COBEM99

S21 Vibrações e Análise Modal

Title:

EXPERIMENTAL AND ANALYTICAL DETERMINATION OF THE VIBRATORY BEHAVIOUR OF BEAMS COUPLED TO DISCRETE SYSTEMS

Summary :

THE PROBLEM OF VIBRATIONS IN SYSTEMS THAT COMBINE CONTINUOUS AND DISCRETE COMPONENTS IS OF GREAT IMPORTANCE IN ENGINEERING, HAVING BEEN THE SUBJECT OF VARIOUS INVESTIGATIONS. BEAMS WITH FLEXIBLE CONSTRAINTS, INTERMEDIATE SUPPORTS, CONCENTRATED MASSES AND DISCRETE VIBRATING ATTACHMENTS ARE QUITE COMMON. IN CONTROL ENGINEERING, AN ACCURATE MODELING OF SUCH SYSTEMS IS VERY IMPORTANT, ESPECIALLY WHEN CONCENTRATED MASSES ARE USED AS PASSIVE OR ACTIVE VIBRATION REDUCERS. THUS, IN AN ACTIVE CONTROL SETUP, WITH THE CONTROL VIBRATING MASSES NOT ANCHORED TO AN AUXILIARY STRUCTURE, CONFIGURATION THAT IS KNOWN AS "SKY-HOOK", IT IS ESSENTIAL TO INCORPORATE THEIR DYNAMIC CHARACTERISTICS INTO THE SYSTEM MODEL. DUE TO THE COMPLEXITY OF THE MODEL, WHICH REQUIRES TRUNCATION AND APPROXIMATIONS, EXPERIMENTAL DATA FROM PROTOTYPES ARE ESSENTIAL FOR . THIS WORK PRESENTS BOTH AN ANALYTICAL MODEL FOR EVALUATING THE NATURAL FREQUENCIES AND THE RESPECTIVE MODE SHAPES OF COUPLED SYSTEMS, COMBINING CONTINUOUS AND DISCRETE COMPONENTS, AND THE RESULTS OBTAINED WITH AN EXPERIMENTAL MODEL OF SUCH A SYSTEM. THIS MODEL CONSISTS OF A CLAMPED-SIMPLY SUPPORTED EULER-BERNOULLI BEAM, WITH TWO SMALL ELECTROMAGNETIC VIBRATION EXCITERS ATTACHED TO SELECTED POINTS OF THE BEAM. THE NATURAL FREQUENCIES OF THE SYSTEM WERE OBTAINED FROM MEASUREMENTS USING A PIEZOELECTRIC ACCELEROMETER AND THE COILS OF THE EXCITERS.

Author :

Medeiros, José Bismark
Vasconcelos, Halei Fagundes
Zindeluk, Moysés 0

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