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.

Glass Knife Geometry as Seen by the SEM

1971 ◽  
Vol 29 ◽  
pp. 454-455
Author(s):  
J. Temple Black
Keyword(s):  
Low Cost ◽  
Amorphous Material ◽  
Stress Concentrations ◽  
Basic Tool ◽  
Tool Materials ◽  
Optical Inspection ◽  
Surface Flaws ◽  
Slip Planes ◽  
Glass Knife ◽  
Diamond Knife

In ultramicrotomy, the two basic tool materials are glass and diamond. Glass because of its low cost and ease of manufacture of the knife itself is still widely used despite the superiority of diamond knives in many applications. Both kinds of knives produce plastic deformation in the microtomed section due to the nature of the cutting process and microscopic chips in the edge of the knife. Because glass has no well defined slip planes in its structure (it's an amorphous material), it is very strong and essentially never fails in compression. However, surface flaws produce stress concentrations which reduce the strength of glass to 10,000 to 20,000 psi from its theoretical or flaw free values of 1 to 2 million psi. While the microchips in the edge of the glass or diamond knife are generally too small to be observed in the SEM, the second common type of defect can be identified. This is the striations (also termed the check marks or feathers) which are always present over the entire edge of a glass knife regardless of whether or not they are visable under optical inspection. These steps in the cutting edge can be observed in the SEM by proper preparation of carefully broken knives and orientation of the knife, with respect to the scanning beam.

scholarly journals Texture and Lattice Strain Evolution during Tensile Loading of Mg–Zn Alloys Measured by Synchrotron Diffraction

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 124
Author(s):  
Xiaohua Zhou ◽  
Changwan Ha ◽  
Sangbong Yi ◽  
Jan Bohlen ◽  
Norbert Schell ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Basal Slip ◽  
Lattice Strain ◽  
Tensile Loading ◽  
Tensile Tests ◽  
Vital Role ◽  
Prismatic Slip ◽  
Synchrotron Diffraction ◽  
Strain Evolution ◽  
Zn Alloys

To explore the effect of neodymium (Nd) on the deformation mechanisms of Mg–Zn alloys, texture and lattice strain developments of hot-rolled Mg–Zn (Z1) and Mg–Zn–Nd (ZN10) alloys were investigated using in situ synchrotron diffraction and compared with elasto-viscoplastic self-consistent simulation under tensile loading. The Nd-containing ZN10 alloys show much weaker texture after hot rolling than the Nd-free Z1 alloy. To investigate the influence of the initial texture on the texture and lattice strain evolution, the tensile tests were carried out in the rolling and transverse direction. During tension, the {002}<100> texture components develop fast in Z1, which was not seen for ZN10. On the other hand, <100> fiber // loading direction (LD) developed in both alloys, although it was faster in ZN10 than in Z1. Lattice strain investigation showed that <101> // LD-oriented grains experienced plastic deformation first during tension, which can be related to basal slip activity. This was more apparent for ZN10 than for Z1. The simulation results show that the prismatic slip plays a vital role in the plastic deformation of Z1 directly from the beginning. In contrast, ZN10 plastic deformation starts with dominant basal slip but during deformation prismatic slip becomes increasingly important.

K-0815 Integrity of structural members with surface flaws under cyclic large plastic deformation

2001 ◽  
Vol I.01.1 (0) ◽  
pp. 409-410
Author(s):  
Satoshi IGI ◽  
Masanori KAWAHARA ◽  
Kazuma KAWANO ◽  
Kazuyoshi SEKINE ◽  
Hiroaki MARUYAMA
Keyword(s):  
Plastic Deformation ◽  
Structural Members ◽  
Large Plastic Deformation ◽  
Surface Flaws

Strength-Flaw Relationship of Corroded Pristine Silica Studied by Atomic Force Microscopy

1994 ◽  
Vol 332 ◽  
Author(s):  
Qian Zhong ◽  
Daryl Inniss ◽  
Charles R. Kurkjian
Keyword(s):  
Optical Fibers ◽  
Strength Degradation ◽  
Force Microscopy ◽  
Silica Glasses ◽  
Spatially Resolved ◽  
Atomic Force ◽  
Silica Fibers ◽  
Surface Flaws ◽  
Relationship Of ◽  
Microscopic Surface

ABSTRACTGlass strength is controlled by microscopic surface flaws. Attempts to quantify the strengthflaw relationship for corroded silica fibers have been unfruitful, principally because of the difficulty in identifying the nanometer-sized, strength-controlling flaws on a uniformly corroded surface. In this paper, studies on corrosion of pristine silica optical fibers by HF vapor are presented. The HF-treated fibers exhibit strength degradation and contain well-defined, spatially-resolved surface flaws, which are characterized with an atomic force microscope. Excellent strength agreement is obtained for all chemically corroded fibers when the flaws are modeled as partially embedded hemispheres (i.e., blunt flaws). The implication of these results to the corrosion and fatigue process of silica glasses is discussed, since all previous analyses have assumed the strength-controlling flaws to be sharp.

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.

