Roughness Deviation Research Articles

Surface roughness and morphology evaluation of bearing steel after grinding with multilayer graphene platelets dispersed in different base fluids

Bearings are widely used in different industries which demand different quality requirements to ensure a long life with low wear rates. In this sense, bearing components should present combination of low surface roughness and tight dimensional deviations, as well as good lubricant retention capacity. So, grinding is an alternative to achieve this combination, however, one of the challenges is the large amount of heat generated in the grinding wheel-workpiece interface when using conventional abrasives grinding wheels, which can lead to surface finish deterioration and thermal damages, thereby reducing the component's life. Thus, several cooling-lubrication techniques have been tested in the past decades to enhance the cooling-lubrication properties of cutting fluids, with a highlight in recent years for the benefits of adding solid particles with good tribological properties to improve grinding efficiency. In this context, this work sought to evaluate the roughness and surface morphology of the bearing steel SAE 52100 (60 ± 2 HRC) after grinding with multilayer graphene (MLG) platelets dispersed in two different cutting fluids (synthetic and semi-synthetic). Tests with traditional MQL (without solid particles) and conventional techniques (flood) were also carried out for comparison. The output variables investigated were surface roughness parameters Ra, Rz, Rku, Rsk, Rk, Rpk, and Rv, images of machined surfaces through a scanning electron microscope (SEM), and the specific grinding energy. The results indicated that the base fluid type significantly affected the grinding performance. Tests with semi-synthetic fluid having MLG decreased the Ra parameter of the ground surface by 9% compared to the traditional MQL technique, with a higher Rvk and negative skewness. For the synthetic fluid also with MLG, about 29% increase in the Ra parameter was observed compared to MQL without nanoparticles, although it resulted in higher values of Rpk with more positive skewness. Presence of MLG in semi-synthetic and synthetic fluids reduced the specific grinding energy by 7% and 14%, respectively. Also, less intense plastic deformation and material adhesion was observed when grinding with MLG.

Mixed Lubrication Analysis of Tapered Roller Bearings and Crowning Profile Optimization Based on Numerical Running-In Method

Tapered roller bearings (TRBs) are widely used in heavy-load rotating machinery. One of the technical problems in TRBs is the existence of sharp spikes of the contact pressure in the vicinity of the two ends of the tapered rollers. To suppress the pressure spikes at the roller ends, a straight roller profile is crowned in cylindrical and tapered roller bearings. However, compared to cylindrical roller bearings, there are few studies on the profile modification of TRBs in the literature, and most of the publications on the EHD analysis of tapered rollers focused on a single roller, using traditional profiles such as logarithmic profiles, dub-off profiles and chamfer profiles. By using the numerical running-in method proposed and used in crowning profiles of cylindrical rollers by the authors, this paper provides the first ever asymmetric optimized profile solution for all TRBs rather than for just a single roller. The results show that the optimized profile has the best performance in smoothing contact pressure distribution in the axial direction compared with the conventional logarithmic profile and is a useful profile form with respect to the elimination of sharp pressure spikes. In addition, considering the effect of temperature and mixed lubrication, this paper analyzes the influences of different axial profiles under radial load (Fr), rotation speed (N) and standard deviation of roughness (Rq) conditions.

Effects of cryogenic cooling on machining of acrylonitrile-butadiene rubber

The basic idea of cryogenic machining of elastomers is to lower the process temperature under glass transition temperature, causing the transformation of the viscoelastic properties of elastomers into brittle with better machinability outcomes. However, because of the heat generated by plastic deformation and chip formation in the primary shear zone and friction between the tool and the workspace, even with cryogenic cooling, the resulting temperature in the cutting area is often higher than the glass transition temperature. As a result, it can cause a partially rubbery state of the workpiece. In this paper, the effect of cryogenic cooling on the milling of acrylonitrile-butadiene rubber was analysed. Three different cooling setups, namely, indirect, direct and flow cooling, were proposed and their influence on temperature distribution in the cutting zone was studied in conjunction with different tool geometries and parameters (depth of cut, rotational speed, and feed rate). Direct cooling provides the best-resulting temperature distribution with the lowest surface roughness (1.27 to 1.47 μm) as it acts as a lubricant between the tool and workpiece and cools the tool and workpiece simultaneously.On the other hand, increasing the depth of cut and rotational speed also increases surface roughness. The best results show samples with grooves obtained with a rotational speed of 5000 rpm, depth of cut 0.25 mm and feed rates between 75 and 300 mm/min with surface roughness between 0.86 and 1.29 μm. Those samples show clean grooves with sharp edges, minimal surface roughness and geometric deviation, with defined ductile chip formation.

