The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
J M P Martins - One of the best experts on this subject based on the ideXlab platform.
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calibration of a modified johnson Cook Model using the virtual fields method and a heterogeneous thermo mechanical tensile test
International Journal of Mechanical Sciences, 2021Co-Authors: J M P Martins, Sandrine Thuillier, A AndradecamposAbstract:Abstract Classical calibration procedures for phenomenological thermo-elasto-viscoplastic constitutive Models usually involve a large number of tests to identify all the material parameters, leading to long experimental campaigns. In the present work, a novel calibration methodology that takes full advantage of full-field measurements of a heterogeneous test is proposed. It relies on an innovative combination of the Virtual Fields Method and a thermo-mechanical heterogeneous test carried out on a Gleeble 3500 system. To assess the feasibility of this novel calibration methodology, a modified version of the Johnson-Cook (J-C) Model and dual-phase steel DP980 are selected. The three terms of the Model that correspond to strain-hardening, temperature, and strain rate effects are calibrated simultaneously for the thermo-mechanical behaviour of this material. The calibration is attempted using a single test carried out at a constant displacement rate. This procedure is repeated for three tests at nominal strain rates of 10 − 4 , 10 − 3 and 10 − 2 s − 1 . Accurate predictions of the flow stress are attained, but the information of a single test is insufficient to capture the positive strain rate sensitivity of the material. The three tests are then combined in an experimental database to calibrate the Model. The results show that the positive strain rate sensitivity is reasonably predicted in the considered range of temperatures. These results unveil the potential of this methodology to simplify the calibration process of thermo-elasto-viscoplastic constitutive Model.
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calibration of johnson Cook Model using heterogeneous thermo mechanical tests
Procedia Manufacturing, 2020Co-Authors: J M P Martins, A Andradecampos, Sandrine ThuillierAbstract:Abstract In the present work, a calibration methodology based on full-field measurements from heterogeneous thermo-mechanical tests is introduced. In order to evaluate the feasibility of this methodology, the widely adopted Johnson-Cook Model is chosen. This calibration methodology relies on the Finite Element Model Updating (FEMU) method to take full advantage of the information contained in full-field measurements and thus, simultaneously calibrate the three terms of the Johnson-Cook Model regarding strain hardening, temperature and strain rate. A virtual experimental database composed of strain fields and load output from three heterogeneous tests performed at different average strain rates is used. The minimisation of the least-square objective function is performed by the gradient-based Levenberg-Marquardt optimisation algorithm. A detailed analysis of the virtual database and objective function is performed and discussed. Furthermore, the robustness of the proposed methodology is tested with noisy data.
V Madhu - One of the best experts on this subject based on the ideXlab platform.
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a modified johnson Cook Model for feconicr high entropy alloy over a wide range of strain rates
Materials Letters, 2018Co-Authors: Ravindranadh Bobbili, V MadhuAbstract:Abstract The objective of the study is to perform experiments on FeCoNiCr high entropy alloy under different strain rates ranging from 0.01 to 3500/s and also at temperatures of 25, 200, 400 and 600 °C. Considering the effects of work hardening and thermal softening at high strain rates, the flow behavior is characterized by employing the modified Johnson-Cook (J-C) and Zerilli–Armstrong (Z-A) Models. The triaxiality data showed the decrease in effective plastic strain at failure as triaxiality increases for all strain rates. Fracture constants have been evaluated.
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effect of strain rate and stress triaxiality on tensile behavior of titanium alloy ti 10 2 3 at elevated temperatures
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Ravindranadh Bobbili, V MadhuAbstract:Abstract In this study, Split hopkinson tension bar (SHTB) has been employed to investigate the dynamic tensile flow behavior of Ti-10-2-3 alloy at high strain rates and elevated temperatures. The combined effect of stress triaxiality, strain rate and temperature and on the tensile behavior of the alloy was evaluated. Johnson-Cook (J-C) constitutive and fracture Models were developed based on high strain rate tensile data. A modified Johnson–Cook Model was established and proved to have high accuracy. A comparative assessment has been done to confirm the accuracy of modified J–C Model based on finite element method (FEM). The improved Model provides better description on the influence of equivalent plastic strain rate and temperature on the plastic flow. The simulation results proved to be in good agreement with the experimental data. The fracture surfaces of specimens tested under various strain rates and temperatures were studied under scanning electron microscopy (SEM).
A Andradecampos - One of the best experts on this subject based on the ideXlab platform.
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calibration of a modified johnson Cook Model using the virtual fields method and a heterogeneous thermo mechanical tensile test
International Journal of Mechanical Sciences, 2021Co-Authors: J M P Martins, Sandrine Thuillier, A AndradecamposAbstract:Abstract Classical calibration procedures for phenomenological thermo-elasto-viscoplastic constitutive Models usually involve a large number of tests to identify all the material parameters, leading to long experimental campaigns. In the present work, a novel calibration methodology that takes full advantage of full-field measurements of a heterogeneous test is proposed. It relies on an innovative combination of the Virtual Fields Method and a thermo-mechanical heterogeneous test carried out on a Gleeble 3500 system. To assess the feasibility of this novel calibration methodology, a modified version of the Johnson-Cook (J-C) Model and dual-phase steel DP980 are selected. The three terms of the Model that correspond to strain-hardening, temperature, and strain rate effects are calibrated simultaneously for the thermo-mechanical behaviour of this material. The calibration is attempted using a single test carried out at a constant displacement rate. This procedure is repeated for three tests at nominal strain rates of 10 − 4 , 10 − 3 and 10 − 2 s − 1 . Accurate predictions of the flow stress are attained, but the information of a single test is insufficient to capture the positive strain rate sensitivity of the material. The three tests are then combined in an experimental database to calibrate the Model. The results show that the positive strain rate sensitivity is reasonably predicted in the considered range of temperatures. These results unveil the potential of this methodology to simplify the calibration process of thermo-elasto-viscoplastic constitutive Model.
