Static friction and surface roughness studies of surface micromachined electrostatic micromotors using an atomic force/friction force microscope

2001 ◽  
Vol 19 (4) ◽  
pp. 1777-1785 ◽  
Author(s):  
Sriram Sundararajan ◽  
Bharat Bhushan
Keyword(s):  
Surface Roughness ◽  
Friction Force ◽  
Static Friction ◽  
Atomic Force ◽  
Friction Force Microscope

AFM Interaction Forces of Lubricity Materials Surface

2012 ◽  
Vol 528 ◽  
pp. 95-98
Author(s):  
Xue Feng Li ◽  
Chu Wu ◽  
Shao Xian Peng ◽  
Jian Li
Keyword(s):  
Atomic Force Microscopy ◽  
Friction Force ◽  
Sliding Friction ◽  
Static Friction ◽  
Adhesive Force ◽  
New Method ◽  
Interaction Forces ◽  
Scanning Angle ◽  
Force Microscopy ◽  
Atomic Force

Micro interaction forces of lubricity surface of silicon and mica were studied using atomic force microscopy (AFM). From different scanning angle and bisection distance of the AFM, a new method of measuring micro static friction of lubricity surface materials was investigated. Results show that the micro coefficients of static and sliding friction of mica are less than the silicon, but the adhesive force is bigger. The mechanism of friction force of the two lubricity materials was discussed.

TEM Observation of Microstructural Change of Silicon Single Crystal Caused by Scratching Tests Using SPM

2004 ◽  
Vol 841 ◽  
Author(s):  
M. Takagi ◽  
K. Onodera ◽  
H. Iwata ◽  
T. Imura ◽  
K. Sasaki ◽  
...  
Keyword(s):  
Single Crystal ◽  
Friction Force ◽  
Amorphous Region ◽  
Silicon Single Crystal ◽  
Microstructural Change ◽  
First Line ◽  
Cross Sectional ◽  
Atomic Force ◽  
Friction Force Microscope

ABSTRACTIn this study, the microstructural change of the surface of Si single crystal (Si(100)) after the scratching tests under very small loading forces was investigated. At first, line-scratching tests and scanning-scratching tests were carried out using an atomic force/friction force microscope (AFM/FFM). Next, cross-sectional TEM observations of the wear marks which were generated by the scratching tests were carried out. As a result of the TEM observations after the line-scratching tests, it was found that dislocations were observed in the area of less than 100nm thickness from the surface of the wear marks which were formed under the loading forces of more than 5μN. In the case of the loading forces of more than 20μN, an amorphous region was also observed just under the wear marks. As a result of the TEM observations after the scanning-scratching tests, it was found that the introduction of dislocations took place and no amorphous region appeared. It was also found that the several atomic layers at the top surface of the wear marks shifted in parallel to (100).

Static Friction and Initiation of Slip at Magnetic Head-Disk Interfaces

1999 ◽  
Vol 122 (1) ◽  
pp. 246-256 ◽  
Author(s):  
S. Wang ◽  
K. Komvopoulos
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Film Thickness ◽  
Contact Resistance ◽  
Friction Force ◽  
Static Friction ◽  
Electric Contact ◽  
Magnetic Head ◽  
Friction Coefficients ◽  
Lubricant Films

The apparent friction force and electric contact resistance at the magnetic head-disk interface were measured simultaneously for textured and untextured disks lubricated with perfluoropolyether films of different thicknesses. The initial stick time, representing the time between the application of a driving torque and the initiation of interfacial slip, was determined based on the initial rise of the apparent friction force and the abrupt increase of the electric contact resistance. Relatively thin lubricant films yielded very short initial stick times and low static friction coefficients. However, for a film thickness comparable to the equivalent surface roughness, relatively long initial stick times and high static friction coefficients were observed. The peak value of the apparent friction coefficient was low for thin lubricant films and increased gradually with the film thickness. The variations of the initial stick time, static friction coefficient, and peak friction coefficient with the lubricant film thickness and surface roughness are interpreted in the context of a new physical model of the lubricated interface. The model accounts for the lubricant coverage, effective shear area, saturation of interfacial cavities, limited meniscus effects, and the increase of the critical shear stress of thin liquid films due to the solid-like behavior exhibited at a state of increased molecular ordering. [S0742-4787(00)03101-5]

