Influence of Free Surface Environment on the Shear Zone in Metal Cutting

1966 ◽  
Vol 181 (1) ◽  
pp. 687-705 ◽  
Author(s):  
P. L. Barlow
Keyword(s):  
Free Surface ◽  
Carbon Tetrachloride ◽  
Strain Hardening ◽  
Shear Zone ◽  
Chemical Reaction ◽  
Cutting Forces ◽  
Metal Cutting ◽  
The Body ◽  
Surface Barrier ◽  
Rehbinder Effect

It has previously been suggested that the reduction in cutting forces obtained by the presence of fluids such as CCl4 on the backface or free surface of the forming chip was due to diffusion of the fluid into the body of the chip in the region of the shear zone. In the present work, experiments with carbon tetrachloride tagged with carbon-14 and with carbon tetrachloride tagged with chlorine-36 were performed with the object of assessing the extent of diffusion of lubricants into the chip when present on the free surface only. The results obtained disprove former hypotheses and suggest that the reduced cutting force is due solely to chemical reaction at the surface of the chip. Confirmation of the sensitivity of the surface of the deforming shear zone to change in surface condition was obtained by removing metal from this region by an electropolishing technique during slow speed cutting. By varying the electropolishing conditions increased or decreased cutting forces could be obtained. It is proposed that the result both of chemical reaction at the surface and of surface removal is to reduce the strain-hardening rate of the metal undergoing shear by reducing the surface barrier to the flow of dislocations out of the metal. The association of the surface reaction of carbon tetrachloride with a change in the strain-hardening characteristics of the metal in the shear zone leads to a classification of the backface phenomenon as a Rehbinder effect and enables this effect to be more closely defined than was hitherto possible. Evidence is also presented which indicates that the backface effect does not contribute to the reduction in cutting forces during rakeface lubrication and is therefore unimportant in practice where flood lubrication of the cutting region invariably occurs.

Mechanics of Metal Cutting for a Material of Variable Flow Stress

1963 ◽  
Vol 85 (4) ◽  
pp. 339-345 ◽  
Author(s):  
P. L. B. Oxley
Keyword(s):  
Flow Stress ◽  
Carbon Tetrachloride ◽  
Cutting Force ◽  
Shear Zone ◽  
Metal Cutting ◽  
Cutting Conditions ◽  
Depth Of Cut ◽  
Variable Depth ◽  
Variable Flow ◽  
Interface Friction

A new analysis is presented in which the variable flow stress property of the work material is taken into account. It is shown that changes in the so-called angle of tool-chip interface friction can result from changes in the shear zone mechanism and, for example, the paradoxical behavior observed when cutting with carbon tetrachloride as a “lubricant” can be accounted for in this way. It is concluded that if actual predictions are to be made about the cutting process, i.e., without first making cutting tests, then the angle of tool-chip interface friction cannot be accepted as given information. The analysis is extended to cutting with a variable depth of cut, and in agreement with experiment it is predicted that, with all other cutting conditions the same, the cutting force will be less for an increasing depth of cut than for a decreasing depth of cut.

Amelioration of Carbon Tetrachloride-Induced Liver Injury by Citrus Leaf Extract

2019 ◽  
Vol 17 (4) ◽  
pp. 426-431
Author(s):  
Jin Xuezhu ◽  
Li Jitong ◽  
Nie Leigang ◽  
Xue Junlai
Keyword(s):  
Carbon Tetrachloride ◽  
Leaf Extract ◽  
Hepatic Injury ◽  
The Body ◽  
Dependent Manner ◽  
Weight Changes ◽  
Citrus Leaf ◽  
Dose Dependent ◽  
And Oxidative Stress

The main purpose of this study is to investigate the role of citrus leaf extract in carbon tetrachloride-induced hepatic injury and its potential molecular mechanism. Carbon tetrachloride was used to construct hepatic injury animal model. To this end, rats were randomly divided into 4 groups: control, carbon tetrachloride-treated, and two carbon tetrachloride + citrus leaf extract-treated groups. The results show that citrus leaf extract treatment significantly reversed the effects of carbon tetrachloride on the body weight changes and liver index. Besides, treatment with citrus leaf extract also reduced the levels of serum liver enzymes and oxidative stress in a dose-dependent manner. H&E staining and western blotting suggested that citrus leaf extract could repair liver histological damage by regulating AMPK and Nrf-2.

