Roughness Ra Values Research Articles

METHOD FOR ASSESSING WINDSCREEN ABRASIVE WEAR

This study addresses safety issues surrounding windscreens use and identifies factors affecting the wear rate for windscreens and windscreen wiper blades. Moreover, it presents an original method for bench-testing the windscreen wear process. The method allows tests to be carried out under near-operational conditions. The paper also describes an automated bench equipped with an abrasive dispenser and methods for measuring windscreen wear. Tests were conducted for the effects of quartz sand, marine sand and electro-corundum on the windscreen. It was demonstrated for marine sand and electro-corundum that even the short-term effect of these forcings on the windscreen reduced light penetration to a level of 70%, i.e., a critical value for windscreens. The change in the roughness Ra value during the impact of quartz sand on the pane was characterised by a much greater variability compared to the interaction of marine sand and electro-corundum. It was also demonstrated that the condition of wiper blades was related to the roughness of the windscreen. The summary presents conclusions concerning the research method described and the study results.

Research on surface microstructures and properties of NiTi shape memory alloy after wire electrical discharge machining

This paper used wire electrical discharge machining (WEDM) to machine Nickel-titanium shape memory alloy (NiTi-SMA). Since NiTi-SMA is very sensitive to temperature, the surface of WEDM will form an altered-metal zone (AMZ), which affects the material performance. For investigating the effects of WEDM on the surface microstructures and properties, the method of experimenting clarified the thermal damage mechanism of NiTi-SAM surface formed by WEDM. After WEDM, an obvious three-layer structure (spattered layer, recast layer, and heat-affected layer) was formed on the machined surface, the grains in the recast layer were refined, and the microhardness of the recast layer was significantly improved, the formed hardened layer inhibits the deformation recovery of NiTi-SAM. For machining defects, multi-cutting methods are used to reduce the impact on the machining of NiTi-SAM. Results show that increasing the cutting passes reduces the size of craters and hard convex edges, producing a smoother surface, the roughness Ra value was reduced from 2.79 µm to 0.12 µm. After main cutting, the spattered and recast layers' thickness reached 18.16 µm, and many microcracks appeared in the AMZ. After the fifth trimming, the thickness of the recast layer gradually decreased to less than 0.3 µm. Due to the excellent surface state and enough thinned recast layer, the sample exhibited good corrosion resistance and shape recovery capability. Experimental results provide a reliable processing method for applying NiTi-SMA in micro-electro-mechanical systems and biomedical fields.

Influence of the Duration of Current Pulses on the Roughness in the Combined Processing of Corrosion Steel 12H18N10T

The competitiveness of engineering products in the world market is often determined not only by the quality and operational characteristics of products, but also by the cost saving level and labor intensity of their manufacture. This became especially relevant when a wide range of high-strength and difficult-to-machine construction materials appeared, the processing of which by conventional methods is difficult and ineffective. In recent years, various methods are increasingly used for the shaping of parts made of these materials, the efficiency of which is higher due to the combination of several types of effects on the processing object - combined methods. So, for example, the methods of electrolytic abrasive machining with abrasive disks on a conductive bond have replaced the traditional grinding. One of the particular cases of method implementation is processing with a periodic change in the current pulse direction: direct polarity for electrochemical softening of the processed surface, reverse polarity for restoring the cutting ability of an abrasive tool. Whereanent, the purpose of the work is to establish the effect of dressing current pulses duration on the surface roughness of products made of corrosion-resistant steel of 12H18N10T grade. For laboratory research, a bench was designed and manufactured to simulate the conditions of combined processing. It has been experimentally proved that the smallest roughness value Ra = 0.26 μm is observed at the following values of the current pulse duration: the current pulse of direct polarity duration τst = 1 s and the current pulse of reverse polarity duration τre = 1 s. This allows us to recommend the indicated values in order to ensure high quality of processed surfaces of products made of corrosion-resistant steel 12H18N10T of grade

