Internal Surface Roughness Research Articles

Systematic oil flow modeling in the Quasi-3D approximation yields additional terms that allows for variable cross-section area tubing

A systematic model development for oil flow in quasi-3D (1D + 2D) is presented. Our approach provides a unified modeling scheme. Besides, additional terms are obtained, which allows for tubing area variation along the flow direction. The area variation can be modeled as analytic function or random fluctuation, as it could be the result of deposits or tubing internal surface roughness. The proposed approach can be used to obtain analytic solutions which provide physical insight into the phenomena under scrutiny, including the validation of software tools, sensor development and sensor placement. One starts from conservation laws as given by kinetic theory and applies the transverse averaging technique (TAT) to extract the one-dimensional approximation in formal grounds. To demonstrate its application, the steady-state Ramey's model, the Hasan's transient model and a simple two-phase model are generated from the obtained equations.

Analysis of the effect of surface roughness on fatigue performance of powder bed fusion additive manufactured metals

An important advantage of AM is to create net-shaped components with no need for further surface machining since it is usually very difficult for complex geometries. The effect of surface roughness on fatigue performance of powder bed fusion additively manufactured metals was evaluated in this work. The intrinsic rough surface of metal AM parts that could act like existing surface cracks and significantly affect fatigue performance is investigated. The effect of processing and post-processing conditions on surface roughness of AM parts are reviewed and the effect of surface roughness on fatigue performance is analyzed. The synergistic effect of internal defects and surface roughness on fatigue performance is also evaluated. Arithmetic mean surface roughness parameter Ra is used here as a representation of surface roughness, since this parameter has been presented in most of the studies dealing with metal AM surface roughness. Surface roughness effect on fatigue performance is shown to be dominant even in the presence of relatively large internal defects and various microstructures. Ra decreases with an increase in power. This consequently increases fatigue limit, although scatter is observed due to the secondary effect of internal defects and microstructure. For similar microstructures, considering synergistic effect of Ra along with average critical internal defect size in combination with the stress amplitude, resulted in improved correlation of the S-N fatigue data.

Survival probability of zirconia-reinforced lithium silicate ceramic: Effect of surface condition and fatigue test load profile

ObjectivesThe present investigation evaluated the step stress accelerated test (SSALT) load profiles on the survival probability of a glass ceramic under two surface conditions (polished or roughened). MethodsSuprinity–ZLS blocks (Vita Zhanfabrik) were shaped into cylinders, cut in a sawing machine, and crystalized according to the manufacturer's instructions. 60 discs were obtained (Ø=12mm, thickness=1.2mm) and randomly assigned into two surface conditions: “p” polished surface (400–1200-grit SiC papers), and “r” roughened surface (200-grit SiC papers). Profilometry was performed in all discs to evaluate average surface roughness prior to flexural fatigue strength testing. 3 discs of each group were submitted to biaxial flexural strength in an universal testing machine (0.5mm/min) and the mean load to failure (N) was calculated to determine SSALT profiles. 27 specimens per surface condition were assigned into three profiles – Mild (n=9), Moderate (n=9), and Aggressive (n=9), and submitted to the fatigue test (60–320N, 140,000 cycles at 1.4Hz). The results were analyzed using the Kaplan-Meier and Wilcoxon tests (5%), 2-way ANOVA and Tukey test (α=5%). ResultsKaplan-Meier and generalized Wilcoxon showed (P=0.002) that polished groups showed higher survival probability than roughened condition (P<0.05). A rough internal surface impacted deleteriously on the fatigue strength and reliability of ZLS ceramic. Both surface conditions were more sensitive to the aggressive profile than the other profiles, even worst for the roughened group. Regardless the load profile, 0% survival probability was observed at 384MPa for polished condition. While for roughened, aggressive tested specimens did not survived 147MPa followed by moderate at 312MPa and mild at 384MPa. The failure modes showed fracture marks originating from superficial grooves for both surface conditions. SignificancePolished specimens are sensitive to the load profile variation, confirming the effect of surface morphology on the fatigue results.

