Fundamentally, these tests are conducted by placing the specimen in a machine that will:
1. Apply a force to the specimen and measure the displacement. The force applied may be static or vary in frequency.
2. Cause a displacement and measure the force. Often the displacement is swept over a frequency and/or distance range.
3. In some cases, velocity and acceleration of the test specimen motion is also measured or controlled. For instance, a frequency sweep of varying displacement that applies a constant acceleration to the Unit Under Test (UUT) may be desired.
Traditionally these applications use servo-hydraulic solutions – actuators and controls. Lately interest has been noted in using electric actuators and servo controllers to provide characterisations not possible with servo-hydraulic solutions, in addition to the “green” factor that electric solutions provide. This is not to imply that electric solutions are superior to servo-hydraulics in all applications. As with most engineering decisions, the best solution depends on the specific requirements.
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