Extension of Oxley’s Analysis of Machining to Use Different Material Models

2003 ◽  
Vol 125 (4) ◽  
pp. 656-666 ◽  
Author(s):  
Amir H. Adibi-Sedeh ◽  
Vis Madhavan ◽  
Behnam Bahr
Keyword(s):  
Strain Rate ◽  
Shear Zone ◽  
Shear Force ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Material Model ◽  
Shear Zones ◽  
Carbon Steels ◽  
Maximum Temperature

The aim of the present work is to extend the applicability of Oxley’s analysis of machining to a broader class of materials beyond the carbon steels used by Oxley and co-workers. The Johnson-Cook material model, history dependent power law material model and the Mechanical Threshold Stress (MTS) model are used to represent the mechanical properties of the material being machined as a function of strain, strain rate and temperature. A few changes are introduced into Oxley’s analysis to improve the consistency between the various assumptions. A new approach has been introduced to calculate the pressure variation along the alpha slip lines in the primary shear zone including the effects of both the strain gradient and the thermal gradient along the beta lines. This approach also has the added advantage of ensuring force equilibrium of the primary shear zone in a macroscopic sense. The temperature at the middle of the primary shear zone is calculated by integrating the plastic work thereby eliminating the unknown constant η. Rather than calculating the shear force from the material properties corresponding to the strain, strain rate and temperature of the material at the middle of the shear zone, the shear force is calculated in a consistent manner using the energy dissipated in the primary shear zone. The thickness of the primary and secondary shear zones, the heat partition at the primary shear zone, the temperature distribution along the tool-chip interface and the shear plane angle are all calculated using Oxley’s original approach. The only constant used to fine tune the model is the ratio of the average temperature to the maximum temperature at the tool-chip interface (ψ). The performance of the model has been studied by comparing its predictions with experimental data for 1020 and 1045 steels, for aluminum alloys 2024-T3, 6061-T6 and 6082-T6, and for copper. It is found that the model accurately reproduces the dependence of the cutting forces and chip thickness as a function of undeformed chip thickness and cutting speed and accurately estimates the temperature in the primary and secondary shear zones.

Material Characterization for Metal-Cutting Force Modeling

1989 ◽  
Vol 111 (2) ◽  
pp. 210-219 ◽  
Author(s):  
D. A. Stephensen
Keyword(s):  
Shear Stress ◽  
Strain Rate ◽  
Cutting Force ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Stress And Strain ◽  
Force Model ◽  
Wide Range

Widely applicable machining simulation programs require reliable cutting force estimates, which currently can be obtained only from process-dependent machinability databases. The greatest obstacle to developing a more basic, efficient approach is a lack of understanding of material yield and frictional behavior under the unique deformation and frictional conditions of cutting. This paper describes a systematic method of specifying yield stress and friction properties needed as inputs to process-independent cutting force models. Statistically designed end turning tests are used to generate cutting force and chip thickness data for a mild steel and an aluminum alloy over a wide range of cutting conditions. Empirical models are fit for the cutting force and model-independent material parameters such as the tool-chip friction coefficient and shear stress on the shear plane. Common material yield behavior assumptions are examined in light of correlations between these parameters. Results show no physically meaningful correlation between geometric shear stress and strain measures, a weak correlation between geometric stress and strain rate measures, and a strong correlation between material properties and input variables such as cutting speed and rake angle. An upper bound model is used to fit four- and five-parameter polynomial strain-rate sensitive constitutive equations to the data. Drilling torques calculated using this model and an empirical turning force model agree reasonably well with measured values for the same material combination, indicating that end turning test results can be used to estimate mean loads in a more complicated process.

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.

