Evolution Of Surface Roughness Research Articles

Effect of overlap and overscan number in laser surface texturing of medical needles

Micro-features are frequently created on medical needles to improve the visibility and friction behavior in ultrasound-guided percutaneous procedures. Ultra-short pulsed laser ablation is the front runner among the current material micro-processing technologies. In this paper, the effect of process parameters in laser surface texturing (LST) of medical needles was studied by experiments based on Taguchi methodology. The evolution of ablation dimension and surface roughness with different process parameters was measured by optical microscope. Based on response surface regression, mathematical models for correlating the machined depth and surface roughness with the overlap and overscan number were developed. Analysis of variance (ANOVA) was carried out to access the adequacy of the developed mathematical models. The results indicate that the developed mathematical models can predict the machined depth and surface roughness during LST operation satisfactorily. Analyses were made to study the effect of the process parameters on the machined micro-channel. From the analysis, it was found that the overlap and overscan number have great influences on the machined depth and surface roughness.

An experimental and numerical investigation on micro rolling for ultra-thin strip

The demand for miniaturized parts and miniaturized semi-finished products is increasing nowadays, because microforming processes can improve production rate and minimize material waste due to less forming passes. However, traditional macro metal forming processes and modelling cannot be simply scaled down to produce miniaturized micro parts. In this study, a 2-Hi micro rolling mill has been successfully built. Experimental and numerical investigations on the micro rolling process for ultra-thin SUS 304 stainless steel strip have been conducted. The experimental results show that the micro rolling deformation of ultra-thin strip is influenced by size effect which results from the specimen size difference and this size effect is embodied in the flow stress and the friction coefficient. Analytical and finite element (FE) models in describing size effect related phenomena, such as flow stress, friction, rolling force and deformation behaviour, are proposed. The material surface constraint and the material deformation mode are critical in determination of material flow stress curve. The analysis of surface roughness evolution with rolling conditions has also been performed. The identified analysis on deformation mechanics provides a basis for further exploration of the material behaviour in plastic deformation of micro scale and the development of micro scale products via micro rolling.

Roughness evolution in mixed lubrication condition due to mild wear

Modelling of surface roughness evolution in time, as a function of the lubrication condition and other operating parameters (i.e. load, sliding/rolling ratio, and initial roughness of both contacting surfaces), is important for the understanding and prediction of various surface damage modes, such as surface distress, wear, and scuffing. Moreover, it is one of the key aspects in understanding friction and running-in phenomena. In the present study, a previously developed model for partial micro-elastohydrodynamic lubrication conditions is combined with a local Archard-type wear model to describe the surface topography evolution during the operation of a rolling/sliding lubricated contact. The model has been compared with a series of experimental results showing similar trends.

Surface Roughness Modelling in Face Milling

The ability to plan the quality of surfaces is very important in manufacturing due to the fulfillment of requirements for parts machined by different methods. A method and a modelling procedure are introduced in the paper based on the definition of the relations between the calculated theoretical and the measured real roughness values of machined surfaces. Cutting experiments were performed for the determination of the real roughness data where the evolution of surface roughness was investigated with varied technological parameters. Finally, the calculated relations between the theoretical and real values are presented,allowing the prediction of the expected roughness of surfaces machined with the given conditions.

On the application of response surface methodology for predicting and optimizing surface roughness and cutting forces in hard turning by PVD coated insert

Article history: Received August 3 2014 Received in Revised Format October 23 2014 Accepted October 23 2014 Available online October 24 2014 This paper focuses on the exploitation of the response surface methodology (RSM) to determine optimum cutting conditions leading to minimum surface roughness and cutting force components. The technique of RSM helps to create an efficient statistical model for studying the evolution of surface roughness and cutting forces according to cutting parameters: cutting speed, feed rate and depth of cut. For this purpose, turning tests of hardened steel alloy (AISI 4140) (56 HRC) were carried out using PVD – coated ceramic insert under different cutting conditions. The equations of surface roughness and cutting forces were achieved by using the experimental data and the technique of the analysis of variance (ANOVA). The obtained results are presented in terms of mean values and confidence levels. It is shown that feed rate and depth of cut are the most influential factors on surface roughness and cutting forces, respectively. In addition, it is underlined that the surface roughness is mainly related to the cutting speed, whereas depth of cut has the greatest effect on the evolution of cutting forces. The optimal machining parameters obtained in this study represent reductions about 6.88%, 3.65%, 19.05% in cutting force components (Fa, Fr, Ft), respectively. The latters are compared with the results of initial cutting parameters for machining AISI 4140 steel in the hard turning process. © 2015 Growing Science Ltd. All rights reserved

