Surface Roughness Factor Research Articles

Macro polypropylene fiber influences on crack geometry and water permeability of concrete

In order to study the effect of macro polypropylene fiber on crack geometry (tortuosity, surface roughness) and water permeability of concrete, the independently designed laser scanner was adopted to obtain the surface coordinates of the crack, the coefficients of crack tortuosity and surface roughness were introduced and the crack tortuosity and surface roughness were evaluated quantitatively through the MATLAB programming, the crack geometry of the specimens reinforced with macro polypropylene fibers and specimens without any reinforcement were compared. A self-designed device was adopted to the water permeability test, the influence of macro polypropylene fibers on water permeability of cracked concrete was studied. The Poiseuille law was modified regarding to the tortuosity factor and surface roughness factor. The results showed that: the coefficients of variation of the tortuosity factor and surface roughness factor were relatively small for all kinds of samples and could be used to verify the crack geometry of concrete. The crack geometry of the concrete was affected by the macro polypropylene fiber and the tortuosity and surface roughness of the crack increased with the increasing of fiber dosage. The modified Poiseuille law could be adopted to predict the water permeability of the cracked concrete.

Retardation of an IGG gas flow along a mine drift due to condensation and temperature decrease

The progress of the GAG gas flow in a conveyor drift is investigated. The output of a calculation model is evaluated and compared with experimental results from full-scale inertisation experiments. Expressions presenting the fastest and most extensive condensation of water resulted in well fitted arrival times of the GAG gas front. A common denominator for the two sets of expressions is that the type of flow is considered and thus better fitted to the actual flow situation. The model was further refined to include the surface roughness factor in the condensation calculations, which resulted in time lengths even closer to the measured time length. The measured rapid temperature increase at certain positions along the conveyor drift was found to fit well with the calculated GAG gas front arrival at the corresponding positions. The magnitude of the GAG flow was found to have a large impact on the arrival time of the GAG gas front. Knowing and understanding the GAG gas behaviour would increase the likelihood of successful inertisation of all or part of a mine.

Evaluation and optimization of machining performance for rotary ultrasonic machining of Al/SiC composite material

In manufacturing industries, Al/SiC composite material is highly demanded due to its excellent properties. However, the difficulties in its machining restrict the application and competitiveness of this material. This investigation is aimed at studying the impact of different experimental conditions (feed rate, spindle speed, and ultrasonic power) on responses of interest (material removal rate, surface roughness, and chipping thickness) in rotary ultrasonic machining of Al/SiC composite material. The experiments have been planned by using full factorial design. Analysis of variance (ANOVA) is also employed to identify the significant factors and the optimized process settings for the different responses. The experimental results showed that feed rate was the most significant factor for material removal rate and surface roughness. However, all the factors were found to be insignificant for chipping thickness. From the surface topography analysis of the machined surface, no surface damage in the form of micro-cracks etc. was visible.

Experimental Study of the Surface Roughness and the Delamination in the Drilling of GFRP and AL/SiCp Composites with Different End Mills

In this research, the influence of the drilling process parameters; three cutters (end mill) of different diameters, three of cutting speeds and five of feed rates on the process responses, i.e. the surface roughness ( ) and the delamination factor ( ) of the drilled hole are studied. The two types of the used composites are GFRP and AL/SiCp. From the analysis of the results, the feed rate and the cutter diameter are had a large effect on surface roughness and delamination factor, while both of them are increased with the increase of cutter diameter and the used feed rates. The results of surface roughness and the delamination factor when drilling GFRP composite are bigger than that values of AL/SiCp composite at all used cutters, cutting speeds and all used feed rates. Also, from the results, using of cutting speed (2500 rpm), end mill of the small diameter ϕ 8mm and low feed rate (10mm/min) are suitable for drilling GFRP and AL/SiCp to get a better surface roughness of the resulted.

Desorption of Aqueous Solution of Lithium Bromide on Enhanced Surfaces in a Single-Stage Lithium-Bromide Absorption Chiller

This article presents values of heat transfer coefficients at pool boiling of aqueous solution of lithium bromide on smooth and fin tubes. The experimental studies were performed under conditions typical of absorption chiller with single-stage desorption. More exactly, the condensation pressure was about 7.8–8.5 kPa, and the concentration of lithium bromide solution was 60–61 wt%. The outer diameter of the smooth and fin tubes was 16.0 mm; the inner diameter was 12.0 mm. The surface roughness factor of the fin tubes ranged from 2.7 to 6.0. The studies have shown that for fin tubes the heat transfer coefficient reduced to a surface unit is up to 30 percent higher as compared with a smooth tube.

