Similarity of ductility between model and real materials

摘要

There is a growing pressure in the metals manufacturing industry for lower production costs. This has been translated into an increased use of forming processes, with emphasis on cold processing and its low heating energy input. Cold forming heightens the risk of material cracking, which is associated with the so-called "cold formability" of the metal. One important aspect of formability is the ductility of the material, commonly studied through standard tests such as tension, compression and torsion. For cold forging, compression is widely used since the stress and strain states generated at the free surfaces bear some resemblance to those commonly found in forging. Another experimental approach in such studies utilizes the superficial forming limit diagrams (SFLDs), which display the locus of superficial strain states causing surface cracking. The application of laboratory ductility results to real cases is difficult. Two techniques have been used in order to alleviate this situation: numerical and physical simulations. The former makes use of computer codes (usually based on the finite element method (FEM)), whereas the latter replaces the real materials with model ones, such as waxes and plasticine. There are no references in the literature covering the application of physical modeling with waxes or plasticine to ductility studies in cold forming. The present paper discusses the possibility of using model materials in order to simulate the cracking behavior of real materials such as carbon steels ABNT 1020 and 1040.