Determining subsurface stress distributions in tribological samples from dislocation cell sizes in low energy dislocation structures

1989 ◽  
Vol 113 ◽  
pp. 297-303 ◽  
Author(s):  
Y Zhu ◽  
D Kuhlmann-Wilsdorf ◽  
T Imura
Keyword(s):  
Dislocation Cell ◽  
Low Energy ◽  
Stress Distributions ◽  
Subsurface Stress

Influence of an Inlet Oil Meniscus Geometry on Parameters of a Point Elastohydrodynamic Contact

1997 ◽  
Vol 119 (1) ◽  
pp. 112-125
Author(s):  
I. I. Kudish ◽  
M. Ya. Panovko
Keyword(s):  
Free Boundary ◽  
Boundary Conditions ◽  
Reynolds Equation ◽  
Contact Region ◽  
Numerical Results ◽  
Contact Boundary ◽  
Frictional Stress ◽  
Stress Distributions ◽  
Pressure Gap ◽  
Subsurface Stress

In the present paper an isothermal elastohydrodynamic problem for a lightly loaded lubricated point contact of elastic bodies is formulated and studied numerically. Mathematical formulation of the problem is based on a steady nonlinear system of integrodifferential equations: Reynolds’ equation, equations of elasticity, boundary conditions for pressure, and the equilibrium condition. Nonlinearity of the problem is caused by nonlinearity of the Reynolds equation and the boundary conditions for pressure describing a free boundary. The inlet contact boundary is considered to be known and located close to the center of the contact. In order to determine the location of the free boundary (exit boundary of the contact region) the problem is formulated as a problem of complementarity by Kostreva (1984a) and Oh (1984). The dimensionless system of equations and inequalities for the elastohydrodynamic lubrication (EHL) problem is solved using the Newton-Raphson method. The inlet boundary of a contact region is considered to have a complex irregular shape (the inlet oil meniscus has some deep notches) which is taken into account while deriving the finite-difference equations. The effect of the shape and location of the inlet oil meniscus on the lubrication film thickness, pressure, gap, sliding and rolling frictional and subsurface stress distributions are considered. Some numerical results are presented for pressure, gap, frictional and subsurface stress distributions in EHL contact. These numerical results show that variations in the inlet meniscus shape and location may cause significant qualitative and quantitative changes in distributions of parameters of a lubricated contact. For instance, the maximum values of pressure may change by 20 percent, and for rolling frictional stress by 100 percent and even more.

Low-energy dislocation cell structures produced by cross-slip

1982 ◽  
Vol 16 (1) ◽  
pp. 105-107 ◽  
Author(s):  
P.J. Jackson ◽  
D. Kuhlmann-Wilsdorf
Keyword(s):  
Dislocation Cell ◽  
Cross Slip ◽  
Low Energy ◽  
Cell Structures

Low-energy dislocation cell structures in ionic cubic lattice crystals

1995 ◽  
Vol 149 (1) ◽  
pp. 275-280
Author(s):  
A. V. Gektin ◽  
V. Ya. Serebryannyi
Keyword(s):  
Dislocation Cell ◽  
Low Energy ◽  
Cubic Lattice ◽  
Cell Structures

Dissociated Σ=27 boundaries in silicon

1988 ◽  
Vol 46 ◽  
pp. 624-625
Author(s):  
A. Garg ◽  
W.A.T. Clark ◽  
J.P. Hirth
Keyword(s):  
Electron Diffraction ◽  
Local Minimum ◽  
Boundary Energy ◽  
Coincidence Site Lattice ◽  
Boundary Plane ◽  
Low Energy ◽  
Theoretical Understanding ◽  
Site Lattice ◽  
Kikuchi Pattern ◽  
Analysis Techniques

In the last twenty years, a significant amount of work has been done in the theoretical understanding of grain boundaries. The various proposed grain boundary models suggest the existence of coincidence site lattice (CSL) boundaries at specific misorientations where a periodic structure representing a local minimum of energy exists between the two crystals. In general, the boundary energy depends not only upon the density of CSL sites but also upon the boundary plane, so that different facets of the same boundary have different energy. Here we describe TEM observations of the dissociation of a Σ=27 boundary in silicon in order to reduce its surface energy and attain a low energy configuration.The boundary was identified as near CSL Σ=27 {255} having a misorientation of (38.7±0.2)°/[011] by standard Kikuchi pattern, electron diffraction and trace analysis techniques. Although the boundary appeared planar, in the TEM it was found to be dissociated in some regions into a Σ=3 {111} and a Σ=9 {122} boundary, as shown in Fig. 1.

