The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Taylan Altan - One of the best experts on this subject based on the ideXlab platform.
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determination of biaxial Flow Stress using frictionless dome test
Procedia Engineering, 2014Co-Authors: Adam Groseclose, Hyunsung Son, Jim Dykeman, Taylan AltanAbstract:Abstract The frictionless dome test can be used to evaluate formability and determine the Flow Stress curve of sheet materials under biaxial forming conditions. The Flow Stress curve, obtained from the frictionless dome test can be determined up to larger strains than in tensile test. As a result the need for extrapolation of the Stress-strain curve is reduced. The objectives of this study are to (a) for a given sheet material determine K and n values in Hollomon's Law (σ = Kɛ n ) by using experimental punch force vs. stroke curve and (b) develop the computer program, “PRODOME”, to automate the calculation of K and n values.
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determination of Flow Stress and interface friction at elevated temperatures by inverse analysis technique
Journal of Materials Processing Technology, 2005Co-Authors: Hyunjoong Cho, Taylan AltanAbstract:Abstract An inverse analysis technique has been introduced to obtain the Flow Stress of the bulk and sheet materials at elevated temperatures. The inverse problem is defined as the minimization of the differences between the experimental measurements and the corresponding FEM predictions. As reference material tests, the ring compression and the modified limiting dome height test (sheet blank with a hole at the center stretched with a hemispherical punch) at elevated isothermal conditions were selected. The friction condition at the tool/workpiece interface is identified from the geometrical changes that occur in deformed samples. It is shown that the developed inverse analysis technique is reliable and can determine the Flow Stress and friction factor simultaneously from one set of material tests.
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effects of Flow Stress and friction models in finite element simulation of orthogonal cutting a sensitivity analysis
Machining Science and Technology, 2005Co-Authors: Partchapol Sartkulvanich, Taylan Altan, Abdullah GocmenAbstract:ABSTRACT The accuracy of the results obtained from FEM simulation of machining operations depends on the accuracy of input data. Especially, the Flow Stress data of the workpiece and the friction along tool–chip interface are extremely crucial for the prediction of cutting variables such as cutting forces, chip formation and temperature distribution. The experimental procedures used to determine Flow Stress and friction are difficult and costly. Understanding how the input variables affect the FEM predictions can lead to more reliable simulation of machining processes. In this study, the sensitivity analysis of Flow Stress and friction on FEM simulation is conducted. A power law equation was assumed to represent the Flow Stress of the workpiece. Magnitudes and dependency of the Flow Stress upon temperature were varied and used in cutting simulations. Sensitivity analysis on friction was conducted by assuming different constant values of friction factors (for shear friction law) and coefficients of frictio...
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determination of Flow Stress for metal cutting simulation a progress report
Journal of Materials Processing Technology, 2004Co-Authors: Partchapol Sartkulvanich, Frank Koppka, Taylan AltanAbstract:Abstract Flow Stress data at high deformation rates, necessary for FEA simulation of machining operations, are usually determined with the Hopkinson’s bar high-speed compression tests. In the present study orthogonal slot milling is used in conjunction with quick-stop tests. A computer program, called OXCUT developed at the ERC/NSM, was used to obtain Flow Stress data from measured forces and primary and secondary shear zone dimensions. Several materials, including AISI 1045, P20 and H13 were tested. The Flow Stress data obtained with the slot milling method were used to predict forces and temperatures using FEM. The predicted cutting forces were within 20% of experimental values. However, the predicted thrust forces were considerably lower, by about 40%, than the experimental values. Work is in progress to reduce these inaccuracies by improving the estimation of the coefficient of friction and the Flow Stress value at lower temperatures.
