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PostPosted: 04 Nov 2015, 03:49 
Sherlock User

Joined: 28 Dec 2014, 21:21
Posts: 10
Dear sir,
1. one quesiton for vibration need your support.
If the vibration PSD profile Freq range < board natural Freq, in sherlock, we can`t get any relibility result(such as TTF/Strain/Displacment/Score..), is it right by sherlock?

E.g.
PSD Freq range:10-60Hz
Board natural: 70Hz
the RV analysis result is empty. see the pciture

2. another question for Natural Freq,
I was running assembly board(2 PCBs) NF analysis, but sherlock just got #1 &#2 NF result, what`s the problem for that? i was set the NF reuslt counter= 5


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PostPosted: 08 Nov 2015, 19:42 
Site Admin
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Joined: 21 Mar 2013, 16:40
Posts: 121
Location: Beltsville, Maryland
Hi,

This type of result is due the displacements being very small which generates generates a damage which is close to zero. These very small numbers cause a divide by zero result and prevents the computation. You can extend the random vibration profile slightly(with a small amplitude) to encompass the 1st natural frequency of the board it should work.

The number of natural frequencies returned are for the frequency range you specify. If only 2 are being returned there are only two results in that frequency range, make the range larger to get more NF results.

Best regards,

_________________
Nathan Blattau, PhD
Senior Vice President
DfR Solutions, LLC
9000 Virginia Manor Rd, Ste 290
Beltsville MD 20705


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