Search

With the progression in technologies, conventional cutting of metal with flood cooling is superseded by some other means, viz. minimum quantity lubrication (MQL). Here, in this current work, we present that hexagonal boron nitride (hBN) nano-fluid particles are used in terms of percentage mixed in SAFCO lubricant oil. The factors, viz. cutting velocity, depth and percentage of nanoparticles are varied to obtain the mathematical models and optimisation of responses, viz. temperature and surface roughness. Desirability function analysis (DFA) approach is adopted for the optimisation process, and regression analysis is executed for the mathematical modelling. Also, criteria importance through inter criteria (CRITIC) approach was implemented to evaluate the weightage of responses first before the DFA application. The analysis of variance reveals that all the factors taken into the existent are significantly affecting the outcomes, and nanoparticles percentage being the most one. The percentage increase of nanoparticles in oil leads to better surface conditions, as depicted by the result. The ideal settings for the optimisation of responses undertaken may be expressed as follows: 600 rpm cutting speed, 0.1 mm of depth and 2% nanoparticle percentage in MQL. The mathematical modelling confirms that first-order linear models are sufficient for both the responses under the given set of design of experiments. [ABSTRACT FROM AUTHOR]

Ceramic matrix composites (CMCs) are highly promising materials for the next generation of aero-engines. However, machining of CMCs suffers from low efficiency and poor surface finish, which presents an obstacle to their wider application. To overcome these problems, this study investigates high-efficiency deep grinding of CMCs, focusing on the effects of grinding depth. The results show that both the surface roughness and the depth of subsurface damage (SSD) are insensitive to grinding depth. The material removal rate can be increased sixfold by increasing the grinding depth, while the surface roughness and SSD depth increase by only about 10%. Moreover, it is found that the behavior of material removal is strongly dependent on grinding depth. As the grinding depth is increased, fibers are removed in smaller sizes, with the fiber length in chips being reduced by about 34%. However, too large a grinding depth will result in blockage by chip powder, which leads to a dramatic increase in the ratio of tangential to normal grinding forces. This study demonstrates that increasing the depth of cut is an effective approach to improve the machining efficiency of CMCs, while maintaining a good surface finish. It provides the basis for the further development of high-performance grinding methods for CMCs, which should facilitate their wider application. HIGHLIGHTS: • Both surface roughness and subsurface damage depth are found to be insensitive to the depth of cut. • The dependence of material removal behavior on grinding depth is revealed. • A technique for high-performance grinding of ceramic matrix composites is demonstrated. [ABSTRACT FROM AUTHOR]

The effect of surface roughness and polishing orientation on fatigue life is investigated. Fully reversed bending fatigue tests are conducted on ASTM A1008 specimens having surface roughness asperities ranging from mirror finish (Ra = 0.05 μm) to coarse (Ra = 1.5 μm). Two polishing directions (i.e., orientations) are examined. For the range of roughness values tested, the results suggest that polishing orientation has a strong influence on fatigue life. Specifically, within the range of surface roughness values tested, fatigue life was found to be relatively insensitive to surface roughness asperities when the roughness orientation was parallel to the direction of surface stress but sensitive to surface roughness asperities when the orientation crossed the direction of surface stress. Results are generalized using the concept of fracture fatigue entropy (FFE). It is shown that, unlike fatigue life, FFE is independent of polishing orientation, a noteworthy result. To explain the behavior of FFE in relation to surface roughness asperities, a fatigue thermodynamics theory is presented that hypothesizes that all specimens of the same material fail at equivalent entropy levels. Highlights: The influence of surface roughness on fatigue life is investigated.Extensive fully reversed bending fatigue tests are performed.Surface roughness lay has a pronounced influence on fatigue life.Fracture fatigue entropy (FFE) is sensitive to the roughness regardless of its lay. [ABSTRACT FROM AUTHOR]

This study focuses on improving the surface properties of Aluminum (Al) sheets for imaging and optical applications. To achieve high efficiency and low damage, novel CNC abrasive lapping (CNC AL) techniques were proposed and tested. The experiments investigated the impact of various parameters, such as spindle speed, feed rate, and depth of cut, using two types of abrasives (PCD and hybrid PCD with Al2O3) on the surface quality (Ra) and reflectance (R) of the Al sheets. Optimal parameters were determined using Taguchi L9 and (S/N) analysis, favoring low spindle speed, low feed rate, and high depth of cut. Surface roughness was measured with Surfcom1400G, while SEM EDX, AFM, and 3D profilometer were used to assess surface microstructures. Significant improvement of 35-96% was observed in the highly reflective Al sheets using UV-VIS spectrophotometry and texture analysis in MATLAB. [ABSTRACT FROM AUTHOR]

