Proposed Experiments for Further Study of the Mechanism of Plastic Deformation

1947 ◽  
Vol 14 (3) ◽  
pp. A217-A224
Author(s):  
J. S. Koehler ◽  
F. Seitz
Keyword(s):  
Plastic Deformation ◽  
Internal Friction ◽  
Single Crystal ◽  
Electrical Resistance ◽  
Glass Fibers ◽  
Pure Metal ◽  
Stress Concentrations ◽  
Single Crystal Specimen ◽  
And Behavior ◽  
Small Plastic Deformation

Abstract The purpose of this paper is to propose new experiments in the field of the plastic deformation of solids. A qualitatively satisfactory theory is discussed and is then used to suggest worth-while experiments. This theory assumes that plastic deformation is a result of the formation and motion of certain crystalline imperfections called dislocations. The nature and behavior of these imperfections are discussed. The origin of these imperfections and the changes produced in them during deformation are considered. Certain new experiments are then proposed. It is suggested that all of these experiments be done using single crystals in an attempt to simplify the interpretation of the experiments: (a) It is suggested that the internal friction, the electrical resistance, and the rate of creep all be measured on the same spectroscopically pure metal single crystal. These three measurements should be made at various temperatures and should be done successively on crystals of various crystallographic orientations. (b) It is also suggested that stress-strain curves be obtained on fine single-crystal wires. In this connection it has been shown in glass fibers that the stress concentrations at the cracks can be reduced in very thin fibers. (c) It is proposed that the electrical resistance and the internal friction of an ordered alloy be measured while the single-crystal specimen is subjected to a very small plastic deformation. (d) An attempt will be made to suggest an experiment which would enable the observer to “see” the dislocations.

A study of the deformation and fracture of single-crystal gold films of high strength inside an electron microscope

1960 ◽  
Vol 255 (1281) ◽  
pp. 218-231 ◽  
Keyword(s):  
Plastic Deformation ◽  
Tensile Strength ◽  
Electron Microscope ◽  
Single Crystal ◽  
High Stress ◽  
High Strength ◽  
Gold Wire ◽  
Detailed Examination ◽  
Stress Concentrations ◽  
High Stress Level

Single-crystal films of gold in (111) orientation, and 500 to 2000 Å in thickness, have been prepared by an evaporation technique. A device has been constructed to allow these films to be strained in a controlled manner while under observation inside the electron microscope (Siemens Elmiskop I). It is shown, by the absence of observable plastic deformation, that the films deform elastically up to abnormally high strain values. This is confirmed, in the case of 500 Å films, by precision electron diffraction measurements, which indicate elastic strains as high as 1 to 1·5%. This represents a tensile strength several times that of hard-drawn gold wire. The high tensile strength occurs despite the presence of a high density of dislocations. Failure occurs once the elastic limit is exceeded. Detailed examination of the fractured specimens reveals that highly localized plastic deformation occurs immediately before fracture. The nature of the fracture process has been deduced from the micrographs, and it is shown that the catastrophic failure occurs as a result of the high stress level which exists when plastic deformation occurs, coupled with the stress concentrations which occur as localized thinning takes place.

Evolution of Microstructure and Texture of Pure Al Single Crystal Having {112} Orientation during Severe Plastic Deformation

2007 ◽  
Vol 26-28 ◽  
pp. 405-408 ◽  
Author(s):  
Naoki Ishida ◽  
Daisuke Terada ◽  
Keizo Kashihara ◽  
Nobuhiro Tsuji
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Single Crystal ◽  
Accumulative Roll Bonding ◽  
Equivalent Strain ◽  
Roll Bonding ◽  
Single Crystal Specimen ◽  
Ultrafine Grained ◽  
The Matrix ◽  
Evolution Of Microstructure

The sheet of pure Al (99.99%) single crystal having (1 12)[110] orientation was deformed up to equivalent strain of 6.4 by the accumulative roll-bonding (ARB) process. The microstructures and orientation of the single crystal ARB-processed by various cycles were characterized by the EBSP measurement. After 1cycle-ARB process, the crystal was macroscopically subdivided into two matrices (macroscopic grain subdivision). These matrices exhibits two different variants of brass orientation, which are (1 01)[121] and (011)[211]. In addition to the macroscopic grain subdivision, microscopic grain subdivision also occurred within the matrix to form an ultrafine grained structure in the single crystal specimen after high strains.

