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Has anybody tried using carbon fiber as a fixture material? Here in the vibration lab, we were brainstorming about alternative fixtures for our products and an outside the box suggestion of carbon fiber came up. We're thinking why not? A foam core would be great for vibration damping, the...

Ok thanks for validating my thoughts. Greg, the best response that I've heard so far is that bare fixture response is close enough to real test conditions and fixing any resonances in the region of interest is better than doing nothing.

We run aerospace parts ranging in size from baseball size up to 1000 pound engines on our shakers. Some customers want to do a bare fixture evaluation and some don't. I've heard some reasons to do it and some reasons for why it's a waste of time but I haven't been able to really delve into it...

Perhaps as a proof of concept, you can download an app for your phone that displays what the built in accelerometers measure. The operative word here is that it's free or at most, a couple dollars. Make sure you remove the phone from the case, first. I have a couple for my iphone, one is...

I used to live in the bay area and moved out of state because of the cost of housing. Can you afford to buy a house for $600,000-750,000? I moved away right before the economy went down, but at the time I could only afford 300k-400k, and we were only able to look at run down, 2 bedroom...

StrikerTech, but once that resonant frequency is found and you dwell at it...what if the resonant frequency changes during the course of the dwell. Say it shifts 3% higher. Do you adjust the frequency on the fly to continuously track it, or do you stay at the original frequency? That's the...

Thanks. I'm having a discussion with my tech about the definition of "Resonance Dwell". At this site, the conventional nomenclature of "Resonance Dwell" specifically means a tracked dwell (follow any frequency shifts) while "Fixed frequency" means stay with one frequency regardless of...

What do the terms "resonance dwell" mean to you? Does it mean tracking dwell or fixed freqency dwell? Or is it more of a general term that further needs to be defined by "track" or "fixed"?

In addition to the microscope, they make software that does this automatically, however it's not cheap. The olympus microscopes that my previous company used were about $45,000 each plus the price of the basic software. Particle counting was extra. Have you thought about outsourcing this work...

No, we were using cheap COTS washers for a somewhat large piece of equipment, not fender washers. This was not an important application.

I've read that lock washer thread before but missed the one Mint linked. Our MS washers also don't have this problem. I didn't think it would matter considering the hundreds, thousands or tens of thousands of pounds of force that a bolt can produce. The only thing I could think of was that...

Maybe I missed this in the search, but I didn't see this topic posted before... Recently, one of the grey beards (or mustache in this case) said to always put a washer on a bolt a certain way. The washers are stamped so often times there is a curve or bow to them and they also have a slight...

Well things just got interesting...I got promoted...in place. It was certainly a shock to me. After thanking the boss, I flatly asked about the "promote in place" policy and he said yeah all the managers are hounding the HR people about it and they are either giving up on the policy or are...

It depends. I've run one SOR where the levels of the tones were so small in comparison to the random level, that the tones either didn't show up or were barely noticable. Also, with our spectral dynamics software, we can choose for the tones to be additive or not. But yes, in general, the...

Thanks all, looks like I was right. We've done it both ways here, with the vast majority having the control accel(s) right next to the unit on the fixture. For the sake of this discussion, I just said "on the unit" for simplicity.

Mike - "The displacement of the UUT relative to the floor/ building/ local 'ground' is what's important." Greg - "But if the accel is on the UUT there is no problem." I think this is where I'm getting confused. Our control accel is on the unit. It seems to me that the displacement relative...

I've been told that at low frequencies, <3ish Hz, that the motion of the whole airbag supported shaker subtracts from the motion of the unit under test, but I'm having a hard time wrapping my head around it. For example, when we ran a dwell at 2 Hz the whole shaker moved, about 1/2", roughly...

Their labor rate is indeed cheaper than the US shop rate, however, the SOTB shop takes twice as long! Ultimately, everybody who buys a plane ticket picks up the tab.

I'm letting management sort it out. My managers agree, the shop should eat the cost, but I know that's not going to be the case. We'll end up having to pass the cost on to our internal customers.

Thanks for the replies; they mirror my thinking and just about everybody else's here. Here's the fun story. I work for a large aerospace company and the machine shop is a group within the company but they are based in an "emerging market" south of the border (SOTB). They have to bid for our...