Surface Topography Parameters Research Articles

Fracture-free surfaces of CAD/CAM lithium metasilicate glass-ceramic using micro-slurry jet erosion.

This paper reports the use of micro-slurry jet erosion (MSJE) on CAD/CAM lithium mesilicate glass ceramic (LMGC) that is capable of achieving the fracture-free surface quality. A computer-controlled MSJE process using a low-pressure and low-concentration alumina slurry was applied to diamond-ground LMGC surfaces with surface and subsurface damage. The MSJE processed and diamond-ground LMGC surfaces were examined using scanning electron microscopy (SEM) to examine surface morphology, fractures, and residual defects. 3D confocal laser microscopy (CLM) was used to quantitatively characterize all machined surface textures as a function of processing conditions. Our results show that surface and subsurface damage induced in diamond-ground surfaces were significantly diminished after 50-cycle MSJE processing. Fracture-free surfaces were obtained after 100 MSJE cycles. Our measured parameters of the 3D surface topography included the average surface roughness, maximum peak-valley height, highest peak height, lowest valley height, and kurtosis and absolute skewness of height distributions. All these parameters were significantly reduced with the increase of MSJE cycles. This work implies that MSJE promises to be an effective manufacturing technique for the generation of fracture-free LMGC surfaces which are crucial for high-quality monolithic restorations made from the material.

An experimental investigation into surface roughness of a hydraulic fracture

The fracture surface roughness is an essential characteristic of the hydraulic fracturing process and has not been fully explored. The surface asperities play a significant role in proppant flow and settlement, fluid leak-off and fracture tip movement. In this study, we performed an experimental investigation to evaluate the fracture surface roughness of a hydraulic fracture generated in the lab tests. The experiments were conducted using a polyaxial cell and a cuboid siltstone block with dimensions of 20 cm × 20 cm × 16.5 cm. The fracturing fluid was injected into a drilled hole in the specimen to initiate and propagate the hydraulic fracture in nearly homogeneous siltstone material. Low injection rates were applied to all lab tests to maintain slow and stable fracture propagation as in the field. The fracture surfaces were digitised by surface mapping techniques utilising high-resolution laser scanning method and analysed using a standard statistical way. Our results showed that the surface topography and roughness parameters are different in various selected segments. However, they follow an increasing trend in radial directions from the initiation point at the wellbore wall toward the specimen borders.

The influence of surface topography on the safety of road and utility surfaces

Abstract The paper presents the relationships between the topography parameters of the usable and mineral surfaces abrasive surface, obtained in various technological processes. Surface properties determine the safety of their use and the main parameters of surface topography are roughness and waviness. The basic use properties include, surface roughness and the associated coefficient of friction, expressed by the coefficient of adhesion of the vehicle wheels to the surface. Practical examples of shaping of stereometric features of surfaces with specific use properties as well as friction coefficient and wheel adhesion values as well as the generated noise intensity depending on roughness, for different types of road surfaces under different operating conditions.

A study on surface quality of thin-walled machined parts

The manufacturing demand for thin-walled parts is quite high. Machining is the most cost effective method to produce a part since it only requires the raw material and machine tool. Achieving the desired surface quality is of great importance for the functional performance of a part. Due to the abstractness of surface topography parameters, engineers usually look at surface roughness created using different manufacturing methods for more perfection. In this paper a set a machining experiments are performed to assess the surface roughness of the specimens used in both physical way as well as analytical way.Profilometer and Statistical software is used for achieving the results. The range of roughness value at various cutting conditions on different specimens are found out as results of experimentation and tabulated in this attempt. So tooling was found as a major concern on the quality of surface topography in such manufacturing environment. Apart from that some interesting trends in interaction between machining parameters were also found out. As per the study conducted suggestions on tooling as well as methods to maintain geometrical tolerences and accuracy are given along with concluding remarks. Scope of further research regarding surface roughness analysis in machined parts is also discussed.

