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. Random RMS is the square root of the area under a spectral density curve. In this approach you get the response of a structure as a function of the frequency. 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. By Harmonic response I think you are talking about a frequency response fea analysis. 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. 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. A good article shows how to establish a random vibration profiles from swept sine tests. However, peak sine acceleration is the maximum acceleration at one frequency. Any waveform is actually just the sum of a series of simple sinusoids of different frequencies, … Similarities in damage potential are considered in the article. Fast Fourier Transform (FFT) FFT Background. This paper is to discuss a mathematical method to compare … The phase difference between the two sine waves refers to the difference between the phases of the waves. (Machine Design/February 6, 1992). 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). 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. NASA requirements differ however between the SV testing requirements provided in Air Force Standard SMC-S-016, Test Requirements for Launch, Upper-Stage … Which one is practical in the feild ? 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 … I saw a PSD signal can be expressed in 2 ways. 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. The article is a good place to start. Can anyone explain the major difference between sine sweep and random vibration, and how to analyze the impact on the electronic products ? Just let me know your e-mail. Sine testing in our lab is a great … Two sine waves are out of phase when they are not at the same points in their cycles at the same time. Often, attempts are made to compare the peak acceleration of sine wave to the root mean square (RMS) acceleration of random vibration and shock. I recently started working on Random Vibration. However, both JPL … One in (G 2 /Hz) and other in ((m/s 2) 2 /Hz). These are not equivalent.