worsen the machining accuracy. Although a titled milling method and a tool error reduction method based on milling-test have been proposed to improve the machining accuracy, a complete analysis of the effects of multiple tool errors on the machining accuracy have not been performed. Therefore, the present work contributes an analytical model to accurately calculate the tool rotation profile under various position and orientation errors. The results reveal that the horizontal off-center error of tool cutting edge is the dominant error among all the tool errors. According to the results, a novel high precision identification process is developed to evaluate the horizontal off-center error in view of the cutting-mark, and subsequently a tool center shift method is proposed to compensate for such error. Finally, experiments on millimeter scale spherical surface, micro sphere array and micro sinusoidal surface confirm that the proposed tool error compensation method can significantly improve the form accuracy. The average form errors (PV) of three test surfaces are reduced from 2.29 μm, 0.90 μm and 0.88 μm, down to 0.61 μm, 0.28 μm and 0.18 μm, respectively. [Display omitted] • An analytical model is established to determine the dominant tool error. • An identification method is developed to calibrate tool off-center error. • A tool center shift method is proposed to compensate tool off-center error. • Surface profile accuracy is significantly improved after tool error compensation. [ABSTRACT FROM AUTHOR]

The geometric error of machine tools can usually be reduced or compensated by various methods, but the influence of encoder performance on machining quality is often ignored. The purpose of this work is to analyze the influence of micro-cyclic error in linear encoders on milling surfaces and establish a compensation method to eliminate the encoder error. First, the origin of the micro-cyclic error of the linear encoder is analyzed. The micro-cyclic errors of the horizontal linear axes of an ultraprecision machine tool are preliminarily measured. The errors are also identified through milling tests. Second, a surface topography model for milling surfaces is established with consideration of the encoder micro-cyclic error. Based on the established model, a compensation method for the encoder micro-cyclic error is proposed. Finally, the error distribution model is validated by diamond ball-end milling experiments. Further experimental results confirm that the proposed compensation method can effectively remove the encoder error-related stripes from machined surfaces. The surface quality is considerably improved. [ABSTRACT FROM AUTHOR]

Perovskite ferroelectrics has great value and many new structures have been synthesized experimentally by doping with new components. But there were few studies on single atom substitution in theory. This article investigates the ferroelectricity of KNbO3 when some of the K atoms are replaced with elements of the same main group. Structural, polarization and electronic of different type KNbO3 were calculated using first principles calculations. Analysis of relaxed structure and electron charge shows that the different atom substitution produces different distortion. The combined analysis leads to the conclusion that the ferroelectricity decreases with increasing radius of the homologous atoms. This provides an explanation for the experimental data from another perspective. [ABSTRACT FROM AUTHOR]

The detection of indoor hazardous gases poses significant complexity and challenges. Based on first-principles theoretical calculations, Y-adsorbed MoS 2 (Y-MoS 2) monolayer is selected to investigate its adsorption, magnetism and sensitivity to NH 3 , HCHO and C 6 H 6 gas molecules. The presence of Y atom profoundly alters the electronic and magnetic properties of MoS 2 while enhancing its gas adsorption capability. The adsorption capacity of Y-MoS 2 monolayer for these indoor hazardous gases follows the order: HCHO > C 6 H 6 > NH 3. Notably, at temperatures around 500 K, the Y-MoS 2 monolayer exhibits potential as a sensor material for NH 3 based on an analysis of recovery performance in the adsorption system. Although the Y-MoS 2 monolayer is not suitable for gas sensing applications with regards to HCHO and C 6 H 6 , it can be effectively employed as a gas cleansing substance. These findings provide valuable insights into detecting indoor hazardous gases and contribute to our understanding of the gas sensing mechanisms exhibited by MoS 2 materials. • The Y-modified MoS 2 (Y-MoS 2) monolayer shows different adsorption ability to NH 3 , HCHO and C 6 H 6. • MoS 2 exhibits magnetic properties after modification with Y atom. • Y-MoS 2 exhibit non-magnetic metallic characteristics after adsorbing HCHO and C 6 H 6. • The Y-MoS 2 monolayer is a promising highly efficient gas sensing material for NH 3. [ABSTRACT FROM AUTHOR]