Surface Nanocrystallization of EN8 Steel: Correlation of Change in Material Characteristics with Corrosion Behavior

The present paper addresses the influence of surface mechanical attrition treatment on the characteristic properties of EN8 steel and, to analyze the correlation between the change in properties of the treated steels with their corrosion behavior in 0.6 M NaCl and borate buffer, evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy studies. Surface mechanical attrition treatment of EN8 steel induced plastic deformation, enabled surface nanocrystallization, increased the surface roughness, microstrain and defects/dislocations and, imparted compressive residual stresses. The change in properties of EN8 steel following treatment has caused a deleterious influence on its corrosion resistance in 0.6 M NaCl but an improvement in corrosion behavior in borate buffer. The possible reasons for the change in corrosion behavior of the treated EN8 steel are suggested. Pictorial models are proposed to explain the evolution of surface roughness and the mechanism of corrosion attack of the treated EN8 steels in 0.6 M NaCl and borate buffer.

Surface Roughness Evolution Model for Finishing Using an Abrasive Tool on a Robot

The polishing process is the final step in the manufacturing workflow for many parts and tools. While previous tasks have evolved technically, the finishing of freeform surfaces is still effected mostly by hand. Many parts are rejected because no control of the process is possible. The main problems are geometrical shape deviations and no repeatability of the process. A new methodology has been developed for the passes of the abrasive on the polished part. This research focusses on the feasibility of robotic polishing and the development of a new evolution model pertaining to the surface roughness for an abrasive tool mounted on a spherical robot. The polishing principle is mechanic and based on dry friction. The tool is multilayered with a compressive foamed core. The combination of rotational and translational movement requires the creation of a model that can predict the footprint on the polished surface. The mathematical model developed for the evolution model permits for making a prediction of the final surface quality in the function of the programmed polishing parameters. Furthermore, the model described allows for setting up polishing parameters in order to reach a desired final roughness with less than 15% deviation. Repeatability is assured and polishing time is reduced down to 1/5 of manually effected procedures.

Surface roughness evolution in a solid-on-solid model of epitaxial growth

The paper presents results from kinetic Monte Carlo simulations of kinetic surface roughening using an important and experimentally relevant model of epitaxial growth—the solid-on-solid model with Arrhenius dynamics. A restriction on diffusing adatoms is included allowing hopping down only at steps of height one monolayer in order to avoid possibly unrealistic events of jumping from arbitrarily high steps. Simulation results and precise analytic expressions representing the time evolution of surface roughness do not depend on the substrate size and clearly put forward the conclusion that for any basic set of parameters, the model approaches in asymptotic limit the usual random deposition process with growth exponent \(\beta =1/2\). At high temperatures, it is preceded by a long transient regime characterized by a smooth surface covered with porous pillars and described by a power law with \(\beta =3/4\).

Investigation on Performance of a CVD Coated Carbide Tool in Face Milling of Ultra-High Strength Steel 30Cr3SiNiMoVA

Ultra-high strength steel 30Cr3SiNiMoVA is a typical difficult-to-cut material. During the machining process of 30Cr3SiNiMoVA, tool wear is an important factor which needs to be investigated seriously. In this work, one kind of CVD coated tools was used to investigate the tool wear mechanism of face milling of Ultra-high Strength Steel 30Cr3SiNiMoVA. Cutting forces during the wear process were measured with a kistler dyna-mometer. Surface roughness and tool wear evolution were determined.

A Study of Mold Friction and Wear in Injection Molding of Plastic-Bonded Hard Ferrite

In injection molding of highly filled polymers, such as plastic-bonded hard ferrite, mold life decreases significantly due to wear and surface damage. This deterioration process leads to lower accuracy concerning the surface finish and the dimensional and geometric tolerance of the molded bonded magnets. In this work, the wear of a steel mold caused by the molding of a plastic-bonded ferrite magnet has been studied with the aim of determining the main wear factors. Furthermore, two different surface treatments have been tested, namely gas nitriding and DLC superlattice coating. Friction and wear induced by part de-molding was investigated by means of tribological pin-on-disc tests. The results of such experiments were analyzed in terms of loads, surface roughness evolution and surface investigations by means of Scanning Electron Microscope observations.