A Model for Contact and Static Friction of Nominally Flat Rough Surfaces Under Full Stick Contact Condition

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
D. Cohen ◽  
Y. Kligerman ◽  
I. Etsion
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Friction Force ◽  
Contact Area ◽  
Rough Surfaces ◽  
Normal Load ◽  
Static Friction ◽  
Contact Condition ◽  
Maximum Friction ◽  
Static Friction Coefficient

A model for elastic-plastic nominally flat contacting rough surfaces under combined normal and tangential loading with full stick contact condition is presented. The model incorporates an accurate finite element analysis for contact and sliding inception of a single elastic-plastic asperity in a statistical representation of surface roughness. It includes the effect of junction growth and treats the sliding inception as a failure mechanism, which is characterized by loss of tangential stiffness. A comparison between the present model and a previously published friction model shows that the latter severely underestimates the maximum friction force by up to three orders of magnitude. Strong effects of the normal load, nominal contact area, mechanical properties, and surface roughness on the static friction coefficient are found, in breach of the classical laws of friction. Empirical equations for the maximum friction force, static friction coefficient, real contact area due to the normal load alone and at sliding inception as functions of the normal load, material properties, and surface roughness are presented and compared with some limited available experimental results.

Micro/nanotribology using atomic force microscopy/friction force microscopy: State of the art

1998 ◽  
Vol 212 (1) ◽  
pp. 1-18 ◽  
Author(s):  
B Bhushan
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Friction Force ◽  
Boundary Lubrication ◽  
Normal Load ◽  
Atomic Scale ◽  
Friction Force Microscopy ◽  
Material Transfer ◽  
Force Microscopy ◽  
Atomic Force

Atomic force microscopy/friction force microscopy (AFM/FFM) techniques are increasingly used for tribological studies of engineering surfaces at scales ranging from atomic and molecular to microscales. These techniques have been used to study surface roughness, adhesion, friction, scratching/wear, indentation, detection of material transfer and boundary lubrication and for nanofabrication/nanomachining purposes. Micro/nanotribological studies of materials of scientific and engineering interest have been conducted. Commonly measured roughness parameters are found to be scale dependent, requiring the need of scale-independent fractal parameters to characterize surface roughness. Measurement of atomic-scale friction of a freshly cleaved highly orientated pyrolytic graphite exhibited the same periodicity as that of corresponding topography. However, the peaks in friction and those in corresponding topography were displaced relative to each other. Variations in atomic-scale friction and the observed displacement have been explained by the variations in interatomic forces in the normal and lateral directions. Local variation in microscale friction is found to correspond to the local slope, suggesting that a ratchet mechanism is responsible for this variation. Directionality in the friction is observed on both micro- and macroscales which results from the surface preparation and anisotropy in surface roughness. Microscale friction is generally found to be smaller than macroscale friction as there is less ploughing contribution in microscale measurements. Microscale friction is load dependent and friction values increase with an increase in the normal load, approaching the macrofriction at contact stresses higher than the hardness of the softer material. The wear rate for single-crystal silicon is negligible below 20 μN and is much higher and remains approximately constant at higher loads. Elastic deformation at low loads is responsible for negligible wear. The mechanism of material removal on a microscale is studied. At the loads used in the study, material is removed by the ploughing mode in a brittle manner without much plastic deformation. Most of the wear debris is loose. Evolution of the wear has also been studied using AFM. Wear is found to be initiated at nanoscratches. AFM has been modified to obtain load-displacement curves and for measurement of nanoindentation hardness and Young's modulus of elasticity, with the depth of indentation as low as 1 nm. Hardness of ceramics on the nanoscale is found to be higher than that on the microscale. Ceramics exhibit significant plasticity and creep on the nanoscale. Scratching and indentation on nanoscales are powerful ways to screen for adhesion and resistance to deformation of ultra-thin films. Detection of material transfer on the nanoscale is possible with AFM. Boundary lubrication studies and measurement of lubricant-film thickness with a lateral resolution on a nanoscale have been conducted using AFM. Self-assembled monolayers and chemically bonded lubricant films with a mobile fraction are superior in wear resistance. Friction and wear on micro- and nanoscales at low loads have been found to be generally smaller compared to that at macroscales. Therefore, micro/nanotribological studies may help define the regimes for ultra-low friction and near-zero wear.

