COBEM99

S21 Vibrações e Análise Modal

Title:

MULTI-REFLECTION LASER INTERFEROMETERS

Summary :

FOR THE ABSOLUTE MEASUREMENT OF THE VIBRATION AMPLITUDE OF A SHAKER TABLE WITH THE INTERFEROMETRIC METHOD, NORMALLY TWO-WAVE LASER INTERFEROMETERS ARE USED. TO COMPENSATE FOR TABLE TILTING AND TO INCREASE THE FREQUENCY LIMIT OF THE CLASSICAL MINIMUM-POINT METHOD, CONFIGURATIONS WITH MULTIPLE REFLECTIONS ON THE VIBRATING TABLE ARE USED. THESE CONFIGURATIONS CAN ALSO BE EMPLOYED IN OTHER FIELDS, FOR INSTANCE TO CHECK STABILITY AND THERMAL DRIFT OF STRUCTURES, IF AN OPTICAL FLAT SURFACE CAN BE DIRECTLY PREPARED OR FIXED ON THE STRUCTURE. THIS PAPER SHOWS THE CHARACTERISTICS OF A FOUR-REFLECTION TWO-WAVE INTERFEROMETER, WHICH CAN BE APPLIED TO ONE OR BOTH SIDES OF THE SHAKER TABLE. IN THE FIRST CASE THE MEASURING BEAM IS REFLECTED FOUR TIMES WHILE IN THE SECOND CASE ALSO THE REFERENCE BEAM IS SIMILARLY REFLECTED TO OBTAIN AN 8-FOLD MULTIPLICATION OF THE VIBRATION AMPLITUDE.IN PARTICULAR INTERFEROMETER INTRINSIC COMPENSATION OF TABLE ROTATIONS, TO AVOID SHIFT AND TILTING OF EXIT BEAM (IMPORTANT FOR MAINTAINING THE SUPERPOSITION WITH THE REFERENCE BEAM) IS ILLUSTRATED. TOLERANCES AND DESCRIPTION OF SYSTEMATIC ERRORS ARE REPORTED. KEYWORDS: LASER INTERFEROMETRY, MULTI-BEAM INTERFEROMETER, ACCELEROMETERS CALIBRATION

Author :

Alasia, Franco 0
Baggia, Sergio 0
Basile, Giuseppe 0

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