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DEVELOPMENT OF AN USER-ORIENTED CAE SYSTEM FOR SIMULATING THE FORMING OF DUCTILE IRON PARTS

Objective

During the past decade, computer simulation has become an integral part of foundry practice for the design of new castings at a better cost and in reduced time. Nevertheless, numerical modelling of casting processes in industry has been limited to heat transfer simulation because of the complex phenomena encountered during solidification and to simple shapes because of the complex geometries involved.

The project aims to develop robust user-oriented numerical models for design purposes.
An integrated software system to simulate the forming process of spheroidal graphite cast iron components including mould filling, solidification and cooling using finite element methods has been developed. In particular, the following methodologies have been developed: development of preprocessors and postprocessors for mesh generation and results visualization for finite element analysis of 3-dimensional casting problems; development of a finite element model for simulating metal flow and heat transfer during mould filling; development of a thermomechanical coupled finite element model for simulating solidification and cooling of spheroidal graphite iron castings; development of iterative and parallel solution algorithms for large equation systems encountered in industrial casting problems; experimental studies to provide physical properties and experimental data to validate the software developed in the project (thermomechanical behaviour of materials (nodular cast iron and sand), cooling, filling, manufacturing parameters); validation and calculations of an industrial part (crankshaft). The final simulation of the crankshaft demonstrated the feasibility of the finite element method simulation of the foundry process, particularly on the thermomechanical aspect.

The software will assist the foundry engineer in the design of nodular cast iron components at a minimum cost and of a better quality. The software developed could be applied to other casting processes. For example, the mesh generator could be used for most of casting processes. The mould filling and thermomechanical models could be used for die casting provided that the constitutive laws for the involved material have been identified. The computer methods (adaptivity and parallel processing concepts) could be adapted to other solvers.

The software reduces the time and cost of manufacturing adjustment of new castings, which is a trial and error process. Numerical simulation permits designing the casting system on a screen, thus avoiding numbers of costly casting tests by making the right modifications earlier during the design process. It optimizes the casting yield and reduces the number of scraps.

The fundamental numerical procedures developed form only a part of the simulation requirements of industry and for full exploitation of the software a comprehensive support system would need additional facilities. In particular, the important aspects of a computer aided design (CAD) link and materials and process database are necessary for computational tools to be considered useful for routine industrial applications. Additionally, software modules which assess the fitness for purpose of the simulated component are also essential. It is also important that such computational tools can be implemented on relatively low cost workstations, which is considered essential for acceptance of the methodology within general foundry industries.
This project includes the following technical tasks :

- Development of a specific iron casting process 3D finite element mesh generator from CAD data including errors estimators and adaptive refinement

- development of a 3D finite element model describing metal flow and heat transfer during mould filling

- development of a 3D finite element thermomechanical coupled model simulating stress/strain and temperature during solidification and cooling including a model for microstructure formation

- identification of consecutive laws taking into account the effects of the following manufacturing parameters on the ductile iron forming process : magnesium treatment, inoculation, chemical composition of melt and mould properties

- finally, numerical methods for solving large practical casting problems will be developed in order to bring the simulation of industrial components at the reach of enhanced workstations. Time incremantation and partitioning techniques together with parallel algorithms for transputer based computers will be developed specifically for the ductile iron casting process.

Coordinator

Renault
Address
9-11 Avenue Du 18 Juin 1940
92500 Rueil-malmaison
France

Participants (4)

Centro International de Metodos Numericos en Ingenieria
Spain
Address
Gran Capitan
08034 Barcelona
ECOLE NORMALE SUPÉRIEURE DE CACHAN
France
Address
61, Avenue Du Président Wilson
Cachan
Fundiciones Miguel Ros SA
Spain
Address
Carretera De Torrelles
08620 Sant Vicenc Dels Horts
ROCKFIELD SOFTWARE LTD.
United Kingdom
Address
Innovation Centre University College Of Wales Swan
SA2 8PP Swansea