The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Chongmin Kim - One of the best experts on this subject based on the ideXlab platform.
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a modified Damage Model for advanced high strength steel sheets
International Journal of Plasticity, 2011Co-Authors: Kwansoo Chung, Taejoon Park, Dongun Kim, Donghoon Yoo, Chongmin KimAbstract:More often than not, better formability in the simple tension test implies better formability performance in other stretching modes, especially in hole expansion performance since deformation in the hole expansion test is perceived to be in the same simple tension deformation mode. However, when the hole expansion formability is evaluated particularly for the twinning induced plasticity (TWIP) steel, its performance is so poor compared to other automotive steels, even though the TWIP steel has significantly superior formability in the simple tension test. Therefore, hole expansion formability was experimentally and numerically studied for advanced high-strength grade steel sheets, TWIP940 and a transformation induced plasticity (TRIP) 590 steel sheet, as well as a high-strength grade 340R steel sheet, particularly in conjunction with formability in the simple tension test and its surface condition sensitivity. In order to characterize mechanical properties, simple tension tests were performed to determine anisotropic properties and strain rate sensitivities. To account for macro-crack formation, an inverse calibration method based on a Damage Model utilizing a triaxiality-dependent fracture criterion and hardening behavior with stiffness deterioration was developed. In this approach, the Damage Model was inversely calibrated by performing numerical simulations and experiments for the simple tension test (with specimens prepared by milling and punching). Then, the Damage Model was applied to formability study in the hole expansion test. The Damage Model along with the anisotropic yield function Hill (1948) incorporated into the ABAQUS/Explicit FEM code performed well to predict hole expansion ratios (HER) and their surface condition sensitivity, elucidating the cause of the lukewarm hole expansion performance and strong surface condition sensitivity of the TWIP steel compared to the others.
Kwansoo Chung - One of the best experts on this subject based on the ideXlab platform.
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a modified Damage Model for advanced high strength steel sheets
International Journal of Plasticity, 2011Co-Authors: Kwansoo Chung, Taejoon Park, Dongun Kim, Donghoon Yoo, Chongmin KimAbstract:More often than not, better formability in the simple tension test implies better formability performance in other stretching modes, especially in hole expansion performance since deformation in the hole expansion test is perceived to be in the same simple tension deformation mode. However, when the hole expansion formability is evaluated particularly for the twinning induced plasticity (TWIP) steel, its performance is so poor compared to other automotive steels, even though the TWIP steel has significantly superior formability in the simple tension test. Therefore, hole expansion formability was experimentally and numerically studied for advanced high-strength grade steel sheets, TWIP940 and a transformation induced plasticity (TRIP) 590 steel sheet, as well as a high-strength grade 340R steel sheet, particularly in conjunction with formability in the simple tension test and its surface condition sensitivity. In order to characterize mechanical properties, simple tension tests were performed to determine anisotropic properties and strain rate sensitivities. To account for macro-crack formation, an inverse calibration method based on a Damage Model utilizing a triaxiality-dependent fracture criterion and hardening behavior with stiffness deterioration was developed. In this approach, the Damage Model was inversely calibrated by performing numerical simulations and experiments for the simple tension test (with specimens prepared by milling and punching). Then, the Damage Model was applied to formability study in the hole expansion test. The Damage Model along with the anisotropic yield function Hill (1948) incorporated into the ABAQUS/Explicit FEM code performed well to predict hole expansion ratios (HER) and their surface condition sensitivity, elucidating the cause of the lukewarm hole expansion performance and strong surface condition sensitivity of the TWIP steel compared to the others.
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evaluation of charpy impact test performance for advanced high strength steel sheets based on a Damage Model
International Journal of Material Forming, 2010Co-Authors: Taejoon Park, Dongyoon Seok, Kwansoo ChungAbstract:The Charpy impact test performance was experimentally and numerically studied for two advanced high-strength steel sheets (AHSS) TWIP940 and TRIP590 as well as for a high strength grade 340R. Uni-axial simple tension tests were performed to determine their anisotropic properties and strain rate sensitivities along with their hardening behaviour. The high speed strain rate sensitivity of TRIP590 and 340R (rate sensitive) was also characterized to account for high strain rates involved in the Charpy impact test. To evaluate fracture behaviour in the Charpy impact test, a new Damage Model, including the triaxiality-dependent fracture criterion and the hardening behaviour with stiffness deterioration, was introduced and the Model was calibrated based on the simple tension and V-notch tests. The new Damage Model along with the anisotropic yield function Hill1948 was incorporated into the ABAQUS/Explicit FEM code, which performed reasonably well to predict the impact energy absorbed during the Charpy impact test.
Carlos G Davila - One of the best experts on this subject based on the ideXlab platform.
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a continuum Damage Model for composite laminates part i constitutive Model
Mechanics of Materials, 2007Co-Authors: P Maimi, P P Camanho, J A Mayugo, Carlos G DavilaAbstract:A continuum Damage Model for the prediction of the onset and evolution of intralaminar failure mechanisms and the collapse of structures manufactured in fiber-reinforced plastic laminates is proposed. The failure mechanisms occurring in the longitudinal and transverse directions of a ply are represented by a set of scalar Damage variables. Crack closure effects under load reversal are taken into account by using Damage variables that are established as a function of the sign of the components of the stress tensor. Damage activation functions based on the LaRC04 failure criteria are used to predict the different failure mechanisms occurring at the ply level.
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a continuum Damage Model for composite laminates part ii computational implementation and validation
Mechanics of Materials, 2007Co-Authors: P Maimi, P P Camanho, J A Mayugo, Carlos G DavilaAbstract:This papers describes the computational implementation of a new Damage Model for laminated composites proposed in a previous paper. The objectivity of the numerical solution is assured by regularizing the energy dissipated at a material point by each failure mechanism. A viscous Model is proposed to mitigate the convergence difficulties associated with strain softening constitutive Models. To verify the accuracy of the approach, analyses of coupon specimens were performed, and the numerical predictions were compared with experimental data.
Wang Dejun - One of the best experts on this subject based on the ideXlab platform.
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a new multiaxial fatigue Damage Model based on the critical plane approach
International Journal of Fatigue, 1998Co-Authors: Shang Deguang, Wang DejunAbstract:A path-independent parameter for multiaxial fatigue Damage is proposed based on the critical plane approach. Both parameters of shear strain and normal strain excursion are considered in this parameter. An equivalent strain is made with both parameters by means of the von Mises criterion. Thus a new multiaxial fatigue Damage Model is given based on the critical plane approach. The results show that multiaxial fatigue Damage Model proposed in this paper may be used under either proportional or nonproportional loading. It is used to predict multiaxial fatigue life. Errors are within a factor of 2.
Sankaran Mahadevan - One of the best experts on this subject based on the ideXlab platform.
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a unified multiaxial fatigue Damage Model for isotropic and anisotropic materials
International Journal of Fatigue, 2007Co-Authors: Sankaran MahadevanAbstract:A unified multiaxial fatigue Damage Model based on a characteristic plane approach is proposed in this paper, integrating both isotropic and anisotropic materials into one framework. Compared with most available critical plane-based Models for multiaxial fatigue problem, the physical basis of the characteristic plane does not rely on the observations of the fatigue crack in the proposed Model. The cracking information is not required for multiaxial fatigue analysis and the proposed Model can automatically adapt for very different materials experiencing different failure modes. The effect of the mean normal stress is also included in the proposed Model. The results of the proposed fatigue life prediction Model are validated using experimental results of metals as well as unidirectional and multidirectional composite laminates.
