Shear Stress in Metal Cutting

1970 ◽  
Vol 92 (1) ◽  
pp. 151-157 ◽  
Author(s):  
B. F. Von Turkovich
Keyword(s):  
Plastic Deformation ◽  
Shear Stress ◽  
Chip Formation ◽  
Main Parameter ◽  
Metal Cutting ◽  
High Strain ◽  
Energy Requirement ◽  
Large Strains ◽  
Dislocation Theory ◽  
Rate Processes

Since the shear stress is the main parameter influencing the energy requirement in machining, the estimation of this stress remains one of the principal problems in the theory of chip formation. An insight in the behavior of the shear stress can be obtained by considering the process of plastic deformation from the viewpoint of dislocation theory. The theory is developed for high strain rate processes and very large strains.

scholarly journals Simulation of plastic deformation and destruction in the process of chip formation

2018 ◽  
Vol 211 ◽  
pp. 17007
Author(s):  
Tanel Tärgla ◽  
Jüri Olt ◽  
Olga Liivapuu
Keyword(s):  
Plastic Deformation ◽  
Formation Process ◽  
Chip Formation ◽  
Rheological Model ◽  
Metal Cutting ◽  
Depth Of Cut ◽  
Key Factors ◽  
Local Zone ◽  
Complex Process ◽  
Relaxing Medium

Metal cutting is a complex process in which several mechanisms are at work simultaneously. The mathematical modelling allows carrying out research into the optimization of machining conditions. This work examines the simulation of chip formation during the process of cutting. The studies demonstrated that the chip formation process, taking into account the plastic deformation and destruction of metal in the local zone, is most appropriately represented by a rheological model in the form of a series connection of elasticductile- plastic relaxing medium of Ishlinskiy (reflecting the process of primary deformation of metal from the cut off layer) and the medium of Voigt with two elastic-dissipative elements (representing the process of deformation and frictions from the convergent shaving). The attained complex rheological model served as the basis for constructing a representative dynamic model for the chip formation process. The key factors that govern the chip formation have been taken into account, such as tool vibration frequency and amplitude, depth of cut, feed rate.

Chip Formation in High-Speed Cutting of Copper and Aluminum

1963 ◽  
Vol 85 (4) ◽  
pp. 365-372 ◽  
Author(s):  
K. J. Trigger ◽  
B. F. von Turkovich
Keyword(s):  
Plastic Deformation ◽  
Chip Formation ◽  
High Speed ◽  
Metal Cutting ◽  
Initial Temperature ◽  
High Speed Machining ◽  
High Speed Cutting ◽  
Work Material ◽  
On Chip ◽  
Cutting Behavior

This paper presents metal-cutting data for the high-speed machining of copper and aluminum, each at two levels of purity, and over a range of workpiece temperatures from −326 deg F (80 deg K) to 550 deg F (560 deg K). It has been found that cutting behavior is influenced by purity of work material, its initial temperature, and extent of tool-chip contact. The influence of plastic deformation on chip hardness has been found to be intimately associated with the purity of the work material.

On the Plane Stress to Plane Strain Transition Across the Shear Zone in Metal Cutting

1988 ◽  
Vol 110 (4) ◽  
pp. 322-325 ◽  
Author(s):  
B. E. Klamecki ◽  
S. Kim
Keyword(s):  
Plane Strain ◽  
Shear Zone ◽  
Plane Stress ◽  
Central Region ◽  
Chip Formation ◽  
Metal Cutting ◽  
High Strain ◽  
Surface Characteristics ◽  
Workpiece Material ◽  
Element Analysis

The effects of the stress state transition from plane stress at the workpiece surface to plane strain in the central region of the chip formation zone were studied. A finite element analysis of the incipient chip formation process was performed. The model included heat generation and temperature induced workpiece material property changes. The primary result is that the unique high strain, high strain rate, large free surface characteristics of the metal cutting process can result in qualitatively different deformation behavior across the shear zone. Temperatures are higher in the regions near the surface of the workpiece than in the central region. In extreme cases, this will result in strain hardening behavior in the plain strain regions and thermal softening of the work material near the surface.

scholarly journals THE INFLUENCE OF MATERIAL MICROSTRUCTURE ON THE CHIP FORMING PROCESS

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Pavel Kovač ◽  
Borislav Savković ◽  
Lepa Siđanin ◽  
Ondrej Lukač ◽  
Ildiko Mankova
Keyword(s):  
Plastic Deformation ◽  
Chemical Composition ◽  
Chip Formation ◽  
Metal Cutting ◽  
Crack Formation ◽  
Forming Process ◽  
Material Microstructure ◽  
Workpiece Surface ◽  
Deformation And Fracture ◽  
Extensive Plastic Deformation