Thin electroless Co(W,P) film growth on titanium–nitride layer modified by self-assembled monolayer

In this work we present a study of the initial nucleation and growth of electroless cobalt–tungsten–phosphorous (Co(W,P)) film on titanium nitride. This cobalt alloy can be applied as barrier or capping layer for copper interconnects in integrated circuits, flexible printed circuit board, micro-mechanical devices and more. The Co(W,P) was deposited from a basic bath on TiN that had been functionalized by silane based self-assembled monolayer (SAM) activated by gold nano-particles (AuNPs). In this paper we report on the results of using two similar silane monomers: aminopropyltrimethoxysilane (APTMS) and N-(3trimethoxysilylpropyl) diethylenetriamine (TPDA); both use amine groups to attract the AuNPs, but differ in molecular conformity. A detailed study of the initial stages of the Co(W,P) layer growth using high-resolution transmission electron microscopy and atomic force microscopy showing the common and different nucleation densities, surface coverages, morphologies and electrical properties of the Co(W,P) layer induced by the two SAM layers is presented. With scaling behavior of the surface roughness evolution we show that Co(W,P) layers grow in 3D, regardless of the SAM type. This effect is probably due to the fact that the dominant mechanism affecting the nucleation and initial growth is the crystallographic misfit between the catalytic layer and the deposited Co(W,P). The 3D growth of Co(W,P) was observed on both SAMs; nevertheless, on APTMS it was controlled by lateral growth, while on TPDA by surface diffusion.

Evolution of Surface Roughness During Electropolishing

The characteristics of surface roughness span a range of length scales determined by the nature of the surface generation process. The mechanism by which material is removed at a length scale determines the roughness at that scale. Electropolishing preferentially reduces the peaks of surface protuberances at sub-micron length scales to produce smooth surfaces. The material removal in electropolishing occurs by two different mechanisms of anodic leveling and microsmoothing. Due to insufficient lateral resolution, individual contribution of these two mechanisms could not be measured by conventional roughness measurement techniques and parameters. In this work, we utilize the high lateral resolution offered by Atomic force microscopy along with the power spectral density method of characterization, to study the evolution of roughness during electropolishing. The power spectral density show two corner frequencies indicating the length scales over which the two mechanisms operate. These characteristic frequencies are found to be a function of the electropolishing time and hence can be used to optimize the electropolishing process.

Effects of grain-scale heterogeneity on surface roughness and sheet metal necking

Abstract Strain localization of sheet metals subjected to plane-strain stretching was simulated by finite-element analysis based on a crystal plasticity model. The ratio of specimen thickness to grain size, denoted by Ng, is varied from 1 to 70, and its influence on the evolution of surface roughness and the occurrence of sheet necking is investigated. Roughening of the free surface of the specimen is induced by the grain-scale strain heterogeneity associated with local grain misorientation. The magnitude of surface roughness depends mainly on the grain size and is less sensitive to Ng. As Ng decreases while maintaining the thickness, the magnitude of surface roughness becomes large with respect to the thickness. As a result, large geometrical imperfection is generated. Therefore, the formability of sheet metal is reduced as Ng decreases. Such an effect is found to be particularly considerable when Ng is less than 30. It is also found that the localization mode shifts from a sharp shear banding mode to a localized thinning mode as Ng increases.

Evolution of slip surface roughness through shear

AbstractA significant part of displacement in fault zones occurs along discrete shear surfaces. The evolution of fault surface topography is studied here in direct shear laboratory experiments. Matching tensile fracture surfaces were sheared under imposed constant normal stress and sliding velocity. The roughness evolution was analyzed using measurements of surface topography before and after slip. We show that shearing reduces the initial surface roughness at all measurement scales. At all wavelengths, the roughness ratio between initial and final roughness increases as a function of the slip distance. For a given test, the roughness ratio increases with wavelength up to a few millimeters, beyond which the ratio becomes wavelength independent. At this region the roughness measured after slip follows a power law similar to that of the initial tensile fracture surface. We interpret this geometrical evolution as a consequence of the deformation stage of interlocked asperities which is followed by shear‐induced dilation.

