scholarly journals An Explanation of the Apparent Bridgman Effect in Merchant’s Orthogonal Cutting Results

1967 ◽  
Vol 89 (3) ◽  
pp. 549-555 ◽  
Author(s):  
P. L. B. Oxley ◽  
M. J. M. Welsh
Keyword(s):  
Shear Strength ◽  
Flow Stress ◽  
Strain Rate ◽  
Hydrostatic Stress ◽  
Orthogonal Cutting ◽  
Shear Angle ◽  
Experimental Results ◽  
Variable Flow ◽  
Rate Dependent ◽  
Work Material

In Merchant’s modified shear angle solution, it is assumed following Bridgman that the shear strength of the work material is a function of the hydrostatic stress. Although Merchant’s experimental results confirm the assumed relation, subsequent workers have failed to obtain such agreement. In this paper, it is shown that Merchant’s results can be explained independently of the Bridgman effect by considering the variable flow stress properties of the work material, which are strain-rate dependent.

Predicting the strain rate in the zone of intense shear in which the chip is formed in machining from the dynamic flow stress properties of the work material and the cutting conditions

1977 ◽  
Vol 356 (1686) ◽  
pp. 395-410 ◽  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Empirical Relation ◽  
Shear Strain Rate ◽  
Equilibrium Equations ◽  
Maximum Shear Strain ◽  
Line Field ◽  
Variable Flow ◽  
Stress Equilibrium ◽  
Work Material

In previous applications of an approximate machining theory in which account is taken of the strain rate and temperature dependence of the work material flow stress properties it has been found necessary to use an empirical relation to determine the maximum value of the maximum shear strain rate in the chip formation zone. In this paper the machining theory is further developed so that this strain rate can be obtained as part of the solution. Predicted values found in this way are shown to be in excellent agreement with the rather limited number of experimental strain rate results which are available. The paper ends by showing that if the work material is allowed to approach the ideal constant flow stress material usually assumed in slip-line field theory then the predicted strain rates become extremely large. However, it is still found necessary in calculating the corresponding hydrostatic stresses to use the stress equilibrium equations for a variable flow stress material as the variable flow stress terms do not diminish as rapidly as might have been expected.

A Modified Peric Model for Al-Mg Alloy Sheet with Rate-Independent Initial Yield Stress at Warm Temperatures

2019 ◽  
Vol 287 ◽  
pp. 3-7
Author(s):  
Yong Zhang ◽  
Qing Zhang ◽  
Yuan Tao Sun ◽  
Xian Rong Qin
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Yield Stress ◽  
Constitutive Models ◽  
Mg Alloy ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Rate Dependent ◽  
Dependent Flow

The constitutive modeling of aluminum alloy under warm forming conditions generally considers the influence of temperature and strain rate. It has been shown by published flow stress curves of Al-Mg alloy that there is nearly no effect of strain rate on initial yield stress at various temperatures. However, most constitutive models ignored this phenomenon and may lead to inaccurate description. In order to capture the rate-independent initial yield stress, Peric model is modified via introducing plastic strain to multiply the strain rate, for eliminating the effect of strain rate when the plastic strain is zero. Other constitutive models including the Wagoner, modified Hockett–Sherby and Peric are also considered and compared. The results show that the modified Peric model could not only describe the temperature-and rate-dependent flow stress, but also capture the rate-independent initial yield stress, while the Wagoner, modified Hockett–Sherby and Peric model can only describe the temperature-and rate-dependent flow stress. Moreover, the modified Peric model could obtain proper static yield stress more naturally, and this property may have potential applications in rate-dependent simulations.