METHODS FOR ESTIMATING THERMFISICAL PROPERTIES OF THE "TOOL - STEEL WORKPIECE" CONTACT PAIR AND THE POSSIBILITY OF THEIR USE IN CALCULATION OF THE PARAMETERS OF THE TURNING PROCESS

The analysis of methods for assessing the properties of contact pairs "hard alloy tool - steel workpiece" with the aim of improving the reliability of the choice of turning modes in generations of CNC systems equipped with technical intelligence. The models for calculating the cutting speed, the cutting force, the value of roughness Ra, have been corrected by introducing into their structure an additional informative value about the properties of each contact pair - the thermoEMF of the trial cut.

Elbow precision machining technology by abrasive flow based on direct Monte Carlo method

The investigation was carried out on the technical problems of finishing the inner surface of elbow parts and the action mechanism of particles in elbow precision machining by abrasive flow. This work was analyzed and researched by combining theory, numerical and experimental methods. The direct simulation Monte Carlo (DSMC) method and the finite element analysis method were combined to reveal the random collision of particles during the precision machining of abrasive flow. Under different inlet velocity, volume fraction and abrasive particle size, the dynamic pressure and turbulence flow energy of abrasive flow in elbow were analyzed, and the machining mechanism of particles on the wall and the influence of different machining parameters on the precision machining quality of abrasive flow were obtained. The test results show the order of the influence of different parameters on the quality of abrasive flow precision machining and establish the optimal process parameters. The results of the surface morphology before and after the precision machining of the inner surface of the elbow are discussed, and the surface roughness Ra value is reduced from 1.125 µm to 0.295 µm after the precision machining of the abrasive flow. The application of DSMC method provides special insights for the development of abrasive flow technology.

Comparative Study of Flank Cams Manufactured by WEDM and Milling Processes

Cam-follower mechanisms are usually employed in different machines, like combustion engines, sewing machines, machine tools, etc. In the present paper, the option to manufacture cams utilizing wire electrical discharge machining (WEDM) has been considered. For this, surface roughness and shape error of cam profiles manufactured by the processes of milling and wire electrical discharge machining (WEDM) are presented. The methodology used covers different stages: design, prototyping, manufacturing, and measurement of the cams. As a reference, a cam-follower mechanism from a motorcycle internal combustion engine has been used. A reverse engineering process has been performed to determine the geometrical parameters of the mechanism, which are used for the synthesis of the profile of the cam and its subsequent design. The manufacturing process of the cams has been assisted by CAD-CAM (Computer Assisted Drawing-Computer Assisted Manufacturing) software. Using fused filament fabrication (FFF), a physical prototype of the cam has been manufactured, in order to validate the goodness of the design. Finally, the roughness and shape parameters have been measured on the contour surface of the cams. The arithmetical mean roughness Ra value of the milled cam was 0.269 μm, below the requirement of 0.4 μm, and shape error was 18 μm, below 50 μm. Shape error of the WEDM cam of 48 μm meets the requirements for cams. However, the Ra value of 1.212 μm, exceeded the limit. For this reason, a finish operation is recommended in this case. Some advantages of WEDM cams over milled cams are that different conductive materials can be employed, more complex shapes can be obtained, and that, in rough operations, the amount of material to be removed in subsequent operations is considerably reduced.

Statistical modeling and optimization of the factors affecting the surface roughness of C45 steel treated by the centrifugal disk mass finishing process

The goal of this study was to find the optimal conditions for improving the surface roughness (Ra) of the C45 steel treated by the centrifugal disk mass finishing process. The factors selected were the grain size of the abrasive media (Gs), the rotational speed of the disc (ω) and the loading volume (V). In order to optimize its parameters and describe the variation of (Ra), a regression model was developed with the response surface methodology. The model was validated with the analysis of variance with a descriptive quality estimated to 98%. The Student test was used to improve the model by neglecting the terms having an insignificant influence. Experimental tests demonstrated that the error between the estimated and the experimentally values did not exceed 2.34%. The lowest roughness value Ra = 1.079 m was obtained analytically by the optimal values of Gs = 4 and ω = 241.8 rpm.

