Introduction

1. Introduction • Objective: investigate the effect of surface conditions on bendability of Advanced High Strength Sheet (AHSS) steels Load vs. Displacement Data • Limited reproducibility for tests • In general, transversely oriented (bending perpendicular to rolling direction) samples performed better than longitudinally oriented ones. • Scratched samples were seen to have lower peak loads than as received samples, and occasionally lower ductilities • Experimental Procedure • Materials • Surface conditions tested: • as received zinc coating • mechanically polished • scratched zinc coating Effect of Surface Condition on Bendability of Zinc-coated Advanced High Strength SteelsEric Lynd1, E. De Moor2, D.K. Matlock21University of Rochester, 2Colorado School of Mines • Summary and Conclusions • Effect of surface conditions on bendability of zinc-coated AHSS steels was studied using a three point bend test • Bending in the transverse direction improved crack resistance while scratching decreased performance • Cracking found to nucleate on the outer bend in all conditions • Cross sections show diagonal (with respect to punch direction) propagation Crack Behavior As Received Polished Scratched Punch DP980 GI References M. Cole, E. De Moor, “Effect of Silicon and Origin of Ductility in Third Generation Advanced High Strength Steels,” Colorado School of Mines, ASPPRC Research Report No MT-SRC-011-010, Sept. 1, 2011. M.D. Taylor, D.K. Matlock, J.G. Speer, and E. De Moor, “Effect of Microstructure on the Fracture Response of AHSS,” Colorado School of Mines, ASPPRC Research Report No. MT-SRC-011-002, September 23, 2011 R. A. Grange, Effect of microstructural banding in steel, Metallurgical and Materials Transactions B, Volume 2, 2 January 1971, Pages 417-426 Rollers DP980 GA Samples’ tests interrupted shortly after load drop TRIP 780 GA Acknowledgements This material is based upon work supported by the National Science Foundation and the Air Force Office of Scientific Research under Grant No. DMR-1062797. The input of the sponsors of the Advanced Steel Processing and Products Research Center, an NSF industry/university cooperative research center at the Colorado School of Mines is gratefully acknowledged. Micrographs DP980 GI DP980 GA TRIP780 GA Cross section of surface cracking in DP980 GA, As Received Sample