Everaldo de Barros

Experimental facilities for modal testing

Purpose The experimental modal analysis requires good knowledge of various engineering fields, such as mechanical vibrations, transducers used in vibration measurement, transducers and system calibration methods, data acquisition systems, digital signal processing and system identification. Test facilities constitute a key factor for improving the quality of the estimated modal model. This paper aims to describe the experimental facilities at the Institute of Aeronautics and Space (IAE) Modal Testing Laboratory in terms of associated instrumentation and data acquisition system, metrological aspects and computational resources. The discussion is completed with a practical application showing a ground vibration testing (GVT) of an unmanned aerial vehicle (UAV). Design/methodology/approach The experimental facilities were evaluated in a typical GVT, using three shakers in both vertical and horizontal excitations and 88 response measurement points. The global excitation method was used to excite all desired modes. The reliability of the experimental modal model was validated by an auto modal assurance criterion matrix for the measured modes of the structure. Findings The experimental facilities were successfully used for validating the dynamical characteristics of the UAV under testing. Originality/value The modal test facilities of the Modal Testing Laboratory at the IAE, the main research center of the Brazilian Air Force, are described in this paper.

A low cost data acquisition system for measuring shock

One of the most common environment tests is the shock testing, widely used to test the mechanical integrity and to ensure the quality and reliability of products. During shock tests, data acquisition systems are normally required for measuring acceleration time histories and processing the shock response spectrum, or SRS. This paper presents a data acquisition and analysis system based on a computer sound card for measuring shock and characterizing the shock severity by its SRS. Since the tasks of shock data acquisition frequently require expensive hardware and software, this low cost system represents a very accurate and inexpensive solution for shock characterization.