A Treatise on the Streamlines and the Stress, Strain, and Strain Rate Distributions, and on Stability in the Primary Shear Zone in Metal Cutting

1972 ◽  
Vol 94 (2) ◽  
pp. 690-696 ◽  
Author(s):  
C. Spaans
Keyword(s):  
Flow Stress ◽  
Hydrostatic Pressure ◽  
Strain Rate ◽  
Shear Zone ◽  
Material Flow ◽  
Metal Cutting ◽  
Rate Increase ◽  
Temperature Distributions ◽  
Strain And Strain Rate ◽  
Strain Rate Increase

It is shown that both the flow stress and the hydrostatic pressure are constant in the greater part of the shear zone. The increase of the temperature with the strain is balanced by a proper strain rate increase, which provides a basis for a model generating the shape and the size of the shear zone, with the streamlines of material flow and the strain, strain rate and temperature distributions. Quick-stop tests make the streamlines visible. There is no reason for instability in the primary shear zone.

The Stress-State in the Shear Zone During Steady State Machining

1979 ◽  
Vol 101 (2) ◽  
pp. 211-216 ◽  
Author(s):  
J. H. L. The´ ◽  
R. F. Scrutton
Keyword(s):  
Flow Stress ◽  
Stress State ◽  
Strain Rate ◽  
Shear Zone ◽  
Deformation Mode ◽  
Deformation Pattern ◽  
Line Field ◽  
Strain And Strain Rate ◽  
Theoretical Predictions ◽  
Simple Shear Deformation

In order to calculate the stress state at any point in the shear zone, a new method has been developed which incorporates the effects of strain—hardening, strain-rate and temperature. Previous attempts have employed a modified slip-line field technique. The method is based on an empirical formula derived from published experimental data over a period of fifteen years relating flow stress values with values of strain, strain-rate, and temperature. From an experimentally derived deformation pattern, the strain and strain-rate distributions may be determined assuming a simple shear deformation mode. By using the empirical flow stress formula, the stresses and temperatures in the plastic zone may be calculated easily. Theoretical predictions agree well with experimentally observed values. The method is applied to a parallel-sided zone.

The Effect of Material Flow Stress on Analytical Simulation of Machining

2010 ◽  
Vol 29-32 ◽  
pp. 1809-1814
Author(s):  
Bing Lin Li ◽  
Ling Ling ◽  
Yu Jin Hu ◽  
Xue Lin Wang
Keyword(s):  
Flow Stress ◽  
Shear Zone ◽  
Analytical Model ◽  
Material Flow ◽  
Model Simulation ◽  
Orthogonal Cutting ◽  
Shear Plane ◽  
Thermomechanical Model ◽  
Workpiece Material ◽  
Flow Stress Data

The flow stress data of the workpiece are extremely crucial for the cutting simulation. The study shows how the input data affect the analytical predictions of cutting force and temperature. The Johnson-Cook material model is used to represent workpiece flow stress in the primary shear zone. A thermomechanical model of orthogonal cutting is proposed based on the main shear plane divides the primary shear zone into two unequal parts. Five different sets of workpiece material flow stress data used in the Johnson-Cook’s constitutive equation are chosen and make the sensitivity analysis for analytical model. Simulation results were compared to orthogonal cutting test data from the available literature, and find the effects of flow stress on analytical model was different from that for finite element model.

Numerical Investigation of Heat Partition in the Primary Shear Zone in Metal Cutting

2005 ◽  
Author(s):  
Vasant Pednekar ◽  
Vis Madhavan ◽  
Amir H. Adibi-Sedeh
Keyword(s):  
Partition Coefficient ◽  
Strain Rate ◽  
Shear Zone ◽  
Metal Cutting ◽  
Plastic Material ◽  
Shear Plane ◽  
Analytical Models ◽  
Machined Surface ◽  
Element Analysis ◽  
Heat Partition