The use of areal surface topography characterisation in relation to fatigue performance

Although the effect of surface topography on fatigue life is widely accepted, the underlying role of surface roughness from first principles is still poorly understood. Currently approaches which consider the influence of surface roughness on fatigue life prediction can be broadly classified into surface corrector factors (Cs) and stress concentration factors (Kt). Those approaches describe the surface according to the manufacturing process (machined, grounded…), or using 2D height descriptor parameters (Ra, Rz…). However, these approaches are not able to correctly describe the effect of roughness on the fatigue performance where it is anticipated a richer set of surface descriptors would show correlation. The present work aims to highlight the inherent limitations of the most commonly employed 2D surface measurement and characterization techniques, and provides an insight into the application of 3D areal surface characterization processes including the use of the latest areal surface topography parameters quantifying amplitude, spatial, and hybrid topographical information which is considered to be important for fatigue performance correlation.

Surface quality and topographic inspection of variable compliance part after precise turning

The paper presents the problem of precise turning of the mould parts with variable compliance and demonstrates a topographic inspection of the machined surface quality. The study was conducted for the cutting tools made of cemented carbide with coatings, in a range of variable cutting parameters. The long shaft with special axial hole, made of hardened 55NiCrMoV6 steel was selected as a workpiece. The carried out study included the stiffness measurement of the machining system, as well as the investigation of cutting force components. In this context, the surface topography parameters were evaluated using the stylus profile meter and analysed. The research revealed that the surface topography, alongside the 3D functional parameters, and PSD influences the performance of the machined surface. The lowest surface roughness parameters values, equalled to Sa=1μm and Sz=4.3μm have been obtained during turning with cutting speed vc=90 m/min. The stable turning of variable compliance part affects the surface texture formation with a unidirectional perpendicular, anisotropic structure. Nevertheless, in case of unstable turning, the characteristic chatter marks are observed, and process dynamics has greater contribution in formation of surface finish than turning kinematics and elastic plastic deformation of workpiece.

Analysis of Anisotropy in Turned Surfaces Using Vision Based 3D Surface Topography

Abstract Anisotropy in machined surfaces has a significant effect on the functional performance of an engineering surface. Complexity in surface topography directly affects a component’s functional performance, such as load bearing, friction, wear, surface roughness, and fluid retention properties. The anisotropic and isotropic nature of surfaces could be disregarded for 2D surface characterization, but they are of fundamental importance to 3D surfaces for characterization, which is a result of cutting motion; thus, the machined surfaces consist of fluctuations, peaks, and valleys. The surface topography of the workpiece can be viewed more precisely by viewing it under micro scale magnification. In the present work, an attempt has been made to investigate the effect of the tool condition in machining processes on different workpiece surfaces and to investigate the resulting 3D surface topography on friction and wear properties of machined components. The 3D surface topography parameters, such as Sa, Sq, Ssk, Sku, and Sdr, are extracted by using commercial software (TalySurf10). Subsequently these parameters are used to compare and analyze the specific-functional performances of the tool. The encouraging results of this work pave the way for the analysis of the machined surface and the development of real-time and reliable tool-condition monitoring systems.

Effects of machined cavity texture on ejection force in micro injection molding

The friction force developed in the demolding phase of the micro injection molding process is mainly determined by mold surface finish, which affects the tribological phenomena occurring at the polymer–tool interface. In this work, the effects on the ejection force of two cavity surfaces machined with different technologies (viz. micro milling and micro electro discharge machining), but with similar value of Ra, were investigated. The relations between different surface topography parameters and the ejection force were then analyzed, in order to identify the parameters that most appropriately describe the friction at the polymer–tool interface. The experimental results showed the strong interactions between the mold surface texture and the micro injection molding process parameters that promote the replication, such as mold temperature and holding pressure. The different machining technologies generated two mold textures that have a similar value of Ra, but their influence on friction can be properly described only using several other surface topography parameters.

