Simulation of the Dynamic Environment for Missile Component Testing: Theory

Abstract

Abstract : The objective of this phase of work was to develop 'generic' sine and random tests for the 3-D vibration test machines. While 3-D testing is a dramatic improvement over conventional 1-D testing, to be able to use the new technology, it is necessary to use conventional test specifications to test in 3-D. In this phase we were to identify what tests should be run for sine and for random testing. In the process it was necessary to reevaluate the theoretical basis of the sine and random tests. We were also to look for any flaws in the 3- D test systems as currently implemented. The sine test has produced two candidate sine tests. By far the simplest and least controversial is a 2-D test where the shaker head is moved in a circle. By using a sine wave in one axis and a cosine wave in the other axis, traditional swept sine tests can be run in two orthogonal axes at one time. Just as current 1-D tests require three test axes, the 2-D sine test would be run in three orthogonal planes. Of course with the 3- D machine this would require no change of axes. The machine could simply go from one axis to another with a short pause between axes. Since the test would excite response from two directions of testing, it would be necessary to double the sweep rate, or halve the duration in some other manner. Three existing 1-D test levels would completely define the specification for such a test. To improve on the 2-D sine test, it is necessary to give up on the sinusoidal test waveform. (aw)