Laser shock peening (LSP) uses plasma shock waves to induce compressive residual stress at the surface of a component which has the potential to improve its fatigue properties. For AM parts, the existence of internal defects, surface roughness, and tensile residual stresses leads to noticeably lower fatigue strength compared to materials produced through conventional processes. Furthermore, there is a tendency for greater scatter in the fatigue behavior of these parts when compared to traditionally manufactured components. In this study, the effect of LSP on the roughness and fatigue behavior of Ti-6Al-4V alloy constructed through Laser Powder Bed Fusion (L-PBF) technique was investigated. Two types of samples were designed and tested: as-built surface air foil samples for four-point bending tests and machined surface straight gage samples for uniaxial fatigue testing. Two sets of process parameters, optimized and non-optimized, were also used for the fabrication of each sample type. It was found that LSP had negative effects on the smooth (i.e., machined) surface samples, whereas for as-built surfaces the roughness was enhanced by decreasing the sharpness of the deep valleys and partially remelting the loosely bonded particles on the peaks. It was found that the scatter of the fatigue data decreased for optimized machined samples, while no clear improvement was observed in their lives. However, all non-optimized samples showed improvements in fatigue lives after the LSP process. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine whether the chemical compositions of Alnico alloys had any effects on the electrical discharge machining (EDM) performance and the surface finish. This article compares the behavior of three different Alnico alloys in electrical discharge machining. The experiments were conducted under different conditions using a BP93L EDM machine (ZAP BP, Końskie, Poland), applying an additional rotary motion to the electrode. A Box–Behnken experimental design was employed to analyze the influence of three factors, i.e., the spark current, the pulse-on time, and the pulse-off time, at three levels for three Alnico alloys. The material removal rate (MRR) was calculated for the different process parameters. After the EDM, the surface roughness was studied using a Talysurf CCI Lite non-contact profiler (Taylor–Hobson, Leicester, UK). The next step of the experiments involved preparing metallographic specimens to be observed by means of scanning electron microscopy (SEM) and optical microscopy (OM). Measurements of the nanohardness were also performed. The experimental data were then analyzed using Statistica software version 10 (64-bit) to determine and graphically represent the relationships between the input and output parameters for the three Alnico alloys. The chemical compositions of the Alnico alloys affected the thickness of the white layer (higher cobalt content, lower white layer thickness) and the material removal rate. The higher the cobalt content, the thinner the white layer and the lower the material removal efficiency. Moreover, the cobalt content in Alnico alloys influenced the shape of the precipitates; these ranged from spheroidal (13% Co) to mix-shaped (21.3% Co) to flake-shaped (32.2%). The hardness of the resulting white layer was 874 HV at10 mN. [ABSTRACT FROM AUTHOR]

Nickel-based alloys are used in marine and aerospace applications due to their mechanical strength and chemical stability at high temperatures. Inconel 800 resists high-temperature corrosion such oxidation and carburization. Inconel 800 is utilised in deaerators, heaters, valves, heat exchangers, pumps, and more. Grinding responses was investigated since these applications demand a clean surface finish. In this study, surface grinding was performed on Inconel 800 under three different cooling conditions: dry, wet, and Nano-MQL. Wheel Speed(vs), feed(f), and Depth of cut(ae) were taken as input parameters, while Surface roughness(ra), the microhardness of the Workpiece, and temperature were taken as output parameters..NMQL circumstances yielded 0.42 μm surface finish and 60–62°C cutting temperature. The microhardness values on the machined surface under different cooling conditions reflect residual stress, which depends on the machining zone temperature. The material's surface residual stresses were tested to determine how grinding affected its mechanical qualities and performance. [ABSTRACT FROM AUTHOR]

To improve the localization of material dissolution and fabrication of microstructures with better surface finish, high process complexity, such as different tool shapes, electrolyte flow, and tool insulation, has been utilised in electrochemical micromachining (EMM). Improvement of mass transport, sludge removal, and continuous dissolution are challenging tasks for EMM because bubbles and sludge increase the shielding effects. To solve the problems and achieve precision machining with a better surface finish, a new multi-step pulse waveform (MSPW) is designed indigenously. By incorporating three different peak voltages with a short duration time in the pulse on time of MSPW, potential fluctuation is intentionally induced during machining. Thus, more pulse fall times, short peak voltage duration times, and fluctuations of potential can improve the reduction of bubble size and its detachment rate. Due to it, ion transport phenomena improve, sludge is properly removed from the machining zone, and material dissolution rates increase. The effects of MSPW in EMM are compared with conventional rectangular pulse waveform (RPW). From mathematical estimation, it is found that the power transmission of MSPW is less than RPW, which plays a significant role in stray current minimization. The proposed method is verified by simulation, where it can be observed that current density decreases with increasing bubble size. By capturing images, it is also noticed that the size of gas bubbles decreases, accompanied by a higher detachment rate. Utilising MSPW, precise microdimples are fabricated with minimum surface roughness (Ra), i.e., 0.0241µm, whereas Ra is 0.251µm for RPW. Further, it is identified from the machined microdimples that etch factor improves, diameter minimises, depth increases, no irregular machining appears on the bottom surface, and surface finish also improves as compared to RPW. These improvements are also observed in machined microholes. [ABSTRACT FROM AUTHOR]

The leading quality indicators of cold-rolled strip products include surface roughness and surface finish. The present study investigates the effects of the reduction ratio and lubrication condition (dry or lubricated) on the surface roughness and surface gloss of S304 stainless steel strips and titanium grade 1 strips processed at room temperature with a rolling speed of 0.33 m/s. The results show that for both materials, the contact ratio between the workpiece and the roller increases with an increasing reduction ratio and gives rise to a higher surface gloss. Moreover, the surface gloss obtained under dry conditions is higher than that obtained under lubricated conditions. The peak cross-sectional and pit cross-sectional areas for both materials decrease as the reduction ratio increases. The corresponding improvement in the surface gloss is particularly apparent under dry conditions due to the absence of oil in the oil pits on the rolled surface. The titanium workpiece has a low yield strength of 170 MPa, and hence a high surface gloss can be obtained under a relatively low reduction ratio of 7%. By contrast, the S304 workpiece has a high yield strength of 215 MPa. As a result, a reduction ratio of at least 17.7% is required to flatten the oil pits and obtain a better surface finish. This study identifies the critical operating parameters of cold rolling affecting surface roughness and glossiness and provides insights into enhancing surface finish. Furthermore, it pinpoints that the valley cross-section area is a critical factor in determining the gloss of a surface with noticeable defects. [ABSTRACT FROM AUTHOR]