Use of Artificial Neural Network (ANN) to Determining Surface Parameters, Friction and Wear during Pin-on-Disc Tribotesting

In tribological analysis of machine elements (such as gears, ball/roller bearings etc.), surface roughness plays very important role, ultimately it affects the friction coefficient, wear, rolling contact fatigue (micro pitting) and other failure mechanisms. Surface geometry and topography changes with time (number of cycles) during rolling/sliding motion of contacting surfaces. So, it is important to show the variation of surface topography parameter during wear process. This work presents the evolution of roughness parameters, wear and friction coefficient during pin-on-disc tribotesting under dry condition. The test is performed using pin on disc apparatus under room temperature condition. The pin (25mm long, 6mm diameter) is made of medium carbon steel (AISI 1038) whereas the disc (165mm diameter, 8mm thickness) is made of high carbon steel (SAE 52100). This works demonstrates the potential of Artificial Neural Network (ANN) for prediction of roughness parameters, friction coefficient and wear coefficient. Experimental results obtained from wear testing are compared with those obtained using artificial neural network (ANN) analysis. A very good agreement in results suggests that a well trained neural network is capable to predict the parameters in wear process.

EFFECTS OF SURFACE PREPARATION ON FRICTION AND WEAR IN DRY SLIDING CONDITIONS

Wear tests were conducted using a ball-on-disc tester T-11. In the experiment, a 42CrMo4 rotating steel disc with a hardness of 40±2 HRC was placed in contact with a 100Cr6 steel ball with a diameter of 6.35 [mm]. The hardness of the ball was set to 62±2 HRC. Finishing treatment applied to the surfaces was sand blasting. Disc samples were prepared to obtain surfaces in similar range of the Sa parameter (arithmetical mean height of the surface) but other surface topography parameters vary. Dry sliding tests were conducted at sliding speeds of v1 = 0.16; v2 = 0.24 i v3 = 0.32 [m/s]. The sliding distance was set to 282.6 [m], and the normal load was set to 9.81 [N]. During the tests, the friction force was monitored as a function of time. Disc and ball wear was measured after the tests using a white light interferometer Talysurf CCI Lite. Profiles were taken in four positions (900 apart) perpendicular to the wear track. Then, using an interferometer software program TalyMap Gold 6.0, they were computed and averaged. It was found that the initial surface topography has a significant influence on friction and wear levels under dry sliding conditions. It was also identified the correlation between several surface topography parameters and wear volume.

Effect of textured surface on the frictional noise under line contact and sliding–rolling conditions

Line contact and sliding–rolling movements exist widely in gears and bearings. In order to investigate the influence of surface microstructure on the frictional noise, a numerical study on the frictional noise generated by textured surfaces under line contact and sliding–rolling conditions by the use of finite element method is presented. The finite element model is established based on real surface topography. To improve the analysis reliability, friction coefficients used in the simulation are measured for different textured surfaces under various loads and speeds. The relationship between the 3D surface topography parameters and the frictional noise are analyzed. Results show that the frictional noise under line contact sliding–rolling conditions increases with load and speed, which can be explained from an energy dissipation perspective. Moreover, the 3D surface topography parameters of mean peak curvature and peak density influence the frictional noise during sliding–rolling under line contact significantly.

Surface characterization of nanoporous aluminium oxide films synthesized by single-step DC and AC anodization

Nanoporous alumina films were synthesized on commercial grade aluminum substrates using single-step anodization technique in 0.3M phosphoric acid at room temperature. Effect of applied voltage (100–130V) on surface characteristics of anodized aluminum oxide (AAO) film was investigated. Surface topography parameters and regularity ratio of nanopores arrangement were characterized using power spectral density (PSD) and fast Fourier transform (FFT) profiles. While DC anodization suffered from filament-like cavities at 130V owing to thermally enhanced dissolution of oxide, AC anodization produced localized flower-like morphology for all the applied voltages. The intensity of localized flower-like morphology was increased monotonically with applied voltage. Evolution of flower-like morphology was discussed on the basis of Pashchanka-Schneider model.