Internal surface roughness enhancement of parts made by laser powder-bed fusion additive manufacturing

In this work, innovative electrochemical methods have been utilized to minimize the internal surface roughness of Inconel 625 laser powder-bed fusion (LPBF) additively manufactured (AM) parts with variable geometries as the performance of many parts depend on it. Initially, the effect of electropolishing time on external surface roughness and thickness loss was investigated. Subsequently, electropolished internal structures were studied and the results showed an average of 80% improvement in roughness. The quick and effective surface enhancement methodology proposed in this research can be applied to improve the performance of AM parts with functional internal and external surfaces.

Rapid thermal transport at rough solid-fluid interface: Evaporation and explosive boiling on concave nanostructure

The concave nanostructure presents a better boiling performance compared to convex one, however, the surface roughness plays a key role in thermal transport at solid-fluid interface. In this work, we adopted the non-equilibrium molecular dynamics simulation to investigate the effect of the internal surface roughness on the boiling heat transfer performance in concave nanostructure. It shows that the presence of atomic-scale roughness leads to heat transfer deterioration and enhancement during the evaporation and the explosive boiling processes, respectively. This finding, which is contradictory with the general understanding, is attributed to the difference in interfacial thermal resistance. It shows that the heat transfer performance is strongly dependent on the configuration of roughness elements. The low solid fraction configuration has a better heat transfer performance and can postpone the start of boiling process.

Experimental Investigation of the Nozzle Roughness Effect on the Flow Parameters in the Mixing Layer of an Axisymmetric Subsonic High-Velocity Jet

The paper presents the results of an experimental investigation of the mixing layer parameters in the initial regions of transonic jets issuing from convergent nozzles with different internal roughness at the same Mach number in the jet core. It is shown that the mixing layer characteristics, namely, the radial profiles of the measured total pressure and the r.m.s. total pressure fluctuations, are self-similar in nature at distances greater than 1.5 of the nozzle exit diameter from the exit. The possibility of applicating nozzles with an increased degree of the internal surface roughness in investigating high-velocity jet flows is shown.

Encapsulation surface roughness effect on the performance of cool storage systems

Cool Storage is a well-known technique that been used to increase the energy efficiency of cooling systems. This paper represents a novel experimental work for the effect of internal capsules surface roughness on the performance of encapsulated cool storage systems. In this study, distilled water was used as a phase change material inside capsules. Internal surface roughness of 0, 3, 7 and 12 μm were tested using the same heat transfer fluid Characteristics. Heat transfer fluid (HTF) composed of 50–50 wt. of (water–ethylene glycol) was used with a fixed volume flow rate of 12 L/min LPM and four different inlet temperatures of −6, −8, −10 and −12 C. The solidified mass fraction, charging rate and energy storage were calculated and plotted versus the charging time to determine the surface roughness effect on the cooling performance of the system. Results showed that the internal surface roughness of capsules had adverse effect on the system performance through increasing the total freezing (charging) time. Results also indicated that the charging time increased by 14–17% at inlet flow temperature of −12 and −6 ̊C, respectively at the higher roughness values compared with the smooth surface capsule e.g. zero roughness parameter.

Monitoring of hole surface integrity in drilling of bi-directional woven carbon fiber reinforced plastic composites

Fiber-reinforced plastic is one of the top priorities lightweight materials with excellent mechanical properties for the aerospace industries in recent years. However, it is difficult to machine despite having unique properties due to its non-homogeneous and abrasive nature in alternate fiber and matrix layers. Thus, it is found to be a challenging task to drill hole on such hard-to-machine materials, which is highly essential for the development of most of the engineering structural components. The present work addresses various drilling-induced defects such as delamination, circularity error, and roughness variations in the hole surface during drilling of quasi-isotropic cross-fiber oriented bi-directional woven-type carbon fiber reinforced plastic laminate using a full factorial design of experiments for different drill geometry. The response surface methodology was considered for the regression model development, which was found to be highly significant. The machining forces with associated torque have also been acquired during drilling, which was divided and further analyzed in time domain to correlate with drilling flaws. The drilling-induced delamination was found to be higher at a high feed rate using a higher drill point angle due to substantial thrust force generation at the initial stages in the drilling cycle. However, the internal surface finish with associated circularity error was reduced for higher spindle speed with less feed rate using a low drill point angle because of low torque fluctuation at the final drilling phases. The axial thrust force was found to be a prime indicator of drilled hole surface delamination, whereas drilling torque precisely indicated internal surface roughness as well as circularity error. The global root mean square, along with a local peak of thrust and torque, both were highly essential to completely characterize the drilled hole quality.

