Coefficient Of Friction Data Research Articles

Behavior of the Coefficient of Friction of Textured Tibial Inserts of Total Knee Replacements under the Conditions Prescribed by ISO 14243-3:2014

This work investigates the effect of surface texturing on the coefficient of friction (COF) of tibial inserts (TIs), of total knee replacements (TKRs), using a servomechanical knee simulator operating under the conditions prescribed by ISO 14243-3:2014, which requires strict control of flexion/extension (FE), anterior/posterior displacement (AP), inward/outward rotation (IOR) movements, and load variation. Tests were carried out lubricating with fetal bovine serum solution with a protein concentration of 20 g/L at 37 ± 2 °C. TIs were manufactured by fused deposition modeling (FDM) using polylactic acid (PLA) because of the advantages associated with rapid prototyping and customization. The acquired COF data were analyzed using statistical parametric mapping (SPM) to determine how the surface of the TIs affects the COF, identifying ranges where significant differences occurred. Textured surfaces led to significant reductions in COF during the swing phase of the walking cycle.

Relationship between Friction Coefficient and Surface Roughness of Stone and Ceramic Floors

Slips and falls are common occupational incidents worldwide. The friction on a floor surface is one of the critical environmental factors affecting the risk of a slip. In this research, we conducted friction measurements on stone and ceramic floor tiles under dry, wet, and water–detergent (WD) solution covered conditions using a horizontal pull slip meter (HPS). Our purposes were to quantify the slip resistance of commonly used stone and ceramic floors under different surface conditions and to validate the curvilinear relationship between the coefficient of friction (COF) and surface roughness of the floors proposed in the literature. The COF data were analyzed together with a surface profile parameter (Ra) of the floor samples. The results showed that the COFs of the stone floors were significantly (p < 0.0001) higher than those of the ceramic floors. All the floors under the dry conditions were slip resistant when adopting the ANSI 1264.2 criterion. Two and five ceramic floors were not slip resistant under the wet and WD solution covered conditions, respectively. Three polynomial regression equations were established to describe the relationship between the COF and Ra. The curvilinear functions of these models indicate that the three-zone (initial growth, steady-growth, and plateau) concept concerning the COF–Ra relationship in the literature was valid when static COF values measured using an HPS were adopted. In addition, the three-zone concept was valid not only on WD solution covered surfaces but also on dry and wet surfaces.

Tribological Characterization of Anionic Supramolecular Assemblies in Post-STI-CMP Cleaning Solution Using a Novel Post-CMP PVA Brush Scrubber

We have shown how different micellar (SDBS) vs. polyelectrolytic (PSSA) supramolecular assemblies in post-CMP cleaning solutions differ in their tribological performance when used in a novel PVA scrubber for 300-mm silicon dioxide wafer cleaning. Significant differences in real-time shear force and coefficient of friction data from the wafer-solution-brush interface (both in time domain as well as frequency domain) have been attributed to differences in each supramolecule’s chemical functionality and structure, which in turn, have been correlated to wafer-level defects. The work has underscored the importance of measuring the tribological attributes of post-CMP cleaning processes in an effort to improve cleaning performance.

Correlating Shear Force and Coefficient of Friction to Platen Motor Current in Copper, Cobalt, and Shallow Trench Isolation Chemical Mechanical Planarization at Steady-State Conditions

In a follow up from our earlier work that focused on highlighting the relationship among platen motor current (PMC), shear force (SF), and coefficient of friction (COF) in non-steady-state cases, we examined whether PMC was a reliable indicator that could be used in place of SF and COF data at steady-state conditions. For the 12 cases studied, we examined 60 distinct steady-state steps from their associated Stribeck+ curves. Data averaging, coupled with a trend matching algorithm, showed that for large time spans at steady-state, PMC was a reasonably good indicator of both SF and COF, as 68.5% of the time, PMC and SF trends matched (ranges between 62% to 86%) for all 60 cases. Regarding PMC and COF, we observed trend matching for 68.8% of the time (ranges between 62% and 86%) for all 60 cases. However, correlations between SF and PMC, and also between COF and PMC were found to be very poor (in most cases, non-existent) since at small timescales PMC was not sensitive enough to capture the instantaneous stick-slip occurrences and other important tribological and fluid dynamics phenomena present in CMP.

