Surface Topography Of Workpiece Research Articles

Fluorescence-Based Calibration Model for In-Situ Measurement of Micro-scaled Lubricant Thickness Distribution at Indentation Interface

This study proposes a model for the measurement of microscale liquid film thickness distribution using fluorescence signals. The interfacial conditions between the tool and the workpiece in mechanical machining are important for understanding these phenomena and mechanisms. In this study, indentation tests with transparent tools were used to observe interfaces; however, it was challenging to obtain the signal from a thin fluorescent liquid film on smooth and steeply inclined surfaces. Therefore, fluorescence-based measurement, such as laser-induced fluorescence, was employed. To measure the absolute thickness of the thin fluorescent film, calibration of the measurement system is necessary. Therefore, a theoretical model was proposed considering the multiple reflections of excitation light and fluorescence at the inclined surface between the indenter and workpiece. By measuring the profile of the surface topography of the indented workpiece and comparing the results with those measured by a surface profiler, the validity of the proposed calibration method and the performance of this measurement system were demonstrated. The measured surface profiles, including scratches of 2–4 µm, were in good agreement, demonstrating the validity of the proposed method.

An online monitoring methodology for grinding state identification based on real-time signal of CNC grinding machine

The grinding state is closely related to machining accuracy, wheel wear, and material removal efficiency. Changes in the grinding state often mean instability of the processing state, which will cause additional costs such as wheel wear and a decline in the processing quality of the workpiece. Various methods for monitoring grinding conditions have been proposed in the past, but none of these methods have been universally successful due to the complex nature of the machining processes. This research presents a new method for real-time monitoring of grinding forces and workpiece surface topography during grinding processing using real-time signals from the computer numerical control (CNC) system of the grinding machine without any additional sensors. By extracting real-time signals during the grinding process for time and frequency-domain analysis, the grinding state can be identified online. Based on this method, the time–frequency domain calibration experiment is carried out. The resolution of the time-domain calibration results reached 6e-5N, which can characterize the real-time change of grinding force during the grinding process. The frequency-domain analysis can achieve real-time monitoring of the spindle state of the workpiece and the grinding spindle state and obtain the frequency-domain transmission path under different processing conditions. The workpiece surface morphology is estimated in real-time using the feedback signal of the grinding machine, and the results are verified in mm, μm, and nm scales. The test results show that the use of real-time signals from the grinding machine to monitor the grinding state has the advantages of high precision, reliability, and convenient implementation.

Effect of Robot Motion Accuracy on Surface Form during Computer-Controlled Optical Surfacing Process

Nowadays, large-aperture optical components are increasingly used in high-power laser systems, remote-sensing satellites, and space-based astronomical telescopes. Fabricating these surfaces with submicron-scale shape accuracy and a nanoscale surface finish has been a great challenge for the optical industry, especially for hard and difficult-to-machine materials. Thus, to achieve the high-efficiency and high-precision polishing of large-aperture aspherical optical parts, this study combined robotic machining technology with computer-controlled optical surfacing (CCOS) technology and investigated the effect of robot motion accuracy on the surface topography of workpieces during polishing. First, a material removal model considering the normal error of the polishing tool was developed based on contact mechanics, kinematic theory, and the abrasion mechanism. Next, in combination with the polishing trajectory, the surface morphology and form accuracy after polishing were predicted under different normal-error conditions. Then, preliminary experiments were conducted to verify the model. The experimental data agreed with the simulation results, showing that as the normal error increased from 0° to 0.5° and 1°, the peak-to-valley (PV) values of the surface profile of the optical element decreased from 5.42, 5.28, and 4.68 μm to 3.97, 4.09, and 4.43 μm, respectively. The corresponding convergence rates were 26.8%, 22.5%, and 5.3%. The root mean square (RMS) values decreased from 0.754, 0.895, and 0.678 μm to 0.593, 0.620, and 0.583 μm, with corresponding convergence rates of 21.4%, 30.7% and 14.0%, respectively. Moreover, a higher motion accuracy enabled the polishing robot to reduce the mid- and high-frequency errors of the optical element.