The fraction of heat generated in the primary shear zone that is conducted into the workpiece is a key factor in the calculation of the shear plane temperature and in calculating the cutting forces based on material flow stress. Accurate analytical, numerical, or experimental determination of this heat partition coefficient is not available to date. This study utilizes a new approach to obtain the heat partition coefficient for the primary shear zone using results for strain, strain rate, and temperature distribution obtained from a coupled thermo-mechanical finite element analysis of machining. Different approaches, using strain rate and equivalent strain, are used for calculating the total plastic power in the primary shear zone and the heat generated by plastic deformation below the plane of the machined surface. The heat carried away by the workpiece is obtained by calculating the heat flow by convection in regions where the conduction is expected to be small. We have used an elastic perfectly plastic material model and constant thermal properties to mimic the assumptions used in analytical models. The fraction of the total heat generated in the primary shear zone that is conducted into the machined workpiece is found and compared to the prediction of different analytical models. It is found that for most of the cutting conditions, the values of heat partition coefficient are closest to those provided by Weiner’s model.

The Contribution of History in Plastic Behavior of Metals in Machining

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
M. R. Vaziri ◽  
M. Mashayekhi ◽  
M. Salimi
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Material Flow ◽  
Constitutive Models ◽  
Shear Zones ◽  
Plastic Behavior ◽  
Mechanical And Thermal Properties ◽  
Mathematical Form ◽  
Face Centered Cubic ◽  
Material Models

Mechanical and thermal properties significantly affect many aspects of machining, such as chip formation, cutting forces, cutting temperatures, and surface integrity of machined products. One of the most important mechanical properties is the material flow stress, which is governed by the field variables including the strain, strain rate, and temperature. Due to the presence of high values of these variables in machining, it is important to evaluate the performance of different material models, typically developed at much lower strains, strain rates, and temperatures. The other issue is to identify the effect of the history of these variables that material microvolume experiences while moving through the shear zones and include them in the model. It is demonstrated that such material models may be suitable choices to describe the material flow in simulation of machining, which leads to an extrapolation from the mathematical form of these models. In addition, this paper discuses the importance of history dependency in flow stress and compares the performance of three commonly employed material constitutive models including the nonhistory-dependent Johnson–Cook (J–C) model, the empirical Oxley model, and the history-dependent Maekawa model. It is demonstrated that among the metals with different crystal structures, the flow stress of face-centered cubic (FCC) metals is highly affected by the strain path and is very little sensitive to temperature and strain-rate changes. In addition, the magnitudes of these effects are discussed.

Sensitivity Analysis of the Material Flow Stress in Machining

Manufacturing ◽  
2003 ◽  
Author(s):  
Ning Fang
Keyword(s):  
Sensitivity Analysis ◽  
Flow Stress ◽  
Aluminum Alloys ◽  
Strain Rate ◽  
Strain Hardening ◽  
Material Flow ◽  
Chemical Compositions ◽  
Wide Range ◽  
Strain Rate Hardening ◽  
Factor Governing

Among the effects of strain hardening, strain-rate hardening, and temperature softening, it has long been argued about which effect is predominant in governing the material flow stress in machining. This paper compares four material constitutive models commonly employed, including Johnson-Cook’s model, Oxley’s model, Zerilli-Armstrong’s model, and Maekawa et al.’s model. A new quantitative sensitivity analysis of the material flow stress is performed based on Johnson-Cook’s model covering a wide range of engineering materials, including plain carbon steels with different carbon contents, alloyed steels, aluminum alloys with different chemical compositions and heat treatment conditions, copper and copper alloys, iron, nickel, tungsten alloys, etc. It is demonstrated that the first predominant factor governing the material flow stress is either strain hardening or thermal softening, depending on the specific work material employed and the varying range of temperatures. Strain-rate hardening is the least important factor governing the material flow stress, especially when machining aluminum alloys.