The Use of Coefficient of Friction (COF) Measurements As a CMP Slurry Development Tool

With the emergence of new and sometimes difficult to measure materials being integrated into advanced technology node integrated circuit film stacks, alternate methods for determining thickness and removal rate during Chemical Mechanical Planarization (CMP) may be required. Measurement of Coefficient of Friction (COF) is one such alternate method that can be used to overcome several technical obstacles, such as films with unknown composition, films with high a refractive index, very thinly deposited films, or films that oxidize heavily during CMP. This work will demonstrate how COF was used during CMP slurry development. The inherent difference in frictional force measured between an active film and the sublayer film upon which it is deposited can be exploited as a means to develop a selective CMP slurry. Coefficient of Friction in CMP is primarily determined by process conditions and the lubrication regime. Mathematically, the interaction of these two is defined by following equation: COF=ωμ/P [1] Where ω is the rotational speed, µ is the slurry viscosity, and P is the polish pressure. To achieve high removal rates on a given film, a CMP process must interact with that film in the boundary lubrication regime. The process parameters of downforce, platen speed, head speed, slurry flow and the slurry chemistry interact with the film to create COF values that are usually > 0.25 (1). With these process parameters fixed to generate boundary lubrication during CMP, one can determine the change in COF as the active film is removed and the sublayer is exposed, as shown in Figure 1. From the change in COF, the removal rate of the active film can be determined. Figure 1: COF Comparison between active film and sublayer The capability of determining removal rate on a difficult to measure film by COF can now be used as a method to observe changes in removal rate when altering a Control formulation with a chemical additive. Two different film types with the same sublayer were polished to clear, in order to expose the sublayer, while in-situ coefficient of friction (COF) measurements were taken. The goal was to chemically modify a Control formulation with a near 1 to 1 removal rate selectivity between the two polished films to increase the selectivity to >4 to 1. This work used a COF methodology that consisted of a fixed CMP process that enabled polishing in the boundary lubrication regime to determine the difference in COF observed between Film 1 and Film 2 and their respective sublayers. With this COF baseline established, the removal rate selectivity could be increased, as determined by COF, between Film 1 and Film 2 by altering the composition of the Control formulation with the addition of two chemical additives. Additive A was used to increase the removal rate of Film 1 and Additive B was used to suppress the removal rate of Film 2. Additive A increased Film 1 removal rate by 64%, but was only marginally selective to Film 1 because it also increased Film 2 removal rate by 25%. Mechanistically, Additive A functions by increasing the overall viscosity of the Control formulation. Additive B reduced Film 2 removal rate by 46% and was completely selective to Film 2, as there was no impact on Film 1 removal rate. Mechanistically, Additive B adsorbs to Film 2 by way of hydrophobic-hydrophobic interaction. Overall, the Film 1 : Film 2 selectivity was increased from 1.39 to 4.63 with the incorporation of Additive A and Additive B to the Control Formulation, demonstrating that the inherent difference in COF observed between two different material types can be used to measure and improve the selectivity performance of a CMP slurry on multiple films. This work demonstrated that coefficient of friction data can be implemented as an alternate methodology to determine removal rates of difficult to measure film types and can thus be used as a CMP slurry development tool. Figure 1

Friction Force Analysis on Diaomond Lapping of Sapphire Wafers

This paper is to design and developing a friction sensor system (FSS) for prediction of endpoint detection (EPD) on diamond lapping of sapphire or mono-crystalline aluminum oxide wafers. The endpoint detection usually includes start region, lapping region, transient region and endpoint region to control the planarization procedure by diamond lapping with variant plate of copper, resin copper, or tin materials. Experiments have been performed with 9 tests composed by three kinds of viscosity of slurry lapping with three kinds of lap plates. The coefficient of friction (CoF) has been obtained by the designed FSS and then compared with different test parameters. The as-lapped sapphire wafers have also measured by coherence surface interferometer, CCI-Lite (Taylor Hobson, UK). Experimental results show that the hardness of plate and viscosity of slurry are critical factors for as-lapped wafer quality. The EPD of diamond lapping with resin copper plate can be determined by the CoF data and that can be used for justifying the appropriate lapping time of sapphire wafers. Future study can focus on the relationship of sub-surface crack caused by the diamond lapping process.

Friction and Forward Slip in High-Speed Cold Rolling Process of Aluminum Alloys

Effects of process parameters on friction in cold strip rolling process have been studied in this article. The prime objective is to examine the major parameters affecting the metal working process. A varying coefficient of friction through the roll contact arc has been determined. A few formulae, commonly used to predict the coefficient of friction from forward slip measurements of a rolling process, have been evaluated according to forward slip measurements and coefficient of friction data. Essentially, this article bridges the industrial constant coefficient friction approach from forward slip measurements with the academic varying coefficient of friction strategy. A systems analysis has been made regarding the effects of potentially important parameters on friction in cold rolling. Based on this analysis, the effects of a few parameters have been identified of most importance.