Influence of distribution parameters of rough surface asperities on the contact fatigue life of gears

The influence of the distribution parameters of asperities, i.e. mean radius of curvature of asperities β, density of asperities η, and standard deviation of asperity heights σ, on the contact fatigue life of gears is first studied in this paper. Based on the elastic–plastic contact model of asperities, the surface contact pressure and subsurface stress field during the gear meshing process are calculated by the iterative calculation method. According to the multi-axis fatigue life model, the calculation method of fatigue life under different distribution parameters of asperities in the gear meshing process is obtained. The quantitative calculation results of fatigue life and measured distribution parameters of asperities are analyzed. The relationship between the fatigue life and the distribution parameters of asperities on the measured gear surface is calculated and analyzed quantitatively. The following conclusions are drawn: (1) when the roughness value Ra is less than 0.3 µm, the contact fatigue life of gears with rough surfaces is close to that of smooth surfaces; (2) when the roughness value Ra ranges from 0.5 µm to 0.9 µm, the contact fatigue failure occurs near the surface (micro-pitting); (3) under the same roughness value Ra, the contact fatigue life of the gear decreases with the decrease of the density of the asperity and the mean curvature radius of the asperity. The mean radius of curvature of the asperity has a greater influence on the contact fatigue life than the density of the asperity.

Study of the Effect of Carbon on the Contraction of Hypo-Peritectic Steels during Initial Solidification by Surface Roughness

In the continuous casting process, the shrinkage of the peritectic phase transition during the initial solidification process has an important influence on the surface quality of peritectic steel. The initial solidification process of 0.10C%, 0.14C%, and 0.16C% peritectic steels was observed in situ by a high temperature laser confocal microscope, and the contraction degree during initial solidification was characterized by surface roughness. The results showed that under the cooling rate of 20 °C/s, the surface roughness value Ra(δ/γ) of 0.10C% peritectic steel was 32 μm, the Ra(δ/γ) value of 0.14C% peritectic steel was 25 μm, and the Ra(δ/γ) value of 0.16C% peritectic steel was 17 μm. With increasing carbon content, the contraction degree of the δ→γ transformation decreased, and the value of the surface roughness Ra(δ/γ) declined. Therefore, surface roughness can characterize the contraction degree of the δ→γ transformation in the initial solidification process of peritectic steel under the condition of a large cooling rate.

Research on the Relationship between Cutting Force and Machined Surface Quality in Micro Ball End-Milling of Potassium Dihydrogen Phosphate Crystal.

Potassium dihydrogen phosphate (KDP or KH2PO4) crystal is widely used as terminal frequency converters in inertial confinement fusion (ICF). However, KDP crystal is a typical difficult-to-cut optical crystal with the characteristic of soft-brittle. In this work, the relationship between cutting force and processed surface quality in micro ball end-milling of KDP crystal with various depth of cut and spindle speed is studied by carried out the micro-milling experiments. Fast Fourier Transform (FFT) algorithm is used to diagnose the recorded cutting force. The periodic change of cutting force and the cutting force after filtering noises can be got through FFT analysis. Through calculating the correlation coefficients between the static component of thrust force and roughness value Ra of machined grooves, as well as the peak-valley (P-V) value of thrust force and dimensional error of machined grooves, the roughness value Ra and dimensional error of machined grooves would be predicted by monitoring the static component and P-V value of the thrust force, respectively. The relatively large spindle speed helps to reduce the roughness value Ra. The spindle speed with moderate value is recommended to reduce the dimensional error of machined groove because the dimensional error of machined groove will increase when the spindle speed is small enough (causing brittle cutting) or large enough (reducing cutting stability).