Laser debinding of parts produced through material extrusion additive manufacturing

A novel cost effective material extrusion additive manufacturing method for metals and ceramics employs filaments embedded with powdered granules which are shaped, debinded, and sintered sequentially until completion of the part. One well known drawback of the technology lies in the time-consuming debinding process, which often requires handling toxic agents (e.g. acetone, cyclohexane, nitric or oxalic acids), as well as complex heating profiles. Debinding is traditionally done after shaping the part, and little investigation has been made to develop the technology to debind locally, in situ, without the use of toxic consumables. Here, we show that full debinding can be achieved efficiently on the bulk of the printed part through an application of local energy by applying it selectively on the top surface, layer by layer, along the 3D volume of as built green parts. A low intensity infra-red laser is integrated in a custom-built machine to create a hybrid device that combines traditional filament extrusion additive manufacturing with in-situ debinding. The results show that the main binder matrix of a Highly Filled (HF) commercially available stainless steel 316L filament can be removed efficiently along the full volume of the part via laser ablation of the organic mass. Defects, surface roughness and topography deviations can be minimized compared to other traditional thermal debinding methods, further showcasing the capability of building consecutive layers on top of a previously debinded layer. We report improvements in debinding time by a magnitude of 248 % compared to traditional thermal debinding, of 595 % compared to solvent debinding at 45 °C, and 943 % compared to solvent debinding at room temperature. The effect of debinding with the use of lasers in-situ, layer by layer, and the effect in the layer adhesion of fully debinded parts, is investigated through optical and electron microscopy, as well as quantifying the binder mass loss. Debinding in-situ offers new routes to reduce processing times of parts produced through FFF.

Pattern Generation using Enamel Coating in Die-sinking EDM

Pattern generation on aluminium (Al)-6061 work surface is performed using green compacts of powder metallurgical (PM) made of copper-tungsten (Cu-W) tool. Compact load (CL) and peak current (Ip) are the variable process factors and surface roughness (Ra) and edge deviation (ED) are considered performance measures. The Ra is obtained in the range of 4.20 µm - 6.56 µm whereas ED is measured in the range of 17.29 µm - 68.98 µm. Field emission scanning electron microscope (FESEM), and energy disperse spectroscopy (EDS) are performed to validate tool particle migration on the pattern surface. It can be concluded that the performance measures depend upon the masking thickness, its resisting capacity to high temperature and the uniformity of the coating.

Отработка методики плазменной резки меди марки М1, алюминиевого сплава Д16Т и титанового сплава ОТ4-1 с использованием плазмотрона с обратной полярностью

Introduction. An important area of research in the field of plasma metal cutting is obtaining a metal cut face characterized by minimal roughness and geometric deviations. It is also important to minimize changes in the structure of the metal under the cutting surface caused by the temperature effects of the plasma jet, including the formation of dross. The solution to the problem of obtaining a quality cut is to optimize the parameters of the cutting process. The plasma arc current and voltage, cutting height and cutting speed are considered to be the main parameters that determine cut quality. However, insufficient attention has been paid to the processes of plasma metal cutting of thicknesses above 20 mm due to the limitations associated with the operation conditions of plasma torches with direct polarity currents. Accordingly, for cutting large thicknesses, the use of a plasma torch operating on currents of reverse polarity seems promising. The aim of this work is to develop the technique of plasma cutting of copper, titanium and aluminum alloy sheets up to 40 mm thick using a plasma torch operating on currents of reverse polarity. Results and discussion. Investigations show that for cutting aluminum alloy (Al 90.9–94.7 %; Cu 3.8–4.9 %; Mg 1.2-1.8 %; Mn 0.3–0.9 %) and titanium alloy (Ti 94.33–97.5 %; Al 1.5–2.5 %; Mn 0.7–2.0 %) it is possible to regulate the cutting speed in a wide range, while for rolled copper (Cu ≥99.96 %) and aluminum alloy with thickness of 40 mm the range of cutting speed regulation is rather narrow. While for aluminum alloy due to excessive precipitation of alloying elements from the solid solution in the heat-affected zone decrease of microhardness is observed, for titanium alloy the microhardness growth due to material hardening is characteristic. Changing the cutting mode parameters allows receiving more homogeneous macrogeometry of a cutting surface, smaller depth of a zone of melting of a material and a heat-affected zone and smaller changes of mechanical properties of a material in a zone of a cut. For the titanium alloy, almost all of the cutting modes used are close to optimum. For alloy aluminum and copper the modes providing the best cutting quality in the considered range of parameters are determined. According to the results of the work it can be concluded that plasma cutting on reverse polarity currents is effective for cutting rolled products of large thicknesses, but the technique requires further development in order to improve the quality of the resulting cut.