Experimental Investigation of the Characteristics of Dynamic Cutting Process

1977 ◽  
Vol 99 (2) ◽  
pp. 410-418 ◽  
Author(s):  
M. M. Nigm ◽  
M. M. Sadek
Keyword(s):  
Experimental Investigation ◽  
Theoretical Model ◽  
High Speed ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Rake Angle ◽  
Experimental Results ◽  
High Speed Photography ◽  
Cutting Coefficients

The dynamic response of the shear plane and the variations of the dynamic cutting coefficients are experimentally investigated at various values of feed, cutting speed, rake angle, clearance angle, frequency, and amplitude of chip thickness modulation. Wave generating and wave removing cutting tests, in which high-speed photography is used to investigate the geometry of chip formation, are carried out. The theoretical model of dynamic cutting developed in [1] is assessed with reference to these experimental results. A comparison between this model and previous models in relation to the experimental results is also presented.

New Development in the Theory of the Metal-Cutting Process: Part II—The Theory of Chip Formation

1961 ◽  
Vol 83 (4) ◽  
pp. 557-568 ◽  
Author(s):  
P. Albrecht
Keyword(s):  
Shear Zone ◽  
Tool Life ◽  
Chip Formation ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Shear Plane ◽  
Cutting Process ◽  
Chip Formation Mechanism ◽  
Bending Stresses ◽  
Set Up

Introduction of the concept of ploughing into the metal-cutting process lead to the abandoning of the assumption of collinearity of the resultant force on tool face and on the shear plane. With this understanding the tool face force is found to produce a bending effect causing bending stresses in the shear zone. Study of the chip formation mechanism when varying cutting speed showed that increased bending action reduces the shear angle and vice versa. A set-up for the development of an analytical model of the chip formation process based on the combined effect of shear and bending stresses in the shear zone has been given. Application of the gained insight to the design of the cutting tool for maximum tool life by controlling of the chip-tool contact was suggested. Brief introduction to the study of cyclic events in chip formation and their relation to the tool life is presented.

Strain localization mechanism of graphitic carbon-bearing rocks: Constraints from microstructure, texture and graphite geothermometry

2021 ◽  
Author(s):  
Meixia Lyu ◽  
Shuyun Cao
Keyword(s):  
Shear Zone ◽  
Strain Localization ◽  
Carbonaceous Material ◽  
Shear Zones ◽  
Graphitic Carbon ◽  
Maximum Temperature ◽  
Low Grade ◽  
High Grade ◽  
Grade Metamorphism ◽  
Average Temperature

<p><strong>Abstracts:</strong></p><p>Graphitic carbon-bearing rocks can occur in low- to high-grade metamorphic units. In low-grade matamorphic rocks, graphitic carbon is often associated with brittle fault gouge whereas in middle- to high-grade metamorphic rocks, graphitic carbon commonly occurs in marble, schist or paragneiss. Previous studies showed that carbonaceous material gradually ordered from the amorphous stage, e.g. graphitization, is mainly controlled by increasing thermal metamorphism and has a good correlation with the metamorphic temperature. Besides, this ordered process is irreversible and the resulting structure is not affected by late metamorphism. Subsequently, the degree of graphitization is believed to be a reliable indicator of peak temperature conditions in the metamorphic rock. In this contribution, based on detailed field observations, the variably deformed and metamorphosed graphitic gneisses to phyllites, located within the footwall and hanging-walls unit of the Cenozoic Ailaoshan-Red River strike-slip shear zone are studied. According to lithological features and temperature determined by Raman spectra of carbonaceous material, these graphitic rocks and deformation fabrics are divided into three types. Type I is represented by medium–grade metamorphism and strongly deformed rocks with an average temperature of 509 °C and a maximum temperature of 604 °C. Type II is affected by low-grade metamorphism and deformed rocks with an average temperature of 420 °C. Type III is affected by lower–grade metamorphism and occurs in weakly deformed/undeformed rocks with an average temperature of 350 °C. Slip–localized micro–shear zone and laterally continuous or discontinuous slip planes constituted by graphitic carbon aggregates are developed in Types I and II. The electron back–scattered diffraction (EBSD) lattice preferred orientation (LPO) patterns of graphitic carbon grains were firstly observed in comparison with LPO patterns of quartz and switch from basal <a>, rhomb <a> to prism <a> slip systems, which indicate increasing deformation temperatures. According to the graphitic slip–planes, micro–shear zones and mylonitic foliation constituted by graphitic carbon minerals, we also propose that the development of fine–grained amorphous carbon plays an important role in rheological weakening of the whole rock during progressive ductile shearing.</p><p><strong>Key Words:</strong> graphitic carbon, strain localization, graphitic thermometry, slip–localized micro–shear zone, rheological weakening</p>

scholarly journals Strain Rate of Metal Deformation in the Machining Process from a Fluid Flow Perspective

