scholarly journals Friction Measurement in MEMS Using a New Test Structure

1999 ◽  
Vol 605 ◽  
Author(s):  
B.T. Crozier ◽  
M.P. de Boer ◽  
J.M. Redmond ◽  
D.F. Bahr ◽  
T.A. Michalske
Keyword(s):  
Steady State ◽  
Normal Pressure ◽  
Test Structure ◽  
Friction Measurement ◽  
Self Assembled Monolayer ◽  
Environmental Loading ◽  
Friction Coefficients ◽  
Surface Conditions ◽  
Lubricating Film ◽  
Test Conditions

AbstractA MEMS test structure capable of measuring friction between polysilicon surfaces under a variety of test conditions has been refined from previous designs. The device is applied here to measuring friction coefficients of polysilicon surfaces under different environmental, loading, and surface conditions. Two methods for qualitatively comparing friction coefficients (µ) using the device are presented. Samples that have been coated with a self-assembled monolayer of the lubricating film perfluorinated-decyltrichlorosilane (PFTS) have a coefficient of friction that is approximately one-half that of samples dried using super-critical CO2 (SCCO2) drying. Qualitative results indicate that µ is independent of normal pressure. Wear is shown to increase µ for both supercritically dried samples and PFTS coated samples, though the mechanisms appear to be different. Super critically dried surfaces appear to degrade continuously with increased wear cycles, while PFTS coated samples reach a steady state friction value after about 105 cycles.

Friction Measurement Between Polyester Fibres Using the Fibre Probe SPM

2006 ◽  
Vol 59 (6) ◽  
pp. 390 ◽  
Author(s):  
Hiroyasu Mizuno ◽  
Mikael Kjellin ◽  
Niklas Nordgren ◽  
Torbjörn Pettersson ◽  
Viveca Wallqvist ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Cationic Surfactant ◽  
Friction Measurement ◽  
Friction Coefficients ◽  
Crucial Element ◽  
Lubricating Film ◽  
Fibre Probe ◽  
Frictional Forces ◽  
Afm Cantilever ◽  
First Time

An SPM has been used to measure frictional interactions between two crossed fibres for the first time. The preparation of the surfaces is briefly described, but the crucial element is that the fibre attached to the AFM cantilever is glued parallel to the long axis. The fibres consist of polyester and frictional forces were measured both in air and solutions of cationic surfactant C14TAB. The friction coefficients reduce markedly with increasing concentration of surfactant which is ascribed to the formation of a boundary lubricating film between the surfaces. On removal of the solution, the subsequent friction coefficient in air was reduced by more than a factor of two compared to its value before immersion.

scholarly journals Worm gear efficiency model considering misalignment in electric power steering systems

2018 ◽  
Vol 9 (1) ◽  
pp. 201-210 ◽  
Author(s):  
Seong Han Kim
Keyword(s):  
Electric Power ◽  
Normal Load ◽  
Contact Point ◽  
Normal Pressure ◽  
Worm Gear ◽  
Electric Power Steering ◽  
Friction Coefficients ◽  
Power Steering ◽  
Worm Wheel ◽  
Gear Efficiency

Abstract. This study proposes a worm gear efficiency model considering misalignment in electric power steering systems. A worm gear is used in Column type Electric Power Steering (C-EPS) systems and an Anti-Rattle Spring (ARS) is employed in C-EPS systems in order to prevent rattling when the vehicle goes on a bumpy road. This ARS plays a role of preventing rattling by applying preload to one end of the worm shaft but it also generates undesirable friction by causing misalignment of the worm shaft. In order to propose the worm gear efficiency model considering misalignment, geometrical and tribological analyses were performed in this study. For geometrical analysis, normal load on gear teeth was calculated using output torque, pitch diameter of worm wheel, lead angle and normal pressure angle and this normal load was converted to normal pressure at the contact point. Contact points between the tooth flanks of the worm and worm wheel were obtained by mathematically analyzing the geometry, and Hertz's theory was employed in order to calculate contact area at the contact point. Finally, misalignment by an ARS was also considered into the geometry. Friction coefficients between the tooth flanks were also researched in this study. A pin-on-disk type tribometer was set up to measure friction coefficients and friction coefficients at all conditions were measured by the tribometer. In order to validate the worm gear efficiency model, a worm gear was prepared and the efficiency of the worm gear was predicted by the model. As the final procedure of the study, a worm gear efficiency measurement system was set and the efficiency of the worm gear was measured and the results were compared with the predicted results. The efficiency considering misalignment gives more accurate results than the efficiency without misalignment.

