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Nathalie Boudeau - One of the best experts on this subject based on the ideXlab platform.
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How to Post-Process Experimental Results from the Flange Bulging Test? Application to the characterization of a Zinc alloy
IOP Conference Series: Materials Science and Engineering, 2018Co-Authors: Nathalie Boudeau, Ludovic Vitu, Nicolas Laforge, Pierrick Malecot, Gérard Michel, Marc Milesi, Stephan ManovAbstract:Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test (SBT) is well recognized in the metal forming community. Different theoretical models of the literature for the evaluation of thickness and radius of the deformed sheet in SBT have been studied in order to get the Hardening Curve of different materials. These theoretical models present the advantage that the experimental procedure is very simple. But Koc et al. showed their limitation, since the combination of thickness and radius evaluations depend on the material. As Zinc alloys are strongly anisotropic with a special crystalline structure, a procedure is adopted for characterizing the Hardening Curve of a Zinc alloy. The anisotropy is first studied with tensile test, and SBT with elliptical dies is also investigated. Parallel to this, Digital Image Correlation (DIC) measures are carried out. The results obtained from theoretical models and DIC measures are compared. Measures done on post-mortem specimens complete the comparisons. Finally, DIC measures give better results and the resulting Hardening Curve of the studied zinc alloy is provided.
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Flange bulging test of zinc alloy : comparison of analyses with analytical models and with stereo-correlation technique
2018Co-Authors: Ludovic Vitu, Nicolas Laforge, Pierrick Malecot, Nathalie Boudeau, Marc Milesi, Stephan ManovAbstract:Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test is well recognized in the metal forming community. Different theoretical models of the literature for the evaluation of thickness and radius of the deformed sheet in sheet bulging test have been studied in order to get the Hardening Curve of different materials. These theoretical models present the advantage that the experimental procedure is very simple. But Koç et al. showed their limitation, since the combination of thickness and radius evaluations depend on the material. As Zinc alloys are strongly anisotropic with a special crystalline structure, a procedure is adopted for characterizing the Hardening Curve of a Zinc alloy. The anisotropy is first studied with tensile test, and sheet bulging test with elliptical dies is also investigated. Parallel to this, Digital Image Correlation measures are carried out. The results obtained from theoretical models and digital image correlation measures are compared. Measures done on post-mortem specimens complete the comparisons. Finally, digital image correlation measures give better results and the resulting Hardening Curve of the studied zinc alloy is provided.
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Evaluation of models for tube material characterization with the tube bulging test in an industrial setting
International Journal of Material Forming, 2018Co-Authors: Ludovic Vitu, Pierrick Malecot, Nathalie Boudeau, Gérard Michel, Aurélien ButeriAbstract:It is now well recognized that the material data obtained from a tensile test is less appropriate than those from a Tube Bulging Test (TBT) for a finite element simulation of tube hydroforming. However, the manufacturers still use classical data (often tensile test data) for designing metal operations due to the lack of standard for the TBT and a more complex post processing analysis of experimental measures. Getting the Hardening Curve from the tube bulging test requires the use of an analytical or numerical model. In this paper, three models for post-processing measures obtained from the TBT are compared based on the same experimental procedure. Thanks to a preliminary step, consisting of the validation of the analytical models through the use of finite element simulations of the TBT, it highlights that the results obtained for the local (stress and strain) and global components (the thickness distribution along the tube and the deformed tube profile) are very close, whatever the models. The test configuration (die radius and free length) seems to have no significant impact on the resulting stress-strain Curve for the three models. The three models are used for post processing tube bulging tests performed on AISI304, INCONEL and Copper tubes validating their capacity for tube characterization on different materials. Finally, this study demonstrates that the Boudeau-Malécot Model can be used to obtain Hardening Curve from TBT without a loss of accuracy compared to more complex post-processing models and with an important gain of quality compared to tensile test.
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How to post-process experimental results from the flange bulging test ? Application to the characterization of a Zinc alloy
2018Co-Authors: Nathalie Boudeau, Ludovic Vitu, Nicolas Laforge, Pierrick Malecot, Gérard Michel, Marc Milesi, Stephan ManovAbstract:Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test (SBT) is well recognized in the metal forming community. Different theoretical models of the literature for the evaluation of thickness and radius of the deformed sheet in SBT have been studied in order to get the Hardening Curve of different materials. These theoretical models present the advantage that the experimental procedure is very simple. But Koç et al. showed their limitation, since the combination of thickness and radius evaluations depend on the material. As Zinc alloys are strongly anisotropic with a special crystalline structure, a procedure is adopted for characterizing the Hardening Curve of a Zinc alloy. The anisotropy is first studied with tensile test, and SBT with elliptical dies is also investigated. Parallel to this, Digital Image Correlation (DIC) measures are carried out. The results obtained from theoretical models and DIC measures are compared. Measures done on post-mortem specimens complete the comparisons. Finally, DIC measures give better results and the resulting Hardening Curve of the studied zinc alloy is provided.
