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Avaliação numérico-experimental da fratura dúctil em processos predominantementetrativos e compressivos

Failure prediction in fracture-free materials under a general stress-strain path has posed a great challenge to researchers. Despite the fact that numerical assessment of ductile failure under tensile stress states has been reasonably well described in the literature, a definition of a failure criterion or modelling approach capable to successfully predict fracture onset under a general stress-strain path has still been object of intense research. This work presents numerical and experimental studies of tensile and upsetting tests aiming at defining a ductile failure criterion able to predict fracture onset for AISI 1045 carbon steel. The computational strategy is based on finite elements, which accounts for an elasto-plastic, fullycoupled damage material model and an implicit time integration scheme. Several ductile failure criteria are also evaluated in association with the classical von Mises material model. The numerical predictions are validated against experimental results for tensile and upsetting tests. In the experimental assessment of the upsetting test, specimens were subjected to progressive deformations and existence of micro cracks was verified using Scanning Electron Microscopy (SEM). Failure onset for tensile tests is also identified using SEM.