Three dimensional surface topography characterization of the electron beam melted Ti6Al4V

The properties of the components fabricated via electron beam melting (EBM) are known to be affected by different processing parameters such as beam current, offset focus, scan speed, layer thickness, powder size and part orientation. This clearly has part design, placement and performance implications and therefore in this study, the effect of part orientation on the surface topography of the EBM Ti6Al4V alloy was investigated. Three different surface finishes were obtained by fabricating disc components in the horizontal (0°), inclined (55°) and vertical (90°) in the EBM build chamber. Their resulting amplitude surface topographies were characterized through white light interferometry and scanning electron microscopy. Comparison of the results revealed a significant difference in numerical values of the 3-D surface roughness parameters. For the average roughness, the horizontal (0°) surface had a smoother surface (Sa = 15.8 μm) whereas the inclined (55°) and vertical (90°) surfaces had rougher surface characteristics with and Sa = 36.8 μm and 54.3 μm respectively. The results showed that part orientation of titanium during EBM can produce surfaces with different characteristics due the anisotropic melting of the powders by the EBM process leading to part design considerations and complexities associated with EBM parts. The selection of the 3-D surface topography parameters and surface morphology characterization were also shown to address the inadequacies of two-dimensional (2-D) surface analysis.

Analysis of Incubation Period Versus Surface Topographical Parameters in Liquid Droplet Erosion Tests

A novel approach to identifying the incubation time in liquid droplet eroded materials/coatings was explored by using metrological methods. Links were investigated between surface texture characteristics and the ending of the incubation period. The usual practice within erosion testing is to record the change in mass of the sample or to observe the appearance of the sample to establish an estimate of the time to failure. The primary objectives of this work were to: (1) measure and compare surface topographical parameters of eroded surfaces in both two dimensional (2D) and three dimensional (3D); (2) identify parameters that could be used consistently and were robust in terms of noise filtering; and (3) analyze the relationship between the incubation period and the variation of the surface topographical parameters. The failure mode of the coating was the most important aspect in the relationship between the two factors investigated. AA2024-T3 clad was shown to have a progressive damage mechanism, due to its ductile nature. The relationship between the Sa (arithmetic mean surface area primary profile) values and the mass loss values was seen to be linear after the incubation period. However, the analyses of the erosion protection coatings showed different failure mechanisms that were not generally preceded by significant changes to the surface condition. The 2D data was seen to be relevant when compared to the 3D areal surface parameters. The incubation period can be identified in certain liquid droplet eroded materials by using the surface topographical data and comparing to experimental results.

Evaluation of the parameters of titanium surface micro-pits on the titanium-PEEK joint fracture toughness

The present work is to investigate fracture toughness of titanium-PEEK by linking the interface fracture toughness to surface parameters of micro-pit on titanium panels during delamination. The relationship between geometrical parameters and failure mechanisms is also explained. The regular micro-pits were fabricated on pure titanium panels by Lithography. The effects of micro-pattern on fracture toughness were systematically evaluated by changing geometrical parameters of surface topography. The results showed that by changing the parameters of surface pattern, the fracture toughness can be manipulated through plastic deformation and molecular bond breaking of PEEK. The optimized wetting angle and surface free energy, having influenced on the real contact area and the stress regions, were obtained by adjusting the geometrical parameters. Finally, it was found that the failure mechanism transition from interface to cohesive was because of the attributed optimal parameters, showing more energy dissipation.

Influence of surface preparation on surface topography and tribological behaviours

Wear tests were conducted using a ball-on-disc tester. In the experiment, a 42CrMo4 steel disc with a hardness of 40HRC was placed in contact with a 100Cr6 steel ball with a diameter of 6.35mm. The hardness of the ball was set to 62HRC. Disc samples were prepared to obtain surfaces in range to the Sq parameter but of less than 0.5μm. Dry tests were carried out. During the tests, the friction force was monitored as a function of time. Disc and ball wear was measured after the tests using a white light interferometer Talysurf CCI Lite. To decrease variations in the experimental results, during the tests, wear debris was continuously removed from the disc surfaces. It was found that the initial surface topography has a significant influence on friction and wear levels under dry sliding conditions. It was also identified the correlation between several surface topography parameters and friction and wear.

