Surface Morphology Of Workpiece Research Articles

Study on sinusoidal lapping micro-structured surface by abrasive stone with staggered abrasive particles

In order to manufacture structured surfaces, firstly, the abrasive stone model with staggered abrasive particles is established with mathematical methods. Secondly, the motion of abrasive particles on the abrasive stone is designed. Finally, the surface morphology of the workpiece is simulated. The simulated workpiece morphology under different machining parameters is compared, and the influence of different machining parameters on the workpiece surface morphology is obtained. The results indicate that the microstructured surface can be lapped by using the abrasive stone of staggered abrasive particles. As the amplitude and frequency of the abrasive stone increase, the number of protrusions increases, and the area of individual protrusions decreases.

Research on the Grinding Performance of an Electroplated Coarse-Grained Diamond Grinding Wheel by Dressing

The coarse-grained electroplated diamond grinding wheels is increasingly favored in precision grinding of hard and brittle materials owing to its high material removal efficiency, high wear resistance and steady surface contour accuracy. However, how to determine whether the dressed grinding wheel surface topography can achieve the desired precision ground surface quality is still a huge challenge to this day. In this paper, a novel numerical simulation model, which was established basing on the statistical features of actual electroplated coarse-grained diamond grinding wheel and the kinetics of the grinding process, was proposed for theoretically and thoroughly studying the influence of the surface dressing depth of coarse-grained electroplated diamond grinding wheel on ground workpiece surface morphology. At first, the statistical features of actual electroplated coarse-grained diamond grinding wheel was acquired and a novel numerical grinding wheel surface model was established. Subsequently, a numerical ground workpiece surface simulation model was also developed. And then, the evolving mechanism of the grinding wheel surface topography with the dressed wheel surface abrasive grain protrusion height was theoretically studied by numerical simulation. Moreover, the influence of the wheel surface abrasive grain protrusion height on the ground surface roughness was thoroughly researched by means of theoretical model and experiments. The simulation and experiments results in this paper indicated that precision ground workpiece surface with nano-scale surface roughness can be acquired by grinding with a dressed grinding wheel with a certain abrasive grain protrusion height of 25% of the typical abrasive size. Comparing with the undressed grinding wheel (grinding wheel with original surface topography and not be dressed), the surface roughness Sa and Sq of the surface ground with a well-dressed wheel can achieving a significant decrease of 97.75–99.77% and 97.57–99.73%, respectively. Therefore, carefully dressing the electroplated coarse-grained diamond grinding wheel is of great significance for obtaining a precision ground workpiece surface quality.

Generation mechanism of the surface morphology on tilted ultrasonic elliptical vibration cutting TC4 titanium alloy

TC4 titanium alloy is utilized in aerospace and a wide range of other applications due to its high strength and corrosion resistance, but its poor thermal conductivity and high ductility introduce challenges in machining. In this paper, firstly, a mathematical model of workpiece surface morphology under tilted ultrasonic elliptical vibration cutting (TUEVC) was established based on the tip trajectory and material removal mechanism, and the variation of workpiece surface morphology was investigated at different tool tilt angles θ, and it was found that the tilt θ in a certain range could significantly reduce the surface residual height compared with that of ordinary ultrasonic elliptical vibration cutting (UEVC). Second, the TUEVC experiment of TC4 titanium alloy was carried out to comparatively analyze the changes in the surface morphology, surface profile, and surface roughness of the workpiece under different tilt θ, the effect of each machining parameter (cutting speed, feed, and ultrasonic amplitude) on surface roughness was explored. The experimental results indicate that as the tilt θ changes from 0° to 90° throughout the process, the workpiece surface morphology flatness decreases and then increases. When the tilt angle θ is 45°, workpiece cutting surface roughness is minimized (Sa = 0.157), compared with the ordinary ultrasonic elliptical vibration cutting roughness is reduced by 47.6 % maximum. Both the surface morphology flatness and the surface roughness of the workpiece are at their smallest, whereas the theoretical profile curve and cutting surface profile curve are at their most consistent. Under the same machining parameters, TUEVC can reduce the surface roughness more effectively compared with UEVC, this technique reduces surface roughness by 16 %, 23 %, and 26 % at maximum for different cutting speeds, feeds, and ultrasonic amplitudes, respectively.

