scholarly journals Initial stages of yield in nanoindentation

1999 ◽  
Vol 14 (6) ◽  
pp. 2219-2227 ◽  
Author(s):  
J. D. Kiely ◽  
K. F. Jarausch ◽  
J. E. Houston ◽  
P. E. Russell
Keyword(s):  
Plastic Deformation ◽  
Plastic Zone ◽  
Applied Load ◽  
Elastic Behavior ◽  
Load Relaxation ◽  
Crystal Surfaces ◽  
Small Deviations ◽  
Single Crystal Surfaces ◽  
Complete Relaxation ◽  
Interfacial Force

We have used the interfacial force microscope to perform nanoindentations on Au single-crystal surfaces. We have observed two distinct regimes of plastic deformation, which are distinguished by the magnitude of discontinuities in load relaxation. At lower stresses, relaxation occurs in small deviations from elastic behavior, while at the higher stresses they take the form of large load drops, often resulting in complete relaxation of the applied load. These major events create a relatively wide plastic zone that subsequently deepens more rapidly than it widens. We discuss these findings in terms of contrasting models of dislocation processes in the two regimes.

Crack Tip Shielding from a Plastic ‘Inclusion’

2011 ◽  
Vol 465 ◽  
pp. 1-8
Author(s):  
M. Neil James ◽  
C.J. Christopher ◽  
Yan Wei Lu ◽  
K.F. Tee ◽  
Eann A Patterson
Keyword(s):  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Plastic Zone ◽  
Crack Growth ◽  
Displacement Field ◽  
Driving Force ◽  
Applied Load ◽  
Elastic Stress ◽  
Ductile Material ◽  
Crack Tip Shielding

This paper presents a very brief overview of the philosophy underlying a plastic inclusion approach to defining the boundary stresses imposed on the applied elastic stress or displacement field by the plastic deformation attendant on crack growth in a ductile material. It leads to two new fracture mechanics parameters, KR and KS. KR defines a retardation component arising from wake contact and the Poisson’s contraction associated with the plastic zone, whilst KS describes a compatibility-induced component arising from shear at the elastic-plastic interface. These additional components imply that KF is not directly comparable with KI, as it describes the net driving force on the crack from the applied load.

scholarly journals Adhesion and Nanomechanical Studies by Interfacial Force Microscopy

1997 ◽  
Vol 3 (S2) ◽  
pp. 1277-1278
Author(s):  
J. E. Houston
Keyword(s):  
Adhesive Bond ◽  
Force Sensor ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Force Microscopy ◽  
Interfacial Force Microscopy ◽  
Self Assembling ◽  
Morphological Defects ◽  
Scanning Force ◽  
Interfacial Force

Scanning probe techniques have shown dramatic growth recently and are presently making significant impact on surface and interfacial problems in material science. The Interfacial Force Microscopy (IFM) differs from other scanning force-probe techniques by its use of a self-balancing, zero compliance force sensor. This allows carefully controlled and mechanically stable force vs. interfacial separation measurements to be obtained which yield unique and valuable information concerning the interfacial adhesive bond and its failure, as well as enabling the study of the mechanical properties of materials, both on the nanometer scale. I will demonstrate the enhanced capabilities of the IFM by presenting two examples involving: 1) the bonding interaction between chemically distinct end groups on self assembling molecules adsorbed on both the sample and probe tip and 2) a study of the effect of morphological defects on the nanomechanical properties of Au(l 11) single-crystal surfacesInterfacial adhesion is of extraordinary technological importance and has long been of intense scientific interest.

Surface reactions observed by photoemission electron microscopy (PEEM)

1992 ◽  
Vol 50 (1) ◽  
pp. 286-287
Author(s):  
H.H. Rotermund
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Work Function ◽  
Chemical Reactions ◽  
Reaction Diffusion ◽  
Dynamic Processes ◽  
Clean Surface ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Photoemission Electron

Chemical reactions at a surface will in most cases show a measurable influence on the work function of the clean surface. This change of the work function δφ can be used to image the local distributions of the investigated reaction,.if one of the reacting partners is adsorbed at the surface in form of islands of sufficient size (Δ>0.2μm). These can than be visualized via a photoemission electron microscope (PEEM). Changes of φ as low as 2 meV give already a change in the total intensity of a PEEM picture. To achieve reasonable contrast for an image several 10 meV of δφ are needed. Dynamic processes as surface diffusion of CO or O on single crystal surfaces as well as reaction / diffusion fronts have been observed in real time and space.

Electronic and Vibrational Properties of Single Crystal Surfaces of NiAl

1986 ◽  
Vol 83 ◽  
Author(s):  
S.-C. Lui ◽  
J. M. Mundenar ◽  
E. W. Plummer ◽  
M. E. Mostoller ◽  
R. M. Nicklow ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Nearest Neighbor ◽  
Surface States ◽  
Active Surface ◽  
Atomic Displacement ◽  
Inelastic Electron ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Nial Alloy ◽  
Bulk Surface

ABSTRACTSurface and bulk electronic structure of the ordered NiAl alloy were measured using angle resolved photoelectron spectroscopy. The measured bulk d-bands (Ni like) were observed to be narrower than theoretically calculated d band widths which are 20 to 40% wider (depending upon what is used as a measure of the width). At least two surface states were observed on both the (110) and (111) surfaces. The nature of these surface states and their relationship to the bulk band structure is discussed. Dispersion of bulk phonons was measured by neutron scattering and fitted with a fourth nearest neighbor Born-von Karman model. Dipole active surface phonons on the (110) and (111) surfaces were observed by inelastic electron scattering and the frequencies also calculated assuming a truncated bulk surface. The calculated surface modes present a qualitative picture of the atomic displacement at each surface and also show that the surface phonon energy and intensity depends upon the structure of the surface.

scholarly journals nnOn the behavior of CTAB/CTAOH adlayers on gold single crystal surfaces

2021 ◽  
pp. 138947
Author(s):  
José M. Gisbert-González ◽  
María V. Oliver-Pardo ◽  
Francisco J. Sarabia ◽  
Víctor Climent ◽  
Juan M. Feliu ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces

scholarly journals Reactions on single-crystal surfaces

1976 ◽  
Vol 9 (7) ◽  
pp. 248-256 ◽  
Author(s):  
Gabor A. Somorjai
Keyword(s):  
Single Crystal ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces

scholarly journals The plastic deformation of iron and the formation of Neumann lines

1925 ◽  
Vol 108 (745) ◽  
pp. 231-231
Keyword(s):  
Plastic Deformation ◽  
Pure Iron ◽  
Crystal Surfaces ◽  
Size And Shape ◽  
Slip Bands ◽  
Wide Range ◽  
Moderate Rate ◽  
Rapid Deformation

The object of the investigation described in the present paper was to ascertain the manner in which wide variations in speed affect the mechanism of deformation in plastic metals. Iron was selected as the first metal for experiment, mainly because it is known that rapid deformation produced by shock is accompanied in this metal by special features, known as Neumann lines or lamellæ. When a piece of nearly pure iron, of suitable size and shape, with one face polished and etched, is subsequently subjected to plastic deformation at a moderate rate, the crystal surfaces, when examined under the microscope after deformation, show the well-known appearance of slip bands (1). The present experiments were undertaken in the first instance to ascertain whether the character, number and appearance of such slip bands would be appreciably affected by varying the rate of deformation over a wide range. For the sake of convenience, deformation by compression has been employed, the metal being used in the form of small rectangular prisms, measuring in some instances 0.44 inch by 0.44 inch in section by 0.7 inch in height.

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