3D surface topography analysis in 5-axis ball-end milling

This article presents a new analytical model to predict the topography and roughness of the machined surface in 5-axis ball-end milling operation for the first time. The model is able to predict the surface topography and profile roughness parameters such as 3D average roughness (Sa) and 3D root mean square roughness (Sq) by considering the process parameters such as the feedrate, number of flutes, step-over and depth of cut as well as the effects of eccentricity and tool runout in 5-axis ball-end milling. This model allows to simulate the effects of the lead and tilt angles on the machined surface quality in the virtual environment prior to the costly 5-axis machining operations. The effectiveness of the introduced surface topography prediction model is validated experimentally by conducting 5-axis ball-end milling tests in various cutting conditions.

Editors' Choice—Efficiency of a CMP Pad at Removing Protective Material from Copper during CMP

The efficiency of a pad asperity and abrasives embedded between the asperity and wafer at removing the protective material on the surface of copper (removal efficiency) during chemical mechanical planarization (CMP) was determined experimentally using current densities from in situ electrochemical measurements while polishing with a slurry containing BTA. The removal efficiency was insentitive to the pressure and sliding velocity, but was dictated by the pad surface topography parameters and abrasive concentration in the slurry. An analytical estimate was derived by comparing the trajectories of a pad asperity and the abrasives embedded in the asperity. Comparison of the experimental and analytical estimate suggests that the asperities are deformed enough by the embedded abrasives to contact the surface of copper at abrasive concentrations up to 1 wt%. At higher concentrations up to 5 wt%, the asperities deflected to a lesser amount, making the force exerted on the copper increase. At these higher concentrations, some of the copper interacting with the squeezed abrasives was plastically deformed, yielding higher removal efficiency than when elastically deformed. The removal efficiency can be used as a standard metric for assessing the material removal ability of various consumables such as slurry, CMP pad and pad conditioner.

Bacterial adhesion on direct and indirect dental restorative composite resins: An in vitro study on a natural biofilm

Statement of problemBoth direct and indirect techniques are used for dental restorations. Which technique should be preferred or whether they are equivalent with respect to bacterial adhesion is unclear. PurposeThe purpose of this in vitro study was to determine the affinity of bacterial biofilm to dental restorative composite resins placed directly and indirectly. Material and methodsFive direct composite resins for restorations (Venus Diamond, Adonis, Optifil, Enamel Plus HRi, Clearfil Majesty Esthetic) and 3 indirect composite resins (Gradia, Estenia, Signum) were selected. The materials were incubated in unstimulated whole saliva for 1 day. The biofilms grown were collected and their bacterial cells counted. In parallel, the composite resin surface morphology was analyzed with atomic force microscopy. Both bacterial cell count and surface topography parameters were subjected to statistical analysis (α=.05). ResultsIndirect composite resins showed significantly lower levels than direct composite resins for bacterial cell adhesion, (P<.001). No significant differences were observed within the direct composite resins (P>.05). However, within the indirect composite resins a significantly lower level was found for Gradia than Estenia or Signum (P<.01). A partial correlation was observed between composite resin roughness and bacterial adhesion when the second and particularly the third-order statistical moments of the composite resin height distributions were considered. ConclusionsIndirect dental restorative composite resins were found to be less prone to biofilm adhesion than direct composite resins. A correlation of bacterial adhesion to surface morphology exists that is described by kurtosis; thus, advanced data analysis is required to discover possible insights into the biologic effects of morphology.

Modeling and simulation of dynamical contact of asperities between flat rough surfaces

Dynamic contact analysis on the level of surface asperities is a powerful means to study the wear behavior of surface and the physical contact properties of interface. This article established an analytical model of asperity contacts between nominal rough planes during sliding process based on the statistical contact analysis of rough surfaces. The analytical expression describes the mathematical relationship between the total number of asperity contacts and its main influencing factors including the nominal contact area, sliding distance, the spacing between two contact planes, and surface topographical parameters. A simulation model of dynamic contact of asperities on rough planes was established to rapidly calculate the number of asperity contacts during the sliding process. The comparison between the calculation results and simulation results of the number of asperity contacts obtained through multifactor and multilevel analysis verified the rationality of the analytical model.