A comparative study of the surface topography in dry and wet turning using the confocal and interferometric modes

This article is concerned with dry and wet turning of C45 steel using sintered carbide tools. The study focused on the surface topography of workpieces obtained by means of a 3D surface measurement system operating in two modes: confocal and interferometric. The main purpose was to compare the corresponding data measured in the two modes, confocal and interferometric. The study also aimed to analyse the tool wear depending on the turning conditions. The use of a scanning electron microscope and a stereoscopic microscope was essential to comprehensively characterise the workpiece surfaces and determine the cutting tool wear. The results obtained in the confocal and interferometric modes differed. The confocal module proved to be better for characterising the surface topography of C45 steel machined by turning. The surface quality after wet turning was higher than after dry turning; hence the lower values of the 2D parameters (Ra, Rq, Rp and Rv) and of the 3D parameters (Sa, Sq, Sp, Sv). The wear visible on the cutting tool after wet turning was half as much as that after dry turning (e.g. surface abrasion indicator VBBmax equal to 0.21 mm for wet turning and 0.39 mm for dry turning). The results prove that the choice of methods for measuring the surface topography (by determining the relevant parameters and functions) and analysing the surface features can play an important role in the characterisation of the machined surface. A well-thought-out research methodology is thus essential. From the experimental data, it is also clear that the use of mineral oil-based cutting fluid for turning with sintered carbide tools improved the surface quality of workpieces and reduced the tool wear.

Circular sawblade vibration suppression by thermal stress stiffening method

In this paper, a temperature-controlled circular saw is proposed by a thermal stress stiffening method, which provides a novel approach that is easy to implement for suppressing sawblade’s vibration and improving machining quality. In this method, the sawblade’s inner boundary is heated by infrared radiation to generate in-plane thermal stress and improve the sawblade’s bending stiffness. Through theoretical calculation and experiment, it is found that increasing the inner boundary’s temperature can effectively increase the natural frequency of the sawblade’s dominant mode. Considering that the saw blade operates near and far from its resonant speed, four cutting experiments are performed on a same beech wood bar under temperature-controlled or uncontrolled conditions. The transverse vibration of the sawblade is measured by a laser displacement sensor, and the surface topography of the cut workpiece is obtained by a three-dimensional surface topography measuring device. This vibration suppression method significantly reduces the vibration amplitude of the sawblade, and effectively improves the machining quality of the circular saw. The experimental results show that using this method can reduce the defect depth of cutting processing by more than 60% when the sawblade rotates near its resonance speed, and is also effective when resonance does not occur.

Two-Dimensional Profile Simulation Model for Five-Axis CNC Machining with Bull-Nose Cutter

Surface topography is closely related to fatigue strength and mating accuracy of workpieces. The profile method is widely adopted to evaluate surface topography. In the present study, a 2D profile simulation model of five-axis CNC machining with a bull-nose cutter is proposed to predict the surface topography of a machined workpiece. To this end, a simplified scallop model is established by analyzing the geometry and motion of the bull-nose cutter. Then, the principles of the 2D profile simulation model for plane and free-form surfaces are described to provide the basis for building 2D profile simulation models. After that, 2D profiles are obtained directly from CL data, tool parameters, and workpiece design models, and an algorithm is proposed to obtain 2D profiles. Finally, the proposed algorithm is verified by different machining experiments on plane and free-form surfaces. The results show that the simulation and measurement results are in good agreement. The proposed simulation model for five-axis CNC machining with a bull-nose cutter can be effectively applied to simulate 2D profiles of plane and free-form surfaces. The present study is expected to provide a reference for optimizing process parameters.

Simulation and Experiment Research on the Surface Deformation and Residual Stress of Fractal Rough Surface Single-Shot Peening

In order to study the influence of workpiece surface topography on deformation and residual stress during shot peening, the paper built a rough surface single-shot peening simulation model and designed a rough surface workpieces shot peening experiment to verify the correctness of the built simulation model, which differed from the smooth surface simulation model and was closer to the actual processing situation. Based on the W-M fractal dimension theory, the shot peening model of the target with a rough surface is established, and the simulation analysis is carried out by finite element software. The effect of different impact positions of the pellet on surface residual stress and surface displacement were also simulated. The simulation found that with the increase of surface complexity, the surface deformation and residual stress would both increase after shot peening. Through shot peening tests on workpieces with different surface roughness, it is found that the error between simulation and experiment results on surface deformation and residual stress are both less than 20%, which verifies the validity of the rough surface single-shot peening model and that the established model could provide a new method on shot peening simulation analysis.

