Okay, I will request forgiveness for the vagueness of my question.
The answer I was told to expect was "Miner's Rule". We do spectral exageration as IRstuff indicated via
(newPSD^4)*newTime = (oldPSD^4)*oldTime
or someother exponent. However how is that arrived at. GregLocock headed...
IRstuff,
Thanks for your response. What you've listed is the method for determining the new spectrum to acheive the new test time.
What I am looking for is people to identify "the underlying premise of test time reduction through amplitude exaggeration"?
I have a question. I'll keep it brief to not lead the response. However I would like to learn some of the background to the response.
Regarding durability testing on shaker tables, here is the question (please fill in the blank):
If you ask any vibration guy in the world the underlying...
electricpete,
Sorry for my lack of clarity. The test time refered to is shaker table test time.
Curiously I think your rule of thumb for doubling the stress S amplitude to half the N cycles is interesting. As a mechanical I would have applied a different ratio.
I have a question. I'll keep it brief to not lead the response. However I would like to learn some of the background to the response.
Here is the question (please fill in the blank):
If you ask any vibration guy in the world the underlying premise of test time reduction through amplitude...
Actually I need the fatigue data for A 656, but if there is a SAE equivalent, perhaps it is in my material database.
Is there any site that just lists equivalencies?
And a broader question is if you don't have fatigue data, and you don't have an equivalent's fatigue data, what is the best way...
BobM3,
Thanks for the help, but that was the paper I already referenced.
TheTick,
I appreciate your advice. Are gages are usually in locations that are difficult to calculate for with loading that isn't measured.
Bribyk,
I just got off the phone with one of the Vishay guys. He said some interesting things.
1) I described our tech using the pneumatic with scotch-brite pad to remove the paint and flatten the surface. As the pad is used, the pad is smoothed, causing the surface to be polished. The...
Another thing! An engineer here argues that the error caused by bad surface prep is small compared with the total error in the data acquisition system.
I say that isn't true, but how?
Does anybody have a referenced study proving this?
In otherwords is there any literature, or convincing description that describes the relationship between adhesive film height/distribution compared with gage length. If the gage is attached to the adhesive, and the adhesive is attached to the steel, and the steel strain causes adhesive strain...
The engineers in our group are having a discussion as to how to convince our tech's they need to be increasing their sand paper fineness when they prepare surfaces for installing gages. (Instead of arguing, it is some times easier to convince.)
Everything I find in the literature make your...
I'm forced to use TurboCAD, first time today. Not allowed to install AutoCAD. I have an AutoCAD background, but when I try to do simple things in TurboCAD (like move an object from a snap-to-point to a snap-to-point) all kinds of crazy junk happens. And I still don't get done what I want...
I ran Matlab's profile routine, which led me to the solution (a solution which I already thought I tried, but on third look wasn't implemented correctly...)
I fixed it by initializing my array as zeros(size) to the fullest size it would see during execution.
I recently went through the rigor of converting an old Fortran code (77, 90?) to a matlab script.
The program is supposed to analyze 45,000 data points, using a couple nested while loops. (FORTRAN code uses several nasty GOTO statements to jump backwards and forwards.)
Compiled Fortran...
We're talking 1000's of parts.
Some of the techniques I've come accross have been tumbling a batch in a basket under near cryogenic temperature, blasting with a softer material... Something that would lead to the thin flash breaking off, but not the thicker regions.
My company is using a Chinese manufacturer to produce the small polycarbonate parts we use in our prototype mechanical devices.
The parts are intended to work closely with each other, where tolerances in the micrometer range are important.
The production quality parts made by the our...
joyem and all,
Thanks for the reply. I'll try your and Liro's method when I get a chance. Earlier I tried picking the individual nodes and coupling their degree of freedom - which I think I did correctly. Then after applying the load, followed by what I thought were the b/c constraints, I...
Alright, I'll admit I don't know how to do something that should be very simple and basic for everyone else who knows how to use I-deas. I'm a newbie and I can't find this in the tutorials or help files.
I have two parts. A small piece of steel glued inside a bulky block of epoxy.
I want to...
jazzyq,
I'm pretty confident you will still need the experimentally determined the critical and arrest fracture energies, or the fracture toughness, to know exactly "when" the crack will propogate and when it will stop.
For instance you can simulate strain energy release rate by measuring the...
