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Interpreting requirements?

Interpreting requirements?

Interpreting requirements?

(OP)
Hi


I need to perform vibration and shock analysis for a rather large crate - 3.1*.5 sq. meters. I have some data in the form of vibration specrtum, and a grms value. I do not have the PSD/ASD graph, or any values from it.
here is an excerpt from the specs:

Vibration:

Truck Transportation    Frequency Range: 10 to 500Hz
Random Vibration Level :
Vertical (Z) - 1.04 Grms
Transverse (Y) - 0.20 Grms,
Longitudinal (X) - 0.70 Grms    
Restrained cargo, At the Shipping Crate Base
MIL-STD-810F, Method 514.5, Procedure I, category 4
System Required to Operate after Exposed to Vibration

Shock:
Truck Transportation    
Half Sine, 10Gpeak, 10msec    
Estimated from Shock Spectrum F.E. Ostram "A Survey of the Transportation and Vibration Input to Cargo" Shock and Vibration Bulletin #42(5), 1972, pp137-151

I'm using MSC/NASTRAN and PATRAN for the simulation, but I only need to know how to interprt the requirements into something more understandable.

RE: Interpreting requirements?

I am enclosing the coordinates for the MIL-STD-810F Truck PSDs.

Tom Irvine
www.vibrationdata.com

Longitudinal
Freq(Hz)  PSD(G^2/Hz)
10    0.00650
20    0.00650
120    0.00020
121    0.00300
200    0.00300
240    0.00150
340    0.00003
500    0.00015

Transverse
Freq(Hz)  PSD(G^2/Hz)
10    0.00013
20    0.00065
30    0.00065
78    0.00002
79    0.00019
120    0.00019
500    0.00001

Vertical
Freq(Hz)  PSD(G^2/Hz)
10    0.015
40    0.015
500    0.00015




RE: Interpreting requirements?

(OP)
Thanks :)
I got my hands on the mil-std-810.
I have a few other spectrums, which are shown in a graph, not in a table like the truck spectrum.
How can I convert the graph to a table?

TIA

Jake.

RE: Interpreting requirements?

If necessary, you can digitize plots using a image of the plot and a Matlab script.  The plots can be linear, log, or any combination thereof.

Do you have access to Matlab?

If so, I can provide a script.

Tom Irvine
www.vibrationdata.com

RE: Interpreting requirements?

(OP)
Thanks.

I have access to MATLAB.
How do I need to scan those pics? I have the PDF version so I can just extract the graph.

thanks again

Jake.

RE: Interpreting requirements?

There are many ways to do this.

For example, you can copy the graph from the PDF document.  Then paste into MS Paint.  You can then save the image as a bmp or jpg file.

Then import the image into Matlab.

Tom Irvine
www.vibrationdata.com

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