Modern weapon systems used on high-performance aircraft have complex electronic assemblies, optical components and sensitive mechanisms that are required to survive and operate in a challenging dynamic environment throughout their complete life cycle. The design of these components depends on knowledge of the environmental loads acting on the weapon system during operational conditions. These include aircraft noise induced by engines, gunfire, etc., mechanical loads induced by aircraft structural response to flight conditions (transferred to the system through the pylons), and aerodynamic noise induced by turbulent boundary layer and shock-boundary layer interaction. The latter is considered to be the most significant source of the in-flight vibratory environment. Aerodynamic noise is expressed as pressure fluctuations in a broadband spectrum (typically up to 10kHz). These loads cause the system to vibrate in a broad spectrum.
The development of weapon systems involves extensive laboratory testing, designed to substantiate the durability of the hardware in flight-like environmental loads. Various types of laboratory tests are used as experimental simulations of in-flight loads, from direct mechanical vibration tests through acoustic tests in reverberant chambers, or progressive wave tubes. The question of interest is which testing method, in terms of boundary conditions and excitation type (mechanical or acoustic), is most adequate to accurately simulate the response of components to flight loads.
To answer that question, a weapon system was tested in mechanical vibration test as well as in acoustic test, in an attempt to replicate the system’s acceleration response that was measured in captive flight. In the mechanical vibration test the system was excited by electro-dynamic shakers, whereas in the acoustic test, the excitation was done by loud speakers in a reverberant chamber. The responses from each test were studied for their frequency content, and compared to the responses measured in captive flight. The seminar will present the tests setups, results, the effect of boundary conditions, and will conclude on the suitability of each test for studying in-flight loads.
