PSI - Issue 19

M. Duchet et al. / Procedia Structural Integrity 19 (2019) 585–594 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

594 10

5. Conclusion

In this work, the objective was to promote the introduction of AHSS grades for the automotive market, and especially to achieve weight saving on chassis parts. The substitution of conventional HSLA steel grades by AHSS ones with much higher mechanical properties combined with improvement in the design shows a real potential to lighten the weight of components supporting the global reduction of CO2 emission for vehicles. Nevertheless, for GMAW assembly, their fatigue strength could be an issue. Consequently, different reinforcement solutions of welds (TIG remelting, transversal oscillating welding and shot-peening) have been investigated to demonstrate that fatigue properties after being reinforced reach higher resistance to replace standard HSLA thick grades by thinner AHSS grades. To achieve this goal, standard lap-joint specimens have been first investigated. In a second phase, specific demonstrators (like-bracket technological specimens), consisting in a U-shape welded on a plate have been developed with the objective of being more representative to a real chassis assembly. These demonstrators can be tested under tension or bending loading thanks to a specific clamping line mounted on a standard servo-hydraulic fatigue machine. It has been demonstrated that the fatigue behaviour of such AHSS welds could be improved using reinforcement solutions. As a result, about 17% of mass reduction was obtained with the three investigated techniques: TIG remelting, transversal oscillating welding and shot-peening. In a final part, a cost analysis of these solutions has been applied on a real application considering a limit at 3€ / kg saved . Depending on the length of GMAW and focusing on welds where reinforcements are necessary, the different investigated solutions are eligible for the automotive market.

Acknowledgements

The authors would like to thank their partner Improvalue for their cost evaluation of weld reinforcement solutions and their support.

References

[1] https://automotive.arcelormittal.com/s-in_motion_solutions , S-in motion® web page [2] https://automotive.arcelormittal.com/products/global_offering/product_catalogue, ArcelorMittal automotive products web catalog [3] Fatigue behavior of arc welded assemblies: paths of improvement, Michel Duchet et al., Fatigue design 2011, November 23-24 th , Cetim, Senlis, France [4] SAE Fatigue Design Handbook, AE-22, third edition, edited by Richard C. Rice, 1997, 470 pages [5] Method of fatigue life estimation for arc-welded structures, T.Kasahara et al., Technical Paper 2000-01-0781, SAE World Congress, Detroit-Michigan, March 6-9, 2000. 10.4271/2000-01-0781.