Full text
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| Author(s): |
César Yukishigue Kiyono
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Escola Politécnica (EP/BC) |
| Defense date: | 2008-03-28 |
| Examining board members: |
Emílio Carlos Nelli Silva;
Júlio Cezar Adamowski;
Jun Sérgio Ono Fonseca
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| Advisor: | Emílio Carlos Nelli Silva |
| Abstract | |
This work aims at the development of a method based on Topology Optimization to design a mechanical structure, called sonotrode, which is a device usually connected to a high power piezoelectric transducer (mechanical device capable of converting electric energy into mechanical displacement or vice-versa). A sonotrode transmits mechanical vibrations of a piezoelectric transducer, adjusting the amplitude and the distribution of these vibrations to fit the design needs of the transducer. Among applications of piezoelectric transducers using sonotrodes, we can cite navigation sonars, ultrasonic cleaning and melting, acoustic tomography, ultrasonic drilling, ultrasonic fabric cutting, etc. The design needs of the sonotrode differs for each application, ranging from obtaining maximum displacement in one single point of its structure, to obtaining uniform displacements on a whole face of the sonotrode. To improve the attainment of the optimum result, in this work \"Topology Optimization\" (TO) is applied to design the sonotrode. TO is a procedure to design the optimal layout of structures by distributing material within a fixed domain. The objective of the developed TO formulation is to find the best topology of the sonotrode that produces maximum and uniform displacements at one of its face. The TO method is implemented using the \"Sequential Linear Programming\" (SLP) as the optimization algorithm, and it is based on the \"Simple Isotropic Material with Penalization\" (SIMP) interpolation for material model formulation. It\'s also presented a study about the material model \"Rational Approximation of Material Properties\" (RAMP), in an attempt to reduce numerical instabilities like localized modes. \"Finite Element Method\" (FEM) is applied to model the sonotrode considering piezoelectric four-node axisymmetric elements. A node-based design variable implementation for continuum structural topology optimization is presented to minimize numerical instabilities such as \"checkerboard pattern\". The ressonance frequencies and modes are computed through Lanczos Method. A \"Modal Assurance Criterion\" (MAC) based formulation is used to track a certain mode, so that, the ressonance frequency related to this mode can be optimized. Examples are presented to verify the efficiency and the generality of the proposed method, and also, a study about the influence of the optimization parameters used in the method. Finally, results that meets all the design requirements are presented, as well as their post-processed topology, and the analysis in the commercial software ANSYS®. (AU) | |