Study on the dynamic influence of the distribution of cutting depth on the ground surface quality in a precision grinding process

Focusing on the excitation mechanisms of self-excited vibration and forced vibration, a time-delay differential model of the radial cutting depth of a single active abrasive grit is presented. Based on the principle of the layered superposition characteristics of each component of radial cutting depth, a full discrete simulation technology is used to analyze the dynamic mechanisms of different vibration excitations on the grinding characteristics. The reliability of the dynamic mechanisms is verified by the corresponding grinding experiments. The verification results demonstrate that static and dynamic components in the grinding dynamics, including radial cutting depth, grinding force, surface roughness and surface morphology of workpiece are greatly influenced by total material removal rate, followed by speed ratio and grinding directions. With the increase of cutting depth, the variation amplitude of grinding process influenced by forced-vibration mechanism are nearly twice larger than those influenced by self-excited vibration mechanism. When speed ratio reduces to a half, surface roughness of workpiece improves by nearly 33 %. The stability of machining process and finish surface of workpiece during up-grinding are better than those during down-grinding, where force reduction by up to 10 % and surface finish improvement by 37 %.

A new algorithm for chatter quantification and milling instability classification based on surface analysis

The unstable statuses in machining, such as chatter and severe forced vibration, limit manufacturing productivity and quality. Although there have been plentiful studies on the on-line sensing signals and off-line surface images to identify these statuses qualitatively, the quantification of chatter severity, which is of great significance on machining stability, has been rarely reported. Workpiece surface morphology is the direct result and thus the objective criteria of unstable machining. This paper proposes a new algorithm to quantify the chatter status based on the milled surface image analysis of end-milling. Besides, the proposed method can also identify the stable, forced vibration, and chatter statuses. Specifically, this proposed algorithm extracts two indexes, called Index_Dmean and Index_Emean, via processing the milled surface image. The definitions and calculations of these two indexes are given in Section 2. Index_Dmean is used to differentiate stable and unstable surfaces and quantify the severity of chatter status, and Index_Emean can distinguish between forced vibration and chatter surfaces. Experimental results demonstrate the availability of the proposed algorithm on the chatter quantification and milling instability classification performance. In addition, an applicable on-line vision system with satisfying performance based on the algorithm is developed.

Multi-Objective Optimization in Ultrasonic Polishing of Silicon Carbide via Taguchi Method and Grey Relational Analysis.

As high-level equipment and advanced technologies continue toward sophistication, ultrasonic technology is extensively used in the polishing process of difficult-to-process materials to achieve efficiently smooth surfaces with nanometer roughness. The polishing of silicon carbide, an indispensable difficult-to-machine optical material, is extremely challenging due to its high hardness and good wear resistance. To overcome the current silicon carbide (SiC) ultrasonic polishing (UP) process deficiencies and strengthen the competitiveness of the UP industry, the multi-objective optimization based on the Taguchi-GRA method for the UP process with SiC ceramic to obtain the optimal process parameter combination is a vital and urgently demanded task. The orthogonal experiment, analysis of variance, grey relational analysis (GRA), and validation were performed to optimize the UP schemes. For a single objective of roughness and removal rate, the influence degree is abrasive size > preloading force > abrasive content > spindle speed > feed rate, and spindle speed > abrasive size > feed rate > preloading force > abrasive content, respectively. Moreover, the optimal process combination integrating these two objectives is an abrasive content of 14 wt%, abrasive size of 2.5 μm, preloading force of 80 N, spindle speed of 8000 rpm, and feed rate of 1 mm/s. The optimized workpiece surface morphology is better, and the roughness and removal rate are increased by 7.14% and 28.34%, respectively, compared to the best orthogonal group. The Taguchi-GRA method provides a more scientific approach for evaluating the comprehensive performance of polishing. The optimized process parameters have essential relevance for the ultrasonic polishing of SiC materials.

