Evaluation of a Multiaxis Shock Fixture Concept

Mechanical shock testing utilizing different types of resonating fixtures is an aerospace environmental testing practice useful in simulating mid-field pyroshock. Qualification tests using these methods may be specified in single or multiple test axes, with each axis performed individually or sometimes all at once. Simple structures such as bars, beams, and plates have been used to repeatably perform single-axis resonant shock tests, while plates of varying sizes along with a 90 degree bracket have been used to perform tests that meet all axes requirements in a single shock test event. This work will evaluate a different fixture concept, used in conjunction with a resonant plate. The fixture is designed to create a controlled resonant response in two axes, which when combined with the plate motion in the third axis can achieve a repeatable resonant shock response in all axes at once, with minimal setup time or operator trial and error. Modal properties of a combined fixture and plate assembly are used as performance objectives for the fixture design. Finite element modeling is used to evaluate and modify the fixture design. A fixture is then fabricated and tested in several configurations to evaluate modal response characteristics, shock response performance, and the performance of the model when predicting those quantities of interest.