The finite element simulation has become an essential tool for the proper design of big size automotive components stamping tooling and their process optimization. Although big improvements have been made in the last years in terms of material and tribological modelling, the accuracy of the current models should be further improved to estimate the final post-forming springback of these components, in both AHSS and mild steels.In the present paper the forming of a B-Pillar reinforcement is numerically analyzed using a DX54D mild steel and a TRIP800 high strength steel. In the first part, the influence of the elastic behavior including variable young modulus, the yield criteria and the hardening law on the final springback is studied for both materials. Secondly, the friction coefficient is defined constant and pressure dependent and springback variation is analyzed in function of this variable.In order to stablish the material and friction variables and their typical deviation, results obtained from material characterization and strip drawing tests are used.
Mechanical characterisation of metallic materials at intermediate strain rates is essential to calibrate and validate computational models for industrial applications such as high-speed forming processes i.e. hammer forging, blanking, forming, etc. The most common devices that perform medium to high loading rate experiments are the servo-hydraulic universal testing machines and Split Hopkinson bar systems. Here we analyse the possibility of employing an in-house designed and constructed DirectImpact Drop Hammer (DIDH) for material mechanical characterisation at medium strain rates, ranging from 100 to 300 s-1. To show the suitability of the DIDH for mechanical characterisation, uniaxial compression experiments on S235JR structural steel are conducted and compared with finite element (FE) simulations performed with an elasticthermoviscoplastic material model previously calibrated with Split Hopkinson Pressure Bar (SHPB) tests.
Hammer forging is a widely employed manufacturing process to produce parts with excellent mechanical properties. Although the rheological behavior and the microstructural transformation phenomena of metals under hammer forging conditions are of great industrial interest, few materials have been tested in such intermediate strain rates (10 s -1 to 10 3 s -1 ) due to the lack of laboratory machines for intermediate-speed testing. With the objective of addressing that gap, this paper presents a novel automatic forging simulator comprised of an instrumented forging hammer capable of performing intermediate speed deformations, up to 5 m/s. Three data acquisition approaches were evaluated to select the most appropriate to obtain valid rheological data from intermediate strain rate tests performed on the developed hammer. First, data obtained by both a high-speed camera and a load cell was combined to calculate reference flow curves. Then, two additional data monitoring approaches were then analyzed, employing independently first the high-speed camera and then the load cell data. It was concluded that flow curves obtained utilizing only the load cell data offered accurate results without the need for an expensive and complex high-speed camera.
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