Study on polyurethane media for mass finishing process: Dynamic characteristics and performance

Aiming at the difficult finishing problem of special parts such as deep groove and narrow slit of high performance parts, a new type of polyurethane media was prepared with high strength, low elastic modulus, and good deformation adaptability. Based on vertical centrifugal mass finishing process, the dynamic behavior of the media with different mass ratio and hardness was analyzed using discrete element method, the experiments were carried out on aluminum alloy wheel hub specimens, the better performance parameters of polyurethane media were determined, and the material removal model of polyurethane media was obtained. The results show that the numbers of polyurethane media with different velocities and energies show Maxwell distribution in the processing. The whole velocity, energy, normal contact force and tangential contact force of the media increase with increasing hardness of the media and mass ratio of polyurethane raw rubber and the abrasive. It also shows that the roughness value Ra can be decreased from 1.209 µm to 0.195 µm, decreased by 83.87%. The maximum material removal ratio can reach 0.147 mg/g·min within 10 min. The experimental results are consistent with the results of the discrete element analysis. The research results in this paper provide a new idea and way for expanding the application range of mass finishing processes.

Roughness, surface energy, and superficial damages of CAD/CAM materials after surface treatment.

The aim of this study was to examine the effects of surface pre-treatment on CAD/CAM materials including ceramics, zirconia, resin-infiltrated ceramic, and resin-based composite. Specimens were made of ten CAD/CAM materials (Celtra Duo, Degudent, D; Vita Suprinity, Vita, D; E.max CAD, Ivoclar-Vivadent, FL; E.max ZirCAD, Ivoclar-Vivadent, FL; Vita Enamic, Vita, D; Cerasmart, GC, B; LAVA Ultimate, 3M, D; SHOFU Block HC, SHOFU, US; Grandio Blocs, VOCO, D; BRILLIANT Crios, Coltene, CH) and pretreated to represent clinical procedures (Hf 20s/5%; phosphoric acid 20s/37%; Monobond etch and prime (Ivoclar-Vivadent, FL); water-cooled diamond bur (80μm; 4μm); Al2O3-blasting (50μm/1bar, 50μm/2bar, 120μm/1bar, 120μm/2bar); untreated; manufacturer's instructions). SEM-analysis (Phenom, FEI, NL) of the surfaces was performed (magnifications ≤ 10,000×). Roughness values Ra, Rz (KJ 3D, Keyence, J), and surface energy SE (OCA15 plus, SCA20, DataPhysics, D) were determined (statistics: non-parametric Mann-Whitney U test/Kruskal-Wallis test for independent specimen, α = 0.05). Kruskal-Wallis revealed significant (p < 0.001) differences for all materials with different surface treatments. Roughness ranged from Ra = 0.05μm (VS; D4)/Rz = 0.41μm (VS; D4) to Ra = 1.82μm (EMA; SB120/2)/Rz = 12.05μm (CS; SB 120/2), SE from 22.7mN/m (VE; M) to 52.8mN/m (CD; M). SEM analysis showed material-dependent damages after pre-treatment. Different CAD/CAM materials require individual pre-treatment for optimized and protective surface activation. Cementation is a key factor for clinical success. Given the variety of available CAD/CAM materials, specific procedures are needed.

Experimental investigations on nanogrinding of RB-SiC wafers

ABSTRACTNanogrinding experiments are performed to investigate the processing characteristics and material removal mechanism of reaction-bonded silicon carbide (RB-SiC) wafers on an ultraprecision grinder using the cup wheel. #120, #600 diamond wheels are used as coarse and semifinished grinding wheels, while #2000 and #12000 diamond wheels are selected as fine and finish grinding wheels, respectively. The experimental results indicate that an ultrasmooth surface with roughness value Ra less than 3 nm and groove depth about 5 nm can be achieved using a diamond wheel whose mesh size exceeds 2000. In addition, Ra less than 1 nm and groove depth about 2 nm will be obtained with a #12000 diamond wheel. The present study reveals the feasibility of ultraprecision grinding RB-SiC materials in the ductile regime and provides technological insights into nanogrinding of hard materials with an ultrasmooth surface.