Three-Dimensional Plasto-Elastohydrodynamic Lubrication (PEHL) for Surfaces with Irregularities

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Ning Ren ◽  
Dong Zhu ◽  
Q. Jane Wang
Keyword(s):  
Plastic Deformation ◽  
Work Hardening ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Continuous Variable ◽  
External Loading ◽  
Surface Irregularity ◽  
Asperity Contact ◽  
Stress Concentrations ◽  
Subsurface Stress

Elastohydrodynamic lubrication (EHL) is one of the most common types of lubrication, which widely exists in many machine elements such as gears, rolling bearings, cams and followers, metal rolling tools, and continuous variable transmissions. These components often transmit substantial power under heavy loading conditions that may possibly induce plastic deformation of contacting surfaces. Moreover, the roughness of machined surfaces is usually of the same order of magnitude as, or greater than, the average EHL film thickness. Consequently, most components operate in mixed lubrication with considerable asperity contacts, which may result in localized pressure peaks much higher than the Hertzian pressure, causing subsurface stress concentrations possibly exceeding the material yield limit. Plastic deformation, therefore, often takes place, which not only permanently changes the surface profiles and contact geometry, but alters material properties through work-hardening as well. Available mixed EHL models, however, do not consider plastic deformation, often yielding unrealistically high pressure spikes and subsurface stresses around asperity contact locations. Recently, a three-dimensional (3D) plasto-elastohydrodynamic lubrication (PEHL) model has been developed for investigating the effects of plastic deformation and material work-hardening on the EHL characteristics and subsurface stress/strain fields. The present paper is a continuation of the previous work done by Ren et al. (2010, “PEHL in point contacts,” ASME J. Tribol., 132(3), pp. 031501) that focused on model development and validation, as well as investigation of fundamental PEHL mechanisms in smooth surface contacts. This part of the study is mainly on the PEHL behavior involving simple surface irregularities, such as a single asperity or dent, which can be considered as basic elements of more complicated surface roughness. It is found that considerable plastic deformation may occur due to the pressure peaks caused by the surface irregularity, even though sometimes external loading is not heavy and the irregularity is concave. The plastic deformation may significantly affect contact and lubrication characteristics, resulting in considerable reductions in peak pressure and maximum subsurface stresses.

scholarly journals Tensile Properties of Natural and Synthetic Rattan Strips Used as Furniture Woven Materials

Forests ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1299
Author(s):  
Yanting Gu ◽  
Jilei Zhang
Keyword(s):  
Plastic Deformation ◽  
Tensile Properties ◽  
Tensile Strain ◽  
Tensile Loading ◽  
Gauge Length ◽  
Test Unit ◽  
Proportional Limit ◽  
Significant Difference ◽  
Evaluation Test ◽  
Unit Loading

This study investigated factors on tensile properties of rattan strips commonly used as woven materials for furniture. The factors were rattan type (bast, core, synthetic), gauge length (100, 140 mm), and unit loading speed (0.1, 0.2, 0.3, 0.4, 0.5 mm/min/mm). Experimental results indicated that natural bast and core rattan strips, when subjected to tensile loading, behaved like synthetic rattan strips in terms of their stress-strain curves showing excessive plastic deformation. There was no significant difference in ultimate tensile strain between bast and synthetic rattan strips. Bast rattan strips had the highest ultimate tensile strength and modulus of elasticity among three materials evaluated in this study, followed by core rattan and synthetic strips. The major tensile properties of natural rattan bast strips can be influenced by their gauge length adapted to their evaluation test. Unit loading speeds, in general, had no significant effects on the major tensile properties of natural bast rattan strips but tended to significantly effect the ultimate strength of synthetic rattan strips, while less significantly for strengths at the proportional limit and yield point.

Mechanical Behavior Experimental Study of Microstructure under Tensile Loading and Electric Field

2011 ◽  
Vol 464 ◽  
pp. 383-386
Author(s):  
Quan Wang ◽  
Ran Hu ◽  
Jin Zhang ◽  
Lei Lei Jiang
Keyword(s):  
Experimental Study ◽  
Plastic Deformation ◽  
Mechanical Behavior ◽  
Failure Modes ◽  
Tensile Loading ◽  
Device Performance ◽  
Mechanical Behaviors ◽  
Fundamental Understanding ◽  
Micromechanical Devices ◽  
Tension Experiments

The mechanics problems can drastically compromise device performance and reliability. To solve these problems, there is a need to develop a fundamental understanding of mechanical behaviors of microstructures in MEMS. Also the increasing use of small micromechanical devices and advanced sensors has led to concern about the failure modes and reliability of these structures. In this paper a micro sample tension machine is made and using it one kind of micro sample fabricated with micromachining is tested. The tension experiments of the micro sample are done under different current to get the comparing data. The experiments yield reasonable and reproducible data. It is shown apparent plastic deformation of the micro sample happens under tension force. Mechanical behavior of the micro sample is distinguished to that of the sample with macro dimension. Micro size effect can be concluded about the micro sample under tension. Under different currents the elastic modulus and the tensile strength of the micro sample decrease with the current increasing. The relationships between them are gotten through experiment. The reliable designing parameters of the material are gained. The glaring outcome is that the uses of the material are depended highly on processing and fabrication techniques. The fabrication techniques can be developed and make the material both practical and reliable.

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