Evolution of TiN Coating Surface Roughness during Physical Vapor Deposition on High Speed Steel Substrate

TiN coatings with different thickness were prepared by arc ion plating (AIP) physical vapor deposition (PVD) on high speed steel (HSS) substrates. TiN coatings surface roughness was investigated by atomic force microscopy (AFM) and 3D optical profilometry and growth kinetics was described using scaling exponents β and α. The growth exponent β is 0.91-1.0 and the roughness exponent α is 0.77-0.81. Due to relatively high value of the exponent α, the surface diffusion is likely predominant smoothening mechanism of TiN growth.

Plastic deformation of rough rolling contact: An experimental and numerical investigation

Quantifying the surface roughness evolution in contacts is a crucial step in the fatigue prediction process. Surfaces are initially conditioned by the running-in process and later altered by surface fatigue. The aim of this study is to understand and predict the evolution of the micro-geometry in the first few over-rolling cycles. Numerical predictions are validated by experiments. A major difficulty in understanding surface degradation is the measurement of the surface roughness evolution at the relevant scales. A twin disc micro-test rig, called μMag, was specially designed for this kind of analysis. The μMag allows the “in situ” observation of changes in the disc surface during interrupted tests, thus avoiding dismounting the specimens, which is a major cause of inaccuracy. The new method also maintains the relative position of the two discs. The precision of the measurements allows one to use the initial surface micro-geometry as input for the numerical contact calculation. Thus, the plastic deformation of the surfaces can be measured during the first cycles and compared to the numerical prediction. Results show a very good agreement between numerical predictions and experimental measurements.

Experimental heat transfer coefficient measurements during hot forming die quenching of boron steel at high temperatures

Hot forming die quenching is used by the automotive industry to produce ultra high strength steel parts with a high strength-to-weight ratio. Crash-resistant structural parts with distributed properties can be obtained by controlling the local cooling rate during the quenching step using heated dies. This procedure requires detailed spatial knowledge of the heat transfer coefficient at the blank/die interface. Hot stamping experiments were conducted on Usibor® 1500P boron steel blanks to investigate how pressure and blank and die temperatures influenced the heat transfer coefficient, which was inferred using inverse heat conduction analysis. The heat transfer coefficient was found to vary throughout the experiment with deformation of the surface roughness peaks and evolution of the blank and die temperatures. Whereas the heat transfer coefficient at the beginning of the stamping process increases with the initial die temperature, it converges to a value that depends only on applied pressure. Moreover, the experimental heat transfer coefficient for zero pressure was found to match the air gap conductance predicted by semi-empirical models, but the pressure-dependent component was lower than the model-predicted solid contact conductance.

Deformation Characterization of Micro Rolling for Stainless Steel Foil

Physical parameters such as microscopic roughness become very important in micro forming process due to increasing surface to volume ratio. As a very important phenomenon in metal forming process, friction size effects are becoming more attracting for researchers because traditional models are not reliable. In this study, the micro rolling deformation characterization has been investigated with SUS 304 stainless steel considering the effect of lubricant, and there exists a sticking area in the contact zone. The evolution of surface roughness and oil film thickness are analyzed. The foil thickness plays an important role in the tribological features of rolling. All the results have been verified experimentally via the desktop 2-Hi micro rolling mills.

A material removal and surface roughness evolution model for loose abrasive polishing of free form surfaces

We report on the development of a simple process model, motivated by a need to predict the evolution of surface roughness and geometrical change over external, three dimensional free form surfaces undergoing a loose abrasive polishing process. To this end, the process model was derived from tribological wear laws and cast in terms of the point sliding velocity and apparent pressure and then benchmarked against data drawn from experiments in three disparate loose abrasive finishing techniques, namely, vibratory finishing, abrasive flow machining and magnetorheological finishing. We conclude with a brief discussion on the potential and limitations of the model in analysing loose abrasive finishing processes.

Process modeling and CFD simulation of two-way abrasive flow machining

The present study examines a simple, zero-order semi-mechanistic approach towards the analysis of the two-way flow abrasive flow machining process, stemming from a need to reduce the number of time-consuming and labor-intensive experimental trials. The description consists of a set of coupled models, which are the following: an inelastic non-Newtonian model to capture the flow behavior of the abrasive media; a wall slip model, as a function of wall shear-rate, to calculate the relative motion between the media and the confining wall; and a previously derived process model describing surface roughness and stock removal evolution. Predicted results were benchmarked against experimental ones obtained from studies on straight tubes with ellipsoidal cross-sections. We end this report with an application example illustrating a method to produce uniform finishing of a tube hole with complex cross-section geometry.