Tribological Characterization of SiC and B4C Manufactured by Plasma Pressure Compaction

The objective of the present study was to assess the tribological properties and the wear behavior of silicon carbide and boron carbide ceramics, produced by the plasma pressure compaction sintering process. Reciprocating sliding tests were executed to evaluate the tribological behavior of silicon carbide and boron carbide. Samples of each material with distinct values of surface roughness Ra were tested. Wear mass loss, coefficients of friction and wear mechanism of the boron carbide and silicon carbide were evaluated by means of microscopes and an energy-dispersive spectroscopy probe. The coefficient of friction of the evaluated boron carbide was found to be 0.8, and the surface roughness affects only the starting transient, while for silicon carbide the steady-state value ranges from 0.5 to 0.8 depending on the roughness value Ra.

Improved magnetorheological honing process for nanofinishing of variable cylindrical internal surfaces

ABSTRACTImproved magnetorheological honing process is developed for nanofinishing of variable cylindrical internal surfaces with better surface integrity. In the present work, finishing performance of existing magnetorheological honing process is enhanced. The present improved process consists magnetorheological honing tool having curved permanent magnet end surfaces. When magnetic field is analyzed using Ansoft Maxwell, the improved magnetorheological honing process results in uniform and higher magnitude of magnetic flux density over its magnetic tool curved end surfaces as compared to the tool having magnetic flat end surfaces. Therefore, an improved magnetorheological honing process has been developed with tool having curved permanent magnet end surfaces. During experimentation, surface roughness values Ra, Rq, and Rz get decreased by 76.28%, 76.67%, and 75.20%, respectively, with improved magnetorheological honing tool having curved end magnetic surfaces, while 47.97%, 46.24%, and 47.08% decreased with tool having flat end magnetic surfaces in same 60 minutes of finishing time. This results in enhancement of finishing performance of the present improved magnetorheological honing process in terms of reduced finishing time and ability to produce good surface integrity. Hence, the present improved magnetorheological honing process performance with tool having curved end magnetic surfaces is found as comparatively better than the finishing tool having flat end permanent magnetic surfaces.

An experimental study on the creep feed grinding of narrow deep grooves of stainless steel

Experiments were carried out machining SUS321 stainless steel workpieces using a single-layer electroplated cubic boron nitride (CBN) wheel; a WinTec MV-45 machining center and creep feed grinding following orthogonal test method were used. Narrow deep grooves were machined. The surface roughness Ra values of the groove side walls were collected and analyzed. The influence of grinding parameters (including wheel speed, feed rate, and cutting depth) on the surface roughness of the grooves was studied. The result showed that the feed rate has the most significant influence on the surface roughness Ra values of the narrow deep groove, the influence of the wheel speed on the surface roughness Ra values is the second, and the effect of the cutting depth on the surface roughness Ra values is the least. The optimum parameters were achieved by orthogonal experiment optimum design and taking vw = 1.5 mm/min, ap = 5 mm, n = 7000 rpm for grinding SUS321 stainless steel. A model predicting the surface roughness Ra values of the machined grooves was established by processing the collected data by partial least square regression. The predictions made by the model match well with the experimental data, and thus, the model can be used to predict the surface quality/roughness in future grinding.

Study on the Influence of Roughness on the Detection for Mechanical Characteristics of the Machined Surface by Surface Acoustic Wave Dispersion Theory

The surface acoustic wave (SAW) technique is a precise and nondestructive method to detect the mechanical characteristics of the precision-machined surface. The paper is concerned with the effect of the roughness of the machined surface on the dispersion of surface acoustic waves propagating in the precision-machined surface which indicates mechanical characteristics of the machined surface. The finite element method (FEM) is employed by establishing a series of models with different roughness Ra value to analyze influences from different roughness Ra value on surface acoustic wave dispersion. The models are established by applying a combined method based on fractal theory and wavelet analysis. The simulation results showed that the roughness of machined surface will cause the dispersion of surface acoustic wave propagation, the effect varies with the different roughness Ra values. A critical Ra value influencing on the surface acoustic wave propagation exists. Accordingly, that the factor of roughness should be considered in advance or not, the situation can be determined through studying and determining the critical roughness Ra value above mentioned. Consequently, the study has the important meaning regarding the detection for mechanical characteristics of the machined surface.