Boundaries Influence on the Flow Field Around an Oscillating Sphere

2013 ◽  
Author(s):  
Domenica Mirauda ◽  
Antonio Volpe Plantamura ◽  
Stefano Malavasi
Keyword(s):  
Free Surface ◽  
Flow Field ◽  
Boundary Conditions ◽  
Damping Ratio ◽  
Water Channel ◽  
Open Water ◽  
Free Surface Flows ◽  
The Body ◽  
Sphere Diameter ◽  
Oscillating Sphere

This work analyzes the effects of the interaction between an oscillating sphere and free surface flows through the reconstruction of the flow field around the body and the analysis of the displacements. The experiments were performed in an open water channel, where the sphere had three different boundary conditions in respect to the flow, defined as h* (the ratio between the distance of the sphere upper surface from the free surface and the sphere diameter). A quasi-symmetric condition at h* = 2, with the sphere equally distant from the free surface and the channel bottom, and two conditions of asymmetric bounded flow, one with the sphere located at a distance of 0.003m from the bottom at h* = 3.97 and the other with the sphere close to the free surface at h* = 0, were considered. The sphere was free to move in two directions, streamwise (x) and transverse to the flow (y), and was characterized by values of mass ratio, m* = 1.34 (ratio between the system mass and the displaced fluid mass), and damping ratio, ζ = 0.004. The comparison between the results of the analyzed boundary conditions has shown the strong influence of the free surface on the evolution of the vortex structures downstream the obstacle.

NUMERICAL SOLUTIONS OF 2D AND 3D SLAMMING PROBLEMS

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
Q Yang ◽  
W Qiu
Keyword(s):  
Free Surface ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Type Equation ◽  
The Body ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Highly Nonlinear ◽  
2D And 3D

Slamming forces on 2D and 3D bodies have been computed based on a CIP method. The highly nonlinear water entry problem governed by the Navier-Stokes equations was solved by a CIP based finite difference method on a fixed Cartesian grid. In the computation, a compact upwind scheme was employed for the advection calculations and a pressure-based algorithm was applied to treat the multiple phases. The free surface and the body boundaries were captured using density functions. For the pressure calculation, a Poisson-type equation was solved at each time step by the conjugate gradient iterative method. Validation studies were carried out for 2D wedges with various deadrise angles ranging from 0 to 60 degrees at constant vertical velocity. In the cases of wedges with small deadrise angles, the compressibility of air between the bottom of the wedge and the free surface was modelled. Studies were also extended to 3D bodies, such as a sphere, a cylinder and a catamaran, entering calm water. Computed pressures, free surface elevations and hydrodynamic forces were compared with experimental data and the numerical solutions by other methods.

scholarly journals Bilge Keel Induced Roll Damping of an FPSO With Sponsons

2016 ◽  
Author(s):  
Babak Ommani ◽  
Nuno Fonseca ◽  
Trygve Kristiansen ◽  
Christopher Hutchison ◽  
Hanne Bakksjø
Keyword(s):  
Free Surface ◽  
Two Dimensions ◽  
The Body ◽  
Proximity Effects ◽  
Roll Damping ◽  
Damping Coefficients ◽  
Free Decay ◽  
Strip Theory ◽  
Decay Tests ◽  
Bilge Keel

The bilge keel induced roll damping of an FPSO with sponsons is investigated numerically and experimentally. The influence of the bilge keel size, on the roll damping is studied. Free decay tests of a three-dimensional ship model, for three different bilge keel sizes are used to determine roll damping coefficients. The dependency of the quadratic roll damping coefficient to the bilge keel height and the vertical location of the rotation center is studied using CFD. A Navier-Stokes solver based on the Finite Volume Method is adopted for solving the laminar flow of incompressible water around a section of the FPSO undergoing forced roll oscillations in two-dimensions. The free-surface condition is linearized by neglecting the nonlinear free-surface terms and the influence of viscous stresses in the free surface zone, while the body-boundary condition is exact. An averaged center of rotation is estimated by comparing the results of the numerical calculations and the free decay tests. The obtained two-dimensional damping coefficients are extrapolated to 3D by use of strip theory argumentations and compared with the experimental results. It is shown that this simplified approach can be used for evaluating the bilge keel induced roll damping with efficiency, considering unconventional ship shapes and free-surface proximity effects.

scholarly journals Microvilli on the External Surfaces of Gastropod Tentacles and Body-Walls