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.

Molecular Dynamics Simulation Study on the Influence of the Abrasive Flow Process on the Cutting of Iron-Carbon Alloys (α-Fe)

The plastic deformation behavior and microstructural changes in workpieces during ultra-precision machining have piqued the interest of many researchers. In this study, a molecular dynamics simulation of nano-cutting iron-carbon alloy (α-Fe) is established to investigate the effects of the fluid medium and cutting angle on workpiece temperature, friction coefficient, workpiece surface morphology, and dislocation evolution by constructing a molecular model of C12H26 as a fluid medium in the liquid phase using an innovative combined atomic approach. It is demonstrated that the presence of the fluid phase reduces the machining temperature and the friction coefficient. The cutting angle has a significant impact on the formation of the workpiece's surface profile and the manner in which the workpiece's atoms are displaced. When the cutting angle is 0°, 5°, or 10°, the workpiece's surface morphology flows to both sides in a 45° direction, and the height of atomic accumulation on the workpiece surface gradually decreases while the area of displacement changes increases. The depth of cut increases as the cutting angle increases, causing greater material damage, and the presence of a fluid medium reduces this behavior. A dislocation reaction network is formed by the presence of more single and double-branched structures within the workpiece during the cutting process. The presence of a fluid medium during large-angle cutting reduces the number of dislocations and the total dislocation length. The total length of dislocations inside the workpiece is shorter for small angles of cutting, but the effect of the fluid medium is not very pronounced. Therefore, small cutting angles and the presence of fluid media reduce the formation of defective structures within the workpiece and ensure the machining quality.

A novel approach for modeling MRR in EDM process using utilized discharge energy

The discharge energy generated during the EDM operation characterizes the productivity of the process. The present research attempts to model the material removal process of EDM by obtaining the actual discharge energy during the spark occurrence. The model incorporates the actual discharge conditions by analyzing the real-time V–I waveforms acquired during the EDM operation to determine the discharge power. The model also establishes that discharge power density is a function of applied heat flux and discharge gap. The model verification is conducted by performing a series of experiments on Titanium grade-5 alloy using a full factorial L18 design. The current study implements tool lift time compensation to achieve accurate MRR from the experimental outcomes. The specific energy obtained using the current approach shows better stability compared to previous literature. The parametric studies show gap voltage to be the most significant parameter in influencing the MRR. The main effects plot show the influence of different process parameters on MRR. Additionally, the surface morphology of workpiece and tool surface through SEM and EDS analysis shows the presence of different anomalies and confirms surface alloying. The predicted outcomes of the model show a maximum deviation of 13.05% from the practical evidence.

Machining Stability Research of Soft-Brittle Crystals Lapping by Fixed-Abrasive Pad

Fixed-abrasive (FA) lapping and polishing process is the main approach to realize the residual-free and low damage processing of soft-brittle crystals. The hardness of matrix and the abrasive micro-fragmentation are the key parameters impacting the stability of the continuous batch machining. The FA pads were prepared with hard and soft matrix, respectively, and the single diamond (SD) and the aggregated diamond (AD) were mixed in the FA pads, respectively. The FA lapping tests were carried out with LN wafers under the applied load of 10.5 kPa. The continuous batch machining stability of four pads tests were evaluated by the evaluation indexes of the material removal rate (MRR), surface roughness Ra and the material removal rate variation (MRRV). The workpiece surface morphology and abrasive wear pattern were analyzed. The results indicate that: hard matrix is not conducive to the shedding and replacement of abrasive grains because of the high holding force, causing a MRRV of 50%. The MRR of the hard matrix pad tests signally decrease from 3.71 μm/min to 1.9 μm/min. By contrast, the low hardness matrix pad can be applied to improve the machining efficiency owing to its MRRV only about 30%. The MRR of the AD pad is over 600 nm/min, which is far more than that of the SD pad, and the MRRV of the AD pad is just about 20%. While MRRV of the SD pad is as high as 75% with the remarkably decline of MRR. At the view of Ra values, the SD pad and the AD pad both attain nanoscale. The Ra values of the SD pad tests are smaller and the workpiece are superior in surface quality. In the rough lapping and fine lapping stage, the SD can be used to prepare FA pad to improve lapping stability.