Fused deposition modelling has become one of the most popular extrusion additive manufacturing technologies over the last decades, since it is easy to handle and user-friendly. However, it still requires special attention regarding its position within different industrial applications; one of the major issues that require additional improvement corresponds to the surface quality. Hence, this work is dedicated to the understanding of the roughness according to three process parameters, namely, printing speed (Spd), layer thickness (Lth), and extrusion temperature (Temp). A Taguchi L27 orthogonal-array was adopted in order to conduct this investigation. Neither post-surface treatments nor any additional surface finishing were applied. Altisurf apparatus was utilized to build 3D images and 2D profiles of the samples' peaks and depths leading to significant surface sampling regarding the statistical analysis that follows. From a quantitative standpoint, the arithmetic roughness Ra ranged between 7.18 and 13.4 µm, while the best surface quality was reached at the higher scan speed, 4000 mm/min; the smoothest surface was produced at the lowest value of the layer thickness, 0.1 mm; finally, the higher extrusion temperature is the best is the produced surfaces. Moreover, a multiway ANOVA was carried-out leading to select the most significant factors and interactions within the set of inputs. Consequently, the resulting analysis has discriminated the most influenced parameters within the following order, Lth, Spd, and the interactions Temp * Spd, and Lth * Temp. Future works will propose a semi-empirical method including fluid dynamics and thermodynamics involving stochastic parameters to understand roughness variability of FDM produced samples. [ABSTRACT FROM AUTHOR]

Ti6Al4V alloy is one of the typical difficult-to-machine materials and often results in rapid tool wear, leading to poor machining quality in aircraft assembling. Compared to conventional helical milling, the ultrasonic assistant helical milling (UAHM) process has indicated its superior performance; however, it is still a great challenge to improve the hole surface quality and accuracy. In addition, few studies have been conducted on the effect of different variables and cooling strategies on the hole-making performance in longitudinal-torsional ultrasonic assisted helical milling (LT-UAHM). This paper, for the first time, reports effects of machining variables on geometric precision and surface roughness in LT-UAHM of Ti6Al4V. In addition, the lubrication/cooling mechanism on the simultaneous application of LT-UAHM and MQL is theoretically analyzed. The design approach of Taguchi experiment was employed to study how major variables such as the cutting speed, tangential feed, axial feed, and the workpiece hardness influence the dimensional and geometrical tolerances and surface roughness. This paper also discussed the effect of three cooling strategies, i.e., dry condition, air coolant, and minimum quantity lubrication (MQL) in LT-UAHM. Theoretical analysis demonstrated that the MQL coolant can be nebulized into hyper-fine droplets owing to the resonant cavitation phenomenon. Combined with the penetrating action caused by the separate-cutting principles of LT-UAHM, the cooling and lubrication performance of MQL was further enhanced. As a result, LT-UAHM with MQL had the most positive effect on circularity, cylindricity, nominal diameter, and surface roughness, contributing to 34%, 32%, 39%, and 40%, respectively. The second important machining factor was the cutting speed, contributing to 31%, 29%, 36%, and 22%, respectively. The tangential feed and workpiece hardness have the negative effect on geometrical accuracy, respectively. [ABSTRACT FROM AUTHOR]

Accurately predicting the surface finish of fused deposition modeling (FDM) parts is an important task for the engineering application of FDM technology. So far, many prediction models have been proposed by establishing a mapping relationship between printing parameters and surface roughness. Each model can work well in its specific context; however, existing prediction models cannot meet the requirements of multi-factor and multi-category prediction of surface finish and cope with imbalanced data. Aiming at these issues, a prediction method based on a combination of the adaptive particle swarm optimization and K-nearest neighbor (APSO-KNN) algorithms is proposed in this paper. Seven input variables, including nozzle diameter, layer thickness, number of perimeters, flow rate, print speed, nozzle temperature, and build orientation, are considered. The printing values of each specimen are determined using an L27 Taguchi experimental design. A total of 27 specimens are printed and experimental data for the 27 specimens are used for model training and validation. The results indicate that the proposed method can achieve a minimum classification error of 0.01 after two iterations, with a maximum accuracy of 99.0%, and high model training efficiency. It can meet the requirements of predicting surface finish for FDM parts with multiple factors and categories and can handle imbalanced data. In addition, the high accuracy demonstrates the potential of this method for predicting surface finish, and its application in actual industrial manufacturing. [ABSTRACT FROM AUTHOR]

