Speaker
Description
As automakers are challenged to improve safety and weight reduction, they continue to search for new solutions to meet the higher performance demands of body structures. The combination of the Laser Welded Blanks (LWB) technology with 3rd generation of Advanced High-Strength Steels (AHSS) for cold stamping is responding to that challenge. The new Fortiform® (3rd generation of AHSS) based LWB combines superior formability and ductility at higher strengths, thus opening significant new opportunities to reduce weight of vehicles while maintaining safety performances.The development of these new solutions could brings additional questions regarding part formability.
In this study, a Nakazima test is used to evaluate the forming behavior of LWB and estimate the Forming Limit Diagram (FLD). Tests are performed for several materials combinations of 3rd GEN AHSS in order to understand the influence of the weld on LWB formability. The experimental tools used are equipped with a Digital Image Correlation (DIC) system in order to measure strains distribution during the tests. We used a dedicated welding process to avoid Brittle Liquid Metal embrittlement and brittle behavior of the weld.Experimental results are used to determine the critical area during this forming test and a dedicated FLD for each material combination. The location of the onset of failure is investigated, from both optical observations, DIC data and modeling. It appears that various failure locations are obtained depending on both AHSS combination and strain paths.
In order to improve the accuracy of the determination of the onset of the failure, a method is under development to forecast the beginning of the instability.The improvement of failure prediction will be very helpful to analyze part formability and provide design recommendations.
Keywords: Forming Limit Diagram, Nakazima test, DIC, Laser Welded Blanks, 3rd Generation Advanced High Strength Steels
| Speaker Country | France |
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