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Abstract(s)
O presente trabalho consiste no desenvolvimento de um programa em Python para a medição
das funções de resposta em frequência, e posterior identificação das frequências e modos
naturais de vibração de uma estrutura unidimensional. Este teve por base uma revisão
bibliográfica sobre os conceitos essenciais ao desenvolvimento do programa. O programa,
realizado em código de fonte aberta, ou seja, não requer licenciamento, subdivide-se na
aquisição e processamento dos sinais, e na posterior análise para a identificação das
frequências e modos. Na rotina de aquisição e processamento é realizada aquisição dos sinais,
os quais são processados para se obterem as funções de resposta em frequência. Na rotina de
análise são identificadas as frequências e os respetivos a partir dos valores de pico das funções
de resposta em frequência medidas. Como forma de validação do programa implementado,
foram identificadas as três primeiras frequências e modos naturais de vibração de uma viga em
aço para a condição livre-livre. O ensaio foi realizado com um martelo impacto e um
acelerómetro fixo numa extremidade da viga, e o sinal adquirido com uma placa de aquisição
da National Instruments ®. Os resultados obtidos foram comparados com as soluções numérica,
realizada no software ANSYS®, e analítica. Os resultados obtidos pelos três métodos encontramse
bastante próximos, pelo que permite validar o programa desenvolvido e o procedimento de
medição experimental. Perspetivaram-se ainda melhorias ao mesmo, nomeadamente a
implementação de um trigger level.
This work consists of developing a Python program for measuring frequency response functions and subsequently identifying the natural vibration frequencies and modes of a one-dimensional structure. It was based on a bibliographical review of the concepts essential to the development of the program. The program, made in open-source code, i.e. it does not require licensing, is subdivided into signal acquisition and processing, and subsequent analysis to identify frequencies and modes. In the acquisition and processing routine, signals are acquired and processed to obtain the frequency response functions. In the analysis routine, the frequencies and modes are identified from the peak values of the measured frequency response functions. As a way of validating the program implemented, the first three frequencies and natural modes of vibration of a steel beam were identified for the free-floating condition. The test was carried out with an impact hammer and an accelerometer fixed at one end of the beam, and the signal acquired with a National Instruments® acquisition board. The results obtained were compared with numerical solutions, carried out using ANSYS® software, and analytical solutions. The results obtained by the three methods are very close, which makes it possible to validate the program developed and the experimental measurement procedure. Improvements to the program are also planned, namely the implementation of a trigger level.
This work consists of developing a Python program for measuring frequency response functions and subsequently identifying the natural vibration frequencies and modes of a one-dimensional structure. It was based on a bibliographical review of the concepts essential to the development of the program. The program, made in open-source code, i.e. it does not require licensing, is subdivided into signal acquisition and processing, and subsequent analysis to identify frequencies and modes. In the acquisition and processing routine, signals are acquired and processed to obtain the frequency response functions. In the analysis routine, the frequencies and modes are identified from the peak values of the measured frequency response functions. As a way of validating the program implemented, the first three frequencies and natural modes of vibration of a steel beam were identified for the free-floating condition. The test was carried out with an impact hammer and an accelerometer fixed at one end of the beam, and the signal acquired with a National Instruments® acquisition board. The results obtained were compared with numerical solutions, carried out using ANSYS® software, and analytical solutions. The results obtained by the three methods are very close, which makes it possible to validate the program developed and the experimental measurement procedure. Improvements to the program are also planned, namely the implementation of a trigger level.
Description
Keywords
Python Natural frequencies Natural modes Experimental test Frequency response function Frequências naturais Modos naturais Ensaio experimental Função de resposta em frequência