Influence of Chemically Etched Roughness on Frictional Resistance of Micro-tubes

Chemical etching is a convenient process for enhancing three-dimensional (3D) roughness of internal surface of micro-tubes. The aim of this research work is to compare the frictional resistance and contact angle in smooth and rough stainless steel micro-tubes. At various inputs of Reynolds number in laminar regime (201.43 < Re < 1929.96), differential pressure has been measured for etched and unetched tubes with deionized water. In order to substantiate the effect of roughness on tube, contact angle is measured before and after etching to calculate roughness parameter. It is found that etching enlarges the inner diameter of the tube; hence new diameter should be considered for Poiseuille number (fRe) calculations. The role of etching on fRe is more significant on tube of inner diameter (ID) 0.932 mm, as compared to tube of ID 1.293 mm. Etching increases the contact angle of hydrophobic surface. This work would be applicable in design improvement of complex micro-devices when relative roughness plays a major role due to small scale.

Brazing, Laser, and Electron-Beam Welding of Additively Manufactured GRCop-84 Copper for Phased Array Lower Hybrid Launchers

Recent advances in selective laser melting 3-D printing technology allow additive manufacturing of lower hybrid current drive (LHCD) RF launchers from a new material, Glenn Research Copper 84 (GRCop-84), a Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, in configurations unachievable by conventional machining. Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Nb crystals pin grain boundaries within the copper matrix resulting in high tensile strength and resistance to annealing at elevated temperatures. Brazing, laser, and electron-beam welding (EBW) techniques are explored for joining a thin-walled GRCop-84 waveguide with zero porosity and minimal internal surface roughness. GRCop-84 wets well with the silver solder, CuSil, and Cusil-ABA brazes, once the durable surface oxide is mechanically removed. GRCop-84 melt pool size and flow during EBW is reduced compared to oxygen-free copper (OFC). Pulsed laser and e-beam welding maintains the Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Nb precipitate size; precipitate coarsening occurs in conduction mode e-beam welding.

Accuracy of down-facing surfaces in complex internal channels produced by laser powder bed fusion (L-PBF)

Additive manufacturing (AM) technology has great potential in manufacturing complex internal channels for several applications such as satellite communication systems, electronics and gas turbine airfoils. These applications can have complex shape and make traditional finishing processes a challenge for additive parts. Therefore, it is desirable that the internal surfaces be as close as possible to the tolerance of the field of application. In this study, a complex component was designed and manufactured in AlSi10Mg alloy through laser powder bed fusion (L-PBF) process. Using the data from the 3D scans, internal surface roughness and deviations from the CAD model were calculated.

Integral fabrication of terahertz hollow-core metal rectangular waveguides with a combined process using wire electrochemical micromachining, electrochemical deposition, and selective chemical dissolution

The application requirements of terahertz hollow-core metal rectangular waveguides with a high-working frequency have become increasingly urgent with the rapid development of terahertz technology. Integral fabrication of terahertz hollow-core metal rectangular waveguides can improve considerably the transmission performance of terahertz signals. However, with current manufacturing techniques, the high-precision integral fabrication of high-working-frequency terahertz hollow-core metal rectangular waveguides is difficult owing to their characteristically small end face size and the need for strict dimensional accuracy and high internal surface quality. In this paper, an innovative combined process of wire electrochemical micromachining, electrochemical deposition, and selective chemical dissolution is proposed firstly to overcome this puzzle. Taking the fabrication of an integral 1-THz hollow-core metal rectangular waveguide as an example, the manufacturing methods involved in each step are described particularly, together with the corresponding experimental investigations. With the end face size of 127 μm × 254 μm, edge radius less than 5 μm, and internal surface roughness less than 0.08 μm, the experimental results satisfy the design requirements for a 1-THz hollow-core metal rectangular waveguide. This study demonstrates that the proposed combined process is flexible, controllable, and suitable for the high-precision integral fabrication of high-working-frequency terahertz hollow-core metal rectangular waveguides.

