Looking at data for a math textbook, I have found a list of vibration rates for various industrial tools (angle grinders, scrapers, drills, etc.) The data is great for what I need (basic stats), but what I don't understand is why the vibration rates are quoted in meters per second squared. That's acceleration, right? Yer masonry drill isn't accelerating, it's just whipping back and forth very quickly. I mean, obviously you can vary its speed, but, again, that would be measured in plain old meters per second.
Enlightenment, please. What am I missing?
If it is oscillating they might be referencing the edge speed, which is not stationary in speed because it is at different points from the center of rotation.
if it's not going at a constant velocity, along the same vector, without changing direction, it's accelerating.
Thanks, Autolex. That's very clear. Weary, I see your point too, but I think Mr. A. has nailed it.
Much obliged!
Anybody else want to jump in?
Something that is "just moving back and forth really fast" constantly accelerating. The stress that imposed on a part by a vibrational loading is due to to the constant acceleration.
The nice thing about working in the acceleration domain is that its relatively easy to measure (with an accelerometer) and you can use it along with a little knowledge of the part to back out the parts displacement (assuming that is what you are looking for)
Actually, it's much less complicated than that. It's entry-level stats (mean, mode, median) and my wife (who is a genius at finding good contexts for math problems) came up with the acceleration rates for various vibrating tools at this UK workplace safety website. I just couldn't see why the figures were for acceleration instead of speed, but I do now, thanks to the GRM hive mind. And I appreciate it!
Our vibration techs use displacement (mils), velocity (inches/sec), and acceleration (G's, rms). Depends on what they're looking at, or what the customer wants to see.
When balancing impellers and rotors, they use the mixed term "gram inch" for the weights. That one drives me nuts.