Low-friction mechanism of silicon carbide and cemented carbide in water

2020 ◽  
pp. 135065012092868
Author(s):  
Fei Guo ◽  
Fan Wu ◽  
Fangyong Wu ◽  
Yuming Wang
Keyword(s):  
Silicon Carbide ◽  
Tribological Properties ◽  
Rotation Speed ◽  
Hydrodynamic Lubrication ◽  
Cemented Carbide ◽  
Matched Pairs ◽  
Low Friction ◽  
Friction Mechanism ◽  
Friction Coefficients ◽  
Test Conditions

The tribological properties of self-mated silicon carbide, self-mated cemented carbide, and cemented carbide/silicon carbide under water lubrication were studied. The three matched pairs could achieve low-friction coefficients (0.01–0.03) under certain test conditions. Additionally, the dependence of the friction coefficients on the rotation speed and load were measured. By combining these results with the observed surface topography and wear measurements, it was determined that the three matched pairs were in the hydrodynamic lubrication. In addition, combined with experiments in ethylene glycol and PAO40, it was shown that the actual viscosity of the lubricant had a significant influence on the realization of low friction. Furthermore, matching materials had an influence on the tribological properties, which may be related to the surface wettability of the lubricant.

Off-Line Testing of Tribo-Systems for Sheet Metal Forming Production

2014 ◽  
Vol 966-967 ◽  
pp. 3-20 ◽  
Author(s):  
Niels Bay ◽  
Ermanno Ceron
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Deep Drawing ◽  
Metal Forming ◽  
Normal Pressure ◽  
Environmentally Benign ◽  
Interface Pressure ◽  
Test Conditions ◽  
Interface Contact ◽  
Very High

Off-line testing of new tribo-systems for sheet metal forming production is an important issue, when new, environmentally benign lubricants are to be introduced. To obtain useful results it is, however, vital to ensure similar conditions as in the production process regarding the main tribo-parameters, which are tool/workpiece normal pressure, sliding length, sliding speed and interface contact temperature. The paper describes a generic methodology for such tests exemplified on an industrial, multistage deep drawing example, where deep drawing is followed by two successive re-drawing operations leading to very high tool/workpiece interface pressure and temperature in the second re-draw. Under such conditions only the best lubricant systems work satisfactory, and the paper shows how the performance of different tribo-systems in production may be predicted by off-line testing combined with numerical modelling in order to ensure proper test conditions.

Comparison between 3 infusion methods to measure cerebrospinal fluid outflow conductance

2010 ◽  
Vol 113 (6) ◽  
pp. 1294-1303 ◽  
Author(s):  
Nina Sundström ◽  
Kennet Andersson ◽  
Anthony Marmarou ◽  
Jan Malm ◽  
Anders Eklund
Keyword(s):  
Steady State ◽  
Experimental Model ◽  
Normal Pressure ◽  
Subjective Assessment ◽  
Clinical Results ◽  
Bolus Infusion ◽  
Steady State Method ◽  
Infusion Method ◽  
Physiological Pressure ◽  
Outflow Conductance

Object There are several infusion methods available to estimate the outflow conductance (Cout) or outflow resistance (Rout = 1/Cout) of the CSF system. It has been stated that for unknown reasons, the bolus infusion method estimates a higher Cout than steady-state infusion methods. The aim of this study was to compare different infusion methods for estimation of Cout. Methods The following 3 different infusion methods were used: the bolus infusion method (Cout bol); the constant flow infusion method, both static (Cout stat) and dynamic (Cout dyn) analyses; and the constant pressure infusion method (Cout cpi). Repeated investigations were performed on an experimental model with well-known characteristics, with and without physiological pressure variations (B-waves, breathing, and so on). All 3 methods were also performed in a randomized order during the same investigation in 20 patients with probable or possible idiopathic normal-pressure hydrocephalus; 6 of these patients had a shunt and 14 did not. Results Without the presence of physiological pressure variations, the concordance in the experimental model was good between all methods. When they were added, the repeatability was better for the steady-state methods and a significantly higher Cout was found with the bolus method in the region of clinically relevant Cout (p < 0.05). The visual fit for the bolus infusion was dependent on subjective assessment by the operator. This experimental finding was confirmed by the clinical results, where significant differences were found in the investigations in patients without shunts between Cout of the visual bolus method and Cout stat, Cout dyn, and Cout cpi (4.58, 4.18, and 6.12 μl/[second × kPa], respectively). Conclusions This study emphasized the necessity for standardization of Cout measurements. An experienced operator could partly compensate for difficulties in correctly estimating the pressure parameters for the bolus infusion method, but for the general user this study suggests a steady-state method for estimating Cout.

