Deliverables
2D-simulations were performed with different FE-packages like MSC.AutoForge, FORGE2, DEFORM2D, Q-Form and eesy-2-form. The second and third forming stage of the investigated part (stub shaft) comprised flash land. Problems in the simulation of the final stage appeared in MSC.AutoForge. To avoid these problems caused by a very small global element size, the narrow flash land was cut away and the simulation was restarted.
The results of 2D-simulations were compared with experimental data like geometry and press load. The simulation results obtained by MSC.AutoForge, FORGE2 and DEFORM2D were similar, but differences were achieved in the geometry of the pre-form and final form occurred. In particular, the form filling differed and the distribution of the equivalent plastic strain was different. The comparison between the calculated press load and the measured press load showed an agreement in the range of 20%.
A survey of representative axisymmetric forging parts was undertaken. These days, 2D-simulations are the state of the art in forming simulations. Consequently the FORGE-NET partners made IFUM spend more time in the field of 3D-simulations.
The partners collected information about the main materials used in European forging industry. This information was assembled in a report also including cross-references between the related European and national standards.
Therefore this document allows a quick overview of:
- Materials mainly used in Europe.
- Cross check between international standards.
- Available material data as found in this project.
This documents is therefore a useful help for process planning engineers and for those engineers doing simulations of metal forming processes. Actually there are 125 materials indicated as being in use at industry. 52 materials are used in cold forging processes, 73 materials are used in hot forging processes. The cross-reference covers DIN-name, DIN-number, EN, SAE, UNI, AFNOR, and BS. Actually there are 26 materials listed as being available at institutions named in the report. A list of literature helps to search for further sources of material data.
In spite of the availability and accuracy of sophisticated 2D and 3D Finite Element methods for simulating the forging process, they do, however, require expertise that may not be available in some (especially) smaller forging companies. Also, they take a considerable amount of time. In industrial practice, especially for estimating costing purposes it is cost effective to predict the outcomes quickly. Methods of fast simulation have been developed in the academic research community and the purpose of this task was to review these methods and make comparisons. Three of the available methods were examined and found to be effective. Published reports describe the detail and potential users needed to refer to the owners for access to the methods.
Simulations were done using flow-stress (tabulated stress/strain curves) material data from several sources for the same material and showing the influence on the simulation results. The deviations between the data sets are shown and the influences on the simulation results are shown.
In addition "artificial" data descriptions were built to study the influences of variations in the curve characteristics. The results allow to judge about "acceptable" inaccuracy in the data sets. The reader learns about what is important for a precise data set and what can be accepted for specific simplified applications.
The report is a useful literature for those engineers doing simulations helping them to get more background about influence of inaccurate data on their results. This is very important because of the very poor situation on the "material data market".
The fundamentals and the state of the art of existing meshing techniques were specified. The comparison between the Delauny, Advancing Front and Quad Mesh algorithms pointed out the disadvantages and the advantages of these methods of meshing and remeshing, respectively.
To compare the mentioned meshing techniques, investigations with example parts were performed. The quality of the global meshing for Delauny, Advancing Front and Overlay (Quad Mesh) was adequate. But in narrow areas the outline of the structure was meshed very rough. One solution to handle this problem was a locally refined mesh (adaptive meshing).
Guidelines for adaptive meshing were developed using example parts. A comparison of CPU-time between FE-simulations with and without adaptive meshing demonstrated a substantial saving of CPU-time by the use of adaptive meshing. The adaptive meshing in actual research work and in commercial 2D FE-packages was monitored.
Conclusion:
- Adaptive meshing saves CPU-time (with adaptive meshing nearly half the time).
- Adaptive meshing is a suitable and a necessary tool for the simulation of parts with flash land or narrow areas.
Engineers can easily find institutions that have experience in R&D in the area and which might be able to help with material data problems or which might be a partner for a common research project.
Areas of applications in general are:
- Yield-stress/strain curves Boundary conditions (friction, heat transfer, etc).
- Microstructure modelling.
For those institutions having provided detailed information the user/reader will find short descriptions of the main research activities and/or their technical equipment to do specific testing. For detailed information concerning boundary conditions the reader should refer to the results related to "Interface properties". Actually this lists shows 33 institutions from 7 countries in Europe and from 1 country outside of Europe.
3D-simulation
It was planned to simulate the provided part with MSC.AutoForge in 3D. Because the simulation with MSC.AutoForge could not be accomplished the simulation with MSC.SuperForge was tested with success. The comparison between simulation and the real part showed a good agreement. The experiment verified the problems predicted concerning form filling. Due to the simulation results being convincing Fucine Umbre purchased a test license of MSC.SuperForge. Pseudo 3D-simulation and 3D-simulation
Pseudo 3D-simulation and 3D-simulation
To perform pseudo 3D-simulations and 3D-simulations Thyssen Umformtechnik und Guss GmbH provided a suitable part (stub shaft). To fulfil all planned investigations, a collaboration between six FORGE-NET partners was organised and managed. Complex 3D parts can be simulated by neclecting details using a pseudo 3D FE-model. For bulk metal forming processes 3D parts can be idealised as axisymmetric and plane strain FE-models.Pseudo 3D simulation performed with an axisymmetric FE-model led to reliable results provided the slices and boundary conditions were well defined. Large deviations of the calculated press load by MSC.SuperForge were detected in comparison to the results achieved by FORGE3 or to experimental results. Furthermore the predicted material flow differed between FORGE3 and MSC.SuperForge or PRINZ (fast simulation package).
Conclusions:
- 2D simulation was suitable to predict the form filling of a real 3D part.
- Effects like under-filling were predictable.
- The use of flow lines was suitable to evaluate pseudo 3D simulations.
3D meshing and remeshing techniques
The usability of three-dimensional meshing and remeshing techniques was investigated and monitored. The Delauny and Hexmesh meshing techniques were compared using three example geometries. Delauny uses triangles in 2D and tetrahedrons in 3D. Hexmesh uses quads in 2D and hexahedrons in 3D.
Conclusions:
- For all geometries the volume loss decreases with an increasing number of nodes.
- For a simple geometry the volume loss is lower for a small number of nodes than for complex parts.
- The volume loss due to a Delauny mesher is lower than the one due to Hexmesh for the same number of nodes.
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