The bio-tribological properties of anti-adhesive agents commonly used during tendon repair

Frictional resistance to tendon gliding is minimized by surrounding loose areolar tissue. During periods of prolonged immobilization, for example, post-tendon-repair, adhesions can form between these two adjacent tissues, thereby limiting tendon function. Anti-adhesive agents can be applied during surgery to prevent adhesion formation, whilst reportedly providing some reduction in friction during in vitro tendon-bony pulley investigations. This bio-tribological study evaluates whether application of these agents can improve the lubrication between the tendon and surrounding tissue, thus potentially reducing the risk of re-rupturing the tendon at the repair site. The use of bovine synovial fluid (BSF) enabled an approximation of the in vivo lubrication regime, and subsequent comparison of the performance of three synthetic agents (50 mg/ml 5-fluorouracil; 5 mg/ml hyaluronic acid; ADCON-T/N). Coefficient of friction data was recorded and then compared with the Stribeck curve. BSF generated a fluid film that separated the two surfaces, giving rise to optimal lubrication conditions. This efficient regime was also generated following application of each anti-adhesion agent. The use of phosphate-buffered saline solution in generating only a boundary lubrication regime highlighted the effectiveness of the agents in reducing friction. Hyaluronic acid (5 mg/ml) was marginally deemed the most effective anti-adhesive agent at lubricating the tendon. Subsequently, it is concluded that the application of anti-adhesive agents post-surgery has secondary, tribological benefits that serve to reduce friction, and thus potentially the risk of failure, at the tendon repair site.

Synthesis, characterization of ceria-coated silica particles and their chemical mechanical polishing performance on glass substrate

Nano-sized ceria particles were coated on the silica surface by the precipitation method using ammonium cerium nitrate and urea as precipitant with poly(vinylpyrrolidone) (PVP) as assistant. The structures and compositions of ceria-coated silica particles were characterized using X-ray diffraction (XRD), field-emission scanning microscopy (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. The results show that nano-size ceria particles were coated uniformly around the surface of silica particles when PVP was used as assistant during coating process, while without PVP, the ceria particles were grown sparsely on the silica particle surface and many ceria particles grow up through independent nucleation in the solution. Then, the chemical mechanical polishing (CMP) behaviors of the as-prepared ceria-coated silica particles on glass substrate were investigated. The CMP test results suggest that the as-prepared ceria-coated silica particles exhibit higher removal rate than pure silica particles without deteriorating the surface quality. In addition, online coefficient of friction (COF) was conducted during the polishing process. The COF data indicate that the COF values of ceria-coated silica particles are larger than those of pure silica particles due to their surface properties.

Mean flow structure in high aspect ratio microchannel flows

An experimental investigation of water flow through a high aspect ratio rectangular microchannel was conducted to further understand fluid dynamic characteristics in microchannels and to test the validity of macroscale theories that are commonly utilized at the microscale. A rectangular microchannel with nominal dimensions of 500 μm in height, 6 mm in width, and 32.8 cm in length was CNC machined into an aluminum blank. The test-section was completed by attaching a cap blank to the microchannel blank. Pressure and velocity data were obtained over a Reynolds number range from 173 to 4830, where the Reynolds number is based upon hydraulic diameter and channel average velocity. Velocity data were obtained using molecular tagging velocimetry (MTV). Laminar dimensionless velocity and coefficient of friction data are in agreement with macroscale theory. Transition from laminar flow, based upon a change in dimensionless velocity profile shape, occurs at a Reynolds number of 2800. This transitional Reynolds number is in excellent agreement with integral results and macroscale experimental results. Fully developed turbulent flow is found to exist at a Reynolds number of 4800. Inner normalized mean velocity profiles scale in the near-wall region, whereas the profiles of Reynolds stress and production of kinetic energy do not scale on inner variables. The inner normalized mean velocity profiles exhibit increasingly logarithmic-like behavior through the transitional regime. The experimental trends for the inner normalized mean velocity, Reynolds stress, and turbulence production are consistent with macroscale experimental and direct numerical simulation data. At this scale, influences reliably attributable to microscale effects were not detected in either the laminar or turbulent measurements of the present study.

Friction properties of chemically modified starch

AbstractStarches of varying chemical structures were esterified with anhydrides, formulated into dry film lubricants with the addition of canola oil, and its friction properties investigated. In the absence of canola, chemically modified starch displayed a very high coefficient of friction (COF). Addition of canola resulted in a sharp decrease in COF, which decreased with increasing [canola] until it attained a minimum and constant value that was independent of the further increase in [canola]. This observation was attributed to the adsorption of the canola oil onto starch due to H‐bonding between the ester groups of the canola triglycerides and the free hydroxyl groups of starch. Analysis of the [canola] vs COF data using the Langmuir adsorption model showed stronger adsorption of canola to modified starch with a lower degree of substitution (DS). This was attributed to the availability of more free hydroxyl group adsorption sites on starches with lower DS than those with higher DS. Copyright © 2008 John Wiley & Sons, Ltd.

