No abstract

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.

Zeharkako ebaketa prozesuak metalezko bobinak ebakitzeko edo aurre-formatuen murrizketetarako erabiltzen dira. Ebaketa eragiketaren emaitzak, ebaketa kalitateari eta prozesuaren indarrei dagokienez, prozesuaren parametroen eta materialaren portaeraren araberakoak dira. Prozesuaren parametroen ondorioak zehazteko, ebaketa prototipo hidrauliko bat erabiltzen da zeharkako ebakidura eragiketak eginez 10 mm-ko lodiera duen erresistentzia handiko altzairuzko xafla batean. Emaitza hauek prozesuaren indar eskakizunak ulertzen eta bezeroen ebaketa kalitatearen baldintzak betetzen lagunduko dute.Hitz gakoak: Zeharkako ebaketa, prozesuaren parametroak, xafla lodiak, ebaketa indarrak eta ebaketaren kalitatea.