OPERATING STRAIN MODE IDENTIFICATION USING ACCELERATION MEASUREMENTS

摘要

The identification of strain critical regions on machinery and equipment, under operating conditions, can be accomplished by knowing the operating strain modes. Operating strain modes are interpreted as a dynamic strain distribution of the structure at a specific time or frequency. Strain measurements are conventionally obtained by strain gauge techniques. However, strain measurements with conventional strain gauges are not always possible, and the gauges are not reusable and cannot be moved from point to point when they have been attached to structures. In this paper, a post-processing technique based on Operating Deflection Shapes (ODS) is evaluated with an experimental test. Operational strain modes of an aluminum plate were identified from accelerations measured using tri-axial accelerometer. The operating modes were analyzed at frequencies close to the plate's natural frequency, previously known by numerical simulation, in the frequency range 0 - 1000 Hz. The plate was excited with random white noise signal. We used the finite element method in the displacement to strain transformation. Operational modes were compared with simulated modes, which were obtained by modal superposition. The comparisons showed consistency between experimentally and numerically identified modes. Regions of greatest strain could be identified graphically in the color map regarding the minimum and maximum strain.