Mechanical properties characterization of resistance spot welded DP1000 steel under uniaxial tensile tests

Ehsan Javaheri; Andreas Pittner; Benjamin Graf; Michael Rethmeier

doi:10.3139/120.111349

Published by De Gruyter May 28, 2019

Mechanical properties characterization of resistance spot welded DP1000 steel under uniaxial tensile tests

Ehsan Javaheri , Andreas Pittner , Benjamin Graf and Michael Rethmeier

From the journal Materials Testing

https://doi.org/10.3139/120.111349

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Abstract

Resistance spot welding (RSW) is widely used in the automotive industry as the main joining method. Generally, an automotive body contains around 2000 to 5000 spot welds. Therefore, it is of decisive importance to characterize the mechanical properties of these areas for the further optimization and improvement of an automotive body structure. The present paper aims to introduce a novel method to investigate the mechanical properties and microstructure of the resistance spot weldment of DP1000 sheet steel. In this method, the microstructure of RSW of two sheets was reproduced on one sheet and on a bigger area by changing of the welding parameters, e. g. welding current, welding time, electrode force and type. Then, tensile tests in combination with digital image correlation (DIC) measurement were performed on the notched tensile specimens to determine the mechanical properties of the weld metal. The notch must be made on the welded tensile specimen to force the fracture and elongation on the weld metal, enabling the characterization of its properties. Additionally, the parameters of a nonlinear isotropic material model can be obtained and verified by the simulation of the tensile specimens. The parameters obtained show that the strength of DP1000 steel and the velocity of dislocations for reaching the maximum value of strain hardening, are significantly increased after RSW. The effect of sample geometry and microstructural inhomogeneity of the welded joint on the constitutive property of the weld metal are presented and discussed.

*Correspondence Address, M.Sc. Ehsan Javaheri, Füge- und Beschichtungstechnik, Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK, Pascalstraße 8-9, 10587 Berlin, Germany, E-mail: ehsan.javaheri@ipk.fraunhofer.de

Ehsan Javaheri studied Computational Sciences in Engineering at the Technische University in Braunschweig, Germany, and now works as a Scientific Assistant at the Fraunhofer IPK in Berlin, Germany.

Dr.-Ing. Andreas Pittner studied Computational Engineering in 2007 at the Stralsund University of Applied Sciences in Stralsund, Germany and has been the Head of the “Arc Welding and Simulation Department” at the Federal Institute for Materials Research and Testing (BAM) in Berlin, Germany since 2011.

Dr.-Ing. Benjamin Graf studied Mechanical Engineering at the Technical University Berlin, with a focus on power engines and machines. After his studies, he started working at the Fraunhofer IPK, Berlin in 2010. His technological field of interest comprises laser metal deposition and its applications in wear protection, repair and additive manufacturing. He is Head of the Department of “Joining Technology” at the Fraunhofer IPKin Berlin, Germany.

Prof. Dr.-Ing. Michael Rethmeier, born 1972, studied Mechanical Engineering at the Technical University in Braunschweig, Germany. Afterwards, he worked at the same university where he received his Ph.D. in 2003. He became Project Manager for production engineering and concepts at the Volkswagen AG group research. In 2007 he received his Full Professorship at the Technical University of Berlin in combination with being Head of the Division “Safety of Joined Components” at the Federal Institute for Materials Research and Testing (BAM) in Berlin. Additionally, he is the Division Director of “Joining and Coating Technology” at the Fraunhofer Institute for Production Systems and Design Technology IPK in Berlin, Germany.

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Published Online: 2019-05-28

Published in Print: 2019-06-01

Mechanical properties characterization of resistance spot welded DP1000 steel under uniaxial tensile tests

Abstract

References

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