It became apparent in the late 1980 that all manufacturing processes in the future would be first simulated before industrial implementation. Sheet metal forming was one of the most important applications where this technology could be applied. One of the issues was to represent the plastic behavior of sheet materials. For accurate numerical simulations information is needed on the initial yielding, subsequent work-hardening and final localization of plastic flow and/or fracture. The forming limits have been studied since the mid-1940s, when Gensamer and Lankford and coworkers carried out their tests with steel and aluminum. In this work we discuss the forming and fracture limits of low carbon steel, stainless steel and aluminum. Experimental results on stretch forming, deep drawing and tensile testing will be presented. Hydraulic bulge testing is employed in the stretch forming experiments. Marciniak-type in-plane tests are carried out to study the limit strains in deep drawing. Laser marked grids are used to measure the surface strains and scanning electron microscopy is employed to measure the thickness strains and to study the fracture surfaces.
Badaniom poddane zostały ograniczenia możliwości odkształcania i pojawianie się pęknięć w blachach ze stali nierdzewnej i aluminium. Test hydraulicznego wybrzuszenia został przeprowadzony w procesie formowania z rozciąganiem. Test typu Marciniaka oraz testy rozciągania zostały przeprowadzone w celu zbadania granicznej odkształcalności. Siatka naniesiona metodą sitodruku i laserem została użyta do pomiaru odkształceń powierzchni próbki. Ponadto, użyto mikroskopu skaningowego do pomiaru odkształceń na grubości i badania powierzchni pęknięć.