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Reusing CAD-models of Die-cast products for FEA
Jönköping University, School of Engineering, JTH, Mechanical Engineering. Jönköping University, School of Engineering, JTH. Research area Computer Supported Engineering Design.
2006 (English)In: NAFEMS Seminar: Prediction and Modelling of Failure Using FEA, 2006Conference paper, Published paper (Refereed)
Abstract [en]

Parts for trimmers, lawnmowers and chainsaws are often manufactured by die-casting in light alloys. These parts often have a complex geometry with thin-walled regions mixed with regions of non thin-walled geometry. This paper discusses the process of creating FEA-models from CAD-models of such parts. The objective of the FEA, in the particular case described in this paper, is to predict the performance of the complete products. Since a FEA-model of the complete product require extensive computational power to solve, it is necessary to keep the computational cost down by f. ex using shell-elements instead of solid-elements where applicable.

The creation of the shell-element mesh based on the solid CAD-model can be time consuming, especially if the CAD-model is complicated as often the case in real products. To aid in the creation of the shell-element mesh there is commercial software available for the extraction of the mid-surfaces in the CAD-model. In this paper two different software for mid-surface extraction are tested, both included in pre-processors for high-end FEA solvers. The software was tested on six different die-cast or injection moulded parts, all components in consumer products available on the market.

The result is that the software can extract the individual mid-surfaces well but the connections between them are often not created properly.

Furthermore the software cannot, as expected, deal with the regions that divert too much from being thin-walled. This paper present an idea on how treat these regions by retrieving suitable representations from a depository of representations known from experience to represent the geometry well and insert them in the appropriate position in the FEA-model automatically.

To show the feasibility of the idea a demonstrator program created in CATIA V5 using VBA is also presented in this paper.

Place, publisher, year, edition, pages
2006.
Identifiers
URN: urn:nbn:se:hj:diva-1726OAI: oai:DiVA.org:hj-1726DiVA, id: diva2:32546
Available from: 2007-08-03 Created: 2007-08-03 Last updated: 2010-01-12Bibliographically approved
In thesis
1. CAD-Model Parsing for Automated Design and Design Evaluation
Open this publication in new window or tab >>CAD-Model Parsing for Automated Design and Design Evaluation
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Product development has both innovative and analytic sides. Starting from the requirements, a design suggestion is generated. In order to assess how well the envisioned design fulfils the requirements, it is sometimes necessary to build a computer model of it for the analysis. The overall motivation of the work presented is to reduce the time spent on creating the model by reusing knowledge gained from developing similar products by suggesting, building and evaluating IT-systems. To verify the systems real design examples, obtained from companies that have participated in the research projects have been used.

The work is based on two major application examples. The first, involving the automated geometrical idealisation of die-cast parts (Paper I-III), and the second involving manufacturability of powder metallurgy pressed and sintered parts (Paper IV-VI). The work starts from the point in the product development process where it exists a design suggestion represented as an arbitrary format CAD-model. In the powder metallurgy case the object is to secure that the geometry is suitable for the production process. In the die-casting case the object is to automatically create an idealised version of the model for shell elements meshing. These two tasks have previously been treated as two separate cases, addressed by completely different software. This thesis suggests a common method for addressing the two cases. The method is based on converting the CAD-models, using the geometrical restrictions of the production processes, into a format with a specialised feature structure, parameterisation and construction history using a feature recognition approach. The features are then automatically reconstructed in a target CAD-system. The resulting, specialised CAD-model can be used for automated design and design evaluation purposes, demonstrated in the thesis. The models are therefore called DAR (Design Automation Ready)-models. The DAR-models are useful in that they separate the conversion from the subsequent treatment of the models providing modularisation, flexibility and user insight in the model structure. In that a construction history and parameterisation have be constructed in the target CAD-system, the advanced geometry manipulation and means for knowledge management often provided in modern CAD-systems can be accessed in a transparent and user manageable way. This extends the usefulness of the CAD-systems from involving only interactive work to managing all components sharing the same production process.

Place, publisher, year, edition, pages
Göteborg: Chalmers Reproservice, 2008. p. 162
Series
Doktorsavhandlingar vid Chalmers Tekniska Högskola, ISSN 0346-718X ; 2856
Keyword
Design automation, CAD, KBE, Feature based modelling, Feature recognition, Product development.
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:hj:diva-10700 (URN)978-91-7385-175-6 (ISBN)
Public defence
2008-12-11, E1405, Tekniska Högskolan i Jönköping, Gjuterigatan 6, 551 11 Jönköping, Jönköping, 10:00 (English)
Opponent
Supervisors
Note
Teknologie DoktorsexamenAvailable from: 2009-11-03 Created: 2009-10-21 Last updated: 2009-11-03Bibliographically approved

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