2020 ◽  
Vol 10 (9) ◽  
pp. 3057
Author(s):  
Keguo Zhang ◽  
Keyi Wang ◽  
Zhanqiang Liu ◽  
Xiaodong Xu
Keyword(s):  
Fluid Flow ◽  
Strain Rate ◽  
High Speed ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Shear Plane ◽  
Cutting Process ◽  
Machining Process ◽  
Rake Face ◽  
Metal Deformation

Metal cutting speeds are getting faster with the development of high-speed cutting technology, and with the increase in cutting speed, the strain rate will become larger, which makes the study of the metal cutting process more inconvenient. At the same time, with the increase in strain rate, the dislocation movement controlling the plastic deformation mechanism of metal will change from thermal activation to a damping mechanism, which makes the metal deformation behave more like a fluid. Therefore, it is necessary to explore new ways of studying machining from the perspective of fluid flow. Based on this, a fluid model of the metal cutting process is established, and a method for calculating the strain rate is proposed from the point of view of flow. The results of the simulation and measurements are compared and analyzed. The results show that the strain rate on the rake face will be affected by the friction between the chip and tool; the nearer the distance between the chip layer and tool rake face, the bigger the strain rate will be. The strain rate in the central shear plane is much larger than in other areas along the shear plane direction, and in which two ends are the biggest. It can achieve rougher, quantitative research. This shows it is feasible to study machining from the viewpoint of fluid flow, though it still needs a lot of theoretical support and experimental confirmation.

Chip Prediction in Finite Element Modeling of the Chip Formation Process during Cutting Ti-6Al-4V Alloy

2011 ◽  
Vol 418-420 ◽  
pp. 1148-1153
Author(s):  
Yu Gang Ye
Keyword(s):  
Finite Element ◽  
Titanium Alloy ◽  
Strain Rate ◽  
Equivalent Stress ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Equivalent Strain ◽  
Forming Process ◽  
Serrated Chip ◽  
Equivalent Strain Rate

Based on the theory of adiabatic shearing, the forming process of a serrated chip during cutting Ti-6Al-4V titanium alloy was analyzed by comparing the results of the finite element (FE) calculations with the cutting experiments. The results show that the equivalent stress, equivalent strain and equivalent strain rate within a ribbon chip varied a little, but they varied a lot within a serrated chip. Moreover, the effect of cutting speed on equivalent strain rate is greater than on the equivalent stress and equivalent strain within a serrated chip. It can also be found from the results that there are small gaps between the simulation results and experimental results for the chip thickness and sawtooth height, while there is a big gap for saw-tooth pitch. This means that the simulation model has its limitations for accurate simulation of micro-geometric shape of a chip during cutting the Ti-6Al-4V titanium alloy, and further research remains to be done.

scholarly journals Crystallographic and Seismic Anisotropies of Calcite at Different Depths: A Study Using Quantitative Texture Analysis by Neutron Diffraction

2019 ◽  
Author(s):  
Michele Zucali ◽  
Daniel Chateigner ◽  
Bachir Ouladdiaf
Keyword(s):  
Neutron Diffraction ◽  
Texture Analysis ◽  
Shear Zone ◽  
Shear Plane ◽  
Shear Zones ◽  
Orientation Distribution ◽  
Western Alps ◽  
Type B ◽  
Fold Belts ◽  
Different Depths