Influence of XHV-adequate atmosphere on surface integrity

In aerospace engineering, high temperature alloys such as titanium are the preferred choice. However, machining of such materials remains a major challenge due to high process forces and process temperatures. Currently, machining is performed almost entirely in the presence of oxygen. This results in a process-inherent oxidation of the metal surface, which leads to higher tool wear during machining. By means of an oxygen-free machining undesirable oxidation reactions will be avoided and thus results in an extension of tool life. In addition, oxygen-free machining in an extreme high vacuum (XHV) adequate environment can influence the resulting workpiece surface and subsurface properties due to change in process forces and chip formation. In the present work, the influence of machining under air and XHV-adequate atmosphere is examined with regard to chip formation, workpiece surface topography and residual stresses. Significant differences can be seen in resulting surface integrity depending on the machining atmosphere.

A New Wire Electrode for Improving the Machining Characteristics of High-Volume Fraction SiCp/Al Composite in WEDM.

In wire electrical discharge machining, due to the random distribution of the insulating SiC particles, frequent wire rupture, low machining efficiency and surface quality when the common brass wire electrode (BWE) is used to process high-volume content SiCp/Al composite often appears. To address this issue, this paper proposes a new preparation method of zinc coating and surface microstructure on wire electrodes (ZCSMWE). The preparation process of ZCSMWE includes casting, coating, annealing and plastic processing. The experimental results show that, compared with BWE, ZCSMWE can increase material removal rate (MRR) by 16.67%, reduce surface roughness (Ra) by 21.18% and reduce wire rupture under the same discharge parameters. The analysis of workpiece surface topography shows that ZCSMWE can significantly decrease the recast layer and microcrack on the machined surface. The improvement mechanism of ZCSMWE main includes: The low work function zinc can promote the forming of the discharge channel. The vaporization of low boiling temperature zinc can reduce the temperature of the discharge gap and promote the ejecting of workpiece material. In addition, the surface microstructure on ZCSMWE can make the discharge spark more uniformly distributed and increase the proportion of the effective discharge, which contributes to making the discharge crater on the workpiece and wire electrode shallower and more uniform. The surface microstructure on ZCSMWE can also effectively improve the dielectric circulation, which can promote discharge debris to be expelled out and reduce the temperature in the discharge gap. Then, the wire rupture and microcracks on the workpiece surface can be reduced.

Investigation on the Micro Cutting Mechanism and Surface Topography Generation in Ultraprecision Diamond Turning.

Revealing forming mechanism of workpiece surface topography plays an important role in improving ultraprecision turning. In this paper, the forming mechanism of the turning workpiece surface topography is analyzed and verified by the theoretical simulation and experiment respectively. First, the factors directly related to the turning process are analyzed, and a volumetric error model is built and discussed, which considered geometric errors, tool geometry, spindle vibrations, feed rate, cut depth, and feed system position change. The vibration mechanism and laws of the spindle system under multi-field coupling is analyzed, and the effect of the spindle axial vibration on the turning surface topography is studied. In addition, influence of coupled vibrations on the turning surface texture is analyzed, and an equivalent machining model is constructed to identify crucial geometric errors of the workpiece surface topography. Finally, a homemade ultraprecision machine tool system is built and used for turning the workpiece surface, and the tested results of the surface topography demonstrate Ra is better, 10 nm and Rv is better, 20 nm. The end face of the workpiece forms periodically fluctuating wave and ripple patterns, and the comparison between theoretical analysis and experimental detection of the surface topography is verified.

Hybrid model based on recursive feature elimination with cross validation and Tradaboost for workpiece surface topography prediction of five-axis flank milling

Hybrid model based on recursive feature elimination with cross validation and Tradaboost for workpiece surface topography prediction of five-axis flank milling

Effect of MQL condition on cutting performance of high-speed machining of GH4099 with ceramic end mills

Ceramic tool materials become an ideal choice for machining superalloy materials because of the excellent tolerance to effect of heat, strong chemical stability and high temperature hardness. The present paper focuses on the effects of different cutting environments which are the dry, MQL (pure-oil) and MQL mixed with water on the milling force in each direction, the variation of flank wear, as well as surface topography of workpiece, simultaneously analyzing in deep to the wear mechanism of the mills during distinct technological environments. The results reveal that the milling force of MQL and MQL mixed with water conditions were decreased by 12.8% and 28.2% respectively compared with the dry milling. In terms of the cutting temperature, it was also significantly reduced up to 9.2% and 17.5% separately. In addition, MQL and MQL mixed with water had been successful in improving the surface quality of the workpiece and limiting the tool wear values. Similar to the tool wear mechanism of dry milling, the wear mechanisms of ceramic end mills under MQL and MQL mixed with water were deemed adhesive wear, diffusion wear and notch wear.