Surface roughness measurements of vanadium-contaminated fluidized cracking catalysts by atomic force microscopy

1996 ◽  
Vol 54 ◽  
pp. 866-867
Author(s):  
H. Kinney ◽  
M.L. Occelli ◽  
S.A.C. Gould
Keyword(s):  
Surface Roughness ◽  
Zeolite Y ◽  
Atomic Level ◽  
Microporous Structure ◽  
Contact Mode ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After ◽  
Roughness Measurements ◽  
Cracking Catalysts

For this study we have used a contact mode atomic force microscope (AFM) to study to topography of fluidized cracking catalysts (FCC), before and after contamination with 5% vanadium. We selected the AFM because of its ability to well characterize the surface roughness of materials down to the atomic level. It is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting that the surface corrugation could play a key role in the FCCs microactivity properties. To test this hypothesis, we chose vanadium as a contaminate because this metal is capable of irreversibly destroying the FCC crystallinity as well as it microporous structure. In addition, we wanted to examine the extent to which steaming affects the vanadium contaminated FCC. Using the AFM, we measured the surface roughness of FCCs, before and after contamination and after steaming.We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.

Brittle Behaviour in Aspirin Crystals: Evidence of Spalling Fracture

2020 ◽  
Author(s):  
Benjamin P. A. Gabriele ◽  
Craig J. Williams ◽  
Douglas Stauffer ◽  
Brian Derby ◽  
Aurora J. Cruz-Cabeza
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Single Crystals ◽  
Spalling Fracture ◽  
Force Microscopy ◽  
Atomic Force ◽  
Afm Imaging

<div> <div> <div> <p>Single crystals of aspirin form I were cleaved and indented on their dominant face. Upon inspection, it was possible to observe strongly anisotropic shallow lateral cracks due to the extreme low surface roughness after cleavage. Atomic Force Microscopy (AFM) imaging showed spalling fractures nucleating from the indent corners, forming terraces with a height of one or two interplanar spacings d100. The formation of such spalling fractures in aspirin was rationalised using basic calculations of attachment energies, showing how (100) layers are poorly bonded when compared to their relatively higher intralayer bonding. An attempt at explaining the preferential propagation of these fractures along the [010] direction is discussed. </p> </div> </div> </div>

Brittle Behaviour in Aspirin Crystals: Evidence of Spalling Fracture

2020 ◽  
Author(s):  
Benjamin P. A. Gabriele ◽  
Craig J. Williams ◽  
Douglas Stauffer ◽  
Brian Derby ◽  
Aurora J. Cruz-Cabeza
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Single Crystals ◽  
Spalling Fracture ◽  
Force Microscopy ◽  
Atomic Force ◽  
Afm Imaging

<div> <div> <div> <p>Single crystals of aspirin form I were cleaved and indented on their dominant face. Upon inspection, it was possible to observe strongly anisotropic shallow lateral cracks due to the extreme low surface roughness after cleavage. Atomic Force Microscopy (AFM) imaging showed spalling fractures nucleating from the indent corners, forming terraces with a height of one or two interplanar spacings d100. The formation of such spalling fractures in aspirin was rationalised using basic calculations of attachment energies, showing how (100) layers are poorly bonded when compared to their relatively higher intralayer bonding. An attempt at explaining the preferential propagation of these fractures along the [010] direction is discussed. </p> </div> </div> </div>

Friction Force and Stresses Analysis for Contact of Assembled Details

2006 ◽  
Vol 113 ◽  
pp. 334-338
Author(s):  
Z. Dreija ◽  
O. Liniņš ◽  
Fr. Sudnieks ◽  
N. Mozga
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Plastic Deformation ◽  
Friction Force ◽  
Sliding Friction ◽  
Friction Model ◽  
Contact Interface ◽  
Finite Element Program ◽  
Elastic Plastic ◽  
Element Program

The present work deals with the computation of surface stresses and deformation in the presence of friction. The evaluation of the elastic-plastic contact is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. Several factors of sliding friction model are discussed: surface roughness, mechanical properties and contact load and areas that have strong effect on the friction force. The critical interference that marks the transition from elastic to elastic- plastic and plastic deformation is found out and its connection with plasticity index. A finite element program for determination contact analysis of the assembled details and due to details of deformation that arose a normal and tangencial stress is used.

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