Theoretical study on sawing force of ultrasonic vibration assisted diamond wire sawing (UAWS) based on abrasives wear

Wire saw cutting of monocrystalline silicon plays an important role in semiconductor manufacturing. The study of wire saw cutting silicon is important, and the grain wear has a great effect on the saw cutting force. Therefore, in this paper, considering abrasive wear on the wire saw, the ultrasonic vibration assisted sawing force theoretical model from a single abrasive to multiple abrasives is established. With the application of equal probability method, the surface profile model of wire saw is established. According to the abrasive wear law of wire saw, the finite element model (FEM) of wire saw with different abrasive wear is established. The influence of different abrasive wear on sawing force and workpiece surface morphology is analyzed by Abaqus. Finally, the experimental verification is carried out. The experimental results show that the sawing force of the ultrasonic vibration assisted diamond wire sawing (UAWS) decreases by 38% on average than that of the conventional diamond wire sawing (CWS), the surface roughness value is reduced, and the surface morphology is improved. With the increase of the abrasive wear value, the sawing force and the numbers of pits firstly decrease and then increase, the surface roughness value distribution firstly concentrates and then disperses, and the scratches show a smooth to intermittent trend.

Design and evaluation of an internal-cooling grooved grinding wheel

To improve the grinding performance of superalloys, a bowl-type internal-cooling grinding wheel with a phyllotactic abrasive pattern has been developed. The internal structure of the grinding wheel is optimized as a two-stage cavity with eight transitional holes by computational fluid dynamics (CFD). And the outlet of the internal channel is set at the center of the abrasive zone to enhance the heat transfer of the coolant. Innovatively, the internal channel is prepared as an independent module through 3D printing technology to explore the influence of different channel diameters (1, 2, 3 mm) on the grinding performance of the grinding wheel. The simulation results show that when the diameter of internal channel is 1 mm, the coolant will be unevenly distributed within the grinding zone. As the diameter of the internal channel increases, the fluidity of the coolant increases, and the phyllotactic abrasive pattern can promote the uniform flow of the coolant within the grinding zone. The experiments of grinding Inconel 718 (flood, internal cooling) demonstrate that the internal cooling method provided better cooling and lubrication performance. Compared to the flood cooling, the grinding temperature of the 1- and 3 mm-diameter internal channels decreased by 23.0%, 48.2%, and the surface roughness decreased by 24.6% and 58.7%, respectively. The residual compressive stress on the machined surface increased by 122.36 MPa and 279.51 MPa, respectively. Further, with the increase of internal-channel diameter, the workpiece surface morphology becomes smoother.

Influence of Lubricant Environment on Machined Surface Quality in Single-Point Diamond Turning of Ferrous Metal.

In the field of single-point diamond turning (SPDT), machining ferrous metal is an important research topic with promising application. For SPDT of ferrous metal, the influence of lubricant on the workpiece surface morphology remains to be studied. In this study, three lubricant machining environments were selected to carry out specific control experiments. The machined surface morphology and cutting force in different lubricant machining environments were analyzed. The experiment results showed that the lubricant environment will have significant impacts on the quality of the machined surface morphology of ferrous metal. In the environment of minimum quantity lubrication machining (MQLM-oil), better machined surface quality can be obtained than that in ordinary dry machining (ODM) and high-pressure gas machining (HGM). Furthermore, the cutting force captured in the ODM and HGM environment increased with the increase of the cutting depth, while the cutting force in the MQLM-oil environment remained almost unchanged. That indicates MQLM-oil can suppress the formation of hard particles to improve the machining quality.