Correlation of wear and work in dual pivoted jaw crusher tests

2018 ◽  
Vol 234 (3) ◽  
pp. 334-349
Author(s):  
Juuso Terva ◽  
Kati Valtonen ◽  
Pekka Siitonen ◽  
Veli-Tapani Kuokkala
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Mass Loss ◽  
Lower Amount ◽  
Jaw Crusher ◽  
Rate Dependent ◽  
Sliding Motion ◽  
The Relationship

A laboratory sized jaw crusher with uniform movement of the jaws, the dual pivoted jaw crusher, was used to determine the relationship between wear and work. Wear was concentrated on the jaw plates opposing each other and was measured as mass loss of the specimens. Work was measured directly from the force and displacement of the instrumented jaw, which allowed work to accumulate only from the actual crushing events. The tests were conducted with several jaw geometries and with two motional settings, where the relation of compressive and sliding motion between the jaws was varied. The tests showed that the relation between wear and work was constant in many of the tested cases. In certain tests with larger lateral and faster contact speed, wear occurred at relatively lower amounts of work. This behavior was more definite when the relation of wear and work was investigated using modified Archards wear equation. The results indicate that the lower amount of needed work could stem from the material reaching a dynamic situation, where the flow stress becomes increasingly strain-rate dependent.

An Investigation of the Predicting Capabilities of a Variable Flow Stress Machining Theory

2001 ◽  
Author(s):  
P. Mathew
Keyword(s):  
Flow Stress ◽  
Material Flow ◽  
Three Dimensional ◽  
Experimental Results ◽  
Two Dimensional ◽  
Variable Flow ◽  
Comparative Results ◽  
Intermittent Cutting ◽  
Theoretical Results ◽  
Modelling Approach

Abstract The Oxley Machining Theory, which has been developed over the last 40 years, is presented in this paper. The capability of the model is described with its initial two-dimensional machining approach followed by the extension to the generalised model for three-dimensional machining. The theoretical results from the model are compared with the experimental results to determine the model capability. A brief description of the work associated with the effect of strain hardening at the interface is presented and comparative results are shown. A further extension of the model to intermittent cutting process of reaming is also presented and a comparison with the experimental results indicates the model developed is quite capable of predicting cutting forces for reaming. In explaining the results obtain, the assumptions made are explained and the inputs required. The limitations of the modelling approach are presented. It is pointed out that the Oxley model is a versatile model as long as proper description of the material flow stress properties is presented.

A Methodology to Determine Work Material Flow Stress and Tool-Chip Interfacial Friction Properties by Using Analysis of Machining

2004 ◽  
Author(s):  
Tug˘rul O¨zel ◽  
Erol Zeren
Keyword(s):  
Flow Stress ◽  
Material Flow ◽  
Orthogonal Cutting ◽  
Material Model ◽  
Interfacial Friction ◽  
Frictional Stress ◽  
Rake Face ◽  
Friction Characteristics ◽  
Work Material ◽  
1045 Steel

In this paper, we develop a methodology to determine flow stress at the machining regimes and friction characteristics at the tool-chip interface from the results of orthogonal cutting tests. We utilize metal cutting analysis originally developed by late Oxley and present some improvements. We also evaluate several temperature models in calculating the average temperatures at primary and secondary deformation zones and present comparisons with the experimental data obtained for AISI 1045 steel through assessment of machining models (AMM) activity. The proposed methodology utilizes measured forces and chip thickness obtained through a basic orthogonal cutting test. We conveniently determine work material flow stress at the primary deformation zone and the interfacial friction characteristics along tool rake face. Calculated friction characteristics include parameters of the normal and frictional stress distributions on the rake face. Determined flow stress data from orthogonal cutting tests is combined with the flow stress measured through split-hopkinson pressure bar (SHPB) tests and the Johnson-Cook work material model is obtained. Therefore, with this methodology, we extend the applicability of Johnson-Cook work material model to machining regimes.

Strain Rate Dependent Flow Stress and Energy Absorption Behaviour of Cast CrMnNi TRIP/TWIP Steels

2011 ◽  
Vol 82 (9) ◽  
pp. 1087-1093 ◽  
Author(s):  
L. Krüger ◽  
S. Wolf ◽  
S. Martin ◽  
U. Martin ◽  
A. Jahn ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Energy Absorption ◽  
Rate Dependent ◽  
Twip Steels ◽  
Dependent Flow

A Methodology to Determine Work Material Flow Stress and Tool-Chip Interfacial Friction Properties by Using Analysis of Machining

