Reserch of Dislocation Theory in Micro Cutting

2012 ◽  
Vol 482-484 ◽  
pp. 2033-2036
Author(s):  
Hong Jun Ding ◽  
Xi Bin Wang ◽  
Zhi Qiang Liang ◽  
Qiang Jia
Keyword(s):  
Fracture Strength ◽  
Paper Analysis ◽  
Fracture Dislocation ◽  
Dislocation Theory ◽  
Line Defect ◽  
Dislocation Mechanism ◽  
Micro Cutting ◽  
Metal Fracture ◽  
Depth Analysis

This paper analysis Griffith 's Theory and the metal theoretical fracture strength, thus introducing a line defect that existence in actual crystal — dislocation; And in-depth analysis the metal fracture dislocation mechanism in the micro cutting, and the formation and expand of the Fracture cracks , provides the theory basis for micro cutting

Tem Studies of Dislocations Generated at Crack Tips

1982 ◽  
Vol 40 ◽  
pp. 472-473
Author(s):  
J. A. Horton ◽  
S. M. Ohr
Keyword(s):  
Stress Intensity ◽  
Fracture Mechanics ◽  
Screw Dislocation ◽  
Stress Intensity Factors ◽  
Dislocation Theory ◽  
Intensity Factors ◽  
Metal Fracture ◽  
Crack Tips ◽  
Dislocation Pileups ◽  
As Stress

Observations of the dislocation structure near the tips of propagating cracks are important in understanding metal fracture. Past TEM observations have shown screw dislocation pileups emitted from Mode I.II cracks. Dislocation theory has been applied to explain these observed pileups. From this analysis, fracture mechanics parameters such as stress intensity factors have been calculated.

A Reseach of Fracture Mechanism in Micro Cutting of 45 Steel Based on Material Properties

2013 ◽  
Vol 675 ◽  
pp. 370-373 ◽  
Author(s):  
Hong Jun Ding ◽  
Xi Bin Wang
Keyword(s):  
Material Properties ◽  
Fracture Process ◽  
Dislocation Theory ◽  
Film Sample ◽  
Fracture Characteristics ◽  
Micro Cutting ◽  
Transmission Electron ◽  
Initiation And Propagation ◽  
Cutting Model ◽  
Ductile Fracture Process

Abstract: Though the observation in micro cutting of 45 steel, the deformation zone of fracture characteristics was studied, and the corresponding cutting model was established; on dynamic tensile and situ observation of 45 steel by transmission electron microscopy , micro cutting ductile fracture process is simulated by the experiment on the steel tensile of 45 film sample, and the mechanism on initiation and propagation of crack in micro cutting fracture was studied with dislocation theory.

Research on the Calculation Method of Vertical Seismic Capacity of the Multi-Ribbed Composite Slab

2010 ◽  
Vol 152-153 ◽  
pp. 1873-1877
Author(s):  
Qi Zhang ◽  
Qian Feng Yao ◽  
Yin Zhang ◽  
Wei Huang ◽  
Dong Bo Li
Keyword(s):  
Theoretical Calculation ◽  
Bearing Capacity ◽  
Influence Factors ◽  
Element Model ◽  
Paper Analysis ◽  
Engineering Practice ◽  
Calculation Formula ◽  
Seismic Capacity ◽  
Depth Analysis ◽  
Vertical Bearing

On the basis of experimental study on 5 standard slabs’ vertical bearing capacity, the paper makes an in-depth analysis on the ratio of axial compression stress to strength, the ratio of height to thickness and the influence of embedded block on the axial bearing capacity of the slabs. By establishing finite element model of the slab, the paper analysis the influence factors by means of numerical simulation and establishing the theoretical calculation formula of the slab. Compared with the experimental results, it is showed that the accuracy of the theoretical calculation formula can meet the practical requirements, which provides theoretical calculation basis for engineering practice.

