Random and constant or swept sinusoidal frequency tests are the typical methods of vibration testing. Random Vibration: As per MIL-STD-883E, Method 2026, this test is conducted for the purpose of determining the ability of the microcircuit; to withstand the dynamic stress exerted by random vibration applied between upper and lower frequency limits to simulate the vibration experienced in various service-field environments. Random vibration is more characteristic of modern field environments produced by missiles, high-thrust jets, and rocket engines. In these types of environments, the random vibration provides a more realistic test. For design purposes, however, a swept frequency sinusoidal test may yield more pertinent design information. Sine vibration testing uses a single frequency to excite resonances within the device under test. In swept sine tests, the vibration sinusoidal tone is ramped up and down through a frequency range for a specific duration. This method is primarily useful for detecting resonant conditions within test devices. It can be useful to identify or simulate worst-case fatigue exposure by finding resonant frequencies of the test item. The most damaging stress conditions for the device can typically be obtained by conducting such a resonant frequency vibration test with increased amplitude. See the standard documentation for more information on test requirements, conditions, and procedures related to your application.
