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- Lara, A., et al.
(författare)
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Sheared edge formability characterization of cold-rolled advanced high strength steels for automotive applications
- 2022
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Ingår i: IOP Conference Series: Materials Science and Engineering. - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- Edge cracking has become a limiting factor in the use of some advanced high strength steels (AHSS) for high-performance automotive applications. This fact has motivated the development of a multitude of experimental tests for edge formability prediction over the last years. In this sense, the Hole Expansion Test (HET) according to ISO16630 has been established in the automotive industry as a standard procedure for edge cracking sensitivity ranking. However, whereas it may be useful for rapid material screening, the results are often not accurate and reliable enough. Consequently, alternative methods based on Digital Image Correlation (DIC) have been proposed aimed at improving the prediction of edge cracking occurrence during forming and obtaining useful strain data that can be implemented in forming simulations. This paper explores the applicability of different DIC-based methods, such as Half-Specimen Dome Tests, Sheared Edge Tensile Tests, and KWI hole expansion tests with a flat nosed punch, for characterizing the edge formability of three cold-rolled AHSS sheets. The results obtained from the different testing methods are compared and validated with a laboratory-scale demonstrator. Finally, the limitations and advantages of the different methods are discussed.
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| 4. |
- Sandin, Olle, et al.
(författare)
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Prediction of sheared edge characteristics of advanced high strength steel
- 2022
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Ingår i: IOP Conference Series: Materials Science and Engineering. - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- In the present work, numerical models are developed for the shearing and cutting process of advanced high strength steel-blanks which can predict the edge morphology in the shear effected zone. A damage model, based on the modified Mohr-Coulomb fracture surface, is calibrated. To increase the predictability of the numerical models, the fracture surface is fine-tuned in areas corresponding to the stress-state of cutting, a methodology called Local calibration of Fracture Surface (LCFS). Four cutting cases with varying clearance are simulated and verified with experimental tests, showing good agreement. It is thus found that the suggested methodology can simulate cutting with adequate accuracy. Furthermore, it is found that solely using plane-stress tensile specimens for calibrating the fracture surface is not enough to obtain numerical models with adequate accuracy.
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| 5. |
- Tarhouni, I., et al.
(författare)
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Assessing the effect of the experimental parameters in the evaluation of the essential work of fracture in high-strength thin sheets
- 2022
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Ingår i: Engineering Fracture Mechanics. - : Elsevier. - 0013-7944 .- 1873-7315. ; 270
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Tidskriftsartikel (refereegranskat)abstract
- The essential work of fracture methodology (EWF) has been successfully adopted to evaluate the fracture toughness of various metals and polymers. However, some aspects of the methodology are still far less understood, such as the influence of the experimental parameters on EWF measurement in thin metal sheets. In the present paper, the ligament range criterion of the EWF approach was revised for several advanced high-strength steels (AHSS). The validity of the upper and lower ligament length limits given by the ESIS protocol is redefined and rationalized according to the necking capability and the plasticity behaviour of the different AHSS grades. The work provides a new criterion to define the minimum ligament length to be tested, based on the minimum distance required by the crack to fully develop the necking capability of the material. The width constraint is too restrictive and has no effect on the deviation from linearity in the upper range. On the other hand, the maximum ligament length is proven to be controlled by the size of the plastic zone as proposed by the ESIS protocol.
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