Disquisition an hydrodynamics-hydromagnetics aspects of film boiling heat transfer
- Autores: Francisco Javier Arias Montenegro
- Directores de la Tesis: Francesc-Josep Reventós Puigjaner (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2009
- Idioma: español
- Tribunal Calificador de la Tesis: Mª del Carmen Pretel Sánchez (presid.), Agustí Pérez Madrid (secret.), Fabio Moretti (voc.), Maria Cristina Galassi (voc.), Ignacio Pagonabarraga Mora (voc.)
- Materias:
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- Resumen
The intention of this research is to go beyond currently available systems for the assessment and selection of Rapid Prototyping processes, hence introducing a new methodology devoted to 'Manufacturing' applications. Specifically the system would include a number of state of the art artificial Intelligence techniques to comprise a fully concurrent methodology, namely: ¿ Expert systems are included to aid in the decision making process with multiple alternatives. Expert systems typically use If-Then-Else or CASE structures so that the available options can be screened specially during the first selection stages.
¿ Fuzzy logic for decision making. Usually in manufacturing, linguistic terms or qualitative parameters are used to define states of properties. For instance it is common to find terms such as 'Good mechanical properties' or 'High absortivity rates' therefore it is necessary to have a method to translate and manage such information. Fuzzy logic has been adopted as a means to translate qualitative terms to quantitative information.
¿ Multi-criteria decision making, aggregation and ranking. Different methods for selecting and ranking alternatives were tested which allows the integration of quantitative vectors with weighting factors that reflect the user preferences. For this purpose the method proposed by Lan et al. (2005) has been adopted as discussed in Chapter 5.
¿ Artificial Neural Networks (ANNs) are being applied for the modelling and simulation of a number of Rapid Manufacturing Methods. Selective Laser Sintering has been modelled using a back propagation algorithm ANN taking as a basis the information provided by the machine software. The ANN simulates a DTM Vanguard SLS machine available at Fundacio CIM-UPC, Barcelona, while the Selective Laser Melting has been modelled with the parameters and settings used by the Concept Laser M2 machine available at the Mechanical Engineering Lab of the Catholic University of Leuven, Belgium. The extracted models exhibit a build-time prediction error rate lower than 10%, which is a significant improvement compared to conventional parametric methods.
¿ Finally, relational databases have been applied for storing and handling materials information. These databases have been stored as Ms Access data which provides the ease to access, filter, screen and plot the required information. This data can be automatically called and extracted by means of an ODBC call deployed within the Matlab environment.
In order to illustrate the functionality of the previous tools put together, a pilot application was designed in Matlab, making use of a number of specialized toolboxes namely: Fuzzy logic, Neural Network, Statistics, Plotting utilities, GUI builder, Database.
The result is a prototype system with a graphic user interface divided in three modules: ¿ General design requirements: which deals with those parameters usually defined in the product PDS, for instance: material type, tolerances, surface roughness, geometrical complexity, etc.
¿ Costing module: which makes use of parametric cost estimation and ANN-based models to perform the calculation of cost per part, and for low volumes ¿ Materials selection: Shows the iterative nature of materials selection through screening steps so that the range of suitable options is limited.