Study The Effect of Process Parameters of CNC Milling Surface Generation Using Al-alloy 7024

A wonderful unique research developments in modeling surface roughness and optimization of the predominant parameters to get a surface finish of desired level since only suitable selection of cutting parameters can get a better surface finish, so the objective of this work is to study the milling process parameters which include tool diameter, feed rate, spindle speed, and depth of cut resulting in optimal values of the surface roughness during machining AL-alloy 7024. The machining operation implemented on XK7124 3-axis CNC milling machine. The effects of the selected parameters on the chosen characteristics have been accomplished using Taguchi’s parameter design approach. The parameters considered are – depth of cut with two levels (0.2, 0.5 mm), tool diameter with two levels (6, 8 mm), spindle speed with two levels (1000, 2500 rpm), and finally feed rate with two levels (200, 500 mm/min). Analysis of the results showed that the optimal settings for low values of surface roughness are large tool diameter (8 mm), high spindle speed (2500 r.p.m), low feed rate (200 mm/min) and high depth of cut (0.5 mm). Response Table for mean of surface roughness showed that tool diameter has the most effected factors (rank one) followed by feed rate (rank two) then depth of cut which is the third effected factors and finally spindle speed with the less effected factors of surface roughness (rank four).

Porous Ni Photocathodes Obtained by Selective Corrosion of Ni-Cu Films: Synthesis and Photoelectrochemical Characterization

In this work, a dealloying technique is proposed as a synthesis method to obtain highly porous Nickel electrodes starting from Ni-Cu co-deposit: pulsed corrosion is applied adopting different corrosion and relaxation times. Different morphologies, pore size distribution and residual copper amount were obtained depending on the corrosion conditions. For the developed electrodes, the surface roughness factor, Rf, was evaluated by electrochemical impedance spectroscopy (EIS). The hydrogen evolution reaction (HER) on these electrodes was evaluated by means of steady-state polarization curves, and the related parameters were derived by Tafel analysis. Finally, a thin layer of NiO on the porous structures was obtained to exploit the semiconductor characteristic of the oxide, so that an extra-photopotential was obtained by the simulated solar light action. Results demonstrate greater apparent activity of the developed electrodes towards HER in comparison with commercial smooth Ni electrode, which can be mainly attributed to the large Rf obtained with the proposed technique.

Experimental investigation on the ball burnishing of carbon fiber reinforced polymer

ABSTRACTThe polymer-based materials are generally used in all industrial applications. Even if polymer bars can be machined easily, they need surface finishing treatment after the machining process. The ductile properties make coarse roughness on the surface that causes the elastic structure of polymer materials. The carbon fiber reinforced composite materials differ from polymer-based materials by high strength and stiffness. Its structure exhibits similar performances such as metallic materials. The effect of ball burnishing on the surface quality of rod workpiece was investigated in this study. To enhance the surface quality of high strength carbon fiber reinforced polymer rod workpiece, burnishing process was performed in three different parameters (force, feed rate, number of passes) and under four different mediums (dry, wet, boron oil, and mineral oil) conditions. The results of the experiments were analyzed, and optimum burnishing parameters were determined and discussed in detail. The best surface roughness value of the CFRP material used in the experiments was obtained as burnishing force: 250 N, feed rate: 0.05 mm/rev, four passes and wet medium. According to the results of variance analysis, it was found that the CFRP workpiece is the important leading factor for surface roughness with a contribution ratio of 62.47%.

Fast corona discharge solver for precipitators using multi‐grid methods on fine grids

A novel approach for modelling the corona problem in the wire-duct precipitators using the finite difference technique integrated with multi-grid methods is adopted in this study. The multi-grid method is applied as a fast convergent iterative solution for the finite difference technique to solve Poisson equation especially on finer grids. Two schemes of the multi-grid method, mainly the V-cycle and the full multi-grid method, are adopted in the present study. Compared with Gauss–Seidel method, the above-mentioned schemes are successfully transcendent owing to timing performance. By using finer grids, the proposed algorithm allows to get a more accurate picture about the performance of the precipitators in the design stage without suffering from the excessive computational time. Accurate results for the potential and current density computations, closed to the previous published experimental measurements, are obtained in comparison with earlier numerical techniques for several design parameters of the precipitators. Finally, the effect of changing the effective ion mobility and the surface roughness factor on the voltage–current density is considered.

