Assessing the failure toughness of metals from the plastic deformation of fracture surfaces

1976 ◽  
Vol 11 (6) ◽  
pp. 658-660
Author(s):  
V. I. Pokhmurskii ◽  
I. P. Gnyp ◽  
V. E. Vlasyuk
Keyword(s):  
Plastic Deformation ◽  
Fracture Surfaces ◽  
Failure Toughness

Plasticity During Fracture of the Au/Al2O3 Interface

1989 ◽  
Vol 170 ◽  
Author(s):  
Ivar E. Reimanis
Keyword(s):  
Plastic Deformation ◽  
Single Crystal ◽  
Fracture Energy ◽  
Stress Corrosion ◽  
Optical Microscope ◽  
Mechanical Tests ◽  
Interface Fracture ◽  
Fracture Surfaces ◽  
Topographic Features

AbstractAu/Al2 O3 interfaces are created by bonding highly textured Au films (25 pm thick) to single crystal A12 O3. Mechanical tests are done under the optical microscope to examine the effect of plastic deformation on the energy of fracture of the interface. Fracture occurs at the interface and is accompanied by plastic deformation in the Au. The relatively large value for the fracture energy measured (50-70J/m2) is attributed to the plastic deformation in the Au. It is also observed that fracture occurs subcritically due to stress corrosion at fracture energies from 10-20J/m2. Topographic features on the fracture surfaces are characterized and discussed briefly.

Characterisation of A508 Steel Cleavage Initiation Sites and Local Plasticity Using Surface Matching Technique

2013 ◽  
Author(s):  
F. McKenzie ◽  
R. J. Smith ◽  
F. Scenini ◽  
A. H. Sherry
Keyword(s):  
Plastic Deformation ◽  
Transition Region ◽  
Cleavage Fracture ◽  
Image Correlation ◽  
Surface Matching ◽  
Local Plastic ◽  
Fracture Surfaces ◽  
Local Plasticity ◽  
Cleavage Initiation ◽  
Local Plastic Deformation

Cleavage fracture in ferritic pressure vessel steels is preceded by local plastic deformation that initiates micro-cracks at carbides or second phase particles within the highly stressed region ahead of a crack tip. The objective of this study is to locate initiation sites of failed Compact Tension fracture mechanics specimens, tested at temperatures within the lower ductile to brittle transition region. A surface matching approach was developed to identify regions of local plastic deformation on the fracture surfaces of tested specimens, using confocal microscopy to acquire accurately mapped topographic images of both fractured surfaces, and then subtracting each pair of images in a virtual environment. This methodology is conceptually similar to the fracture surface topography analysis (FRASTA) technique but uses a home developed MATLAB software based on image correlation. The residual mismatch (interference) between the two datasets was used to identify the regions of local plasticity on both fracture surfaces of each test specimen studied that is believed to be associated with the cleavage initiation sites. The size and location of the localised plasticity was found to be consistent with scanning electron microscopy observations of cleavage initiation sites located directly ahead of the fatigue pre-crack tips in tested specimens. Finite element modelling was used to identify the magnitude of stress at the identified regions of cleavage initiation for the specimens studied, providing new insights into the mechanism of cleavage initiation in the lower transition region. This study suggests that this is a promising methodology for the identification of the initiation sites of cleavage fracture.

scholarly journals Roughening of Fracture Surfaces: The Role of Plastic Deformation

2004 ◽  
Vol 92 (24) ◽  
Author(s):  
Eran Bouchbinder ◽  
Joachim Mathiesen ◽  
Itamar Procaccia
Keyword(s):  
Plastic Deformation ◽  
Fracture Surfaces

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.

New Dimensions in Freeze-Etching

1969 ◽  
Vol 27 ◽  
pp. 202-203 ◽  
Author(s):  
Russell L. Steere ◽  
Michael Moseley
Keyword(s):  
Fracture Surfaces ◽  
Aluminum Specimen ◽  
Specimen Holder ◽  
Freeze Etching ◽  
The Right

A redesigned specimen holder and cap have made possible the freeze-etching of both fracture surfaces of a frozen fractured specimen. In principal, the procedure involves freezing a specimen between two specimen holders (as shown in A, Fig. 1, and the left side of Fig. 2). The aluminum specimen holders and brass cap are constructed so that the upper specimen holder can be forced loose, turned over, and pressed down firmly against the specimen stage to a position represented by B, Fig. 1, and the right side of Fig. 2.

Stereo Electron Microscopy Applied to High Resolution Freeze-Etch Replicas

1970 ◽  
Vol 28 ◽  
pp. 306-307
Author(s):  
L. Andrew Staehelin
Keyword(s):  
Electron Microscopy ◽  
Plastic Deformation ◽  
High Resolution ◽  
Smooth Surfaces ◽  
Small Particles ◽  
Membrane Surfaces ◽  
Wide Acceptance ◽  
New Information ◽  
Number Of Particles ◽  
Small Holes

Freeze-etched membranes usually appear as relatively smooth surfaces covered with numerous small particles and a few small holes (Fig. 1). In 1966 Branton (1“) suggested that these surfaces represent split inner mem¬brane faces and not true external membrane surfaces. His theory has now gained wide acceptance partly due to new information obtained from double replicas of freeze-cleaved specimens (2,3) and from freeze-etch experi¬ments with surface labeled membranes (4). While theses studies have fur¬ther substantiated the basic idea of membrane splitting and have shown clearly which membrane faces are complementary to each other, they have left the question open, why the replicated membrane faces usually exhibit con¬siderably fewer holes than particles. According to Branton's theory the number of holes should on the average equal the number of particles. The absence of these holes can be explained in either of two ways: a) it is possible that no holes are formed during the cleaving process e.g. due to plastic deformation (5); b) holes may arise during the cleaving process but remain undetected because of inadequate replication and microscope techniques.

Plastic Deformation in Microtomed Sections

1971 ◽  
Vol 29 ◽  
pp. 458-459
Author(s):  
J. Temple Black
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Applied Stress ◽  
Elastic Strain ◽  
High Strain ◽  
Tool Material ◽  
Cutting Edge ◽  
Material Structure ◽  
Geometrical Constraints

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.

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