Design and Analysis of Microchannels for Heat Dissipation of High-Energy VCSELs Based on Laser 3D Printing

For the problem of high waste heat in the active area of high-power VCSEL arrays and the difficulty of heat dissipation, we took advantage of laser 3D printing technology and combined it with the relevant principles of fluid-structure coupling, three kinds of microchannel heat sink with different structures of pin-fin, honeycomb, and double-layer reflow were designed. The heat dissipation capacity of three kinds of heat sinks to the heat flux density 200 W/cm2 VCSEL array and the influence of the key characteristics of the microchannel on the heat dissipation capacity was studied. The results show that the double-layer reflow microchannel heat sink has the strongest heat dissipation capability, with the minimum thermal resistance value of 0.258 °C/W when the microchannel diameter and the cooling mass flow rate were 0.5 mm and 24 L/h, respectively. The inner wall roughness of the pure copper microchannel prepared by 3D printing technology was 7.08 μm, and the heat sink thermal resistance was reduced by 0.7% compared with the smooth channel wall. The deviation of the microchannel diameter from the design size (500 μm) was −10 μm, and the heat sink thermal resistance was reduced by 0.8% compared to the theoretical value, which shows that the surface roughness and size deviation of the 3D printed microchannel had beneficial effect on enhancing heat dissipation. The actual thermal conductivity of the 3D printed pure copper after heat treatment was 310.4 W/m-K, at which point the thermal resistance was 0.306 °C/W, and the maximum temperature was 35.3 °C, which satisfied the operating temperature range of the chip. This study provides a theoretical basis and implementation method for the fabrication of heat sinks for high-energy VCSEL arrays using laser 3D printing technology.

AWJC of NiTi interleaved r-GO embedded carbon/aramid fibre intermetallic laminates: Experimental investigations and optimization through BMOA

ABSTRACT Laminated metal-composite structures or fiber metal laminates (FMLs) are advanced engineering materials currently being utilized in several distinct applications, especially in aircraft and automobile manufacturing industries where an improved impact and fatigue resistance are required. Machining of FMLs is an important task in obtaining near-net shapes for joining and assembly of the components. However, the delamination occurs during conventional machining making FMLs as difficult-to-machine materials. Therefore, the present study will look into the abrasive water jet cutting (AWJC) of novel fiber intermetallic laminates (FILs) made of with alternatively stacked carbon/aramid fiber adhesively bonded with r-GO filled epoxy resin matrix and Nitinol shape memory alloy sheet embedded laminates. The AWJC experiments were performed on fabricated FILs to investigate the cut quality features including kerf taper (K t ), surface roughness (Ra) and kerf deviation (KD) by varying addition of r-GO from 0-2 wt% in the laminates, traverse speed (400-600 mm/min), waterjet pressure (200-300MPa) and nozzle height (2-4 mm), respectively. Statistical results obtained through ANOVA reveals that the traverse speed and nozzle height are the utmost significant variables which influencing the cut quality characteristics followed by waterjet pressure. Surface morphology analysis shows the wear and erosion mechanism of FILs at varying AWJC conditions. For an improved cut quality, the optimal AWJC parameters are achieved through a metaheuristic-based Barnacles Mating Optimization Algorithm (BMOA).