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an inverse energy approach to determine the Flow Stress of tubular materials for hydroforming applications
Journal of Materials Processing Technology, 2004Co-Authors: Matteo Strano, Taylan AltanAbstract:Abstract The accuracy of finite element method simulations of tube hydroforming (THF) is strongly dependent on the parameters of the Flow Stress law used to describe the plasticity of the tubular materials used. The hydraulic bulge test has been previously proposed as a quality control tool on incoming tubular materials, as well as a simple and effective way to obtain hardening and formability data directly from the tubes, rather than from the sheets used to roll-form the tubes. The present study describes an inverse approach for the determination of the Flow Stress of tubular materials from the bulge test, based on an energy balance. The proposed technique is very simple and therefore suitable to be used on any hydroforming press, as well as in simple bulging tooling.
Tugrul Ozel - One of the best experts on this subject based on the ideXlab platform.
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a methodology to determine work material Flow Stress and tool chip interfacial friction properties by using analysis of machining
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2006Co-Authors: Tugrul Ozel, Erol ZerenAbstract: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 Nmax, 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, e, 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. DOI: 10.1115/1.2118767
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determination of work material Flow Stress and friction for fea of machining using orthogonal cutting tests
Journal of Materials Processing Technology, 2004Co-Authors: Tugrul Ozel, Erol ZerenAbstract:Finite element analysis based techniques are available to simulate cutting processes and offer several advantages including prediction of tool forces, distribution of Stresses and temperatures, estimation of tool wear and residual Stresses on machined surfaces, optimization of cutting tool geometry and cutting conditions. However, work material Flow Stress and friction characteristics at cutting regimes are not always available. This paper utilizes a metal cutting model developed by Oxley and presents an improved methodology to characterize work material Flow Stress and friction at primary and secondary deformation zones around the cutting edge by utilizing orthogonal cutting tests. In this paper, Johnson–Cook (JC) constitutive work Flow Stress model is used to characterize work Flow Stress in deformation zones. The friction model is based on estimation of the normal Stress distribution over the rake face. The Stress distribution over the tool rake face can either directly be entered in FEA software or used in determining a coefficient of the friction at the tool-chip interface. The methodology is practical and estimates the unknowns of both the work material constitutive model and the friction model over the rake face. © 2004 Elsevier B.V. All rights reserved.
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a methodology to determine work material Flow Stress and tool chip interfacial friction properties by using analysis of machining
ASME 2004 International Mechanical Engineering Congress and Exposition, 2004Co-Authors: Tugrul Ozel, Erol ZereAbstract: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.© 2004 ASME
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determination of workpiece Flow Stress and friction at the chip tool contact for high speed cutting
International Journal of Machine Tools & Manufacture, 2000Co-Authors: Tugrul Ozel, Taylan AltanAbstract:Abstract This paper presents a methodology to determine simultaneously (a) the Flow Stress at high deformation rates and temperatures that are encountered in the cutting zone, and (b) the friction at the chip–tool interface. This information is necessary to simulate high-speed machining using FEM based programs. A Flow Stress model based on process dependent parameters such as strain, strain-rate and temperature was used together with a friction model based on shear Flow Stress of the workpiece at the chip–tool interface. High-speed cutting experiments and process simulations were utilized to determine the unknown parameters in Flow Stress and friction models. This technique was applied to obtain Flow Stress for P20 mold steel at hardness of 30 HRC and friction data when using uncoated carbide tooling at high-speed cutting conditions. The average strain, strain-rates and temperatures were computed both in primary (shear plane) and secondary (chip–tool contact) deformation zones. The friction conditions in sticking and sliding regions at the chip–tool interface are estimated using Zorev's Stress distribution model. The shear Flow Stress ( k chip ) was also determined using computed average strain, strain-rate, and temperatures in secondary deformation zone, while the friction coefficient ( μ ) was estimated by minimizing the difference between predicted and measured thrust forces. By matching the measured values of the cutting forces with the predicted results from FEM simulations, an expression for workpiece Flow Stress and the unknown friction parameters at the chip–tool contact were determined.
Swadesh Kuma Singh - One of the best experts on this subject based on the ideXlab platform.