Towards the understanding the effect of surface integrity on the fatigue performance of silicon carbide particle reinforced aluminium matrix composites

The fatigue performance of metal matrix composites (MMCs) is highly related to their surface integrity due to the intensive tool-particle interactions and metallographic alterations of matrix, especially under extreme cutting parameters, which could largely result in surface morphologic defects and subsurface damage on the components. Although the fatigue performance of bulk MMCs has been extensively studied, the influence of machining-induced surface anomalies on the fatigue failure mechanism still needs to be understood. This paper investigates the effect of two distinct surface integrities induced by two cutting regimes (ductile, and semi-brittle regime) on the fatigue performance of MMCs. The ductile and semi-brittle regime were represented by different surface integrities regarding the particle behaviours and their effect on the mechanical and metallographic alterations of matrix materials. In-depth analysis in terms of surface topography, subsurface damage, and residual stresses of the machined workpieces has been carried out before the three-point bending fatigue test. The results showed that the samples machined by finish milling (very low feed – semi-brittle regime) unexpectedly presented lower fatigue lives compared to the rough-milled counterparts (high feed – ductile regime), despite the former displayed compressive residual stress and lower surface roughness. It was found that the particles have pronounced influence on the fatigue performance in two different ways: under low cycle fatigue, the particles were prone to be fractured by the high stress applied (which accelerated the formation of crack initiations and therefore shortened the fatigue life), while under high cycle fatigue, the reinforcement particles were not fractured and instead they could inhibit the crack growth up to some extent. Therefore, fatigue lives of the rough-milled samples (high feed – ductile regime) were enhanced due to the retardation of reinforcement particles.

Surface Topography of the Metal surface in Robot Polishing under Control Force

Polishing is an important finishing process in the field of manufacturing, which enhances product quality and increases its life span. Compared with manual polishing, robotics polishing has advantages in terms of cost and productivity. This paper presents a new study on the surface topography of metal workpiece in the robotic polishing test. Various workpieces with different surface roughness were polished with the industrial robot under similar polishing parameters, and the variation of surface topography with polishing was studied utilizing microscopic scanning.

Kinematic modeling of surface topography ground by an electroplated diamond wheel

This paper presents a three-dimensional kinematic simulation of surface topography ground by a D301 electroplated diamond wheel. For an individual cubo-octahedron diamond grain, its cutting process is modeled by decomposing it into active grain edges and discrete cutting points. By successively integrating the material removal caused by all the grains, the ground surface topography of workpiece is successfully predicted. The predicted surface roughness is close to the theoretical and experimental values with relative errors of − 7.9% and − 3.3% for aluminum and fused silica, respectively. The study reveals that the other amplitude parameters, e.g., kurtosis and skewness, of surface profiles can reflect the material removal mechanisms. The lateral pile-up of plastic aluminum alloy in grinding increases the kurtosis while the fracture of brittle fused silica results in a prominently negative skewness. For a fresh grinding wheel, the surface roughness Ra reaches a plateau after a rapid increase as the grinding depth increases to 1.25 times the SD of the grain protrusion heights. By contrast, the effects of grinding depth on the surface topography are negligible when the wear depth is beyond a certain value. As the feed rate increases, the number of active abrasive grains gradually increases. Meanwhile, the effect of the grain circumferential distribution on the workpiece surface topography becomes significant.

Comprehensive study on Inconel 718 surface topography after grinding

The correct selection of cutting parameters is crucial to provide tribological conditions that contribute to meet the required workpiece surface topography characteristics, especially considering abrasive processes such as grinding. The present work sought to evaluate the influence of several cutting parameters on surface topography of Inconel 718 after grinding. Surface finish and morphology were used to assess topography of workpiece. Cutting forces and coefficient of friction were also analyzed. The results showed that, although workspeed promoted negligible effects, varying depth of cut and wheel speed strongly affected tribological conditions at contact zone, resulting in significant changes on topography. Reducing abrasive grit size improved surface finish and resulted in Rsk close to zero.

