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Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
Without any chemicals, tools and short of an x-ray detector and source to do xrf, I'm stuck with a square plate of an unknown metal and a roll of tape to suspend it in mid-air. However, there's an experimentally trivial way to probe the elastomechanical properties of the sheet in question: Chladni resonances, as the transverse (shear) standing wave solutions to the problem with open boundaries are called. Maybe that's not exactly the "linear 1d medium with periodic boundaries" textbook example, but I'll ask you anyway before it ends in sleep deprivation for me: What's the shear modulus? Anyone? *grabs physics textbook and leafs through it*
]118x118x1.2mm_metal_sheet_spectrum.txt[/file]
(spectrum of the ringing after slapping the sheet with a pen)
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
hboy007 wrote ...
Without any chemicals, tools and short of an x-ray detector and source to do xrf, I'm stuck with a square plate of an unknown metal and a roll of tape to suspend it in mid-air. However, there's an experimentally trivial way to probe the elastomechanical properties of the sheet in question: Chladni resonances, as the transverse (shear) standing wave solutions to the problem with open boundaries are called. Maybe that's not exactly the "linear 1d medium with periodic boundaries" textbook example, but I'll ask you anyway before it ends in sleep deprivation for me: What's the shear modulus? Anyone? *grabs physics textbook and leafs through it*
Young's Modulus - E - could be derived from the density and shear velocity - group velocity, I suppose.
Then we could look it up in a table. The range of E for different allotropes of the same substance could be large, but as with most types of analysis, that range would include some substances, and exclude others, so we'd have a broader base for our deductions, and progress would have been made.
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
Alright.. I wish I had the time to solve the puzzle... but calculating the modal spectrum of the plate would be too much of a challenge right now (have to start writing my diplom thesis).
spoiler: I determined the weight, with 75g for the thing (4.5g/cm³) it looks like I have a piece of Ti.
Registered Member #599
Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624
Here is a great video about spark testing different materials. Sometimes its difficult to tell titanium from aircraft aluminum by strength or other physical properties.. :)
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guessing a metal by its sound