Anomalies in silicon carbide polytypes

1963 ◽  
Vol 272 (1351) ◽  
pp. 490-502 ◽  
Keyword(s):  
Silicon Carbide ◽  
Basic Structure ◽  
Microscopic Investigation ◽  
Unit Cell ◽  
Dislocation Theory ◽  
Dislocation Mechanism ◽  
Space Group ◽  
X Ray ◽  
Unit Cells ◽  
Surface Examination

Frank’s dislocation theory of the origin of polytypism received direct experimental support from the observation of a correlation between the step height of growth spirals on silicon carbide polytypes and the heights of their X-ray unit cells (Verma 1952, 1957). A detailed X-ray diffraction and microscopic investigation of silicon carbide structures has revealed anomalies that cannot be explained on the dislocation theory. Three new unusual polytypes 36 H a , 36 H b and 90 R are described in detail. The structures 36 H a and 36 H b were found in a single crystal piece and have identical lattices with a = b = 3.078 Å and c = 90.65 Å. Both structures belong to the space group P 3 m . The polytype 90 R belongs to the space group R 3 m with hexagonal unit cell dimensions a = b = 3.078 Å, c = 226.6 Å. The detailed atomic structure of type 90 R has been worked out and has a Zhdanov symbol [(23) 4 3322] 3 . It is shown that the polytypes 36 H a and 36 H b are based on the 6 H phase while type 90 R is based on the 15 R phase. The creation of such polytypes requires a screw dislocation with a Burgers vector which is an integral multiple of the c spacing of the basic structure, and is therefore not understood on Frank’s theory. A surface examination of the faces of these crystals does not reveal any growth spirals, showing that they have not grown by the dislocation mechanism. The growth of the different polytypes of silicon carbide is discussed and it appears that screw dislocations determine the surface structure but not the contents of the unit cell and therefore the cause of polytypism needs to be reconsidered.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

Doping effects on the geometric and electronic structure of tin clusters

2019 ◽  
Vol 21 (44) ◽  
pp. 24478-24488 ◽  
Author(s):  
Martin Gleditzsch ◽  
Marc Jäger ◽  
Lukáš F. Pašteka ◽  
Armin Shayeghi ◽  
Rolf Schäfer
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Beam Deflection ◽  
Functional Theory ◽  
Doping Effects ◽  
Depth Analysis ◽  
Trajectory Simulations

In depth analysis of doping effects on the geometric and electronic structure of tin clusters via electric beam deflection, numerical trajectory simulations and density functional theory.

Delay Discounting in Impulsive Behavior

2019 ◽  
Vol 24 (4) ◽  
pp. 312-321 ◽  
Author(s):  
Diana Moreira ◽  
Fernando Barbosa
Keyword(s):  
Delay Discounting ◽  
Human Subjects ◽  
Empirical Studies ◽  
Cochrane Collaboration ◽  
Initial Assessment ◽  
Impulsive Behavior ◽  
Manual Search ◽  
Study Results ◽  
Depth Analysis ◽  
The Future

Abstract. Delay discounting (DD) is the process of devaluing results that happen in the future. With this review, we intend to identify specificities in the processes of DD in impulsive behavior. Studies were retrieved from multiple literature databases, through rigorous criteria (we included systematic reviews and empirical studies with adult human subjects), following the procedures of the Cochrane Collaboration initiative. Of the 174 documents obtained, 19 were considered eligible for inclusion and were retained for in-depth analysis. In addition, 13 studies from the manual search were included. Thus, a total of 32 studies were selected for review. The objectives/hypotheses, results, and the main conclusion(s) were extracted from each study. Results show that people with pronounced traits of impulsivity discount rewards more markedly, that is, they prefer immediate rewards, though of less value, or postponed losses, even though they worsen in the future. Taken together, the existing data suggest the importance of inserting DD as a tool for initial assessment in conjunction with measures of addiction and stress level, as well as the consideration of new therapies.

No Depth Analysis for Freud

1958 ◽  
Vol 3 (6) ◽  
pp. 145-148
Author(s):  
ROBERT R. HOLT
Keyword(s):  
Depth Analysis
Sign in / Sign up

Export Citation Format

Share Document