Cato Dørum

Aluminium and Magnesium Castings - Experimental Work and Numerical Analyses

The long-term objective of this work is to develop design and modelling tools that allow the structural behaviour of thin-walled cast components to be predicted when subjected to static and dynamic loads such as in crash situations. The approach consists of the following ingredients: casting of generic geometry relevant for automotive design, component and materials testing, constitutive modelling and validation simulations using the finite element method. Here, HPDC components of both AM60 and AlSi7Mg have been subjected to axial crushing and 3-point bending. An existing elastoplastic constitutive equation has been calibrated and evaluated based on material tests. Next, validation analyses of the generic structural components subjected to static loading were performed. The thin-walled cast components are modelled in the explicit FE-code LS-DYNA using shell elements. So far, it has been found that an elastoplastic material model based on the isotropic yield criterion of von Mises reasonably well captures the behaviour of HPDC components subject to both axial loading and 3-point bending. In addition, the ultimate loads in the different load cases are over-predicted analytically with the use of Eurocode 9 (EC9).

Numerical Modeling of the Structural Behavior of Thin-Walled Cast Magnesium Components Using a Through-Process Approach

A through-process methodology for numerical simulations of the structural behavior of thin-walled cast magnesium components is presented. The methodology consists of casting process simulations using MAGMAsoft, mapping of data from the process simulation onto a FE-mesh (shell elements) and numerical simulations using the explicit FE-code LS-DYNA. In this work, generic High Pressure Die Cast (HPDC) AM60 components have been studied using 3-point bending and 4-point bending tests. The experimental data are applied to obtain a validated methodology for finite element modeling of thin-walled cast components subjected to quasi-static loading. The cast magnesium alloy is modeled using a user-defined material model consisting of an elastic-plastic model based on a non-associated J2-flow theory and the Cockcroft-Latham fracture criterion. The fracture criterion is coupled with an element erosion algorithm available in LS-DYNA. The constitutive model and fracture criterion are calibrated both with data from material tests and data from the process simulation using MAGMAsoft.

Energy Absorption Capacity for HPDC Components

The long-term objective of this work is to develop design and modeling tools that allow the structural behavior of thin-walled cast components to be predicted when subjected to static and dynamic loads such as in crash situations. Here, the energy absorption potential of High Pressure Die Cast components made of magnesium alloys AM20, AM50, AM60, AZ91 and the aluminum alloy AlSi7Mg is investigated using a shear-bolt principle. For the AM60 alloy, single plates cast with different thickness have been tested in order to investigate the effect of plate thickness on the shear-bolt mechanism. It is found that this deformation principle gives an approximately constant mean force during the deformation process. The behavior seems to be very robust, especially for the magnesium alloys. A simple empirical model for prediction of the mean shearing force as a function of plate thickness and bolt diameter is proposed.