Bore’s Surface Condition on Single Multifunctional Insert Tools Turning

Turning is a utilized machining work. It is performed with a large types of tools adapted for required geometries. If starting from a full blank, a drilling operation is called in the beginning. In that case, the number of utilized tools increased. The use of a multifunctional tool for drilling followed by bore turning is an efficient solution. In this research, the case of single insert multifunctional tool is studied. The paper describes the quality of the surfaces obtained by using of this tool. The general idea is to verify the use of only one multifunctional tool for execution of all operations, from full drilling to finished surface. This was made by measuring the roughness Ra in three experiments with different materials: titanium, stainless steel and low carbon steel. Performed experiments lead to the idea of a recommended limit for feed speed to obtain a roughness Ra value below 0.8μm. This limit depends with the material type, but for some materials, it seems impossible to achieve this value!

Hybrid electrostatic and elastomer adhesion mechanism for wall climbing robot

In this paper a hybrid solution to the problem of robots climbing on featureless surface is presented. The research focus of wall climbing robot is on the adhesion and the mechanism of locomotion. An efficient, robust, standalone and scalable mechanism is often desired for such robots to perform many critical tasks. The performance of electrostatic adhesion can be enhanced by using flexible and soft elastic material as the dielectric to improve its resistance against peeling force. A novel multiple stage fabrication process of the layered hybrid adhesive using blade coating technique is proposed in this work. This yields a track structure that is compliant on the surface, electrically functional, and geometrically controllable. When excited by high voltage, the track becomes an active actuator. It also passively adheres to smooth surfaces with the elastomer effect. Inspired by the climbing strategy of the gecko, a solution for track locomotion is proposed by utilizing electrostatic, elastomer adhesion and tail forces simultaneously. The biomimetic tail is implemented with torsion spring design. As a result, the robot prototype ELAD (electrostatic and elastomer adhesion) can climb a slope of 80° on smooth surfaces at speed of 4cm/s, and perch for more than 2h using on-board power. Effects of tail design and hybrid adhesion with force analysis are numerically evaluated and presented. It is also demonstrated that the elastomer material properties for the hybrid adhesive are suitable for stable climb on vertical surfaces. Further, analysis has shown that the hybrid adhesive is able to work on surfaces with roughness value Ra within 300nm.

Effect of cutting parameters on surface quality in ductile cutting of KDP crystal using self-developed micro PCD ball end mill

Micro-milling is widely accepted as the most promising approach to repair the micro-defects on the KH2PO4 (KDP) surface. In order to get excellent surface quality of workpiece, the ductile cutting of KDP crystal should be achieved. Compared to plastic materials (e.g., metals), the ductile cutting of KDP crystal is more sensitive to the geometrical parameters of tools and cutting parameters, as a result of the soft brittle properties of KDP crystal. In this work, the variable regularity of peak to valley (P-V) value of cutting force on cutting parameters was obtained through simulations, which was matched well with the results obtained from the single-factor experiments using the self-designed micro polycrystalline diamond (PCD) ball end mill. Meanwhile, the ductile cutting parameters of KDP crystal were also obtained through the single-factor experiments. Then, the orthogonal experiments were explored which reveal that the axial depth of cut and the feed speed had maximal and minimal influences on the roughness value Ra, respectively. Moreover, the optimal cutting parameters which are the spindle speed (7 × 104 r/min), axial depth of cut (0.5 μm), and feed speed (30 mm/min) were also gained. At last, the optimal cutting parameters obtained above which were used in the repairing experiments were proved to be good cutting parameters because the good surface quality of repairing outlines was achieved; meanwhile, the repairing performance of self-developed micro PCD ball end mill was also verified.