Interpreting requirements?

[JakeLiv]

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.

 

[tomirvine]

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

Tom Irvine

http://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

 

[JakeLiv]

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.

 

[tomirvine]

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

http://www.vibrationdata.com

 

[JakeLiv]

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.

 

[tomirvine]

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

http://www.vibrationdata.com