Effect of Pad Groove Designs on the Frictional and Removal Rate Characteristics of ILD CMP

Real-time coefficient of friction (COF) analysis was used to determine the extent of normal and shear forces during chemical mechanical planarization (CMP) and identify the lubrication mechanism of the process. Experiments were done on a scaled polisher using IC-1000 pads with various surface textures, and Fujimi’s PL-4217 fumed silica slurry over a wide range of applied pressures and relative pad-wafer velocities. Stribeck curves showed that pad texture dictated the overall lubrication mechanism of the system. Average COF results yielded valuable information regarding the overall range of frictional forces associated with each type of surface texture. The linear correlation between COF data and interlayer dielectric (ILD) removal rate was consistent with previously published correlation graphs involving a variety of conventional pad textures and fumed silica concentrations. Spectral analysis of real-time friction data was used to elucidate the lubrication mechanism of the process in terms of the stick-slip phenomena and to quantify the total amount of hydrodynamic chattering as a function of various pad surface textures. For a given lubrication mechanism, analysis of the spectra for various textures indicated significant differences that were attributed to the amount of slurry present in the pad-wafer interface. © 2004 The Electrochemical Society. All rights reserved.

Comparing two methods of data collection for walkway friction measurements with a portable slip meter and a force platform

The objective was to investigate how two distinct data collection procedures, raw coefficient of friction (COF) data versus averaged COF data, may affect the outcome and interpretation of statistical analysis of friction tests and thus the reliability of slip resistance assessments. A prototype portable slip meter (PSM) and a force platform (FP) were used for evaluating floor friction transients over contaminated surfaces. A one-way ANOVA was performed to estimate significant differences between the PSM and the FP using raw COF data (55 measurement points) and averaged COF data (five measurement points) respectively. For comparing the FP with the portable slip meter, the best approach is to use averaged friction data. When the portable slip meter is used independently for walkway friction measurement, either the averaged or the raw data can be used to present the test results. However, the larger sample size is always the preferred choice.

Effects of Counterface Roughness and Conformity on the Tribological Performance of Crosslinked and Non-crosslinked Medical-Grade Ultra-High Molecular Weight Polyethylene

AbstractThe tribological behavior of crosslinked ultra-high molecular weight polyethylene (UHMWPE) was compared to that of non-crosslinked UHMWPE, used as control sample. A reciprocating pin-on-disk tribometer was used to determine the effects of countersurface roughness and conformity on wear mechanisms occurring during the initial stage of sliding. Pin samples of two different radii of curvature were slid against medical-grade Co-Cr alloy disks with surface roughness ranging from 0.005 to 0.04 μm in a lubricant of bovine serum. Normal loads were chosen to provide physiological contact stresses. The focus of this study was on the dependence of early wear mechanisms on surface roughness and conformity. Although a correlation between coefficient of friction data and dominant wear mechanisms was not observed, different wear mechanisms were found between control and crosslinked UHMWPE. The results of this study provide insight into the differences of the initial wear behavior of noncrosslinked and crosslinked UHMWPE used in total joint replacements.

Pulsed Electrode Surfacing of Steel with TiC Coating: Microstructure and Wear Properties

In the present study, pulse electrode surfacing (PES) technique was employed to deposit ultrahard and wear-resistant titanium carbide (TiC) coating on AISI 1018 steel. Wear resistance of the coated surface increased significantly. An attempt was made to correlate the thermodynamic predictions and experimental observations. A composite coating that is adherent, crack free, and defect free in nature was obtained, with TiC being the most stable phase. Islands of TiC of various shapes and sizes are present in the Fe-rich matrix in the coating. Microhardness measurements suggest high hardness values in the coating region. Tribological properties such as wear resistance and coefficient of friction were also measured. The coefficient of friction data do not show significant fluctuations. Wear and friction phenomena in such a coating have been explained on the basis of a model based on composite/multiphase material.

A Correlation Between Static Adhesion Data and the Dynamic Friction Coefficients for Two Cobalt Alloys and Iron Under Vacuum Conditions

An investigation of the static adhesion between cobalt-50 iron and cobalt-25 molybdenum-10 chromium alloy couples under ultraclean conditions has provided an excellent correlation between adhesion data and the dynamic coefficient of friction data as provided by independent experiments. When the materials and conditions of experiment were identical, the dynamic coefficient of friction which was predicted from the static adhesion data for Co-50Fe was given as f = 1.2 and that value observed was f = 1.2 – 1.3. Similarly, the predicted coefficient of friction for the Co-25 Mo-10 Cr alloy was 0.31 and observed was f = 0.25. These relationships coupled with those data for ultrahigh purity iron establish the operating spectrum for material behavior in metallic contact phenomena which includes asperity deformation, load support and contact fracture mechanisms. The investigative system provides a very rapid analysis of the effects of materials factor in contact systems devoid of contaminant film effects. Presented...