Effect of double-excitation ultrasonic elliptical vibration turning trajectory on surface morphology

To explore the formation law and influence factors of three-dimensional geometry in axial turning surface, the turning experiment of 7075 aluminum alloy was carried out by using double excitation three-dimensional ultrasonic elliptical vibration method. Based on the theory of turning kinematics, the tool tip trajectory model of three-dimensional ultrasonic elliptical vibration turning (3D-UEVT) was established, and the related mechanism in surface residual height, surface topography formation characteristics, and turning transmission was given. Through single factor simulation and turning test, the influence of spindle speed, feed speed, amplitude, and phase difference on the surface microstructure and roughness of workpiece was analyzed contrastively. The results show that, compared with the traditional turning, the double excitation ellipse assisted turning can affect the surface topography and quality of the workpiece by causing the dynamic change of the cutting angle of the tool tip and the residual height of the material. Combined with the analysis of simulation and experimental results, it is found that the ideal microstructure and roughness can be obtained with low speed, slow feed, small amplitude, and small phase difference. Meanwhile, the tool workpiece separation characteristics, surface topography, roughness, and surface defect level can be effectively improved under the three-dimensional ultrasonic elliptical assisted vibration.

Generative Adversarial Network for Prediction of Workpiece Surface Topography in Machining Stage

Surface topography plays a key role in the service performance of parts, and is often used as a metric for detecting machining states as well. Hence, it is of great importance to online predict the surface topography to avoid surface deterioration and machining faults. However, alternative solutions for this purpose remain to be developed. This article presents a generative adversarial network to predict the statistical distribution of surface topography conditioned on cutting parameters, measured cutting forces, as well as system vibrations. The local dynamic characteristics and global quasi-static trend of measured process quantities are extracted by short-time spectrum technique, then mapped into the local surface features patch by patch. To improve the network performance, we embed several useful tricks, such as recursive residual block, skip connection, and global residual architecture into the surface generator so as to enhance its capacity of learning the complicated nonlinear mapping against limited training data. The model performance is evaluated and validated using the structure similarity index, the distance of extracted features by the visual geometry group network, as well as the perceptual index. The results indicate that the recursive architecture performs better than nonrecursive one on learning the nonlinear correlation between surface topography and measured process quantities. Besides, by applying adversarial learning, the texture characteristics can be well-captured to avoid the blur of high-frequency details.

Silica-assisted fixed agglomerated diamond abrasive polishing

The fixed agglomerated diamond abrasive pad had been used to planarize ultra-hard and brittle materials such as sapphire and SiC. However, the processing stability and surface integrity of sapphire remain to be improved. A silica-assisted fixed agglomerated diamond abrasive polishing (SA-FADAP) process was developed to solve the above mentioned problems. The material removal mechanism of the SA-FADAP was explored by analyzing material removal rate gradient (MRRG), surface topography of workpieces, the pad abrasion, and wear debris in the slurry wastes. The effects of silica grains on the self-conditioning processes of fixed agglomerated diamond abrasive pads were discussed. The efficient and stable SA-FADAP was mainly realized by the chemical-mechanical interaction produced by agglomerated diamond abrasives and silica polishing slurry.

Electrode catalyst layer of electrochemical device, membrane electrode assembly of electrochemical device, and electrochemical device

The fixed agglomerated diamond abrasive pad had been used to planarize ultra-hard and brittle materials such as sapphire and SiC. However, the processing stability and surface integrity of sapphire remain to be improved. A silica-assisted fixed agglomerated diamond abrasive polishing (SA-FADAP) process was developed to solve the above mentioned problems. The material removal mechanism of the SA-FADAP was explored by analyzing material removal rate gradient (MRRG), surface topography of workpieces, the pad abrasion, and wear debris in the slurry wastes. The effects of silica grains on the self-conditioning processes of fixed agglomerated diamond abrasive pads were discussed. The efficient and stable SA-FADAP was mainly realized by the chemical-mechanical interaction produced by agglomerated diamond abrasives and silica polishing slurry.