Mechanical characterization and modelling of iron ore pellets

University dissertation from Luleå tekniska universitet

Abstract: Transportation and storage are important parts in the process chain for producers of iron ore pellets. Knowledge and optimization of these processes are very important for further efficiency progress and increased product quality. The existence of a numerical simulation tool with accurate material characteristics will significantly increase the possibility to predict critical forces in developing new and existing transportation and storing systems and thereby decrease the amount of damaged, fractured or crushed pellets (fines). The objective is to increase the knowledge of the mechanical stresses in iron ore pellets and its effects on the level of damaged material in the handling chain. This includes a better understanding of the iron ore pellets mechanical properties and fracture behaviour. Both experimental and numerical modelling works have been completed to increase the knowledge in these fields. Modelling and characterization of iron ore pellets are carried out at different length scales. Material parameters for an elastic plastic granular continuum material model are determined for modelling large quantities of iron ore pellets. A flow model of iron ore pellets in silos using smoothed particle (SP) method is presented. From experimental two point load tests, a finite element (FE) model of single iron ore pellets is worked out with statistical data for an elastic plastic constitutive model with a fracture criterion. In order to find the relation between the behaviour of iron ore pellets at different length scales, e.g. compare the stresses in a silo to the critical stress inside a single iron ore pellet, mechanical testing and modelling of iron ore pellets on an intermediate length scale is established. A method of instrumented confined compression tests is developed for measuring the global response on a limited amount of iron ore pellets. The same experiment is virtually reproduced with a multi particle finite element model (MPFEM) consisting of individual discretized models of the iron ore pellets. This work has given a better understanding of the mechanical behaviour and fracture of iron ore pellets. Another outcome is refined experimental methods to determine mechanical properties and fracture of iron ore pellets. Constitutive data and numerical models for iron ore pellets are also worked out.

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