Analysis of discharge channel characteristics based on three-phase flow dielectric characteristics in USV-MF assisted WEDM-LS

In this paper, considering the effects of the characteristics of the three-phase flow dielectric in the discharge gap flow field on the discharge channels in the ultrasonic vibration and magnetic field assisted low speed WEDM (USV-MF assisted WEDM-LS), the model of discharge channel including discharge position and size of discharge channel is established. Firstly, a mechanism of bubble-particle bridging breakdown was proposed under working condition of cutting workpieces with large thickness. Then a prediction model of the discharge point position in USV-MF assisted WEDM-LS under three-phase flow dielectric characteristics based on the breakdown mechanism was performed, and FEM software COMSOL was used to simulate and analyze this model. By comparing with the experimental results of discharge point position captured by high-speed camera, the accuracy of the prediction results of discharge point position in USV-MF assisted WEDM-LS was verified, it showed that the model can explain the dielectric breakdown more accurately. Next, the model of radius of discharge channel including magnetic field intensity, electric field intensity, medium pressure, and surface tension of discharge channel was established, and the influence of USV and MF on the size of discharge channel was analyzed theoretically. The radius of discharge channel in USV-MF assisted WEDM-LS was obtained by solving the partial differential equation in MATLAB. According to discharge point position and radius of the plasma discharge channel, surface morphology of workpiece was simulated by COMSOL. Finally, the experiment of photographing the discharge channel in USV-MF assisted WEDM-LS was carried out to verify the above model. It showed that the trend of the simulated results of discharge channel position is the same as that of the experimental results, and the error of peak height value between simulated and experimental results is within 6%.

Analysis on ground surface in ultrasonic face grinding of silicon carbide (SiC) ceramic with minor vibration amplitude

Compared to conventional grinding, ultrasonic face grinding of SiC ceramic with vibration amplitude more than 3 μm has been proved to improve the machining efficiency but usually face the problem of reducing the workpiece surface quality. The material removal mechanism and ground surface quality by ultrasonic face grinding using minor vibration amplitude (less than 1 μm) still remains uncertain and needs to be further investigated. In the present work, experiments of ultrasonic face grinding of SiC ceramic are carried out to study the influence of processing parameters (e.g. depth of cut, wheel speed and ultrasonic vibration amplitude) on the surface finish. The results show that both the grinding forces and ground surface roughness increase significantly with the increase of depth of cut and the decrease of wheel speed. However, with the increase of ultrasonic vibration amplitude, the grinding forces decrease rapidly first and then keep steady, and the ground surface roughness shows three variation stages: dropping, climbing and stabilizing, which achieves the smallest value of 0.04 μm at the amplitude of 0.216 μm. From the analysis of acquired workpiece surface morphology and image processing result, the proportion of chunks and pits on the workpiece surface is reduced due to ductile removal in case of ultrasonic vibration amplitude less than 0.2 μm, but increases when the amplitude is more than 0.2 μm because the material is removed in brittle domain. Finally, a sample machined at relatively high wheel speed and minor vibration amplitude is provided to support the findings. The proposed investigation provides a new approach to achieve mirror surface of SiC ceramic using ultrasonic face grinding.

STUDY ON MAGNETIZATION TREATMENT AND CUTTING PERFORMANCE OF A NEW-TYPE OF TRIETHANOLAMINE BORATE CUTTING FLUID

The composition of water-based cutting fluid and emulsion is different, and it has not been reported whether the magnetization treatment will affect the performance of water-based cutting fluid. In this study, a newly developed triethanolamine borate water-based cutting fluid is used as the research object to study the magnetization treatment technology and the law of its influence on cutting performance systematically. The cutting fluid magnetization experimental system was set up based on the principle of magnetization and the influence of magnetization parameters (magnetic field strength, magnetization duration) on the results of magnetization was further studied. The experimental results are measured by force measuring instrument, temperature measuring instrument, roughness measuring instrument and scanning electron microscope, and the parameters such as milling force, milling temperature, surface roughness, cutting specific energy, friction coefficient and workpiece surface morphology are comprehensively analyzed through data processing; the performance of cutting fluid before and after magnetization is also compared. The test results show that the magnetization effect is best when the magnetic field strength is 10000GS and the magnetization time is 40 minutes. The mechanism of magnetization treatment is to change the macromolecular group into a small molecular group, and the disordered array of molecules becomes ordered.