1963 ◽  
Vol s3-104 (68) ◽  
pp. 495-504
Author(s):  
NANCY J. LANE
Keyword(s):  
Free Surface ◽  
Surface Area ◽  
Body Surface ◽  
Body Wall ◽  
Free Cell ◽  
The Body ◽  
Outer Cell ◽  
Lamellar Bodies ◽  
Cell Surfaces ◽  
Histochemical Tests

In Helix aspersa the ‘cuticle’ on the free surface of the external epithelial cells of the optic tentacles has been shown to consist of a layer of microvilli. Microvilli are also present in the same species on the free cell borders of the body-wall, and in the slug Arion hortensis, on the outer cell surfaces of the external epithelium. In all three cases the microvilli are arranged in a hexagonal pattern. There are indications that branching may possibly occur. The microvilli have granular cores with cross- and longitudinal-striations and there are fibrillar connexions between their tips. On the tentacular and body surfaces of H. aspersa, the microvilli increase the surface area 15 and 12 times, respectively. On A. hortensis the increase in surface area is only 4 times. In H. aspersa, beneath the microvilli on the tips of the optic tentacles there is a layer, about 3 to 4 µ deep, composed of vertical, horizontal, and tangential fibres. Some of these fibres are attached to lamellar bodies, which may have a lipid content. Granules are also found among the fibres. Further, a greater depth of cuticle is found to be present on the tips of the inferior tentacles of H. aspersa than on their sides; this seems to indicate that a fibrillar layer, similar to that on the optic tentacles, may lie beneath the cuticle of microvilli on the tips of the inferior tentacles. A thicker cuticle is also found on the tips of the optic tentacles in other stylommatophoran pulmonates. It has not been found possible to ascertain whether the fibrillar layer is intracellular or extracellular, although the evidence points to the latter. Histochemical tests indicate that mucopolysaccharide is present on the surface of the cuticle. Electron micrographs show a granular precipitate caught on and between the fibrillae connecting the tips of the microvilli. It is suggested that the function of the microvilli is to hold the mucous secretions on the body-surface, which would give protection to the animals.

RADIATION CHEMISTRY OF CYCLOHEXANE: VI. DILUTE SOLUTIONS OF CARBON TETRACHLORIDE AND CHLOROFORM IN CYCLOHEXANE

1964 ◽  
Vol 42 (3) ◽  
pp. 669-681 ◽  
Author(s):  
J. A. Stone ◽  
P. J. Dyne
Keyword(s):  
Carbon Tetrachloride ◽  
Chemical Reaction ◽  
Physical Process ◽  
Radical Scavenging ◽  
Radiation Chemistry ◽  
Hydrogen Yield ◽  
Halogenated Compounds ◽  
Dilute Solutions ◽  
Hydrogen Atoms

A study of the effect of the addition of small amounts (<3.5%) of the halogenated compounds CCl4, CHCl3, and CDCl3 on the radiolysis of cyclohexane has shown that processes other than radical scavenging occur. At the lowest concentrations of solute that it was practical to employ (0.004 M) cyclohexyl radicals were scavenged without a corresponding reduction in the hydrogen yield. At higher solute concentrations G(H2) was reduced by a physical process which did not involve the scavenging of thermal hydrogen atoms but did lead to chemical reaction involving the solute.

Nonlinear Aspects of Subcritical Shallow-Water Flow Past Two-Dimensional Obstructions

1978 ◽  
Vol 22 (04) ◽  
pp. 203-211
Author(s):  
Nils Salvesen ◽  
C. von Kerczek
Keyword(s):  
Free Surface ◽  
Shallow Water ◽  
Flow Problem ◽  
Free Stream ◽  
The Body ◽  
Two Dimensional ◽  
Third Order ◽  
Submerged Body ◽  
The Mean ◽  
The Waves

Some nonlinear aspects of the two-dimensional problem of a submerged body moving with constant speed in otherwise undisturbed water of uniform depth are considered. It is shown that a theory of Benjamin which predicts a uniform rise of the free surface ahead of the body and the lowering of the mean level of the waves behind it agrees well with experimental data. The local steady-flow problem is solved by a numerical method which satisfies the exact free-surface conditions. Third-order perturbation formulas for the downstream free waves are also presented. It is found that in sufficiently shallow water, the wavelength increases with increasing disturbance strength for fixed values of the free-stream-Froude number. This is opposite to the deepwater case where the wavelength decreases with increasing disturbance strength.

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