For a number of alloys the process of metal cutting is accompanied by extensive plastic deformation and fracture. In the paper we investigate quick stop samples of the chip formation of materials with different chemical composition and microstructure. The type of chip formation is classified according to the mechanism of crack formation and propagation. During cutting, most samples that are used, quasi-continuous chips with built-up edge (BUE) are obtained. The formation of BUE is undesirable since it is a highly deformed body with a semi stable top which periodically breaks away giving rise to poor workpiece surface quality.

On the Metal Physical Considerations in the Machining of Metals

1972 ◽  
Vol 94 (4) ◽  
pp. 1215-1224 ◽  
Author(s):  
S. Ramalingam ◽  
J. T. Black
Keyword(s):  
Plastic Deformation ◽  
Strain Hardening ◽  
Chip Formation ◽  
Metal Cutting ◽  
Dynamic Equilibrium ◽  
Experimental Studies ◽  
Second Phase ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Strain Hardening Behavior

Experimental studies of plastic deformation produced during metal cutting have shown that a dynamic equilibrium is established between strain hardening and recovery during chip formation. Recrystallization studies on interrupted cut specimens show that the chip is formed by shear on a thin plane or surface which segments the chip into a lamella structure. Scanning and transmission electron microscopy studies on the lateral surfaces of prepolished interrupted cut specimens substantiate the evidence obtained from the recrystallization studies. The chip formation process has thus been found to be strongly sensitive to the metal physics and defect strticture of the material undergoing plastic deformation. The important variables involving dislocation interactions during chip formation are the number and orientation of operable slip systems, certain characteristic dislocation parameters such as stacking fault energy, the interaction of dislocations with vacancies and solute atoms or with second phase particles (both coherent and noncoherent types), the short and long range order of the material, and the temperature of the deformation, all of which affect the strain hardening behavior of the material. In addition, those factors which govern the kinetics of dynamic recovery such as outright collision of dislocation segments, cross slip, and climb induced by a supersaturation of point defects produced in the course of deformation must be considered.

Deformation in Orthogonal Cutting

1970 ◽  
Vol 92 (1) ◽  
pp. 93-102 ◽  
Author(s):  
S. Ramalingam
Keyword(s):  
Plastic Deformation ◽  
Chip Formation ◽  
Deformation Process ◽  
Metal Cutting ◽  
Orthogonal Cutting ◽  
Cutting Process ◽  
Shear Surface ◽  
Grid Deformation ◽  
Plastic Deformation Process ◽  
Surface Active

This paper examines the plastic deformation process involved in chip formation during orthogonal cutting. Results of the grid deformation studies carried out on polymeric workpieces are reported. Chip formation is shown to result from the action of a curved shear surface, and it is shown that the configuration of the deformation volume during orthogonal cutting is fully determined by the orientation and curvature of the shear surface active during the cutting process. Implications of this model in metal cutting are discussed.

On Wedge Indentation and Its Relationship With Incipient Plastic Deformation in Metal Cutting

1977 ◽  
Vol 99 (3) ◽  
pp. 702-707 ◽  
Author(s):  
K. J. Weinmann
Keyword(s):  
Plastic Deformation ◽  
Plane Strain ◽  
Chip Formation ◽  
Metal Cutting ◽  
Rake Angle ◽  
Wedge Indentation ◽  
Wedge Plate

This paper deals with plane strain indentation of annealed brass by both symmetric and half wedges, and the connection between wedge indentation and incipient chip formation by a positive rake angle tool. Indentation forces and wedge-plate contact lengths were measured, and plastic deformation underneath the indenters was studied by microhardness scanning and discussed. Half-wedge indentations at decreasing distances from the plate corner were shown to result in a transition from wedge indentation to chip formation.

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.

scholarly journals A New Set-Up to Investigate Plastic Deformation of Face Centered Cubic Metals in High Strain Rate Loading

2014 ◽  
Vol 8 (2) ◽  
Author(s):  
Ehsan Etemadi ◽  
Jamal Zamani ◽  
Alessandro Francesconi ◽  
Mohammad V. Mousavi ◽  
Cinzia Giacomuzzo
Keyword(s):  
Plastic Deformation ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Face Centered Cubic ◽  
Cubic Metals ◽  
Face Centered ◽  
Set Up ◽  
Strain Rate Loading
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