Fatigue of additive manufactured Ti-6Al-4V, Part II: The relationship between microstructure, material cyclic properties, and component performance

Part I of these two-part paper series focused on the process and structure relationships, effect of powder feedstock, fabrication parameters, and post fabrication treatments on the resulting microstructure, defect characteristics, and surface quality of the fabricated Ti-6Al-4V parts. This second part extends the study by evaluating the effect of the aforementioned factors on axial, torsion, and multiaxial fatigue behavior of the additively manufactured (AM) Ti-6Al-4V specimens. Despite the advantages of additive manufacturing techniques discussed in Part I, they are still rarely used in fatigue critical load carrying applications, partly due to insufficient understanding of fatigue behavior and its dependence on variations in material microstructure and defects. This becomes even more challenging when other process characteristics of AM including build orientation, residual stresses, and surface roughness are considered. This paper discusses these effects, as well as machine-to-machine variability and the effects of specimen geometry and size, post heat treatment, and multiaxial stress state. Experimental uniaxial, torsion, and multiaxial fatigue test results recently generated by the authors for laser beam powder bed fusion- produced Ti-6Al-4V alloy are reviewed. The observed behaviors and the influence of the aforementioned effects are then related to the resulting microstructure and defect characteristics discussed in Part I. Fatigue life prediction results for specimens based on the effective defect size calculated by extreme value statistics (EVS) of the internal defects and surface roughness are also presented and compared with experimental data. The observed behaviors and specimen test results are then used for fatigue life analysis and predictions of a link component as an illustrative application example.

On the possible role of gravity waves in the ocean in T-phase excitation by earthquakes

Recent applications of a time-domain spectral-element method to obtain full-wave solutions of seismo-acoustic problems by Bottero et al. [J. Acoust. Soc. Am., 144, EL222–EL228 (2018)] and especially their investigation of T-phases in the Mediterranean [Bottero et al., J. Acoust. Soc. Am., 141, 4045 (2017)] challenge the existing understanding of the mechanisms of seismic energy conversion into T-waves, which propagate at the speed of sound in water. Motivated by these results, this paper aims to evaluate the contribution of scattering by hydrodynamic waves into T-phase generation. Ocean is modeled as a range-independent waveguide with superimposed volume inhomogeneities due to internal gravity waves and surface roughness due to wind waves and sea swell. Guided acoustic waves are excited by volume and surface scattering of ballistic body waves. The size of the effective source of T-waves and their amplitudes are calculated in the single scattering—multiple reflections approximation. Efficiency of the gravity wave-mediated conversion of seismic energy will be compared to that of the conversion that occurs on a seafloor slope.

Investigation on grinding force and machining quality during rotary ultrasonic grinding deep-small hole of fluorophlogopite ceramics

Fluorophlogopite ceramics is widely used in the fields of aerospace and biomedicine, and the machining of deep-small hole for fluorophlogopite ceramics is a focus in the field of precision and ultra-precision machining. In this work, the trajectory and brittle-to-ductile transition depth of single abrasive during rotary ultrasonic grinding process were analyzed. The rotary ultrasonic grinding and common grinding tests of deep-small holes for fluorophlogopite ceramics were performed on an ultrasonic vibration and precision machining center. The axial grinding force was obtained by wavelet denoising, the roundness deviation was calculated by using Canny and gray level detection methods, and the internal surface roughness was measured by using laser scanning confocal microscopy. The experimental results indicated that compared with the common grinding, rotary ultrasonic grinding could effectively decrease the grinding force, roundness deviation, and the value of surface roughness. In addition, the grinding force, roundness deviation, and the value of surface roughness decreased as the spindle speed and ultrasonic power increased, and they increased as the feed speed increased. This work was of significance for realizing the high efficiency and precision machining of deep-small holes of the hard-brittle materials.

Fatigue of additively manufactured 316L stainless steel: The influence of porosity and surface roughness

AbstractThe fatigue behaviour of additively manufactured (AM) 316L stainless steel is investigated with the main emphasis on internal porosity and surface roughness. A transition between two cases of failure are found: failure from defects in the surface region and failure from the internal defects. At low applied load level (and consequently a high number of cycles to failure), fatigue is initiating from defects in the surface region, while for high load levels, fatigue is initiating from internal defects. Porosities captured by X‐ray computed tomography (XCT) are compared with the defects initiating fatigue cracks, obtained from fractography. The fatigue data are synthesised using stress intensity factor (SIF) of the internal and surface defects on the fracture surface.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ В ИССЛЕДОВАНИЯХ ШЕРОХОВАТОСТИ ПРИМЕНИТЕЛЬНО К ВНУТРЕННИМ ПОВЕРХНОСТЯМ