Eight samples of limestones and marbles were studied by neutron diffraction to collect Quantitative Texture (i.e. Crystallographic Preferred Orientations or CPO) of calcite deforming at different depths in the crustal profile. We studied the different CPO patterns developed in shear zones at different depth and their influence on seismic anisotropies. Samples were collected in the French and Italian Alps, Apennines and Paleozoic Sardinian basement. They are characterized by different mesoscopic fabrics, from isotropic to highly anisotropic (e.g. mylonite shear zone). Mylonite limestones occur as shear zone horizons within the Cenozoic Southern Domain in Alpine thrust-and-fold belts (Italy), the Briançonnais domain of the Western Alps (Italy-France border), the Sardinian Paleozoic back-thrusts or in the Austroalpine Upper units. The analyzed marbles were collected in the Carrara Marble, in the Austroalpine Units in the Central (Mortirolo) and Western Alps (Valpelline). The temperature and depth of development of the fabrics vary from shallow, < 100°C, to more than 800°C at depth of about 30 km. Quantitative Texture Analysis shows different types of patterns for calcite CPO, from random (Type A) to strongly textured (Type B); Type B may be further separated in orthorhombic and monoclinic, based on the angle defined with the mesoscopic fabrics, namely the shear plane. Seismic anisotropies were calculated by homogenizing the single crystal elastic tensor, using the Orientation Distribution Function calculated by the Quantitative Texture Analysis. The resulting P- and S-waves anisotropies show a wide variability due to the textural types, depth within the crustal profile, and dip of the shear planes.

Influence of Material and Constitutive Models on Friction Analysis for Modelling in Machining Cellular Metal Structures

2015 ◽  
Vol 727-728 ◽  
pp. 292-298 ◽  
Author(s):  
Rafael Guerra Silva ◽  
Uwe Teicher ◽  
Andreas Nestler ◽  
Alexander Brosius
Keyword(s):  
Constitutive Model ◽  
Constitutive Models ◽  
Chip Thickness ◽  
Shear Plane ◽  
Cutting Parameters ◽  
Contact Length ◽  
Friction Model ◽  
Maximum Temperature ◽  
Metal Structures ◽  
Selection Of

The selection of an adequate friction model is an important aspect inthe finite element modeling of machining. Previously, different friction modelshave been compared, but the influence of the constitutive model or theworkpiece material have not been considered. This article focuses on theinfluence of the material and the constitutive model on the evaluation of thefriction model in machining. Numerical experiments are performed on threedifferent materials using different constitutive models. For every combinationof material and constitutive model, several simulations using different Coulombcoefficients, but the same cutting parameters, are performed. Several variablesare evaluated: cutting force, shear plane angle, chip-tool contact length,maximum temperature and maximum stress. The results reveal that the workpiecematerial plays an important role in the evaluation of the friction model. Theyalso show that there is significant influence from the constitutive models oncontact length, curvature ratio and chip thickness.

Prediction of Temperature and Stress Distribution During Micro-Cutting of Ti-6Al-4V

2007 ◽  
Author(s):  
Dong Lu ◽  
Jianfeng Li ◽  
Yiming Rong ◽  
Jie Sun ◽  
Zhongqiu Wang
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Maximum Shear Stress ◽  
Cutting Temperature ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Machining Process ◽  
Maximum Temperature ◽  
Uncut Chip Thickness ◽  
Micro Cutting

A finite element method (FEM) for predicting the temperature and stress distribution in micro-cutting of Ti-6Al-4V is presented. The flow stress of Ti-6Al-4V is taken as a function of strain, strain rate and temperature in order to reflect realistic behavior in machining process. Diamond cutting tool is used. From simulation, cutting force, thrust force, cutting temperature and distribution of cutting temperature and stress are obtained. The effects of cutting speed and uncut chip thickness on the maximum temperature and maximum shear stress are analyzed and size effect is observed. The simulation results show that in micro-cutting of Ti-6Al-4V the maximum temperature locates on the shear plane. And the maximum shear stress locates on the stick region. The maximum temperature decreases as the uncut chip thickness decreases, and it increases with an increase in cutting speed. The maximum shear stress increases as the uncut chip thickness decreases, and it decreases with an increase in cutting speed.

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