Formation of Nanoscale Structures on the Ge(111) Surface Under Mechanical Loading

1998 ◽  
Vol 05 (01) ◽  
pp. 37-42 ◽  
Author(s):  
V. Korsukov ◽  
A. Lukyanenko ◽  
B. Obidov
Keyword(s):  
Single Crystal ◽  
Mechanical Loading ◽  
Applied Load ◽  
High Stress ◽  
External Stress ◽  
Surface Layers ◽  
Nanoscale Structures ◽  
Stress Lattice

Surface layers of Ge(111) under external mechanical loading have been investigated by EELS on plasmons and RHEED techniques. The positions of plasmon peaks and the diffraction patters were found to be strongly influenced by the external stress. Lattice dilatation in the layers 1 and 10 nm thick was estimated from the energy shifts of plasmon peaks under the applied load. It has been concluded that under high stress values of the order of 1 GPa the surface layers of Ge(111) undergo a transformation from the single-crystal to nanocrystallin state.

The Effect of the EHD Pressure Spike on Rolling Bearing Fatigue

1987 ◽  
Vol 109 (3) ◽  
pp. 444-450 ◽  
Author(s):  
L. Houpert ◽  
E. Ioannides ◽  
J. C. Kuypers ◽  
J. Tripp
Keyword(s):  
Pressure Distribution ◽  
High Stress ◽  
Surface Damage ◽  
Rolling Bearing ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Surface Layers ◽  
Rolling Bearings ◽  
Life Model ◽  
Pressure Spike

A recently proposed fatigue life model for rolling bearings has been applied to the study of lifetime reduction under conditions conducive to microspalling. The presence of a spike in the EHD pressure distribution produces large shear stresses localized very close to the surface which may account for early failure. This paper describes a parametric study of the effect of such spikes. Accurate stress fields in the volume are calculated for simulated pressure spikes of different height, width and position relative to a Hertzian pressure distribution, as well as for different lubricant traction coefficients and film thicknesses. Despite the high stress concentrations in the surface layers, reductions in life predicted by the model are modest. Typically, the pressure spike may halve the life, with the implication that subsurface fatigue still dominates. In corroboration of this prediction, preliminary experimental work designed to reproduce microspalling conditions shows that microindents due to overrolling particles are a much more common form of surface damage than microspalling.

Structure and Properties of Single Crystal Al2O3 Implanted with Chromium and Zirconium

1981 ◽  
Vol 7 ◽  
Author(s):  
C. J. Mchargue ◽  
H. Naramoto ◽  
B. R. Appleton ◽  
C. W. White ◽  
J. M. Williams
Keyword(s):  
Fracture Toughness ◽  
Single Crystal ◽  
Single Crystals ◽  
Solid Solutions ◽  
Rutherford Backscattering ◽  
Structure And Properties ◽  
Indentation Fracture ◽  
Surface Layers ◽  
Indentation Fracture Toughness

ABSTRACTSingle crystals of Al2O3 were implanted with chromium and zirconium to fluences of 1 × 1016 to 1 × 1017 ions cm−2. Rutherford backscattering-channeling studies showed the surface layers to be damaged but crystalline with the implanted ions randomly distributed. The microhardness and indentation fracture toughness were higher for the random solutions than for conventionally formed solid solutions. Changes in structure and properties caused by annealing in air at temperatures up to 1800°C were studied.

Constitutive Model for Anisotropic Creep Behaviors of Single-Crystal Ni-Base Superalloys in the Low-Temperature, High-Stress Regime

2012 ◽  
Vol 43 (6) ◽  
pp. 1861-1869 ◽  
Author(s):  
Yoon Suk Choi ◽  
Triplicane A. Parthasarathy ◽  
Christopher Woodward ◽  
Dennis M. Dimiduk ◽  
Michael D. Uchic
Keyword(s):  
Low Temperature ◽  
Constitutive Model ◽  
Single Crystal ◽  
High Stress ◽  
Stress Regime ◽  
Anisotropic Creep

Electron Microscopy of Stress-Induced Martensite and Pretransition Microstructures in Ni62.5Al37.5

1991 ◽  
Vol 246 ◽  
Author(s):  
D. Schryvers ◽  
L.E. Tanner
Keyword(s):  
Electron Microscopy ◽  
Stress Intensity ◽  
High Resolution ◽  
Single Crystal ◽  
High Stress ◽  
High Resolution Electron Microscopy ◽  
Transverse Displacement ◽  
Transition Sequence ◽  
Resolution Electron ◽  
Defect Sites

AbstractStatic configurations of stress-induced martensite and pretransition microstructures in Ni62.5A137.5 have been studied with conventional as well as high resolution electron microscopy using single crystal TEM specimens containing defect sites of extremely high stress intensity. From images of different regions around such defects it can be concluded that the austenite lattice develops transverse displacement modulations with increasing amplitude and correlation directly related to the {110}<110> shear-plus-shuffle displacements required to form the martensite structures. Different steps in this transition sequence are presented and discussed.

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