Effect and optimization of photochemical machining process parameters for manufacturing array of micro-hole

The stainless steel-304 is used in various surgical instruments due to its low carbon content and better corrosion resistance. SS-304 is machined using photochemical machining process (PCM) to obtain the components with micro-dimensions. The statistical methods of signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) are applied to investigate effect of concentration of etchant, time of etching and temperature of etchant using DoE (L27) orthogonal array. The performance characteristics like material removal rate (MRR), surface roughness (Ra), undercut (UC) and etch factor (EF) are optimized during the investigation. The ANOVA technique is used to evaluate significance and percentage contribution of each parameter. The regression model for PCM of SS-304 is developed. The ANN technique is used to compare the predicted and experimental results of machining. The MRR, Ra, EF and UC are showing improvement of 0.38 mm3/min, 1.271 µm, 0.11 and 0.028 mm, respectively, after the confirmatory test. The developed model is used to manufacture the array of micro-holes (5 × 5) with hole size of 220 µm, 280 µm and 370 µm which are used for metering of medicine in biomedical applications.

Temporally-Resolved Ultrafast Hydrogen Adsorption and Evolution on Single Platinum Nanoparticles.

The hydrogen evolution reaction (HER) was studied on single platinum nanoparticles (NPs) using a microjet NP collision system. By ejecting NPs onto a closely positioned ultramicroelectrode (UME), one can study single-particle collision electrochemistry in acid concentrations as high as 3 M or 750 mM on the electrode surface. This is nearly 2 orders of magnitude greater than previously reported in NP-collision studies. The use of high-bandwidth recording and higher acid concentration allows us to temporally resolve the ultrafast hydrogen adsorption and evolution processes in HER on single colliding Pt NPs. Moreover, the electroactive surface area (EASA) and roughness factor ( Rf) of single Pt NPs can be readily derived from the integrated hydrogen adsorption charge. The use of high acid concentrations is critical toward obtaining a full monolayer of adsorbed hydrogen before overlapping with the evolution process. This method allows one to study electrochemical and electrocatalytic behavior of metal NPs in a chemical environment that is close to that used in real applications, for example, fuel cells and electrolyzers.

Efficient charge transport in surface engineered TiO2 nanoparticulate photoanodes leading to improved performance in quantum dot sensitized solar cells

Cold argon plasma treated TiO2 nanoparticulate photoanodes have been utilized for fabrication of quantum dot sensitized solar cells (QDSSCs). After plasma treatment the TiO2 nanoparticles got assembled in a closely spaced manner with increase in surface roughness factor owing to surface etching by the highly energetic ions, electron and radicals present in the plasma output. The photoanodes possess high inter-particle contact delivering fast charge carrier transport network minimizing the loss of charge carriers. The increase in conductivity was probed through conducting-AFM measurements. This morphological variation significantly inhibits the interfacial recombination by 3.5 times at the TiO2/NC/electrolyte interface as confirmed through electrochemical impedance spectroscopy. Moreover, the increase in Ti3+ as suggested by X-ray photoelectron spectroscopy also contributes in the enhancement of conductivity providing additional electron donor states. The power conversion efficiency increased from 3.65% to 5.01% for CdSe0.4S0.6 alloy nanocrystals (NCs) sensitized solar cells utilizing these plasma treated TiO2 photoanodes. Thus our strategy paves promising direction for the efficiency enhancements in QDSSC devices.

Transition of predominant mechanism for the deviation of micro-gap dc gas breakdown character with electrode gap changing

This paper explores the predominant mechanisms for the deviation of micro-gap dc gas breakdown and the transition between different mechanisms as the electrode separation d changing under a pin-to-plate electrode configuration using 2d3v particle-in-cell simulation with Monte Carlo collisions. The deviated breakdown characteristic curves as a function of d or gas pressure p are investigated and both present a plateau region. Through researching the position of discharge path, it is found that a self-modulation effect manages to maintain the breakdown voltage at the minimum value defined by Paschen’s curve in a certain d or p range and forms the plateau. The ranges of d and p for the plateau are also established. Theoretical calculation on the secondary electron emission coefficient induced by ion-enhanced field and determined by a surface roughness factor confirms that the ion-enhanced field emission effect affects the breakdown voltage significantly when d is below a critical value. The smaller the surface roughness factor is, the smaller the critical d will be. Under this effect, the breakdown voltage is decreased with d decreasing (also referred to as an increasing left branch with d increasing). Conclusively, the deviation characters of micro-gap gas breakdown are controlled by different mechanisms at different d ranges. The predominant mechanism for the deviation is the self-modulation effect, serving as the main reason for the plateau region, at moderate d of several micrometers and will transit to the ion-enhanced field emission effect, which is responsible for the increasing left branch at smaller d.