Surface integrity and tool wear mechanism of 7050-T7451 aluminum alloy under dry cutting

In this paper, we present an experimental study on the effects of cutting parameters on the surface integrity and tool wear mechanism of AA7050-T7451 aluminum alloy under dry cutting. We perform single-factor cutting tests and finite element simulations to observe how cutting parameters affect cutting force, cutting temperature, workpiece surface morphology, work hardening, residual stress, and tool wear. The results show that the three cutting factors significantly affect cutting force, cutting temperature, and workpiece surface roughness. Higher cutting speeds and lower feed rates can improve surface roughness, whereas cutting depth does not make much difference to surface roughness. Work hardening first increases and then decreases with increasing cutting speed and feed rate, whereas work hardening degree is negatively correlated to cutting depth. Residual stress occurs as a “ladle” with changing cutting parameters. Cutting speed and feed rate affect residual stress considerably. The maximum residual compressive stress layer is 120 μm deep, and the subsurface maximum residual tensile stress layer is 300 μm deep. Tool wear typically involves abrasive wear under low speed, adhesive wear under medium speed, and oxidation wear under high speed.

Simple Discriminatory Methodology for Wear Analysis of Cutting Tools: Impact on Work Piece Surface Morphology in Case of Differently Milled Kinetics Steel H13.

Recently, there is growing interest in optimisation of finishing process thanks to the technologies to follow online the wear of cutting tools. In the present paper, one of the cheapest and simplest non-contact methodologies is described in detail and investigated with robustness evaluation. To simulate the finishing operation of a die, in this study, two cavities were designed in AISI H13 steel. Different inserts corresponding to PVD-(Ti,Al)N coated cemented carbide tool were tested. The described methodology is easy to be applied in manufacturing cutting machining with the opportunity to be implemented on machining processes to follow reasonably wear process of cutting tools.

A curious observation of phenomena occurring during lapping/polishing processes.

We demonstrate that the kinematics of the polishing process is more intriguing than an idealized planetary movement as all the previous studies reported. In reality, the workpiece is pseudo-constrained by the planetary carrier and because of this its relative motion to the polishing pad also incurs a 'parasitic' movement that previously has not been observed. Here, we report and model this parasitic movement and quantify its effect upon the workpiece surface roughness. Using a motion capture system, the principal and 'parasitic' movements between the sample and polishing tool have been tracked and our models validated. It is proved that considering this parasitic movement the prediction of workpiece surface morphology can be significantly improved when compared with the idealized approach (i.e. planetary). Our observations and modelling framework open the avenue to carefully consider the compliance between the tools and workpiece in other manufacturing processes for accurate predictions of the process outcomes.

Study on Grinding Mechanism of Brake Pad with Copper Matrix Composites for High-Speed Train

The processing mechanism of copper matrix composites is very complex, for the particle phase and lubricating phase are randomly distributed in the copper matrix phase, and the characteristics of the three phases are completely different. Aiming at understanding the chip formation and the influence of each phase of the material on the workpiece surface morphology, a single abrasive grain cutting experiment is carried out. Experiment results show that the cutting force increases with the increase in the cutting depth, but the increase amplitude is smaller. Extrusion of the abrasive particles causes plastic deformation of the copper matrix phase and brittle fracture of the particle phase and graphite phase. It results in the defects on the groove surface, such as pits, collapses and cracks, and holes. The brittle fracture of the graphite phase and the breaking and falling off of the particle phase block the plastic deformation of the copper alloy, which makes the copper alloy not forming ductile chips. The chip is mainly powdery. It shows that the brittle fracture is the main removal form of the brake pad material. The copper matrix phase on the surface of the groove produces obvious plastic deformation. The plastic deformation at the bottom is larger and has a certain degree of fibrosis appearing.