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Characterization of zinc alloy by sheet bulging test with analytical models and digital image correlation
2018Co-Authors: Ludovic Vitu, Nicolas Laforge, Pierrick Malecot, Nathalie Boudeau, Stephan Manov, Marc MilesiAbstract:Zinc alloys are used in a wide range of application such as electronics, automotive and building construction. Their various shapes are generally obtained by metal forming operation such as stamping. Therefore, it is important to characterize the material with adequate characterization tests. Sheet Bulging Test (SBT) is well recognized in the metal forming community. Different theoretical models of the literature for the evaluation of thickness and radius of the deformed sheet in SBT have been studied in order to get the Hardening Curve of different materials. These theoretical models present the advantage that the experimental procedure is very simple. But Koç et al. showed their limitation, since the combination of thickness and radius evaluations depend on the material. As Zinc alloys are strongly anisotropic with a special crystalline structure, a procedure is adopted for characterizing the Hardening Curve of a Zinc alloy. The anisotropy is first studied with tensile test, and SBT with elliptical dies is also investigated. Parallel to this, Digital Image Correlation (DIC) measures are carried out. The results obtained from theoretical models and DIC measures are compared. Measures done on post-mortem specimens complete the comparisons. Finally, DIC measures give better results and the resulting Hardening Curve of the studied zinc alloy is provided.
José Valdemar Fernandes - One of the best experts on this subject based on the ideXlab platform.
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On the determination of the work Hardening Curve using the bulge test
International Journal of Mechanical Sciences, 2016Co-Authors: L.c. Reis, Marta Oliveira, Abel D. Santos, José Valdemar FernandesAbstract:Abstract Hydraulic bulge test represents nowadays an important means to obtain higher accuracy on material characterization. One reason is the possibility of using the obtained biaxial stress–strain data to largely extend the Hardening information extracted from the tensile test. The other reason is the use of biaxial data as input information when determining parameters for current most advanced yield criteria. This contribution aims to obtain the material stress–strain Hardening Curve from the bulge test using a simpler experimental equipment, in which the output data is the hydraulic bulge pressure and the pole bulge height. This information is used to determine the sheet thickness and corresponding radius of curvature at the pole of the cap, which is the needed data to calculate the biaxial stress–strain Curve, the stress being determined based on Laplace׳s equation from the membrane theory, a standard approach for this kind of analysis. Analytical models are proposed relating the radius of curvature and the sheet thickness with the pole bulge height. These models are based in an extensive analysis of different material behaviors, which in turn are related to characteristic properties of sheet metals, as well as different geometries of bulge test. Geometric variables include bulge die diameter and the fillet radii located at the entrance of the die. The analytical formulas also include the material variables associated with the Hardening behavior and the sheet anisotropy, with different interaction and weighting impact. The extensive study also permits a deeper theoretical understanding of relations among the interconnecting variables and their influence on the accuracy of sheet thickness and radius of curvature determination, which directly influences the obtained biaxial stress–strain Curve. This means, for example, the understanding between sheet thinning evolution or bulge curvature evolution during bulging and the corresponding relation with material plastic properties, Hardening and anisotropy. The validation of the methodology and the proposed analytical models is performed with experiments, both from developed experimental system and also from literature with different bulge geometric relations.
Dachang Kang - One of the best experts on this subject based on the ideXlab platform.
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A study on determining Hardening Curve for sheet metal
International Journal of Machine Tools and Manufacture, 2003Co-Authors: Hao Bin Tian, Dachang KangAbstract:Abstract The Hardening Curve for sheet metal can be determined from the load–displacement Curve of tensile specimen with rectangular cross-section. The previous researches, however, have paid little attention to its use in large deformation. Moreover, it varies with materials, deformation conditions and so on, and there are not enough Hardening Curves available in manuals. In order to study metal behavior, it is very important to establish a method to create a large strain Hardening Curve based on the normal mechanical test. In this paper, two new kinds of specimens are proposed, one is a multi-stepped specimen that can be traced to the three-stepped specimen, and the other is a tapered specimen which decreases the complexity of the multi-stepped specimen in manufacture. In this study, circle grids are imposed on the specimen surface to calculate true strains at different positions of the specimen. It is found that the load added to the different segments of specimen just before fracture can be determined by the maximum load and breaking load. True strains and corresponding true stresses can be determined after the specimen is pulled to fracture, so the Hardening Curve can be easily achieved. After a great deal of experiment, the results show that the tapered specimen has almost the same key parameters as the multi-stepped specimen, and the former is more easily used. Meanwhile, the work-Hardening exponent (n) and the coefficient of normal anisotropy (r) can be obtained conveniently, and the forming limit line can also be approximately induced.