An analytical model for gas leakage through contact interface in proton exchange membrane fuel cells

Sealing performance between two contacting surfaces is of significant importance to stable operation of proton exchange membrane (PEM) fuel cells. In this work, an analytical micro-scale approach is first established to predict the gas leakage in fuel cells. Gas pressure and uneven pressure distribution at the interface are also included in the model. At first, the micro tortuous leakage path at the interface is constructed by introducing contact modelling and fractal porous structure theory. In order to obtain the leakage at the entire surface, contact pressure distribution is predicted based on bonded elastic layer model. The gas leakage through the discontinuous interface can be obtained with consideration of convection and diffusion. Then, experiments are conducted to validate the numerical model, and good agreement is obtained between them. Finally, influences of surface topology, gasket compression and gasket width on leakage are studied based on the model. The results show that gas leakage would be greatly amplified when the asperity standard deviation of surface roughness exceeds 1.0 μm. Gaskets with larger width and smaller thickness are beneficial to sealing performance. The model is helpful to understand the gas leakage behavior at the interface and guide the gasket design of fuel cells.

Design and experiments of ultra-precision aerostatic turning machine tool

Ultra-precision turning is one of the commonly machining methods to obtain high-quality optical components. Ultra-precision turning machine tools are the industrial equipment that realize ultra-precision turning process. In this paper, a combined design, performance analysis and experimental verification are carried out to build an ultra-precision aerostatic turning machine tool (UPATMT), which adopts aerostatic support systems for the spindle system and the feed system. Firstly, the mathematical model and physical model of UPATMT are established, and the dynamic performance of UPATMT model is carried out and analyzed by finite element method. In addition, the electromechanical control system is simulated and analyzed to obtain better dynamic performance. Finally, the modal tests and turning experiments are carried out on a homemade UPATMT platform. The machined workpiece surface roughness is measured, the arithmetical mean deviation of the workplace surface roughness is Ra 7.4 nm, and the maximum peak valley height of workplace surface roughness Rz 34.4 nm. The results show that electromechanical coupling analysis can obtain high machining performance of UPATMT.

Masking in EDM for pattern generation on Al-6061 work surface

ABSTRACTElectro discharge machining (EDM) is the most preferred non-traditional method for generating complex-shaped geometric pattern required in industrial and automotive applications. The present study shows the complex-shaped pattern generation by EDM process using polyvinylchloride masking material. Powder metallurgical (PM) green compact tool made of tungsten and copper is utilised to make patterns on aluminium (Al) 6061 workpiece. The effects of contributing parameters i.e. compact load (CL), peak current (Ip) and pulse on-time (Ton) are investigated with respect to performance measures such as surface roughness (Ra) and edge deviation (ED). The selected parameters are optimised using particle swarm optimisation (PSO) technique to determine the optimal levels of CL, Ip and Ton for achieving minimum Ra and minimum ED. The minimum Ra of 5.30 µm and a minimum ED of 43.53 µm are measured at optimal settings of CL of 20 ton, Ip of 2 A, and Ton of 200 µs. Analysis of variance (ANOVA) shows that Ip contributes the most to achieve the lowest Ra, while CL contributes the most to achieve the lowest ED. On the pattern surface FESEM, XRD, and EDS investigations are performed to study the surface morphology and to confirm the transfer of tool particles.

SURFACE MORPHOLOGY AND MACHINABILITY ASPECTS IN WIRE-EDM OF INCOLOY-800 SUPERALLOY: AN EXPERIMENTAL EVALUATION AND MICROSTRUCTURE ANALYSIS

