Mainly research efforts have been put in the characterization of material under the manufacturing process conditions. The material behaviour have been explained from the micro and macro structural points of view, developing separated and combined models in both fields.
A complete micro structural evolution model has been created, to consider all possible options for a material to evolve when submitted to thermal loads. This model has been developed in general terms for all the materials considered in the project. Also a more particular model has been developed to simulate material evolution on thermo-mechanical processes.
Isotropic and anisotropic damage models have been developed for Mikalor's and Wezel steels, since it was noted than this subject had a big effect on the material macro behaviour.
Kinematic hardening was also modelled, specially important to calculate spring back after the stamping stage. To characterize this effect, a pure bending test machine has been developed between LMT Cachan and Mikalor, and a patent request will be sent out in September 2001.
The project succeeded in producing 3 different software systems applied to each of the applications and each utilising the subset of the material models developed during the project. For example, for the sheet stamping system the kinematic hardening and anisotropic effects were most important in the macro model and it was shown that the plasticity induced during the forming had little effect on the grain growth during the thermal treatment - the effects could therefore be treated as uncoupled which, incidently, has major advantages for industrial use. For tube rolling a thermo-mechanical approach was also needed but it was important that a more complicated micro-structure model was coupled directly with the macro-material model to adequately simulate the whole manufacturing process. For the gear forging on the other hand a coupled thermal-mechanical approach was needed in the simulations and the effect of damage was critical; the same grain growth model as for the Mikalor application was used but cementation simulation was needed. Inverse analysis was used here in order to obtain the damage material characteristics since this represented a faster and cheaper method than experimentation.
Industrial validation at the end of the project showed that the software systems produced adequate results that were used during the project by the industrial partners concerned:
* Mikalor focussed on the simulation of the manufacture of a steel clasp using a progressive die including 15 steps followed by the thermal treatment for their validation. Simulation and industrial results were very close and helped improve the production process. The clasps are being manufactured at a rate of approximately 20 million a year costing € 0,12 a piece (annual income € 2.400.000)
* Dalmine, who used their research branch FUDETEC, carried out validation on 2D tubes and flat rolled sheets since this provided an easier means of testing the initial software. The intention is to use the software for rolled tubes but only brief simulations were made.
* Wezel carried out extensive simulation and validation coupled with numerical parameter studies on a shift gear that improved the production process of this piece (currently under production). During the project Wezel introduced a clutch gear on which tooling had only just began and simulations enabled alterations to the production process to be made. Production starts in July 2001 at a rate of 100.000 parts over the next year at a total income of € 300.000.
Objectives and content
The industrial goal of the research is to develop an
integrated computer based environment incorporating
extensive laboratory testing, mathematical and
constitutive modelling, inverse analysis techniques and
numerical simulation codes that will enable manufacturers
of bulk and sheet metal products to optimise their
processes with the aim of reducing the overall number of
operations, leading ideally to an as formed product,
thereby increasing their productivity while saving
important resources like raw materials, energy, etc. The
need for an integrated computer environment allowing the
analysis of both bulk and sheet forming processes is
essential for characterising three dimensional (3D) and
pseudo - 3D material behaviour typical of bulk and sheet
forming situations. A system of this kind is also of
practical importance for companies like Partner I
producing sheet metal products ranging from very thin to
relatively thick shapes.
The following tasks will form the core of the project
Development of adequate constitutive models to describe
the evolution of microstructure in selected steel and
aluminium alloys during thermomechanical processes
occurring in bulk and sheet metal forming.
Laboratory tests to validate the predictive capability
of the selected microstructural models in representative
Coupling of the microstructural evolution models with
material models written within the unified framework of
continuum rigid-plastic/viscoplastic and elasto-plastic
Laboratory tests to determine the parameters of the
micro/continuum constitutive models by means of inverse
Development of a micro/continuum material database for
the steel and aluminium alloys selected. 6.
Implementation of the micro/continuum constitutive models
and database in finite element programs for analysis of
bulk and sheet metal forming operations.
Integration and implementation at the end user premises
of a multi-user computer based system for enhanced design
and manufacturing of as-formed bulk and sheet metal
products (hereafter termed the FORMAS system).
Validation of the predictive capability of the
resulting FORMAS system using data acquired via
industrial testing in metal working operations such as
sheet stamping and bending (Partner 1), hot tube rolling
(Partner 2) and cold forging (Partner 3). Examples of
these applications are shown in figure 1. The purpose of
the partners is to exploit both internally and externally
the FORMAS system developed in the project. The
industrial partners predict that the average design time
of as-formed components could be reduced in 30% and that
they collectively could save 4 MEcu within three years of
using the FORMAS system. A fully operational commercial
FORMAS package is expected to be available after two
years of completion of the project and will be marketed
by Partners 4 and 5. Spin-off applications of the
research include the application of the FORMAS
methodology to a wider range of forming processes such as
extrusion, superplastic forming, powder compaction,
injection moulding of plastics, glass forming, infusion
forming and composite material forming among others.
Funding SchemeCSC - Cost-sharing contracts
SA2 8PP Swansea