accelerate sine vibration test
accelerate sine vibration test
(OP)
2 m/s^2 in 5 million cycles is the demands for a sine vibration test on a simple shaker table.
could this value bee converted in a simple way so we could perform less cycles?
im looking for some rules to accelerate this test.
could this value bee converted in a simple way so we could perform less cycles?
im looking for some rules to accelerate this test.





RE: accelerate sine vibration test
TTFN
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RE: accelerate sine vibration test
The Basquin law gives a relationship between the number of cycles N and strain S. The product of the both terms is constant. Actually not exactly the product of N by S, but rather N*S^b=Constant. In this equation, b is a very important coefficient. Practicaly, b is fixed between 5 and 8.
Now, the reduction rule of the test duration is :
reduced acceleration = real acceleration * (Real time/ Reduced time)^(1/b)
That's it!
RE: accelerate sine vibration test
I found this in a letter called PIE9301T.pm5 from www.ttiedu.com:
"It follows that if a test is performed with an input vibration
level of st on a test item that experiences an input vibration
level of se in its service environment, the test duration Tt
needed to produce the same damage as a service vibration
environment of duration Te is
Tt = Te (se/st)b"
This letter also mentions the b material constant and state MIL-STD-810E[7] reccomends a value of b=6 for sinusoidial vibration tests.
I just get very low values, if i use youre equation Amanuensis i can go from 5 mill cycles to 2 mill cycles just by raising the acc from 2 to 2,33 m/s^2 could this really be true?
RE: accelerate sine vibration test
Now these equations are terrific if your system is behaving like a nice piece of steel in a torsional test in a lab, but the 64000 dollar question is how do you prove it?
Developing robust testing plans is an art form, sadly one I know little about.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: accelerate sine vibration test
The item being tested is a cooler consisting of: alu element, steel shroud, motor bracket, motor and fan assembly.
The shaker table we use is a simple construction of a thick aluminum plate with a motor shaft connected to a adjustable mass where you can adjust the "off center" distance.
RE: accelerate sine vibration test
Fatigue is taken into account (using Woeler curve) for reducing time of vibration test.
If you perfectly know this standard, you don't need to be an artist!
RE: accelerate sine vibration test
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?