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constitutive models to predict Flow Stress in austenitic stainless steel 316 at elevated temperatures
Materials & Design, 2013Co-Authors: Ami Gupta, V K Anirudh, Swadesh Kuma SinghAbstract:Strain, strain rate and temperature have a significant impact on the Flow Stress of a material. To study the impact of these factors on Flow Stress, quite a few empirical, semi-empirical constitutive models have been reported. In this work, four such models are being presented for estimation of Flow Stress on Austenitic Stainless Steel 316. While the Johnson Cook model, Modified Zerilli–Armstrong model are semi-empirical models, the Arrhenius type equation is a physical based equation. The Artificial Neural Network model on the other hand is trained based on the training data and employed to predict the Flow Stress on the testing data. The experiments for these data were conducted at various strain rates (0.1–0.0001 s−1) and at various temperatures (323–623 K). Values of Stress were taken at strain intervals of 0.05 (from 0.05 to 0.3) to evaluate the material constants of the constitutive models. A comparative study on the reliability of the four models has also been made at the end. The correlation coefficient values observed were 0.9423 (JC model), 0.9879 (modified ZA model), 0.9852 (modified Arrhenius type equation) and 0.9930 (ANN model).
Erol Zeren - One of the best experts on this subject based on the ideXlab platform.
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a methodology to determine work material Flow Stress and tool chip interfacial friction properties by using analysis of machining
Journal of Manufacturing Science and Engineering-transactions of The Asme, 2006Co-Authors: Tugrul Ozel, Erol ZerenAbstract: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 Nmax, 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, e, 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. DOI: 10.1115/1.2118767
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determination of work material Flow Stress and friction for fea of machining using orthogonal cutting tests
Journal of Materials Processing Technology, 2004Co-Authors: Tugrul Ozel, Erol ZerenAbstract:Finite element analysis based techniques are available to simulate cutting processes and offer several advantages including prediction of tool forces, distribution of Stresses and temperatures, estimation of tool wear and residual Stresses on machined surfaces, optimization of cutting tool geometry and cutting conditions. However, work material Flow Stress and friction characteristics at cutting regimes are not always available. This paper utilizes a metal cutting model developed by Oxley and presents an improved methodology to characterize work material Flow Stress and friction at primary and secondary deformation zones around the cutting edge by utilizing orthogonal cutting tests. In this paper, Johnson–Cook (JC) constitutive work Flow Stress model is used to characterize work Flow Stress in deformation zones. The friction model is based on estimation of the normal Stress distribution over the rake face. The Stress distribution over the tool rake face can either directly be entered in FEA software or used in determining a coefficient of the friction at the tool-chip interface. The methodology is practical and estimates the unknowns of both the work material constitutive model and the friction model over the rake face. © 2004 Elsevier B.V. All rights reserved.
C. J. Fang - One of the best experts on this subject based on the ideXlab platform.
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Flow Stress behavior of commercial pure titanium sheet during warm tensile deformation
Materials & Design, 2012Co-Authors: L.c. Tsao, Hungyi Wu, J. C. Leong, C. J. FangAbstract:Abstract The Flow Stress behavior of commercial pure titanium (CP-Ti) sheet was studied by uniaxial warn tension tests at temperatures ranging from 623 K to 773 K and strain rates from 5.0 × 10 −2 to 8.3 × 10 −4 s −1 . A mathematical model using an updated Fields–Backofen (FB) equation was established to describe the Flow Stress behavior of CP-Ti during warm tensile testing. The results show that the Flow Stress of CP-Ti is evidently affected by both deformation temperature and strain rate, i.e., the Flow Stress decreases with the decrease of strain rate and the increase of deformation temperature, and a typical characteristic of dynamic recrystallization softening. The Flow Stress curves analyzed by FB equation shows good agreement with experimental Flow curves for different temperatures and strain rates for CP-Ti sheet.