Material extrusion-based polymer 3D printing, one of the most commonly used additive manufacturing processes for thermoplastics and composites, has drawn extensive attention due to its capability and cost effectiveness. However, the low surface finish quality of the printed parts remains a drawback due to the nature of stacking successive layers along one direction and the nature of rastering of the extruded tracks of material. In this work, an in-process thermal radiation-assisted, surface reflow method is demonstrated that significantly improves the surface finish of the sidewalls of printed parts. It is observed that the surface finish of the printed part is drastically improved for both flat and curved surfaces. The effect of surface reflow on roughness reduction was characterized using optical profilometry and scanning electron microscopy (SEM), while the local heated spot temperature was quantified using a thermal camera. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced plastic/titanium alloy (CFRP/Ti) stacks are widely used in the aerospace field based on their high strength to weight ratio and heat resistance. High-quality bolt hole assembly is critical for the safety of the aerospace industry. Reaming is a crucial process in precision machining and is extensively used to improve the quality of bolt holes. Due to the different properties of the material, machining with conventional reaming (CR) presents some challenges, such as tolerance variations across the hole group and difficulty in controlling thrust. In this paper, ultrasonic vibration is applied to the reaming process. A geometrical model of ultrasonic vibration reaming (UVR) was established to analyze its kinematic law. UVR experiments on CFRP/Ti stacks were carried out to study the influence of different ultrasonic amplitudes on reaming thrust and the influence of tool speed on thrust, dimensional accuracy, and surface roughness under optimal ultrasonic amplitude. The average thrust forces in UVR decreased by over 57% (Ti) and 40% (CFRP), respectively, compared to CR. The roughness of CFRP is reduced by 20% with UVR and 28% for titanium alloys. The surface topography of the holes is significantly improved by UVR. This work guides the manufacture of high-quality bolt holes for CFRP/Ti stacks. [ABSTRACT FROM AUTHOR]

When workpieces require tight tolerance or a good surface finish, grinding is usually the best solution. Yet this process is characterised by generating a great amount of heat that needs to be controlled. The minimum quantity lubrication (MQL) system emerged as an alternative to the flood cooling system. Nevertheless, the employment of the former in austempered ductile iron (ADI) surface grinding is still an unexplored topic. This research seeks to experimentally study the applicability of MQL and the influence of the wheel speed and workspeed, in the surface topography of ADI samples subjected to different conditions of surface grinding. ADI surface topography was acquired, then the roughness parameters and surface hardness alterations were determined. The results show that the application of MQL in ADI surface grinding is possible. The surface roughness is similar to that of the flood cooling system and the surface hardness alterations are small. [ABSTRACT FROM AUTHOR]

In this work, the design, manufacture and measurement process of constant-breadth cams is presented. The motion law of the cam was designed by means of Bézier curves and the corresponding design desmodromic constraints. The cams were manufactured in two different materials employing two different processes: PLA cams with fused filament fabrication (FFF) and aluminium cams with computer numerical control (CNC) milling. The main aim of this work is to compare both types of cams regarding dimensional accuracy and surface finish, in order to evaluate if it would be possible to temporally replace a metallic cam with a plastic one during the repair of the first one. Dimensions were measured with micrometres and surface roughness with a contact roughness meter. The results show that, in diametral dimensions, similar dimensional error values were obtained for both the 3D-printed and the machined cams. However, in longitudinal dimensions, whose direction is perpendicular to the 3D-printed layers, the 3D-printed cams showed higher dimensional error than the machined ones. The average roughness Ra in the 3D-printed cams was 20 times higher than in the milled cams. According to the results, it would be recommended to temporally replace metallic cams with plastic ones in applications of low-power transmission. Given that in the literature little information is available about the measurement of 3D-printed desmodromic cams, this work will contribute to the study and analysis of this kind of 3D printed mechanism. [ABSTRACT FROM AUTHOR]

In this paper, we present the first known experimental results in using hybrid additive-subtractive laser powder bed fusion (h-LPBF) to make a type of passive radio frequency component called a quarter wave resonator (QWR). The h-LPBF process uses in-situ, interlayer vertical milling to machine certain inaccessible, critical internal features of the QWR device during printing. Using h-LPBF, the as-built surface roughness of functionally important features improved to Ra ~ 2 µm compared to Ra ~ 8 to 20 µm for conventional (additive only) LPBF-processed QWRs. Additionally, the dimensions of certain critical features were closer to their intended design. These metrological improvements resulting from h-LPBF reduced RF losses by a factor of almost 2. Consequently, the RF performance (Q-factor) of h-LPBF-processed QWR components were 1.5 to 2 times superior compared to their conventional LPBF counterparts, and the performance advantage was sustained on stress relief and chemical etching. These results were verified with theoretical electromagnetic simulations. [ABSTRACT FROM AUTHOR]

The most critical phase of all the stages needed for quality sample preparation for microscopic study is perhaps surface polishing. Magnetic abrasive polishing is a nonconventional finishing operation that can finish different materials and produce nano-finished surfaces. This study emphasizes the fabrication of a magnetic abrasive polishing setup for metallurgical polishing of specimens. Utilizing this test arrangement, exploratory investigations have been conducted to analyze the impact of five significant interaction factors, specifically the gap between the magnetic pole and the workpiece (G), the quantity of diamond-based sintered magnetic abrasives (Q), the rotational speed of the magnetic pole (RPM), the grit size of sintered magnetic abrasives (S), and machining time (T). The abrasives used in this study were diamond-based sintered magnetic abrasives. The percentage change in surface roughness (PCSR) of the stainless steel SS304 workpiece is the response variable. From the results of the ANOVA study, the most important factor affecting the PCSR of the stainless steel SS304 workpiece is the abrasive grit size (49.49%), and the least important factor is the machining time (4.89%). The differences in scanning electron microscopy (SEM) images and surface profiles of workpieces demonstrate that the developed setup can polish stainless steel SS304 plane workpieces. [ABSTRACT FROM AUTHOR]

