Resonant Bar Shock Test Equipment under Offset Loading

Mechanical shock testing utilizing different types of resonating fixtures is an aerospace environmental testing practice useful in simulating mid-field pyroshock. The resonant bar shock test method was developed in the 1980s to perform controlled single-axis resonant shock tests on aerospace components. In this method, a test article is attached to one end of a bar, and then the opposite end of the bar is struck with a projectile, resulting in a transient acceleration that rings down at the natural frequency of the longitudinal extension mode of the assembly. If the impact of the projectile occurs on the longitudinal axis of the bar, nearly all the test article acceleration is in the longitudinal direction; acceleration response in transverse directions is very low. In recent testing, it is found that substantial transverse acceleration of the test article, on an order similar to the longitudinal acceleration, can be achieved if the projectile impact is offset from the longitudinal bar axis. This effect was investigated on a legacy resonant bar test assembly and on a new resonant bar test assembly designed to exploit the potential for transverse acceleration shock response. The controlled acceleration response achieved using these techniques has the potential to meet a shock response specification in three response directions simultaneously in a single shock test.