The Geometrically Irregular Foil Bearing

1974 ◽  
Vol 96 (2) ◽  
pp. 224-227
Author(s):  
J. L. Dais ◽  
T. B. Barnum
Keyword(s):  
Steady State ◽  
Numerical Results ◽  
State Problem ◽  
Circular Shape ◽  
Lubricating Film ◽  
Foil Bearing ◽  
Geometric Deviation ◽  
Steady State Problem

Equations are derived for the steady state problem of a foil moving relative to a drum with a geometric deviation from the perfectly circular shape. The fluid in the lubricating film is considered as incompressible and the foil as perfectly flexible but possessing mass. Numerical results are presented for the problem of a stationary foil stretched over a rotating circular drum with a flat.

scholarly journals Sliding abrasive wear when combining WEDM conditions and polishing treatment on H13 disks over 1045 carbon steel pins

2021 ◽  
Author(s):  
Antonio J. Sánchez Egea ◽  
Vitaliy Martynenko ◽  
Alejando Simoncelli ◽  
Gil Serrancoli ◽  
Daniel Martínez Krahmer
Keyword(s):  
Surface Roughness ◽  
Surface Properties ◽  
Electrical Discharge ◽  
High Speed ◽  
Electrical Discharge Machining ◽  
Wire Electrical Discharge Machining ◽  
Initial Surface ◽  
Friction Coefficients ◽  
Surface Conditions ◽  
Aisi 1045

AbstractForging dies are crucial in forging to manufacture accurate workpieces. These dies are generally made of AISI H steel series and hardened and tempered medium carbon alloy steel. Dies are processed by using high-speed milling + polishing or electrical discharge machining + polishing. The surface quality of the workpiece depends on the surface properties of these dies, where surface roughness, material hardness, and wear evolution of their surfaces are critical aspects to consider. This research analyzes different wire electrical discharge machining surface conditions combined with polishing treatment to describe their influence on friction and wear. Wire electrical discharge machining defines the disks’ surface properties in finishing and roughing conditions, and polishing treatment varies in time and paper sand depending on the roughness. Abbott-Firestone curves and Rsk-Rku roughness parameters characterize the surface roughness of each studied configuration. Room temperature pin-on-disk tests were performed to analyze friction coefficients and wear rate for AISI 1045 pins and AISI H13 disks. On average, the highest (0.284) and the lowest (0.201) friction coefficients were found for the combination of finishing wire electrical discharge machining + polishing and roughing wire electrical discharge machining conditions, respectively. Scanning electron microscope images were taken to describe the wear tracks and pin degradation for different sliding abrasive configurations. The diagram correlating the surface morphology and the friction coefficient predicts the wear damage on initial surface conditions, which is crucial in the forging industry to determine tool maintenance or replacement.

Numerical Simulation of Unsteady Laminar Flow Over Vibrating Bodies (Planar Flow)

1991 ◽  
Vol 35 (03) ◽  
pp. 230-249
Author(s):  
N. Kolluru Venkat ◽  
Malcolm Spaulding
Keyword(s):  
Steady State ◽  
Laminar Flow ◽  
Strouhal Number ◽  
Pressure Wave ◽  
Fourier Transforms ◽  
Amplitude Ratio ◽  
The Body ◽  
Series Data ◽  
Friction Coefficients ◽  
Highly Nonlinear

A model is developed to simulate two-dimensional laminar flow over an arbitrarily shaped body, a part of which is subjected to simple harmonic motion. The vibration amplitude ratio, Ho, and the Reynolds number, Re, are maintained at 0.1 and 1000, respectively. The Strouhal number, St, is varied in the range 0.0 ≤ St ≤ 1.0. The computer code is tested for the flow in a square cavity and also over a flat plate. The friction and pressure coefficients over the vibrating portion of the body are determined. Fast Fourier Transforms are performed on the time series data of these coefficients. For low-frequency vibrations (low Strouhal number) the pressure and friction coefficients match the steady-state results for flow over a sinusoidal bump. A small-amplitude pressure wave generated by the oscillating plate propagates downstream with the flow. For high-frequency vibrations (high Strouhal number) the pressure and friction coefficients over the vibrating portion of the body deviate from the steady-state results and a high-amplitude pressure wave propagates downstream. The pressure at one chord length upstream is also affected. As St increases, the flow becomes highly nonlinear and higher harmonics appear in the downstream flow. Subsequent analysis indicates that the nonlinearity is controlled by the term v(Əu/Əy).

Condition monitoring of mechanical seals: Detection of film collapse using reflected ultrasonic waves

2000 ◽  
Vol 214 (9) ◽  
pp. 1187-1194 ◽  
Author(s):  
D Anderson ◽  
J Jarzynski ◽  
R. F. Salant
Keyword(s):  
Steady State ◽  
Piezoelectric Transducer ◽  
Ultrasonic Waves ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Reflected Waves ◽  
Bench Tests ◽  
State Tests ◽  
Lubricating Film ◽  
Film Collapse

A method for detecting the collapse of the lubricating film in a mechanical seal has been developed. A piezoelectric transducer is placed behind the non-rotating seal face and is used to generate ultrasonic waves, which propagate towards the interface between the two seal faces. The same transducer is used to detect the reflected waves, whose amplitude is a measure of the degree of contact between the faces. The results of bench tests, steady-state tests and transient tests show that the method is effective.

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