This article deals with electrical discharge machining (EDM) of an alnico alloy, focusing on how key process parameters affect the surface finish. The experiments were conducted using a BP93L EDM machine. The Box–Behnken design was employed to study the effects of three factors, i.e., spark current, pulse-on time, and pulse-off time, each at three levels, on the surface quality. A specially designed system was employed to increase the effectiveness of the machining process by imparting an additional rotary motion to the tool and an additional rotary motion to the workpiece. The aim was to efficiently remove the eroded metal particles and create a surface with smaller craters. The workpiece surface roughness was measured with a Talysurf CCI lite non-contact profiler. During this precision machining process, the arithmetical mean height (Sa) was less than 1 µm. The surface quality was examined also using scanning electron microscopy (SEM) and optical microscopy (OM). The experimental data were analyzed by means of Statistica to determine and graphically represent the relationships between the input and output parameters. [ABSTRACT FROM AUTHOR]

Advanced fabrication methods with high efficiency are needed to meet the rising demand for precision optical components. This study proposes a plasma-based isotropic polishing method to remove fused silica's surface defects and subsurface damaged layers. Hence, a medium-pressure plasma process is developed to serve this purpose. The qualitative analysis of the plasma and atom emission spectrum explores the plasma generation and scattering of the activated fluorine (F*) radicals inside the plasma chamber. Material removal rate (MRR) and surface roughness variations with different total pressures of 5–30 mbar and substrate dimensions (i.e., varying length between 5 and 45 mm with fixed width and thickness of 5 and 2 mm) at fixed process parameters, i.e., radio-frequency power of 80 W, pressure ratio of 1:1, gas composition of 90:10, have been investigated. The highest and lowest MRR, i.e., 0.039 mm3/min and 0.0061 mm3/min, are achieved at 5 and 30 mbar total pressures on substrates having lengths 45 and 5 mm, respectively. The highest and lowest percentage change in surface roughness observed are 86.4 % and 17.1 % at 5 mbar and 30 mbar for substrates with 5 and 45 mm lengths, respectively. Surface morphology analysis shows the micro-cracks are reduced after plasma processing. The presence of elements, i.e., F and C, through EDX analysis, confirms the reactions on the plasma processed surface. Moreover, The XPS findings demonstrated that minimal radicals could be incorporated onto the fused silica surface during He/O 2 /SF 6 plasma processing. At lower pressure, the surface roughness value increases due to the increased excitation and ionization rate caused by more interaction between the fluorine and surface atoms. The MRR increases with substrate dimension with constant pressure. Larger substrate dimensions result in increased MRR at lower pressure. • The plasma polishing process is developed to remove cracks and reduce sub-surface defects of optical materials. • Significant plasma parameters are observed as RF power, pressure ratio, gas composition, total pressure, and process time. • The highest and lowest MRR, i.e., 0.039 and 0.0061 mm3/min, are achieved at 5 and 30 mbar total pressures, respectively. • Surface morphology analysis shows the micro-cracks were reduced after plasma processing. • XPS findings demonstrated that minimal radicals could be incorporated into the fused silica during plasma processing. [ABSTRACT FROM AUTHOR]

Material extrusion-based polymer 3D printing, one of the most commonly used additive manufacturing processes for thermoplastics and composites, has drawn extensive attention due to its capability and cost effectiveness. However, the low surface finish quality of the printed parts remains a drawback due to the nature of stacking successive layers along one direction and the nature of rastering of the extruded tracks of material. In this work, an in-process thermal radiation-assisted, surface reflow method is demonstrated that significantly improves the surface finish of the sidewalls of printed parts. It is observed that the surface finish of the printed part is drastically improved for both flat and curved surfaces. The effect of surface reflow on roughness reduction was characterized using optical profilometry and scanning electron microscopy (SEM), while the local heated spot temperature was quantified using a thermal camera.

The aim of current study is to present and study the bimodal dynamic Scanning Thermal Microscope (SThM) for nanomachining. Bimodal SThM is the same as conventional SThM where the base is excited simultaneously at a frequency close to the 1st and 2nd resonance frequency of probe. Bimodal excitation makes two separated channels for monitoring sample data for different purposes. Thus, a mathematical model for bimodal SThM is provided. The nonlinear coupled equations of motion are solved analytically. The presented model is compared with the literature and the behavior of bimodal SThM is compared with conventional type. It is shown that the shifted resonance frequencies are independent of the type of excitation and bimodal excitation increases amplitudes at all shifted resonance frequencies. By decreasing ratio of base excitation amplitudes, the amplitude in the 2nd base excitation frequency and all shifted resonance frequencies increase. Bimodal technique amplifies the amplitudes at the 2nd shifted resonance frequency, this data can improve resolution in thermal images. Then, the effects of tip radius on the final surface are simulated. It is shown that the nanomachining depth increases significantly for bimodal SThM and nanomachined surface roughness is increased. It is declared increase in temperature gradient does not necessarily improve the roughness and the final surface always depends on the interactions of three parameters: the tip radius, the total shape of the vibrational response and the location of the peaks with large amplitudes. [ABSTRACT FROM AUTHOR]