The article considers the problems of mathematical modeling roughness of surfaces obtained in the cutting process. Roughness is related with the technological parameters of the system “machine-fixture-tool-workpiece” and the problem of fine finish of internal threads. There have been analyzed the existing mathematical models of finished surface roughness and stated the need to develop a mathematical model of internal surface roughness. There has been worked out a mathematical model of threaded profile roughness of the internal thread made by the tap in the details made from high-strength corrosion-resistant DI-8 grade steel that is popular in ship equipment building, by using methods of planning experiments. Geometric parameters of the tap cutting part have been taken as independent: angle of the intake cone, face and rear grinding angles. There have been listed parameters for qualitative evaluating and rating sharpened surfaces that are given in GOST 2789-73: altitudinal, step, profile bearing surface parameters. A mean-square deviation of microroughness profile was suggested to use as a roughness parameter. Impression method was used to evaluate roughness, light section device МИС-11 of V.P. Linnik was used to measure mold surface roughness. The method of planning experiments of predicting the roughness of internal surfaces has been found efficient. Theoretical studies are based on metal cutting methods, as well on methods of experiment planning with application of regression analysis; experimental research was conducted under laboratory conditions by using a computation machine. The research results allow to greatly improve the surface finish technologies in shipbuilding.

The Effect of Internal Pipe Wall Roughness on the Accuracy of Clamp-On Ultrasonic Flowmeters

Clamp-on transit-time ultrasonic flowmeters (UFMs) suffer from poor accuracy compared with spool-piece UFMs due to uncertainties that result from the in-field installation process. One of the important sources of uncertainties is internal pipe wall roughness which affects the flow profile and also causes significant scattering of ultrasound. This paper purely focuses on the parametric study to quantify the uncertainties (related to internal pipe wall roughness) induced by scattering of ultrasound and it shows that these effects are large even without taking into account the associated flow disturbances. The flowmeter signals for a reference clamp-on flowmeter setup were simulated using 2-D finite element analysis including simplifying assumptions (to simulate the effect of flow) that were deemed appropriate. The validity of the simulations was indirectly verified by carrying out experiments with different separation distances between ultrasonic probes. The error predicted by the simulations and the experimentally observed errors were in good agreement. Then, this simulation method was applied on pipe walls with rough internal surfaces. For ultrasonic waves at 1 MHz, it was found that compared with smooth pipes, pipes with only a moderately rough internal surface (with 0.2-mm rms and 5-mm correlation length) can exhibit systematic errors of 2% in the flow velocity measurement. This demonstrates that pipe internal surface roughness is a very important factor that limits the accuracy of clamp on UFMs.

Reducing the roughness of internal surface of an additive manufacturing produced 316 steel component by chempolishing and electropolishing

Surface roughness of an as produced AM component is very high, which prohibits the direct utilization of additively manufactured (AM) components for the intended applications. Reducing surface roughness is exponentially more challenging for the internal surfaces of an AM component. This paper reports our research in the area of postprocessing of interior surfaces of an AM component. We have investigated electropolishing and chemical polishing (chempolishing) methods to reduce the surface roughness of the internal surface. We found that chempolishing was effective in simultaneously reducing the internal and external surface roughness of 316 steel AM components. Chempolishing is found suitable for any complicated AM shape and geometry. Our electropolishing methodology was effective in reducing the surface roughness of the internal or external surfaces provided that a counter electrode could be positioned in the proximity of the surface to be polished. We have performed optical profilometry, scanning electron microscopy, and contact angle measurement study to investigate the difference between electropolishing and chemical polishing methods.

Electrolytic Plasma Surface Polishing of Complex Components Produced by Selective Laser Melting

The applicability of electrolytic plasma surface polishing to complex components produced by selective laser melting (SLM) is analyzed. By electrolytic plasma polishing by electrolyte spraying, the surface quality of components produced by SLM may be improved. This technology is found to decrease the surface roughness from Ra = 5.6 μm to 1.4 μm. The optimal pressure of the electrolyte jet is 0.02–0.05 MPa. At high pressures, the process becomes unstable. By electrolytic plasma polishing on the basis of electrolyte jets, uniform external and internal surface roughness of components produced by SLM may be ensured.