Strain rate-dependent tensile behavior of wire arc additive manufactured (WAAM) ER70S-6 steel thin-walled plates

ABSTRACT This study investigates the strain-rate-dependent tensile behavior of wire arc additive manufactured (WAAM) thin plates built with ER70S-6 steel which has a length-to-thickness ratio of approximately 46:1, with an emphasis on intermediate strain rates relevant to transportation and structural applications. Quasi-static tests were performed at 0.01 s⁻¹, while intermediate strain rates of 70, 170, and 200 s⁻¹ were examined using a custom-built intermediate rate tensile testing apparatus (IRTTA). Two specimen geometries were evaluated, with gauge lengths of 32 mm and 9.53 mm, across three build orientations (0°, 45°, and 90°). Results demonstrated that both the yield strength (YS) and ultimate tensile strength (UTS) increased with the strain rate by up to 50% and 32% respectively, whereas elongation showed no consistent trend. The oorientation effects were limited, although mild anisotropy was observed. The shorter gauge length specimens exhibited higher elongation and more uniform ductile dimples, while the longer gauge length specimens contained more inclusions and voids, correlating with reduced ductility. The fracture surfaces revealed predominantly ductile failure by dimples, with inclusions of SiO₂ acting as crack initiation sites. Constitutive models based on Johnson–Cook and Voce formulations were fitted to the data, showing good agreement within the effective strain range (5 to 15%) when using the least-squares approach. These results provide insight into the dynamic performance of the ER70S-6 WAAM single bead thin-walled steel plate and its applicability in automotive and structural crash-relevant conditions.