Aim: The aim of the present study was to evaluate the influence of the surface roughness on the torsional resistance of polished and unpolished nickel-titanium BR4C endodontic instruments. Materials and Methods: Ten instruments of each type (electropolished and unpolished) were evaluated with a profilometer to quantify the surface roughness on the working part of the instruments and then subjected to torsional stress to evaluate the maximum torque and angular deflection at failure. Torsion was applied using a custom-made device attached to the crosshead of a universal testing machine (Emic DL 10.000, São José dos Pinhais, PR, Brazil). Data obtained from the maximum torque, angular deflection and from the roughness of the polished and unpolished instruments were statistically analysed by Student t-test. Results: The profilometer analysis showed that the surface grooves on the unpolished instruments were deeper compared with their electropolished counterparts. Significant differences in roughness (peak and valley) (P < 0.05) were observed between the polished and unpolished specimens. In the torsion tests, the maximum torque and angular deflection were not significantly different (P > 0.05). Conclusion: This study showed that the depth of the surface grooves resulting from machining during the manufacturing process did not affect the maximum torque and angular deflection of the instruments tested. [ABSTRACT FROM AUTHOR]

Ball end magnetorheological finishing (BEMRF) is a novel finishing process used to finish variety of surfaces ranging from flat, curved, complex, two dimensional, three di-mensional and non linear. The residual stress and surface finish play an important role in overall efficiency and durability of the components. The present work is aimed to relieve the residual stress of work-piece surface with the improvement in surface finish using pulse DC power supply (PDCPS) in BEMRF process. The preliminary experiments have been conducted on flat EN-31 steel with and without pulse DC power supply (WPDCPS). The process parameters during experiments were considered as magnetiz-ing current (MC) of 2.5A, tool rotational speed (TRS) 500 rpm, and working gap (WG) 1.5 mm with finishing time 35 minutes and 55 mm/minute feed rate given to the work-piece. The responses such as residual stress and surface roughness have been measured before and after experimentation. Residual stress of EN-31 surface was measured with X-ray residual stress analyzer using Cosα method. It has been observed that the residual stress was found reduced from 130 to 66 MPa and surface roughness was reduced drastically with the use of pulse DC power supply in BEMRF process. After preliminary experi-mentation, the statistical analysis with design of experiment has been conducted with pulse DC power supply on EN-31 steel to visualize the effect of various process parame-ters on residual stress using RSM technique. [ABSTRACT FROM AUTHOR]

Nowadays, when the aluminium metal matrix is machined, the devices are prematurely decepted mainly by adhesive wear. The adhesive wear leads to deterioration of surface texture and changes the cutting tool signature. Change of tool signature leads to over power consumption, reduction in effective use of the cutting tool and increase of surface roughness. The surface roughness on the machined component and formation of lay is dependent on the machining parameters, tool signature and machining conditions. This paper demonstrates the effect of Built Up Edge (BUE and Built Up Edge (BUL) on the surface roughness of the composites of fly ash in aluminium using K10. The results achieved were compared with Al6061 aluminium and Al6061 fly ash composites for different cutting edge speeds and feeds at a constant deep cut. The results of the experiment established the significant impact of cutting edge speed and feed on the making of the built-up edge and coating creation that rises surface rugging. Investigation specifies that the cutting edge speed and feed has the uppermost influence on the built-up edge and built-up layer creation while machining such as Al6061 aluminium and Al6061 fly ash composite and hence variation in surface roughness. [ABSTRACT FROM AUTHOR]

Reverse micro electro-discharge machining (RµEDM) is a promising and cost-effective technology for fabricating unconventional shaped single and arrayed micro-pins of high aspect ratio. However, dimensional inaccuracies, poor surface finish and long machining time are of great concern. An experiment-based detailed investigation of process parameters for analyzing various machining responses has been performed in this article. Taguchi's L16 orthogonal array design of experiments has been used to frame out the experimental runs. Discharge voltage, capacitance and feed rate have been considered as process parameters whereas, material removal rate, taper root angle, surface roughness and machining time as responses for the fabrication of a single micro-pin. Additionally, the feasibility of a novel high-pressure suction flushing technology implemented for RµEDM has been demonstrated. The performance of this technology is verified for better surface quality and lesser machining time. It is observed that by using the proposed suction technology, along with the suitable parametric settings, the micromachining time significantly improved (~20%) while fabricating an arrayed micro-pins in elliptical cross-sections profile. [ABSTRACT FROM AUTHOR]

Surface quality is an important performance indicator of laser metal deposition. Based on annular laser beam internal powder feeding technology, the effect of higher energy of the outer side of the annular beam on the surface roughness and waviness of thin-wall parts is studied in this paper. The influences of laser power, scanning speed, and powder feeding rate on the surface finish of thin-wall parts are investigated. The results show that the laser power has a significant effect on surface finish. With the increase in laser power, the roughness decreases and the waviness increases first and then decreases. High laser power can improve surface finish. As the scanning speed increases, the roughness decreases first and then increases, and the waviness decreases. The scanning speed has a significant influence on surface waviness. Increasing the powder feeding rate is not beneficial to surface quality because the value of the roughness and the surface waviness will add with its rising. [ABSTRACT FROM AUTHOR]

Ductile-to-brittle transition in cutting mode is an important phenomenon in the ultra-precision machining and surface finish of brittle materials. Using a newly-developed coarse-grained molecular dynamics technique, we systematically explore the effect of depth of cut on the cutting mode and the evolution of roughness. Our simulations demonstrate that the transitional depth of cut (TDoC) model accurately predicts the material removal mechanisms, which are affected by both the material's properties and the cutting depth. When the cutting depth increases, the operating mechanism shifts from shearing-induced serrated chip formation to cleavage-cracking chip breakage. The RMS roughness study demonstrates that the roughness is a direct outcome of the chip formation mechanism and is, in general, higher when chip breakage occurs. [Display omitted] • Simulating, for the first time, the process of roughness creation induced by cutting. • Elaborate the material removal as a competition between plastic shearing and fracture. • Investigating the effect of depth of cut on material removal mechanism. • Discussing surface roughness as a function of the material toughness and depth of cut. [ABSTRACT FROM AUTHOR]