2005 ◽  
Vol 128 (1) ◽  
pp. 119-129 ◽  
Author(s):  
Tuğrul Özel ◽  
Erol Zeren
Keyword(s):  
Flow Stress ◽  
Normal Stress ◽  
Material Flow ◽  
Orthogonal Cutting ◽  
Material Model ◽  
Interfacial Friction ◽  
Rake Face ◽  
Friction Characteristics ◽  
Work Material ◽  
1045 Steel

In this paper, we develop a methodology to determine flow stress at the machining regimes and friction characteristics at the tool-chip interface from the results of orthogonal cutting tests. We utilize metal cutting analysis originally developed by late Oxley and present some improvements. We also evaluate several temperature models in calculating the average temperatures at primary and secondary deformation zones and present comparisons with the experimental data obtained for AISI 1045 steel through assessment of machining models (AMM) activity. The proposed methodology utilizes measured forces and chip thickness obtained through a basic orthogonal cutting test. We conveniently determine work material flow stress at the primary deformation zone and the interfacial friction characteristics along the tool rake face. Calculated friction characteristics include parameters of the normal and frictional stress distributions on the rake face that are maximum normal stress σNmax, power exponent for the normal stress distribution, a, length of the plastic contact, lp, length of the tool-chip contact, lc, the average shear flow stress at tool-chip interface, kchip, and an average coefficient of friction, μe, in the sliding region of the tool-chip interface. Determined flow stress data from orthogonal cutting tests is combined with the flow stress measured through split-hopkinson pressure bar (SHPB) tests and the Johnson-Cook work material model is obtained. Therefore, with this methodology, we extend the applicability of a Johnson-Cook work material model to machining regimes.

scholarly journals An Improved Johnson–Cook Constitutive Model and Its Experiment Validation on Cutting Force of ADC12 Aluminum Alloy During High-Speed Milling

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1038
Author(s):  
Xinxin Meng ◽  
Youxi Lin ◽  
Shaowei Mi
Keyword(s):  
Aluminum Alloy ◽  
Flow Stress ◽  
Constitutive Equation ◽  
Constitutive Model ◽  
Strain Rate ◽  
Cutting Force ◽  
High Speed ◽  
Cutting Speed ◽  
Experimental Results ◽  
Element Analysis

Because of the massive work and high cost of milling experiments, finite element analysis technology (FEA) was used to analyze the milling process of ADC12 aluminum alloy. An improved Johnson–Cook (J–C) constitutive equation was fitted by a series of dynamic impact tests in different strain rates and temperatures. It found that the flow stress gradually increases as the strain rate rises, but it decreases as the test temperature rises. Compared with the J–C constitutive model, the predicted flow stress by the improved J–C constitutive model was closer to the experimental results when the strain rate was larger than 8000 s−1 and the temperature was higher than 300 °C. A two-dimensional cycloidal cutting simulation model was constructed based on the two J–C constitutive equations which was validated by milling experiments at different cutting speeds. The simulation results based on the improved J–C constitutive equation were closer to the experimental results and showed the cutting force first increased and then decreased, with cutting speed increasing, reaching a maximum at 600 m/min.

Experimental Study on Effects of Feed per Tooth on Shear Angle and Friction Angle in Orthogonal Milling of Titanium Alloy

2014 ◽  
Vol 941-944 ◽  
pp. 1947-1951
Author(s):  
Wan Zhu Liu ◽  
Qiang Liu
Keyword(s):  
Titanium Alloy ◽  
Physical Phenomenon ◽  
Orthogonal Cutting ◽  
Friction Angle ◽  
Milling Process ◽  
Shear Angle ◽  
Experimental Results ◽  
Force Modeling ◽  
Increase With Increase ◽  
Cutting Model

Shear angle and friction angle are the two characteristic parameters in orthogonal cutting model. This paper investigated effects of feed per tooth on shear angle and friction angle in orthogonal milling of titanium alloy Ti6Al4V by experimental approach. Three different straight tooth milling tool with different rake angles are used in this research. Experimental results reveals that in orthogonal milling of Ti6Al4V alloy, shear angle will decrease with increase of feed per tooth and friction angle will increase with increase of feed per tooth. And then variation of shear angle and friction angle affect the values of force coefficients. The experimental results provide deep understand of basic physical phenomenon in milling process and sheds light on more accurate cutting force modeling.

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