This study investigated various performance measures — material removal rate (MRR), surface roughness (SR), and dimensional deviation (DD) — in wire cut electrical discharge machining of the Incoloy-800 superalloy under the effect of purposefully varied process inputs. Superalloys comprise a bright category of alloys that possess excellent mechanical strength at elevated temperatures, superior surface stability, magnificent creep resistance, and corrosion and oxidation resistance. Analysis of variance was performed to reveal influential and crucial inputs for machining measures; results were interpreted and modeled statistically. After conducting the experimental runs, the novel attempt has further been made to conduct the multi-response optimization with the desirability method and the teaching-learning-based optimization (TLBO) algorithm to develop the best process setting for optimizing all considered measures jointly. Furthermore, machined sample’s microstructure analysis was conducted with the scanning electron microscopy (SEM) analysis. The optimized parametric setting was obtained as follows: pulse on time: 2 [Formula: see text]s, pulse off time: 4 [Formula: see text]s, peak current: 2 A, and wire feed rate: 5 m/min. Obtained experimental values for MRR, SR, and DD were 0.936 mm/min, 3.797 [Formula: see text]m, and 0.084 mm, respectively, with the combined desirability value of 0.601. Optimization values of MRR, SR, and DD through the TLBO method varied from predicted values by 3.01%, 6.86%, and 6.32%, respectively.

A New Method of the Positioning and Analysis of the Roughness Deviation in Five-Axis Milling of External Cylindrical Gear

Abstract Five-axis milling is a modern, flexible and constantly developing manufacturing process, which can be used for the machining of external cylindrical gears by means of cylindrical end mills and special disc mills on universal multi-axis machining centres. The article presents a new method of positioning the tip and the axis of the end mill and the disc cutter in order to ensure a constant value of deviation of the theoretical roughness Rth along the entire length of the tooth profile. The first part presents a mathematical model of the five-axis milling process of the cylindrical gear and an algorithm for calculating the Rth deviation values. The next section describes the positioning of the end mill and the disc cutter. Then, a new method for the empirical determination of the distribution of the involute root angle Δui and the data description by means of the interpolation function are presented and described. In the conducted numerical tests, the influence of the geometrical parameters of the cylindrical gear on the deviation Rth is determined, assuming a constant Rth value in the five-axis milling process.

The Effect of Finishing and Polishing with Proprietary Vs Interchanged Polishing Kits on the Surface Roughness of Different Ceramic Materials.

To evaluate the surface roughness of glazed and polished monolithic ceramic materials and to use this as a baseline for comparison after adjustment and polishing with both the recommended kit for the specific materials as well as interchanged polishing kits. Flat ceramic specimens (n = 150) were fabricated from IPS ZirCAD Prime, IPS E.max, and Vitabloc Mark II. The specimens were adjusted and polished using either the proprietary polishing kit for the material or interchanged kits. The surface roughness was objectively assessed using Atomic Force Microscopy (AFM) and profilometer. Subjective assessment of surface finish was performed using a scanning electron microscope (SEM). Gravimetric weight loss of each sample was measured before and after polishing using a digital microscale. The mean surface roughness and standard deviation was calculated for each ceramic- polisher pair. A factorial ANOVA was used to compare the mean surface roughness values in nanometers between multiple groups (α = 0.05). The subjective results from the SEM were reported as descriptive statistics RESULTS: The zirconia polishing system produced surfaces with the lowest surface roughness regardless of the ceramic material. The polisher-ceramic combination was found to have a statistically significant effect on both Ra and RMS values when the AFM was used (p = 0.039 and 0.010, respectively). The zirconia polishing system resulted in the lowest surface roughness values regardless of ceramic materials tested. The zirconia polishing system also did not result in significant gravimetric weight loss regardless of the ceramic material used.

An Experimental Study of Downfacing Surfaces in Selective Laser Melting

This article presents an investigative study to evaluate the effect of process parameters on surface roughness and dimensional accuracy of downfacing surfaces. The material used in the study is Corrax steel and is fabricated using selective laser melting (SLM) technology. The fabrication process of the downfacing surface is different from the fabrication of the main or core region due to the poor thermal conductivity of loose powder particles beneath each layer. The processing parameters, namely, laser scanning speed, laser power, and layer reference, are investigated using a full factorial design of experiments method to discover their influence on surface roughness and dimensional deviation. Results show that the investigated factors are significantly affecting the quality of downfacing surfaces and controlling them will greatly influence achieving required surface properties.