Jan Heijne - One of the best experts on this subject based on the ideXlab platform.
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work Hardening descriptions in simulation of sheet metal forming tailored to material type and processing
International Journal of Plasticity, 2016Co-Authors: Henk Vegter, Hans Mulder, Peter Van Liempt, Jan HeijneAbstract:In the previous decades much attention has been given on an accurate material description, especially for simulations at the design stage of new models in the automotive industry. Improvements lead to shorter design times and a better tailored use of material. It also contributes to the design and optimization of new materials. The current description of plastic material behaviour in simulation models of sheet metal forming is covered by a Hardening Curve and a yield surface. In this paper the focus will be on modelling of work Hardening for advanced high strength steels considering the requirements of present applications. Nowadays work Hardening models need to include the effect of hard phases in a soft matrix and the effect of strain rate and temperature on work Hardening. Most material tests to characterize work Hardening are only applicable to low strains whereas many practical applications require Hardening data at relatively high strains. Physically based Hardening descriptions are used for reliable extensions to high strain values.
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Tailored Work Hardening Descriptions in Simulation of Sheet Metal Forming
2013Co-Authors: Henk Vegter, Hans Mulder, Peter Van Liempt, Jan HeijneAbstract:In the previous decades much attention has been given on an accurate material description, especially for simulations at the design stage of new models in the automotive industry. Improvements lead to shorter design times and a better tailored use of material. It also contributed to the design and optimization of new materials. The current description of plastic material behaviour in simulation models of sheet metal forming is covered by a Hardening Curve and a yield surface. In this paper the focus will be on modelling of work Hardening for advanced high strength steels considering the requirements of present applications. Nowadays work Hardening models need to include the effect of hard phases in a soft matrix and the effect of strain rate and temperature on work Hardening. Most material tests to characterize work Hardening are only applicable to low strains whereas many practical applications require Hardening data at relatively high strains. Therefore, physically based Hardening descriptions are neede...
Raphaël Velasco - One of the best experts on this subject based on the ideXlab platform.
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Error evaluation on experimental stress-strain Curve obtained from tube bulging test
International Journal of Material Forming, 2010Co-Authors: Abdel Hakim Ben Ouirane, Gérard Michel, Raphaël Velasco, Nathalie BoudeauAbstract:The paper is focused on a sensitivity analysis developed to study the relevance of experimental Hardening Curves obtained from tube bulging test to quantify the influence and the contribution of experimental uncertainties on the response variability. The experiments are based on “online” measurements of the internal pressure and the bulge height. A semi analytical model developed from a geometrical representation of the bulged tube and equilibrium of infinitesimal volumes (slab method) permits to evaluate the stress-strain Curve. The differentiation of all the equations of the model and the evaluation of all the input parameters allow to get the total uncertainty on the resulting Hardening Curve and to identify the critical experimental parameters. Hence the results of this sensitivity analysis open up ways of improvements for conducting experimental tube bulging test.
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Tube bulging test : Theoretical analysis and numerical validation
Journal of Materials Processing Technology, 2007Co-Authors: Raphaël Velasco, Nathalie BoudeauAbstract:Abstract To perform pertinent numerical simulations of tube hydroforming process, it has been demonstrated that material data obtained from tube bulging test were more suitable than the classical tensile test. Theoretical developments based on a novel geometrical modeling have led to an analytical evaluation of the strain and stress states all over the bulged part of the tube. Errors due to imprecision of the measure location and geometrical imperfection of tube can be linked to errors on stress and strain evaluation by a differential analysis of the analytical model. At last, to validate the model, numerical results obtained from FE simulation of tube bulging test have been used as experimental data. In that way, it is shown that: - Hardening Curves can be obtained through the measurement of internal pressure and bulge height; - thickness variation along the bulged part of the tube can be calculated; - scattering on the Hardening Curve can be evaluated by using inaccuracy of the measurement point location during experiments and manufacturing tolerances on tube thickness.
