Plastic Deformation of Alkali Halide Crystals at High Pressure: Work‐Hardening Effects

1969 ◽  
Vol 40 (11) ◽  
pp. 4507-4513 ◽  
Author(s):  
L. A. Davis ◽  
R. B. Gordon
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Work Hardening ◽  
Alkali Halide ◽  
Pressure Work ◽  
Alkali Halide Crystals

On the Kinetics of Plastic Deformation of Some Alkali Halide Crystals

1967 ◽  
Vol 19 (2) ◽  
pp. 533-541 ◽  
Author(s):  
S. N. Komnik ◽  
V. Z. Bengus ◽  
E. D. Lyak
Keyword(s):  
Plastic Deformation ◽  
Alkali Halide ◽  
Alkali Halide Crystals ◽  
Kinetics Of

Investigation on Machined Surface Quality During Cutting of GH4169 Under High-Pressure Cooling

2020 ◽  
Vol 12 (7) ◽  
pp. 994-1003
Author(s):  
Ming-Yang Wu ◽  
Wei-Xu Chu ◽  
Ke-Ke Liu ◽  
Shu-Jie Wu ◽  
Yao-Nan Cheng
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
High Pressure ◽  
Tensile Stress ◽  
Surface Quality ◽  
Work Hardening ◽  
Surface Plastic ◽  
Residual Tensile Stress ◽  
Machined Surface ◽  
Machined Surface Quality

The aerospace component material GH4169 has low thermal conductivity and poor machinability, resulting in difficulty to guarantee good surface quality after conventional cutting. High-pressure cooling assisted machining technology can effectively improve the problem. In order to study the effect of high-pressure cooling assisted processing technology on the machined surface quality of GH4169, in this paper, Deform-3D was first used to construct a thermo-mechanical coupling finite element model for turning GH4169 under high-pressure cooling conditions, to analyze the turning temperature and surface residual stress. Then, analysis was carried out on the residual stress, work hardening behavior, and metamorphic layer of the GH4169 machined surface, in combination with the turning experiment. The results show that, under the conditions of little feeding and highspeed cutting, the GH4169 turning surface generates residual tensile stress along with both the feeding and turning directions. Moreover, the residual tensile stress gradually turns into the residual compressive stress along the depth direction. The application of high-pressure coolant can reduce the residual tensile stress of the machined surface. As the cooling pressure increases, the residual tensile stress of the machined surface decreases. The coupling effect between thermal deformation and plastic deformation when turning GH4169 can cause the work hardening of the surface, and the hardening degree decreases with the increase of cooling pressure. The high-pressure cooling assisted machining technology can effectively reduce surface plastic deformation, and promote the lessening of grain refinement degree of the material surface, thereby reducing the thickness of the metamorphic layer.

Mechanoluminescence of Coloured Alkali Halide Crystals

2015 ◽  
Vol 361 ◽  
pp. 121-176 ◽  
Author(s):  
B.P. Chandra ◽  
V.K. Chandra ◽  
Piyush Jha
Keyword(s):  
Plastic Deformation ◽  
Solid State ◽  
Impact Velocity ◽  
Alkali Halide ◽  
Applied Pressure ◽  
Gas Discharge ◽  
Mechanical Interaction ◽  
Dislocation Band ◽  
Alkali Halide Crystals ◽  
The Impact

The present paper reports both the experimental and mathematical aspects of elastico-mechanoluminescence (EML), plastico-mechanoluminescence (PML) and fracto-mechanoluminescence (FML) of coloured alkali halide crystals in detail, and thereby provides a deep understanding of the related phenomena. The additively coloured alkali halide crystals do not show ML during their elastic and plastic deformation. The ML emission during the elastic deformation takes place due to the mechanical interaction between bending dislocation segments and F-centres, and the ML emission during plastic deformation takes place due to the mechanical interaction between the moving dislocations and F-centres. The ML emission during fracture is also caused by the mechanical interaction between the moving dislocations and F-centres; however, in certain hard crystals like LiF, NaCl, NaF, etc., fracto ML also occurs due to the gas discharge caused by the creation of oppositely charged walls of cracks. The EML, PML, and solid state FML spectra of coloured alkali halide crystals are similar to their thermoluminescence spectra and afterglow spectra. However, the fracto ML spectra of certain hard crystals like LiF, NaCl, NaF, etc., also contain gas discharge spectra. The solid state ML spectra of coloured alkali halide crystals can be assigned to deformation-induced excitation of halide ions inV2-centres or in other hole-centres. Whereas, the intensity of EML and FML increases linearly with the applied pressure and the impact velocity, the intensity of PML increases quardratically with the applied pressure and the impact velocity because of the plastic flow of the crystals. Both Imand ITincrease with the density of F-centres in the crystals and strain rate of the crystals; however, they are optimum for a particular temperature of the crystals. The ML of diminished intensity also appears during the release of applied pressure. Expressions are derived for the elastico ML, plastico ML and fracto ML of coloured alkali halide crystals, in which a good agreement is found between the experimental and theoretical results. Many parameters of crystals such as band gap between the dislocation band and interacting F-centre energy level, radius of interaction between dislocations and F-centres, pinning time of dislocations, work hardening exponent, velocity of cracks, rise time of applied pressure, lifetime of electrons in the dislocation band, lifetime of electrons in shallow traps, diffusion time of holes, critical velocity of impact, etc., can be determined from the ML measurements. The ML of coloured alkali halide crystals has potential for self-indicating method of monitoring the microscopic and macroscopic processes; mechanoluminescence dosimetry; understanding dislocation bands in crystals; interaction between the dislocations and F-centres; dynamics of dislocations; deformation bleaching of coloration, etc. The ML of coloured alkali halide crystals has also the potential for photography, ML memory, and it gives information about slip planes, compression of crystals, fragmentation of crystals, etc.Contents of Paper

X-Ray Topographic Study of Vibrating Dislocations in Ice Under an Ac Electric Field

1969 ◽  
Vol 13 ◽  
pp. 526-538 ◽  
Author(s):  
K. Itagaki
Keyword(s):  
Plastic Deformation ◽  
Dielectric Constant ◽  
Electric Field ◽  
Alkali Halide ◽  
Dislocation Motion ◽  
Dielectric Measurements ◽  
Dislocation Mechanism ◽  
X Ray ◽  
Ac Electric Field ◽  
Alkali Halide Crystals

The behavior of charged dislocations in alkali-halide crystals has been drawing attention in connection with the charge transfer which occurs during plastic deformation.1-9 Recently, Itagaki proposed a charged dislocation mechanism to account for the dielectric properties of ice.10 His theory is in part supported by the dielectric measurements o f strained ice made by Ackley and Itagaki.11 Brantley and Bauer12 derived similar equations for the dielectric constant based on charged dislocation motion. They also proposed a new mechanism for apparent piezoelectricity based on moving charged dislocations in an electric field .

High-Pressure Work Hardening of Alumina

2021 ◽  
Author(s):  
Deng He ◽  
Fangming Liu ◽  
Shixue Guan ◽  
Duanwei He
Keyword(s):  
High Pressure ◽  
Work Hardening ◽  
Pressure Work
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