Damage Detection of Bridge Structures Under Vehicle Loads Using Moving-Window Correlation Coefficient of Signals with Limited Sensors

Based on the moving-window correlation coefficient of signals, a damage detection method is proposed for bridge structures. The signals collected by two sensors during the vehicle crossing the bridge are intercepted as windowed pair time series, and the damage index is defined based on the correlation of them. The damage vector is composed of damage indices from the beginning to end according to the moving direction of the window, and the damage location can be determined by the peak information of all the damage vectors which are obtained by different sensor pairs. First, the damage detection method and corresponding detection steps are introduced. Then, the proposed method is validated by numerical simulation, and the influence of moving window length, moving step, the number of sensors, deviation of vehicle parameters and road-surface roughness on damage localization are discussed, respectively. Finally, the proposed method is validated by experiments using a two-axis vehicle and a steel–concrete composite beam. The results show that the proposed method can effectively identify the damage location. High-pass filtering of the raw data to remove trend items and wavelet noise reduction can significantly improve the accuracy of damage detection, and can accurately locate the damage in the presence of road-surface roughness. The damage detection result is not sensitive to vehicle parameter deviation, and the damage location can still be accurately identified when the vehicle weight or speed deviates 50% from the vehicle parameters in the reference data. In addition, the proposed method can make full use of the damage information between sensors, and can accurately identify the damage location with limited sensors. The number of sensors can be flexibly determined considering both accuracy and economy.

Effect of printing parameters and post-process on surface roughness and dimensional deviation of PLA parts fabricated by extrusion-based 3D printing

Effect of printing parameters and post-process on surface roughness and dimensional deviation of PLA parts fabricated by extrusion-based 3D printing

Influence of cutting parameters on surface topography in high-speed milling of slots in titanium alloy TC4

This paper summarizes the experimental investigation of influence of process parameters on surface quality and dimensional accuracy of slots milled in titanium alloy TC4. Samples were milled using a 10 mm HXT coated monolith end mill for HSM milling of superalloys and titanium alloys. Process parameters, such as rotational speed, feed rate, and depth of cut were selected based on the Taguchi L9 method. After machining samples were measured, including surface quality parameters such as roughness, waviness and dimensional deviations. Measurement results indicate that within inspected parameter range rotational speed to feed ratio has a greater influence on surface quality than the depth of cut while having less influence on dimensional accuracy.

Effect of EDMed rake face grooves on the chip breaking capability of twist drills during deep hole drilling of Al 6061 aluminum alloy

ABSTRACT Deep hole drilling of ductile materials like Al6061 with conventional twist drills is challenging due to premature tool failure caused by chip clogging. Chip breakers, in the form of grooves of varying angles (0°, 5° & 10°) and depth (0.4 & 0.5 mm), created using EDM on the rake face, are proposed to overcome chip clogging. Tool wear, hole roughness, and diameter deviation were measured and analyzed along with chip morphology study for the six grooved tools and compared with plain drill. The grooved tools were successful in breaking the chips which allows for easy evacuation without any clogging. Grooved drills produced desired spiral chips compared to string chips produced by plain drill thus resulting in lesser tool wear rate. While the grooved tools showed stable but slightly higher roughness values, the conventional tools exhibited a linear increasing trend as the drilling progressed. The machined hole surfaces had defects such as feed marks, pitting, grooves, and burnished surfaces. The grooved tools produced comparatively more diameter deviation probably because the well broken chips entered into the drill land/hole surface space. From the results it is clear that groove angle and depth have significant effect on the drill machinability characteristics.

Analysis of the Inconel 718 properties after roller burnishing

Experimental studies were performed to investigate the influence of roller burnishing (RB) parameters, as the temperature and the number of RB operations, on the subsurface microstructures and microhardness, surface roughness and roundness deviation of the Inconel 718 alloy. The experimental results indicate that the RB enhance the surface quality, reduces the surface roughness by 76.7% and increase the microhardness by 20.9% compared to the turned part. RB affects the microstructural morphology of the subsurface grains and improves roundness deviation of Inconel 718 parts. The presence of precipitates in the plastic deformation zone contributes to increase the mechanical strength of the subsurface. The RB operation, both at room temperature and at 310°C, proved to be very efficient in reducing the surface roughness of the Inconel 718. About roundness deviation, the increase of the RB temperature induces a greater specimen roundness deviation, and the hot RB operation is not favourable to improve the circularity of the specimen.