| 1. |
- Barlo, A, et al.
(författare)
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Proposal of a New Tool for Pre-Straining Operations of Sheet Metals and an Initial Investigation of CR4 Mild Steel Formability
- 2023
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Ingår i: IOP Conference Series: Materials Science and Engineering. - 1757-899X. ; 1284
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Tidskriftsartikel (refereegranskat)abstract
- With the increased focus on reducing carbon emissions in the automotive industry, more advanced materials are introduced to reduce the vehicle weight, and more complex component geometries are designed to both satisfy customer demands and to optimize the vehicle aerodynamically. With the increase in component complexity, the strain paths produced during the forming operation of car body components often display a highly non-linear behavior which makes the task of failure prediction during the manufacturing feasibility studies more difficult. Therefore, CAE engineers need better capabilities to predict failure induced by strain path nonlinearity. This study proposes a new tool designed for creating bi-linear strain paths, by performing a pre-strain of a sheet large enough to cut out Nakajima specimens to perform the post-straining in any direction. From five pre-straining tests the tool present a stable pre-straining operation with a uniform strain field in a radius of 100 [mm] from the centre, corresponding to the region of interest of a Nakajima specimen. From the five pre-strained samples, different Nakajima specimens are cut transverse and longitudinal to the rolling direction and a failure prediction approach in an alternative, path independent evaluation space was used to predict the onset of necking with promising results.
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| 2. |
- Tuan Pham, Quoc, et al.
(författare)
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Improvement of modified maximum force criterion for forming limit diagram prediction of sheet metal
- 2023
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Ingår i: International Journal of Solids and Structures. - : Elsevier Ltd. - 0020-7683 .- 1879-2146. ; 273
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a new criterion (MMFC2) for predicting the forming limit curve (FLC) of sheet metal. The strain path evolution of a critical element examined in a uniaxial tensile test is elaborated by incorporating the results of experimental measurement, finite element simulation, and theoretical prediction via the Modified Maximum Force Criterion (MMFC). A scaling factor is introduced to mimic the theoretical evaluation with the simulated one. It is believed that the rotation of the principal axes of the theoretically considering material point, which is initially co-axial with the external load coordinate, implicates the macro track of the strain path change. Furthermore, an optimal event of the second derivative of the axial rotations is proposed to indicate the strain localization and formulate the FLC. The performance of the proposed criterion is compared with that of the original MMFC in predicting the FLC of three automotive sheet metals, of which all related data were published in the Benchmark of Numisheet 2014 conference. The use of three different hardening laws and three yield functions is examined in the analogy. The comparison reveals that the results of MMFC2 are more sensitive to the employed constitutive model than that of MMFC. Furthermore, the proposed MMFC2 presents concordant results with the experimental data. Nakajima tests are conducted for CR4 mild steel sheets to validate the capacity of the proposed criterion. Well agreement between the experimentally measured data and theoretical prediction based on the Yld2k yield function verifies its usefulness in practice. © 2023 The Author(s)
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| 3. |
- Tuan Pham, Quoc, et al.
(författare)
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Modeling the strain localization of shell elements subjected to combined stretch–bend loads : Application on automotive sheet metal stamping simulations
- 2023
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Ingår i: Thin-walled structures. - : Elsevier Ltd. - 0263-8231 .- 1879-3223. ; 188
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a modeling approach for predicting strain localization during sheet metal stamping processes focused on automotive engineering applications. The so-called stretching-to-bending ratio, ρ, is proposed to characterize the loading conditions acting on an element during stamping processes. Then, localized strain or necking strain is suggested to be a function of ρ. Different stretch–bending tests with different tool radii, i.e., R3, R6, R10, and R50 are conducted for two automotive sheet metals, DP800 and AA6010, to identify their forming limits under combined stretch–bend loads. The calibrated necking limit curve of the AA6016 sheet is then employed in AutoForm R10 software to predict the necking and failure of a stamped panel. Agreement with the experimental observation of failure positions of the panel validates the usefulness of the proposed modeling approach in practice.
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| 4. |
- Tuan Pham, Quoc, et al.
(författare)
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Prediction of forming limit diagram of automotive sheet metals using a new necking criterion
- 2023
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Ingår i: Materials Research Proceedings. - : Materials Research Forum LLC. - 9781644902462 ; , s. 705-710
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Konferensbidrag (refereegranskat)abstract
- A theoretical model for predicting the forming limit diagram of sheet metal, namedMMFC2, was recently proposed by the authors based on the modified maximum force criterion(MMFC). This study examines the application of MMFC2 for two automotive sheets, DP800 andAA6016, which are widely used in making car body parts. Uniaxial tensile and bulge tests areconducted to calibrate constitutive equations for modeling the tested materials. The developedmaterial models are employed into different frameworks such as MMFC, MMFC2, and Marciniak-Kuczynski (MK) models to forecast the forming limit curve (FLC) of the tested materials. Theirpredictions are validated by comparing with an experimental one obtained from a series ofNakajima tests. It is found that the derived results of MMFC2 are comparable to that of MK modeland agreed reasonably with experimental data. Less computational time is the major advantage ofMMFC2 against the MK model. (PDF) Prediction of forming limit diagram of automotive sheet metals using a new necking criterion.
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