[Display omitted] • A semiempirical model to describe the grinding removal rate is proposed. • A method to optimize the grinding direction of conical indenter is developed. • Relationship between the grinding ability factor and roundness error is disclosed. • Tip pyramid phenomenon is weaken and the surface quality is improved. Mechanical grinding of a high-precision diamond conical indenter is difficult due to the strong grinding removal rate anisotropy. In the existing literature, theoretical models have been established to predict the strength anisotropy of diamond on the (100), (110) and (111) planes, which provide a theoretical basis for the fabrication of pyramid diamond indenters, such as Berkovich, Vickers or Knoop indenters. However, investigations on the anisotropic characteristics in processing of diamond curved surface are rarely carried out. To solve the anisotropy problem in grinding of diamond conical indenter, this work contributes a theoretical model to predict the anisotropic characteristics in grinding of diamond cone face, and provides an effective method to optimize the grinding direction for enhancing the fabrication precision. Based on a proposed grinding-ability factor model, a general method is developed to analyze the grinding ability along different directions according to the formation process of the cone face. The results suggest that the optimized mechanical grinding direction can be determined by minimizing the standard deviation of the grinding-ability factors of the crystal planes. The proposed method is validated by grinding experiments on indenters, with the <100> or <111> orientation along the indenter axis. The experimental observations confirm that the optimized grinding direction can weaken the pyramid phenomenon, yielding a roundness error of 0.12 μm. In addition, the grinding removal rate-dependent roughness petal phenomenon is suppressed, which considerably enhances the conical surface quality. [ABSTRACT FROM AUTHOR]

Diamond turning is an effective technology for processing metal mirrors used in photoelectric communications, radar, and other fields. In diamond turning, the precipitated phase is an essential factor that influences the surface quality of the metal mirrors. However, in previous studies, the precipitation phase has typically been handled as a random variable in a surface morphology model to evaluate its influence on the surface roughness, instead of determining the formation mechanism and proposing suppression solutions. In this study, a new phenomenon is observed in the diamond turning of metal mirrors, that is, the micro diamond tool can reduce the protrusion of the precipitated phase under a small feed rate and improve the surface quality. Investigating the turning process using diamond tools with varying tool nose radii at small feed rates (<1 μm/r), the underlying transformation mechanism of the precipitation phase is determined with the advanced material characterization technologies. The growth of the precipitated phase with an increase in the tool nose radius is explained using the energy gradient theory. The results showed that the increased material strain on the machined surface decreased the activation energy of solute diffusion in the material, causing solute accumulation and precipitate phase growth. With a further increase of tool nose radius to around 1000 μm, the β'' phase breaks and rotates. The representative volume element method shows that when undergoing severe plastic deformation, dislocations and grain boundaries quickly aggregate and slide on the precipitated phase, which will lead to the fracture and rotation of β'' phase. These findings provide a theoretical basis for the development of highly smooth mirrors. [Display omitted] • The mechanism of precipitation phase change on the surface of workpiece is discussed. • With the increase in tool nose radius, the volume of the precipitated phase increases. • As the tool nose radius further enlarges, the precipitated phase is torn and evenly distributed. • Reducing the plastic deformation can lessen the protrusion of the precipitated phase. [ABSTRACT FROM AUTHOR]

The processing of cemented carbide (WC-Co) with mechanical methods has become problematic in the production of functional parts and molds due to the great brittleness and hardness. The application of ductile-regime machining to process the WC-Co has been attempted, but the outcomes are not satisfactory. To better understand the processing of WC-Co, the Vickers indentation, nanoindentation, single point diamond turning, and taper cutting experiments are carried out by referring to the empirical parameters, instrument options, and published works. Firstly, the effectiveness of the reported models in predicting the critical uncut chip thickness of brittle-ductile transition of WC-Co are verified and discussed in terms of the experimental observations. Then the impact of diamond turning on the morphologies and mechanical properties of the machined surface are examined. After that, the defects that affect the surface quality of WC-Co are analyzed. The results indicate that the deterioration of surface quality is dominantly decided by the breakage of WC grain. The grain breakage induced defects and further observations of taper cutting on the WC-Co reveal that the critical uncut chip thickness (40–50 nm) required to produce a super-smooth surface is much smaller than the depths predicted by the reported models of brittle-ductile transition (0.674–1.008 μm). Such difference may be derived from the improper use of fracture toughness and application of models that treat the workpiece material as a continuous and evenly distributed medium. Finally, a modified diamond turning process is conducted to verify the effectiveness of the analysis. • Hardness of WC-Co at different scales were discussed. • It is the behaviors of WC grains affecting surface quality of WC-Co at nano scale. • Fracture toughness cannot describe critical loads for WC grains breaking in WC-Co. • The porosity of WC-Co should be suppressed to achieve super-smooth surface. [ABSTRACT FROM AUTHOR]

