Nice work. Just a few more words on the concept that the assumption of the COF at 0.3 would be useful. Otherwise I would say it is a useful assumption that allows a simple experiment to go forward and it does tend to pan out. The other comment is that a slightly more complex view of the neck is caused when the boundary isn't free at the shoulder as it is at the open end of the neck. If the neck was just a cylinder with simple boundaries at each end, then the simple pressure concept would be more valid.We have a much less rigid "hoop" when there is nothing but the free end or more cylinder next to part of the neck, versus, when that neck blends into the shoulder and is much more rigid. The plots show this effect in several ways and it bears mentioning. Nothing wrong with the simplifications, I am just suggesting that not all the viewers have an scientific or engineering background and this is the right place to open that can of worms just a little, then carry on to see what pans out. The time based smooth stroke is okay, but what about a displacement transducer like an LVDT or Pot to actually plot the axis in displacement instead of time?I enjoyed the video very much and hope you keep going!
@PounderLabs
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Dino C… Thank you for your feedback and encouragement. From your comments, I can tell you have a good background on these topics and as you note we're making a swag with COFk = 0.3. Over the last several months, we studied the literature for COF for different material interfaces. We found a range for the various materials can go from 0.21 to 0.44 and the closest ones for brass/copper are in this range. We have the model open so as we get better data we can improve results estimates. Also, we have in-plan a COF measurement set-up because we must get materials in-hand and find the relationships empirically. You're correct, the shoulder does play into this and over time we will try to better understand this boundary condition. Working with the hoop stress thin-wall assumption with the interference allowances in the 2.0 to 3.5 mil range we thought we would introduce what we have and, as you say, we're open to more input and discussion. We are currently working on thinning the walls, do the seating and put the numbers up for discussion… Stay tuned and thank you for mentioning this. Force/time vs force/displacement another great comment. We put this proof-of-concept together using off-the-shelf technology and the minimal amount of additional engineering work. We're hoping a lot of the reloading community can relate to this and we can move the discussion forward. We just posted a seating test video using the Instron UTS. That would be a great way to go but we're going to need more budget ;-)
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