This work deals with the optimization of crucial process parameters related to the abrasive flow machining applications at micro/nano-levels. The optimal combination of abrasive flow machining parameters for nano-finishing has been determined by applying a modified virus-evolutionary genetic algorithm. This algorithm implements two populations: One comprising the hosts and one comprising the viruses. Viruses act as information carriers and thus they contribute to the algorithm by boosting efficient schemata in binary coding to facilitate both the arrival at global optimal solutions and rapid convergence speed. Three cases related to abrasive flow machining have been selected from the literature to implement the algorithm, and the results corresponding to them have been compared to those available by the selected contributions. It has been verified that the results obtained by the virus-evolutionary genetic algorithm are not only practically viable, but far more promising compared to others as well. The three cases selected are the traditional “abrasive flow finishing,” the “rotating workpiece” abrasive flow finishing, and the “rotational-magnet or heological”abrasive flow finishing. [ABSTRACT FROM AUTHOR]

The surface finish is an important characteristic in the incremental sheet forming (ISF) process and is often influenced by numerous factors within the forming process. Therefore, this research was aimed at identifying the optimal forming parameters through the Taguchi method to produce high-quality formed products. The forming tool radius, spindle speed, vertical step increment, and feed rate were chosen as forming parameters in the experimental design, with surface roughness as the response variable. Taguchi L16 orthogonal array design and analysis of variance (ANOVA) test were used to identify the parameter’s optimal settings and examine the statistically significant parameters on the response, respectively. Results confirmed that a significant reduction in surface roughness occurred with a drop in vertical step size and an increase in feed rate. In detail, the vertical step size has the most significant influence on the surface roughness, followed by the feed rate and the forming tool radius. In conclusion, the optimum level settings were obtained: forming tool radius at level 3, spindle speed at level 1, vertical step size at level 1, and feed rate at level 4. Additionally, confirmation experiment results based on the optimal settings indicated a good agreement against the experimental observation. Further, the response surface methodology (RSM) was also exploited to devise a mathematical model for predicting the surface roughness. The results comparison confirmed that both techniques could effectively improvise the surface finish.

Selective laser melting (SLM) is a powder bed fusion additive manufacturing technology that allows the production of high-performance metal parts with geometrically complex shapes, such as curved surface, can be used in practical engineering applications. In recent years, systematic attempts have been made to uncover the material-process-microstructure-property linkage in SLM-fabricated planar-surface metal parts; however, little is known on the performance and quality of SLM-fabricated metal parts with curved surfaces. In this paper, we studied the effects of build orientation on the geometric performance of SLM-built 316L stainless steel (SS) samples with a sinusoidal curved surface. The results indicated that the average values of profile roughness Ra and surface texture attributes Sa, Sk, and Vmc decreased with the increase in build orientation. Moreover, the locations at curvatures C2 and C4 exhibited the best surface finish at the build orientation of 75 deg and 90 deg. In addition, the least square method was used to fit the actual profile of the curved surface of as-built samples fabricated at each build orientation, and it was found the actual profile demonstrated the best consistency with the designed one at 90 deg build orientation. In this paper, the process-curvature-geometric performance relationship of SLM-built metal parts with curved surface was uncovered. In addition, this paper provides keen insights into assessing the geometric performance of SLM-built curved-surface metal parts and establishes a roadmap toward SLM-fabrication of metal parts with complex geometries for practical engineering applications. [ABSTRACT FROM AUTHOR]

Purpose: Limited research has attempted to reveal the different modes of the melt pool formation in additive manufacturing. This paper aims to study the mechanisms of surface roughness formation, especially on the aspect of melt pool formation which determine the surface profile and consequently significantly influence the surface roughness. Design/methodology/approach: In this study, the conditions under which different modes of melt pool formation (conduction mode and keyhole mode) occur for the case of as-fabricated Hastelloy X using direct metal laser solidification (DMLS) are derived and validated experimentally. Top surfaces of uni-directionally built samples under various processing conditions are cut, grinded, polished and etched to reveal their individual melt pool morphologies. Similarly, up-skin (slope angle < 90°) and down-skin (slope angle > 90°) melt pool morphologies are also investigated to compare the differences. Surface tension gradients and resultant Marangoni flow, which dominate the melt flow in the melt pool, is also calculated to help better evaluate the melt pool shape forming. Findings: Two types of melt pool formation modes are dominating in DMLS: conduction mode and keyhole mode. Melt pool formed by conduction mode generally has an aspect ratio of 1:2 (depth vs width) and is in elliptical shape. Appropriate selection of scanning laser power and speed are required to maintain a low characteristic length and width ratio to prevent ballings. Melt pool formed by keyhole mode has an aspect ratio of 1:1 or less. High-energy contour promotes formation of key-hole-shaped melt pool which fills the gaps between layers and smoothens the up-skin surface roughness. Low-energy contour scan is necessary for down-skin surface to form small melt pool profiles and achieve low Ra. Originality/value: This paper provides valuable insight into the origins of surface quality problem of DMLS, which is a very critical issue for upgrading the process for manufacturing real components. This paper helps promote the understanding of the attributes and capabilities of this rapidly evolving three-dimensional printing technology and allow appropriate control of processing parameters for successful fabrication of components with sound surface quality. [ABSTRACT FROM AUTHOR]