Soil Moisture Retrieval From SAR and Optical Data Using a Combined Model

Remote sensing inversion of vegetation-covered soil moisture is often affected by crop canopy, surface roughness, and other factors. In order to eliminate the scattering influence of vegetation effectively, this paper developed a modified vegetation backscattering model to retrieve vegetation-covered soil moisture based on multi-temporal RADARSAT-2 data and field measurements. This model combined the advantages of optical and radar methods by considering scattering contributions of underlying bare soil and vegetation canopy. Vegetation coverage was used to separate the scattering mechanism of the vegetation from bare soil component in a pixel. In addition, advanced integral equation method was presented to define the scattering of underlying bare soil. PROSAIL optical model was applied to calculate crown water content, which is an important variable associated with the scattering of vegetation canopy. Results demonstrated that the modified model on March 29, 2014 performed better in soil moisture retrieval than that at other growth stages with R 2 of 0.806 and root-mean-square error of 0.043 m3·m−3, respectively. Soil moisture can be effectively retrieved by using the modified model in an agricultural region where the surface type is ranging from relatively sparse to full cover. Overall, the modified model provides an insight into extensive application of vegetation-covered soil moisture retrieval in agricultural regions.

Optimization of surface roughness and delamination factor in end milling of graphene modified GFRP using response surface methodology

Abstract Glass fibre reinforced polymer (GFRP) composites are used in most of the applications like aerospace industries, marine, sport goods due to its better mechanical properties with high strength to weight ratio. Application of nanoparticle in matrix material has increased the mechanical and thermal properties of GFRP. In this study, end milling operation is conducted on neat GFRP and GFRP modified with different weight % of graphene using solid carbide end mill. Experimental parameters like feed rate and spindle speed with weight % of graphene were taken as input parameters. Response surface method was used to optimize these input parameters and analyze the surface roughness and delamination factor. Conducted experiment showed that weight % of graphene was the most influenced parameter for both delamination factor and surface roughness. Result concluded that low feed rate and high spindle speed with high weight % of graphene within used range of parameters value provided less surface roughness and delamination damage.

Dynamics of Bubble Behavior in Nucleate Boiling of R134a in an Enhanced Horizontal Tube

The design of tubes in heat exchangers has a significant influence on heat transfer coefficients (HTCs), affecting nucleate boiling at heat exchanger surfaces. Many researchers have explained heat transfer enhancement techniques applied to tubes by identifying empirical correlations, both dimensional and non-dimensional, for HTCs in terms of surface roughness factor, vapor density, and liquid density based on their experimental results. However, there has been a lack of research analyzing the mechanisms that affect the HTCs in depth. For example, the influence of bubble density, surface roughness factor, and the dynamics of bubble behavior have rarely been explained. In this regard, the present study focuses on mechanism analysis in terms of the value of HTC, specifically revealing the dynamics of bubble behavior. Additionally, this study reports the results of an experimental investigation of pool boiling heat transfer of R134a in a plain tube, a low-fin tube, and an enhanced (Thermoexcel-E) tube as well as results of examining the dynamics of bubble behavior observed on the surface of an enhanced tube. Ultimately, all these investigations aim to determine the heat transfer characteristics of the enhanced tube. In this study, however, circulated water flowing inside an evaporator is used as a heat source instead of a cartridge heater. The heat transfer enhancement ratio of the Thermoexcel-E tube is 2.69–4.13 in the range of heat fluxes tested when the values of HTC from the Thermoexcel-E tube are compared to counterparts from a plain tube. Meanwhile, analysis of the dynamics of bubble behavior observed on the surface of the enhanced tube allows determination of the enhanced tube’s heat transfer characteristics. The findings of this study can provide the refrigeration industry with a basic framework for better design using high-efficiency evaporators.