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calibration of johnson Cook Model using heterogeneous thermo mechanical tests
Procedia Manufacturing, 2020Co-Authors: J M P Martins, A Andradecampos, Sandrine ThuillierAbstract:Abstract In the present work, a calibration methodology based on full-field measurements from heterogeneous thermo-mechanical tests is introduced. In order to evaluate the feasibility of this methodology, the widely adopted Johnson-Cook Model is chosen. This calibration methodology relies on the Finite Element Model Updating (FEMU) method to take full advantage of the information contained in full-field measurements and thus, simultaneously calibrate the three terms of the Johnson-Cook Model regarding strain hardening, temperature and strain rate. A virtual experimental database composed of strain fields and load output from three heterogeneous tests performed at different average strain rates is used. The minimisation of the least-square objective function is performed by the gradient-based Levenberg-Marquardt optimisation algorithm. A detailed analysis of the virtual database and objective function is performed and discussed. Furthermore, the robustness of the proposed methodology is tested with noisy data.
He Yang - One of the best experts on this subject based on the ideXlab platform.
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a modified johnson Cook Model for nc warm bending of large diameter thin walled ti 6al 4v tube in wide ranges of strain rates and temperatures
Transactions of Nonferrous Metals Society of China, 2018Co-Authors: Zhijun Tao, He Yang, Xiaoguang Fan, M A Jun, Li HengAbstract:Abstract Numerical control (NC) warm bending is a proven strategy to form the large diameter thin-walled (LDTW) Ti–6Al–4V tubes, which are typical light-weight and high-performance structural components urgently required in many industries. In virtue of unveiling the thermo-mechanical coupled deformation behaviors, uniaxial tensile tests were conducted on Ti–6Al–4V tube within wide ranges of temperatures (25–600 °C) and strain rates (0.00067–0.1 s−1). Moreover, a modified Johnson–Cook (JC) Model is proposed with a consideration of nonlinear strain rate hardening and the interaction between strain hardening and thermal softening. Resultantly, the present Model gives more accurate predictions for flow stress over the entire deformation ranges and the maximum error decreases by about 90%. By employing proposed Model to NC warm bending, preferable precision is obtained in predicting forming defects including fracture, wrinkling and over thinning. The present work lays foundation for the forming limit prediction and process optimization in NC warm bending of LDTW Ti–6Al–4V tubes.
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a modified johnson Cook Model for tensile flow behaviors of 7050 t7451 aluminum alloy at high strain rates
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015Co-Authors: Jin Qiang Tan, Mei Zhan, Shuai Liu, Tao Huang, Jing Guo, He YangAbstract:Abstract The uniaxial quasi-static and dynamic tensile tests were conducted at different strain rates (10 –3 s −1 , 800 s −1 , 1900 s −1 and 2900 s −1 ) for 7050-T7451 aluminum alloy. Then, research of the strain rate hardening coefficient in the original Johnson–Cook Model at different strains and strain rates showed that the coefficient is a function of strain and strain rate from the tensile experimental results. Furthermore, a modified Johnson–Cook Model was proposed to describe the flow behaviors of the studied alloy based on the correction to the strain rate hardening coefficient. Comparisons between the experimental data and predicted results using the original JC Model, Khan–Liu (KL) Model and the modified JC Model showed that a better agreement can be obtained applying the modified Model than the other two Models. Verifications for predicting three new high strain rates (1500 s −1 , 2500 s −1 and 3500 s −1 ) experimental data demonstrated the modified JC Model can provide an accurate description for the dynamic behaviors of the studied alloy.
Mark Haney - One of the best experts on this subject based on the ideXlab platform.
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computational Modeling of titanium structures subjected to thermo chemo mechanical environment
International Journal of Solids and Structures, 2010Co-Authors: Caglar Oskay, Mark HaneyAbstract:Abstract This manuscript provides a new coupled thermo-chemo-mechanical computational Model for titanium structures subjected to extreme loading and environment. The proposed Model accounts for the formation of oxygen enriched (alpha-case) titanium, as well as the coupling effects between the response characteristics of mechanical and oxygen infiltration processes into titanium at high temperature environment. The formation of alpha-case at the surface of the structure is Modeled as diffusion of oxygen into the titanium substrate. The mechanical response of the structure is idealized using the Johnson–Cook Model, which is generalized to account for the effects of oxygen induced embrittlement and hardening. The interplay between mechanical damage, oxygen infiltration and temperature on the chemo-mechanical response is evaluated using numerical simulations. The fully coupled mechanical and diffusion processes are solved based on a staggered coupling algorithm. The capabilities of the computational Model are assessed by the analysis of a panel composed of Ti-6Al-2Sn-4Zr-2Mo titanium alloy subjected to thermal shock loading.