APPLICATION OF THE MECHANICAL IMPEDANCE CONCEPT TO SHOCK AND VIBRATION TESTING.
Abstract
Until recently, the mechanical impedance concept has been ignored in connection with shock and vibration. In testing, the applications must be carefully planned. One compromise is to operate the shaker as an approximation to an infinite-impedance or a zero-impedance source according to the relationship of the average impedance of the tested item of equipment fo that of the structure o which the item is attached while in use. If a zero-impedance source is favored, it is desirable to make a transition to infinite-impedance at the lowest frequencies. Impedance is controlled simply by equalization. Another compromise is to adjust the spectrum of motion prior to mounting the equipment to be tested and require that the impedance of the shaker correspond to an upper envelope of the impedance of the structure on which the item is to be used. This involves a complicated servomechanism problem which must be solved for each test fixture and perhaps for each item to be tested. Simulating the exact impedance of the structure rather than an envelope is not feasible. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 09, 1960
- Accession Number
- AD0608030
Entities
People
- Charles T. Morrow
Organizations
- TRW Inc.