Characterisation methods and simulation of deformation and failure in metal forming processes

Tools for numerical analysis is a prerequisite in product development. Variations of the finite element method is widely used for simulation of metal manufacturing processes, for example sheet metal forming and hot stamping. However accurate the models are, there is still the issue of parameter estimation for the constitutive models used in the simulations.The increased use of high-strength steel in metal manufacturing processes necessitates forming at elevated temperatures. Formblowing and hardening (FH), where an austenitized profile blank is formed in a closed tool by injection of pressurised gas followed by rapid water cooling, is a recent development.The objectives are to increase knowledge regarding: characterisation methods for parameter estimation in constitutive models; numerical simulations of metal forming processes at elevated temperatures.Experimental material characterisation tests have been performed for deformation levels beyond plastic instability in standard tests. Methods for field measurements of deformation have been applied. Measurements were combined with inverse modelling for parameter estimation. Thermomechanical simulation models of the FH process have been developed. Complete process simulations were performed and compared with experiments. A pre-bursting failure criteria were implemented and compared with experimental burst tests.Godkänd; 2010; 20100210 (gorlind); DISPUTATION Ämnesområde: Hållfasthetslära/Solid Mechanics Opponent: Professor Larsgunnar Nilsson, Linköpings universitet Ordförande: Professor Hans-Åke Häggblad, Luleå tekniska universitet Tid: Fredag den 12 mars 2010, kl 10.00 Plats: E 231, Luleå tekniska universite