Precise Material Properties as a Prerequisite for FE-Analysis of the Hydroforming of Tailored Welded Blanks

Abstract

Tailored welded blanks are already used in the series production of deep drawn parts, and are now considered also for other forming technologies, like for example hydroforming. As new materials come into the market, also their combinations in the production of new tailored welded blanks increase, improving on the one hand the possibilities of matching material and functional requirements, but making the material characterisation more difficult on the other hand. For this reason new methods for a fast, precise and flexible characterisation of the mechanical and tribological properties of tailored welded blanks are needed. In particular the FE‐analysis, a powerful instrument for the definition and optimisation of forming processes, needs precise and reproducible material data in order to deliver accurate results. Therefore, when working with tailored welded blanks, it is crucial that the weld line is modelled using mechanical and tribological properties which refer to its structure and surface. This work summarises the methods used for the characterisation of the mechanical properties of the weld line at the chair of manufacturing technology in Erlangen and presents the results obtained for four different steel grades (FeP04, ZStE340, DP450 and TRIP800) and the tailored welded blanks obtained by their combinations. The accuracy of the results obtained in tensile and in friction tests were verified in simple experiments by comparing results from the tests with results from the finite element analysis. These were seen to be in very good accordance, confirming the accuracy of methods used in the material characterisation.

Numerical simulation modeling of tailor welded blank forming

“…In most forming processes like stamping or bending, it is suffi cient to adopt the constant friction coeffi cient for contact between the base metal and the tool. Tolazzi and Merklein showed that considering friction coeffi cients of the weld seam could considerably improve the accuracy of the FEM model (Tolazzi and Merklein, 2005).…”

Mechanics of Tailor Welded Blanks: An Overview

“…Ghoo et al used tensile tests for the evaluation of work hardening and strength indexes of weld metal [8]. They concluded that normalized workhardening indexes of the welded metals are lower than the mean value of those of the parent materials (further approved by results of Tolazzi and Merkein [17]). However, the strength indexes of the welded metals are higher than the mean value of those of the base metals.…”