In this work, to investigate the effect of tool rake angle in diamond turning of KDP crystal, a novel theoretical model that considers the material properties, tool geometries, cutting parameters and the suppression of hydrostatic pressure is established by formulating the relative length of crack (RLC). Subsequently, interrupted-cutting experiments with different tool rake angles are performed, and an effective method for crack evaluation is used to acquire the experimental results of RLC. Moreover, using the inverse analysis for material model parameters by nanoindentation test and dimensional analysis method, a novel 3D hybrid model with the use of smoothed particle hydrodynamics and finite element method is constructed to simulate the diamond turning process of KDP crystal. As expected, the dynamic distribution of hydrostatic pressure ahead of the active cutting edge is successively investigated to reveal the underlying mechanism of tool rake angle, which is a significant factor that affects crack propagation, surface generation and chip formation. The results show that the developed theoretical model which considers the suppression of hydrostatic pressure has a satisfactory accuracy in predicting the quantitative relationship between tool rake angle and crack propagation. Large negative rake angles from −25° to −45° are suggested for the diamond turning process of KDP crystal. [ABSTRACT FROM AUTHOR]

The interface between explosive crystal and binder polymer plays a critical role in the stabilities of energetic materials. In the present work, we investigate the mechanical properties of cyclotetramethylenetetranitramine (HMX)–polystyrene (PS) interface by performing molecular dynamics simulations of uniaxial tension, nanoindentation and nanoscratching tests. Our simulation results indicate that the HMX–PS interface has a mediate strength between HMX of high strength and PS of low strength. In particular for nanoindentation and nanoscratching, the distance of indentation position or scratching position to the HMX–PS interface has a strong influence on mechanical deformation behavior of HMX–PS system. Specifically, the HMX–PS interface has the lowest indentation force and scratching force than both the HMX and the PS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cutting performance improvement of diamond tools by focused ion beam were evaluated. • Modification parameters of diamond tools were clarified through theories and experiments. • Wear resistance mechanism of modified diamond tools was explained by surface energy and chemical bond based on first principal calculations. • The decreasing degree of cutting force components was positively related to the dose. • The improving degree of surface quality machined was more obvious at a great dose. The modified diamond tools (MDT) by focused ion beam (FIB) can reduce tool wear to a certain extent while avoiding the pollution of traditional cutting fluid. This paper investigates the dry single-point diamond turning (DSPDT) process for Al6061 alloy with MDT. DSPDT tests showed that MDT produced lower cutting forces and generated smoother machined surfaces. Furthermore, MDT has a lighter wear compared with the unmodified diamond tools. The reasons why the cutting performance of MDT is better than the unmodified diamond tools are the reduced surface energy of modified diamonds proved by the first principle calculations and contact angle tests, and the change of the C–C bond energy and bond length according to the first principle calculations. Therefore, it is feasible and promising to apply the MDT in the DSPDT of Al6061 alloy, which will contribute to carbon neutralization manufacturing. [ABSTRACT FROM AUTHOR]

Gallium ion implantation is an important solution to modify the physical properties of diamonds, in which the critical condition of gallium ion implantation-induced amorphization of diamond has a crucial influence on the modification effect. Therefore, this work attempts to establish an analytical prediction model of the critical implantation dose for diamond amorphization considering the acceleration voltage, implantation angle and crystal orientation. The prediction accuracy of the model is validated with the electron backscatter diffraction pattern technology. The results show that the model has a satisfactory prediction accuracy when the acceleration voltage is higher. Moreover, the atomic-scale observation of gallium ion implantation-induced amorphization of natural diamonds is realized on a spherical aberration projection electron microscope. The results presented in this work are significant to modify the natural diamond tool for service life improvement with focused ion beams in the future as well as to guide doping diamonds to manufacture n-type semiconductor diamonds. • The clarity of EBSP is used to observe the amorphous evolution of diamond. • The evolution of diamond amorphization is directly observed at the atomic scale. • An analytical prediction model for the critical dose of diamond amorphization is established. [ABSTRACT FROM AUTHOR]

Pointed diamond tool has been widely used in ultraprecision manufacturing of V-grooves. This article provides a wear law and wear characteristics of pointed diamond tool during V-grooves machining with the consideration of the cutting stress and the strength of diamond, which could be used to estimate the tool wear state and control the V-grooves machining quality. In this research, the model of cutting stress distribution and cutting force in V-grooves machining are established, which indicate that the maximum normal stress is independent on the cutting depth. Then, the tool tip fracture condition and cutting edge wear law of pointed diamond tool are further explored. The obtained law and experiments results shows that the tool wear is reflected in the cutting edge radius increasing while the wear rate is high at the beginning and then decreases gradually. Besides, the wear characteristic of the tool tip is different from the side cutting edge due to the diamond strength anisotropy. Raman spectra analysis indicates the wear mechanism of the tool is mechanical friction wear in machining of Al 6061 V-grooves. [ABSTRACT FROM AUTHOR]