Obtaining Shock Pulse Input Data from Shock Response Spectrum

[rocketscientist628]

I need some help determining how to convert from a Shock Response Spectrum plot back to the appropriate Shock Pulse level and duration. The customer spec. contains a four coordinate plot which I think is called a Fourier/Pseudo-Velocity Spectrum. This plot shows the "pseudo-velocity" on the vertical axis and the "frequency" on the horizontal. Ascending diagnals show "displacement" and descending diagonals show the "acceleration." Can someone please point me in the right direction to determine how to obtain the shock pulse magnitude and duration from this plot?

 

[IRstuff]

I think it's a one way trip.

If you have a copy of E. W. Clement's NRL report 7396 for 901 shock, "Shipboard Shock and Navy Devices for its Simulation," there is a brief discussion about the curves you mention. However, it's not obvious that you can get a meaningful time function from the spectra.

TTFN

 

[CESSNA1]

ROCKET...:

This is the first time I have heard of going backward in SRS. Usually the input is specified and the response is plotted. The input shold specify the G level, the type of pulse and the duration; such as: a 2G half-sine for .3 seconds. I do not understand how you can have an SRS response and not know what it is based on. You, maybe, could do this for a single degree of freedom system, but I am not sure it would work with a multi-degree of freedom system. You may want to discuss this with someone who uses SRS regularly, or the people who gave you the response

Regards
Dave

 

[rocketscientist628]

Thanks for your help guys! I've come to the point that I'm going to have to either ask the customer for clarification or iterate using various input values and see what SRS I get. The main difficulty with doing this is that the SRS that I have been given by the customer is a "pseudo-velocity" response plotted on four coordinate paper. In other words, the velocity is plotted on the ordinate axis, frequency on the abscissa, and acceleration and displacement plotted at angles on the same graph. I'm not finding much material on how to graph the SRS on this coordinate system.

 

[NormPeterson]

I remember of a program available at a previous employer called ARSINV, for ARS Inverse. So it appears that somebody has investigated this.

If my memory on this is still intact after 15 or 20 years, the task involving that program was scrapped.

Norm

 

[rocketscientist]

Actually, we have a program here at my company that will create the SRS from inputed half sine data, so I have been iterating trying to replicate the SRS information that I have been given by the customer. Unfortunately, the customer info is on a nomograph and our output is 2 coordinate log plots. If someone is familiar with interpretting these nomograph shock response plots, that would be very helpful! Thanks again to all for your help!

 

[nyptschuck]

Google Wayne Tustin. He has been teaching and writing on shock and vibration for years. He is very accessible. Give him a phone call.