The mechanical properties of pure iron tested in compression over the temperature range 2 to 293 °K

1967 ◽  
Vol 261 (1121) ◽  
pp. 253-287 ◽  
Keyword(s):  
Mechanical Properties ◽  
Flow Stress ◽  
Strain Rate ◽  
Single Crystals ◽  
Yield Stress ◽  
Low Temperatures ◽  
Pure Iron ◽  
Constant Strain Rate ◽  
Frictional Stress ◽  
Strain And Strain Rate

The mechanical properties of pure iron single crystals and of polycrystalline specimens of a zone-refined iron have been measured in compression over the temperature and strain rate ranges 2.2 to 293 °K and 7 x 10 -7 to 7 x 10 -3 s -1 respectively. Various yield stress parameters were determined as functions of both temperature and strain rate, and the reversible changes in flow stress produced by isothermal changes of strain rate or by changes of temperature at constant strain rate were also measured as functions of temperature, strain and strain rate. Both the temperature variation of the flow stress and the strain rate sensitivity of the flow stress were generally identical for the single crystals ( ca. 0.005/M carbon) and the polycrystalline specimens ( ca. 9/M carbon). At low temperatures, the temperature dependence of the yield stress was smaller than that of the flow stress at high strains, probably because of the effects of mechanical twinning, but once again the behaviour of single and polycrystalline specimens was very similar. Below 10 °K, both the flow stress and the extrapolated yield stress were independent of temperature. The results show that macroscopic yielding and flow at low temperatures are both governed by the same deformation mechanism, which is not very impurity sensitive, even in the very low carbon range covered by the experiments. The flow stress near 0 °K is ca. 5.8 x 10 -3 u where [i is the shear modulus. On the basis of a model for thermally activated flow, the activation volume at low temperatures (high stresses) is found to be ca. 5 b 3 . The exponent in the empirical power law for the dislocation velocity against stress relation is ca. 3 near room temperature, but becomes quite large at low temperatures. The results indicate that macroscopic deformation at low temperatures is governed by some kind of lattice frictional stress (Peierls-Nabarro force) acting on dislocations.

An Integral Method to Determine Workpiece Flow Stress and Friction Characteristics in Metal Cutting

2015 ◽  
Vol 9 (6) ◽  
pp. 775-781
Author(s):  
Norfariza Wahab ◽  
◽  
Yumi Inatsugu ◽  
Satoshi Kubota ◽  
Soo-Young Kim ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Cutting Forces ◽  
High Speed ◽  
Metal Cutting ◽  
Cutting Edge ◽  
Cutting Process ◽  
Machining Parameters ◽  
Friction Characteristics ◽  
High Speed Cutting

In recent times, numerical simulation techniques have been commonly used to estimate and predict machining parameters such as cutting forces, stresses, and temperature distribution. However, it is very difficult to estimate the flow stress of a workpiece and the friction characteristics at a tool/chip interface, particularly during a high-speed cutting process. The objective of this study is to improve the accuracy of the present method and simultaneously determine the characteristics of the flow stress of a workpiece and friction at the cutting edge under a high strain rate and temperature during the cutting process. In this study, the Johnson-Cook (JC) flow stress model is used as a function of strain, strain rate, and temperature. The friction characteristic was estimated by minimizing the difference between the predicted and measured results of principal force, thrust force, and shear angle. The shear friction equation was used to estimate the friction characteristics. Therefore, by comparing the measured values of the cutting forces with the predicted results from FEM simulations, an expression for workpiece flow stress and friction characteristics at the cutting edge during a high-speed cutting process was estimated.

Fundamentals of Extrusion

2000 ◽  
pp. 1-29
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Extrusion Ratio ◽  
Strain And Strain Rate ◽  
Plastic Theory

Abstract This chapter discusses the basic differences between direct and indirect extrusion, the application of plastic theory, the significance of strain and strain rate, friction, and pressure, and factors such as alloy flow stress and extrusion ratio, which influence the quality of material exiting the die and the amount of force required.

The Energy Required for High-Speed Shearing of Steel

1971 ◽  
Vol 13 (2) ◽  
pp. 110-115 ◽  
Author(s):  
T. A. C. Stock ◽  
A. L. Wingrove
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
High Speed ◽  
Carbon Steels ◽  
Adiabatic Heating ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
Strain And Strain Rate

Some results are presented relating to the effects of shearing velocity on the energy required for shearing of both high and low carbon steels. Analyses of these results suggest an explanation of some of the apparently contradictory findings of other workers. The results obtained may be explained in terms of the relative imbalance between plastic softening due to adiabatic heating and increase in flow stress due to strain and strain rate.

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