Fundamentals in Metal Plasticity: From the Initial Contact to Non-Stationary, Dynamic Chip

2020 ◽  
Author(s):  
Wolfgang Lortz ◽  
Radu Pavel
Keyword(s):  
Plastic Deformation ◽  
Internal Friction ◽  
Metal Cutting ◽  
Plastic Material ◽  
Glass Fibers ◽  
Plastic Region ◽  
Cutting Process ◽  
Experimental Result ◽  
Carbon Composites ◽  
Initial Contact

Abstract The process mechanics phenomena play an important role in all metal cutting processes. Conditions are changing progressively not only to high velocities and deformation, but also to the interfacial friction between two different materials — tool and workpiece, and inside the same material, as a result of material flow with high temperatures. It will be shown, that during the ploughing effect in the interface between tool and chips there are two different kinds of friction, external and internal friction. All the existent models ignore this reality. Therefore, an alternative must be found to model the real phenomena during metal plastic flow in a more appropriate manner. In this study, we will consider the cutting process in fundamental terms based only on mathematics and physics. In connection with this fundamental development a question arises, “Which parameters are the best for characterizing the cutting process and can the equations be proven after processing, because nearly each parameter will disappear, such as stress, strain, friction or temperatures etc.”? It might be that only the plastic material deformation in connection with the external and internal friction can be identified and visualized after the cutting process for comparing the developed theoretical result with the experimental result of the chip formation region. That leads to the fact that, as long as agreement between theoretical and experimental result can be demonstrated, there is evidence that stress and strain, as well as friction and temperatures are correctly estimated. Therefore, this paper is focused on the plastic deformation ds in the plastic region during the cutting process. This plastic deformation will be expressed for the non-stationary, dynamic cutting process with non-uniform feed (toolworkpiece contact evolving from rubbing to material separation) and chip flow. This process behavior is relevant for the milling operation of metals as well as for carbon composites with glass fibers. For carbon composites with glass fibers, additional environmental and human safety aspects will arise, as described in this paper.

Sem Examinations of Glass Knives

1970 ◽  
Vol 28 ◽  
pp. 282-283
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Tensile Loading ◽  
Resultant Force ◽  
Stress Concentrations ◽  
Edge Chipping ◽  
Surface Flaws ◽  
Edge Defects ◽  
Microscopic Surface

There are two types of edge defects common to glass knives as typically prepared for microtomy purposes: 1) striations and 2) edge chipping. The former is a function of the free breaking process while edge chipping results from usage or bumping of the edge. Because glass has no well defined planes in its structure, it should be highly resistant to plastic deformation of any sort, including tensile loading. In practice, prevention of microscopic surface flaws is impossible. The surface flaws produce stress concentrations so that tensile strengths in glass are typically 10-20 kpsi and vary only slightly with composition. If glass can be kept in compression, wherein failure is literally unknown (1), it will remain intact for long periods of time. Forces acting on the tool in microtomy produce a resultant force that acts to keep the edge in compression.

AN INTERNAL FRICTION STUDY OF N-H AND O-H PAIRS IN SINGLE CRYSTAL OF NIOBIUM AT LOW TEMPERATURES

1981 ◽  
Vol 42 (C5) ◽  
pp. C5-757-C5-761 ◽  
Author(s):  
R. Hanada ◽  
M. Shinohara ◽  
Y. Sado ◽  
H. Kimura
Keyword(s):  
Internal Friction ◽  
Single Crystal ◽  
Low Temperatures ◽  
Friction Study

Micromachining Imposed Subsurface Plastic Deformation in Single-Crystal Aluminum

2020 ◽  
Author(s):  
Sudhanshu Nahata ◽  
Marzyeh Moradi ◽  
Yoosuf N. Picard ◽  
Nithyanand Kota ◽  
O. Burak Ozdoganlar
Keyword(s):  
Plastic Deformation ◽  
Single Crystal

Amplitude dependent internal friction of an aluminum single crystal

1965 ◽  
Vol 13 (10) ◽  
pp. 1083-1084 ◽  
Author(s):  
R.R. Hasiguti ◽  
N. Igata ◽  
K. Tanaka
Keyword(s):  
Internal Friction ◽  
Single Crystal ◽  
Aluminum Single Crystal
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