This paper describes a new method to evaluate the friction coefficient at the tool-work interface in machining process where high stress and temperature are caused. In order to examine the feasibility of the proposed method, the present report introduces the method and the results obtained only at room temperature. Ti6Al4V, SUS304, AISI1045, FCD 700, FCD 450 and FC300 were used as work materials, while TiN coated carbide tool, TiAlN coated carbide tool and P15 were used as tool materials. The proposed method provided the friction coefficients of different coatings against different work materials, and demonstrated the variability of friction coefficient and the anisotropy of surface roughness. • This paper proposes a new friction test between commercially available cutting tool and work material. • Low friction coefficients were observed for high hardness materials such as FCD700 and for low adhesive K15 self-friction. • High friction coefficients were observed for low-hardness ductile cast iron FCD 450 and for high adhesive Ti6Al4V self-friction. • Adhesiveness between work and tool material was found to have strong relationship with variability of friction coefficient. • Friction coefficient of FCD 450 with TiN coated carbide tool showed more variability than FCD 700. [ABSTRACT FROM AUTHOR]

Die-sinking electrical discharge machining (EDM) is the principal method used to machine critical components made of Al6061 alloy for space applications. Geometrical precision and surface roughness are among the most important acceptance criteria for these machined parts. The purpose of this research work is to identify the most significant parameters affecting the material removal rate (MRR), the electrode radius wear rate (EWR), and the surface roughness (Sa) when machining Al6061-T6 aluminum alloy by die-sinking electrical discharge machining and to use this knowledge in future work to generate accurate predictive models. To this end, ten universal machining parameters were selected, and using a Plackett–Burman Design of Experiments (DOE) approach, their influence and relative impact on MRR, EWR, and Sa were calculated and validated using experiments. A comprehensive Analysis of Variance (ANOVA) was then conducted based on the obtained results. It was found that the discharge current, the discharge duration, and the system voltage significantly affect the MRR, while these same three parameters plus the delay between two series of discharges significantly affect the EWR. The surface roughness was affected by the discharge current, the discharge duration, the voltage, the delay between two discharges, and the delay between two series of discharges. The obtained results were analyzed in terms of the relationship between energy input during machining and the surface modification of the material. [ABSTRACT FROM AUTHOR]

In internal turning of hardened steel carried out with cubic boron nitride (CBN) tools, the main concern is with the workpiece surface finishing, usually aiming to achieve a surface roughness similar to the attained in grinding processes along with gains in productivity. However, vibrations from the process often cause premature chipping in the tool and/or damage to the workpiece finishing. To minimize vibration, one solution is the use of passive and active dampers with different types of construction. Passive damper contrasts with active damper due to its low cost and simpler construction. The use of particle impact passive damper aided by compressed air to promote workpiece surface roughness reduction was studied. For this, different materials, particle size, packing ratio, and overhang boring bar were tested. Based on the results, it was possible to conclude that the airflow aided particle damper reduced the mean surface roughness by around 60% compared to non-airflow damping in 120 mm (L/D = 6) boring bar overhang. [ABSTRACT FROM AUTHOR]

This work presents the first practical application of ionic electrolytes for electropolishing of nickel-based superalloys. It contains the results of an experiment-driven optimization of the applied potential and electrolyte temperature during electropolishing of laser powder bed-fused IN625 components containing surfaces oriented to the building platform under angles varying from 0 to 135°. For comparative purposes, the roughness profilometry and confocal microscopy techniques were used to characterize the surface finish topographies and the material removal rates of IN625 components subjected to electropolishing in ionic and acidic (reference) electrolytes. After 4 h of electropolishing in both electrolytes, a roughness of Ra ≤ 6.3 μm (ISO N9 grade number of roughness) was obtained for all the build orientations. To elaborate, both electrolytes manifested identical roughness evolutions with time on the 45° (75% Ra reduction) and 90°-oriented (65% Ra reduction) surfaces. Although the roughness reduction on the 135°-oriented surface in the ionic electrolyte was 17% less than in the acidic electrolyte, the former provided a more uniform roughness profile on the 0°-oriented surface (30% Ra reduction) and 44% higher current e°ciency than the acidic electrolyte. This work proves that ionic electrolytes constitute a greener alternative to industrial acidic mixtures for electropolishing of three-dimensional (3D)-printed parts from nickel-based superalloys. [ABSTRACT FROM AUTHOR]

Polishing is a surface machining technique to produce a high-quality finished surface on the product. It is a multistage process, in which each subsequent stage uses a finer abrasive. This paper aims to design and fabricate a polishing machine that performs polishing stages continuously, eliminating the idle time in the polishing process. The designed machine consists of four spindle heads, each of which carries a unique flap wheel. The flap wheels can raise or lower according to the size of the workpiece to be polished. Three types of rollers were adopted in the machine: a mild steel roller coated with heat resistant rubber, a hylam roller and a nylon roller. A pneumatic clamping system was placed at the feeder to fix and hold the workpiece. In addition, the compressor pressure is regulated by a pressure regulator. A prototype of the polishing machine was fabricated according to the design, and used to polish several types of workpieces. The results show that this machine can polish stainless-steel flat bars, square tubes and rectangular tubes into 10mm-150mm width products, operate at a high speed of 2,000~3,000 rpm, and, most importantly, execute multiple polishing operations continuously. The proposed polishing machine is helpful to the automation of the polishing industry. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)