The article is a good place to start. Any waveform is actually just the sum of a series of simple sinusoids of different frequencies, … In vibration testing, the interest is not so much the phase of an individual wave, but the phase difference between a sine wave and a reference wave. One in (G 2 /Hz) and other in ((m/s 2) 2 /Hz). A good article shows how to establish a random vibration profiles from swept sine tests. Often, attempts are made to compare the peak acceleration of sine wave to the root mean square (RMS) acceleration of random vibration and shock. Two sine waves are out of phase when they are not at the same points in their cycles at the same time. Just let me know your e-mail. In this approach you get the response of a structure as a function of the frequency. Can anyone explain the major difference between sine sweep and random vibration, and how to analyze the impact on the electronic products ? However, peak sine acceleration is the maximum acceleration at one frequency. NASA requirements differ however between the SV testing requirements provided in Air Force Standard SMC-S-016, Test Requirements for Launch, Upper-Stage … Sine testing in our lab is a great … Best Practices for Use of Sine Vibration Testing Background of SV Testing SV testing is required by NASA-STD-7002 and most launch vehicle organizations as a final dynamic qualification of the payload to demonstrate acceptability for flight. JPL and GSFC have both similarities and differences in their spacecraft level vibration test approach: JPL uses a random vibration input and a frequency range usually starting at 5 Hz and extending to as high as 250 Hz. Similarities in damage potential are considered in the article. Several conditions were defined for which vibration could be equated on selected bases, and an interim vibration (constant period random amplitude vibration) was added between the sinus- oidal and operational vibration … These are not equivalent. sinusoidal and random vibration, to seek relationships that could eventu- ally result in definition of a conversion factor for human performance from sinusoidal to random vibration. I recently started working on Random Vibration. However, both JPL … GSFC uses a sine sweep vibration input and a frequency range usually starting at 5 Hz and extending only to the limits of the coupled loads analysis (typically 50 to 60 Hz). By Harmonic response I think you are talking about a frequency response fea analysis. Which one is practical in the feild ? I saw a PSD signal can be expressed in 2 ways. Random RMS is the square root of the area under a spectral density curve. This paper is to discuss a mathematical method to compare … For simple sine waves the vibration frequency could be determined from looking at the waveform in the time domain; but as we add different frequency components and noise, we need to perform spectrum analysis to get a clearer picture of the vibration frequency. The phase difference between the two sine waves refers to the difference between the phases of the waves. (Machine Design/February 6, 1992). Fast Fourier Transform (FFT) FFT Background. I do not have an electronic copy of this article, but if you would like I could scan it to a file and then e-mail it to you.