Multi-axis, complex mode pneumatically actuated annular frame shaker for

Abstract

Pneumatically driven vibrators coupled to resonating, self-attenuating structures define a shaker which, when included in a vibration system, enables a test item to be vibration tested under controlled conditions of multi-frequency, multi-degree-of-freedom acceleration history, to achieve a frequency spectrum and acceleration-level control of a broadband quasi-random vibration output in the frequency range, for example, from 40 Hz to 2 kHz for vibration testing of equipment. The driving set of annular structure responds to an intense vibration spectrum, created by the attached pneumatic vibrators, with multi-modal forced and resonant frequencies in limited directions. The driven set of annular structure, holding the test hardware, responds with forced and harmonic oscillations to a vibration field transmitted from the driving set of structure through a specially designed elastomeric path. Specific design of the size, mass, and resonant behavior of the driving and driven structure sets with appropriate transmissibility characteristics of the elastomeric interface results in a controlled multi-modal, uniform RMS acceleration, multi-degree-of-freedom, wide-frequency-range vibration testing method. The annular arrangement of structure takes advantage of the complex amplitude-displacement behavior of the circumference of a ring excited into multi-modal in-plane and out-of-plane bending and torsional activity by the attached vibrators. Changes in pneumatic vibrator operating pressure change vibrator frequencies and expand available modal density.