Experimental investigation in photochemical machining process through response surface methodology for manufacturing of micro mould

Photochemical machining (PCM) is used as one of the best micromachining technique for machining of difficult-to-cut material with appropriate machining parametric combinations. Ferric chloride is used as etchant for machining of Stainless Steel-304. In the present study, the effect of process parameters such as time of etching, temperature of etchant and concentration of etchant on material removal rate (MRR), surface roughness (Ra), undercut (Uc) and etch factor (EF) in PCM of SS-304 is evaluated by using response surface methodology (RSM) and the optimum machining condition is evaluated. The central composite design (L20) is used to understand the behaviour of responses with change in levels of machining parameters. The optimum machining parameters evaluated are temperature of etchant at 54.65°C, time of etching at 47.14 min. and concentration of etchant at 727.80 g/l. The confirmatory result shows the improvement in performance quality with setting of machining parameter at optimum level. The optimum machining parameters are used to manufacture the array of micro mould with size of 139 µm, 204 µm and depth of 15 µm, 13 µm used in different engineering and biomedical application.

Experimental investigation in photochemical machining process through response surface methodology for manufacturing of micro mould

Photochemical machining (PCM) is used as one of the best micromachining technique for machining of difficult-to-cut material with appropriate machining parametric combinations. Ferric chloride is used as etchant for machining of Stainless Steel-304. In the present study, the effect of process parameters such as time of etching, temperature of etchant and concentration of etchant on material removal rate (MRR), surface roughness (Ra), undercut (Uc) and etch factor (EF) in PCM of SS-304 is evaluated by using response surface methodology (RSM) and the optimum machining condition is evaluated. The central composite design (L20) is used to understand the behaviour of responses with change in levels of machining parameters. The optimum machining parameters evaluated are temperature of etchant at 54.65°C, time of etching at 47.14 min. and concentration of etchant at 727.80 g/l. The confirmatory result shows the improvement in performance quality with setting of machining parameter at optimum level. The optimum machining parameters are used to manufacture the array of micro mould with size of 139 µm, 204 µm and depth of 15 µm, 13 µm used in different engineering and biomedical application.

Optimization of Process Parameters of Wire Electric Discharge Machining on AISI 4140 Using Taguchi Method and Grey Relational Analysis

Abstract In this study main focus is on the minimized value of the response variables such as surface roughness and kerf width by setting process parameters of wire electric discharge machining at the optimum level. Single objective optimization is done by using Taguchi L9 orthogonal array and for multi-objective optimization grey relational analysis is used. For experimentation pulse on time (Ton), pulse off time (Toff), servo voltage (SV), wire feed (WF) those process parameters are to be varied while other parameters such as input current (Ip), gap voltage (V), water pressure (WP), wire tension (WT) and servo feed (SF) those parameters are taken as fixed parameters. The major application of AISI 4140 material is in the defense due to its high hardness and high strength. Literature review available on wire electric discharge machining of AISI 4140 is very scanty because of that reason AISI 4140 material is taken for this study. Regression analysis and analysis of variance (ANOVA) find out with help of Minitab software. ANOVA helps to identify the major influencing process parameter for surface roughness and kerf width. From ANOVA major influencing factors for surface roughness, kerf width is the pulse on time and servo voltage respectively. Result analysis shows that for single objective optimization using Taguchi method gives decrement in surface roughness, kerf width individually are 15.65% and 19.35% respectively. In the case of grey relational analysis decrement of surface roughness, kerf width simultaneously at the optimal condition as compared to the initial condition is 9.39% and7.62%.

Quantitative Relation of the Frequency Dispersion of Double Layer Capacitances to Surface Roughness

Frequency dispersion of double layer (DL) capacitances, which can be represented by the power law of the frequency or the constant phase element, is modeled by the Arrhenius equation with the activation energy which has a linear relation with the free energy change in the orientation of solvent dipoles. The Arrhenius equation has a form of a differential equation of the number of oriented dipoles. The solution is the power law of the time, being equivalent to the DL capacitance with the power law of the frequency. The power number is associated with the surface roughness of the electrode on the assumption that a dipole is oriented with the help of interaction on a given local area of the electrode. Then it has an approximately linear relation with the surface roughness. Surface roughness of highly oriented pyrolytic graphite electrodes is varied unintentionally by peeling-off processes and intentionally by electrochemical oxidation. The power numbers determined by acimpedance techniques are compared with surface roughness obtained by scanning probe microscopy. They are approximately proportional to the surface roughness factor when the scanned domain on the surface is less than (40nm), which is much smaller than the domain for the fractal structure.