Transfer optics for high spatial resolution electron spectroscopy

1988 ◽  
Vol 46 ◽  
pp. 666-667
Author(s):  
G. G. Hembree ◽  
Luo Chuan Hong ◽  
P.A. Bennett ◽  
J.A. Venables
Keyword(s):  
Magnetic Field ◽  
Scanning Transmission Electron Microscope ◽  
Low Energy ◽  
Objective Lens ◽  
State University ◽  
Arizona State University ◽  
Initial Field ◽  
Resolution Electron ◽  
Scanning Transmission ◽  
Low Energy Electrons

A new field emission scanning transmission electron microscope has been constructed for the NSF HREM facility at Arizona State University. The microscope is to be used for studies of surfaces, and incorporates several surface-related features, including provision for analysis of secondary and Auger electrons; these electrons are collected through the objective lens from either side of the sample, using the parallelizing action of the magnetic field. This collimates all the low energy electrons, which spiral in the high magnetic field. Given an initial field Bi∼1T, and a final (parallelizing) field Bf∼0.01T, all electrons emerge into a cone of semi-angle θf≤6°. The main practical problem in the way of using this well collimated beam of low energy (0-2keV) electrons is that it is travelling along the path of the (100keV) probing electron beam. To collect and analyze them, they must be deflected off the beam path with minimal effect on the probe position.

Performance Evaluation of a Novel Type of Low-Energy Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 354-355
Author(s):  
Bertholdand Senftinger ◽  
Helmut Liebl
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Field Strength ◽  
Numerical Aperture ◽  
Low Energy ◽  
Energy Electron ◽  
High Resolution Imaging ◽  
Lens System ◽  
Resolution Imaging ◽  
Low Energy Electron

During the last few years the investigation of clean and adsorbate-covered solid surfaces as well as thin-film growth and molecular dynamics have given rise to a constant demand for high-resolution imaging microscopy with reflected and diffracted low energy electrons as well as photo-electrons. A recent successful implementation of a UHV low-energy electron microscope by Bauer and Telieps encouraged us to construct such a low energy electron microscope (LEEM) for high-resolution imaging incorporating several novel design features, which is described more detailed elsewhere.The constraint of high field strength at the surface required to keep the aberrations caused by the accelerating field small and high UV photon intensity to get an improved signal-to-noise ratio for photoemission led to the design of a tetrode emission lens system capable of also focusing the UV light at the surface through an integrated Schwarzschild-type objective. Fig. 1 shows an axial section of the emission lens in the LEEM with sample (28) and part of the sample holder (29). The integrated mirror objective (50a, 50b) is used for visual in situ microscopic observation of the sample as well as for UV illumination. The electron optical components and the sample with accelerating field followed by an einzel lens form a tetrode system. In order to keep the field strength high, the sample is separated from the first element of the einzel lens by only 1.6 mm. With a numerical aperture of 0.5 for the Schwarzschild objective the orifice in the first element of the einzel lens has to be about 3.0 mm in diameter. Considering the much smaller distance to the sample one can expect intense distortions of the accelerating field in front of the sample. Because the achievable lateral resolution depends mainly on the quality of the first imaging step, careful investigation of the aberrations caused by the emission lens system had to be done in order to avoid sacrificing high lateral resolution for larger numerical aperture.

TEM study on fine carbide precipitates and dislocation cell structure

1990 ◽  
Vol 48 (4) ◽  
pp. 904-905
Author(s):  
Mengzhe Chen ◽  
Siqin Wang ◽  
Jun Ke
Keyword(s):  
Carbide Particle ◽  
Cell Structure ◽  
Ferrite Matrix ◽  
Dislocation Cell ◽  
Isothermal Treatment ◽  
Particle Sizes ◽  
Dislocation Cell Structure ◽  
Thin Foils ◽  
Hsla Steels ◽  
Fine Carbide

A series of investigations have been conducted into the nature and origin of the dislocation cell structure. R.J.Klassen calculated that the dislocation cell limiting size in pure ferrite matrix is about 0.4 μm. M.N.Bassion estimated the size of dislocation cell in deformed ferrite of HSLA steels to be of the same order.In this paper, TEM observation has been concentrated on the interaction of fine carbide precipitates with dislocation cell structure in deformed Fe-C-V (0.05%C, 0.13% and 0.57%V) and Fe-C-Nb (0.07 %C and 0.04%Nb) alloys and compared with that in Fe-C (0.05%). Specimens were austenitized at 1500 “C/20 min and followed by isothermal treatment at 750 °C and 800 “C for 20, 40 and 120 minutes . The carbide particle sizes in these steels are from 9 to 86nm measured from carbon extraction replicas. Specimens for TEM were cut from differently deformed areas of tensile specimens deformed at room temperture. The thin foils were jet electropolished at -20 C in a solution of 10% perchloric acid and 90% ethanol. The TEM observation was carried out in JEM 100CX , EM420 at 100kv and JEM 2000FX at 200kv.

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