Re: Re: Re: Bell annealing


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Posted by Rick Denney on February 03, 2003 at 15:42:37:

In Reply to: Re: Re: Bell annealing posted by Paul Gramann on February 03, 2003 at 14:54:14:

Age hardening is a slow process that affects the relaxation of internal stresses in the metal. Initially, internal stresses remaining in the metal relax over time as vibration causes it to yield microscopically (at least that is my current working theory), and then age-hardening (which is a slow chemical change that affects the crystalline structure of the metal) raises the yield point of the material making it more difficult for further relaxation to take place. Annealing removes all grain and crystal structures in the metal associated with hardening either due to cold working or age.

That said, I don't think that the sound of a tuba is that much affected, though the feel of it might be. The tuba vibrates sympathetically with sound, and we feel that in our hands and bodies. But I don't know how that affects the sound reaching the audience. The original poster might try listening to a recording of himself to determine if the sound is really all that different.

My Holton is extremely resonant, and it vibrates freely when I play it. It is both old and the bell has been ironed out (without annealing--the lacquer is still there), so I expect that it is pretty hard. But hardness has no effect on the stiffness, which is what controls how it vibrates. It could affect the residual stress, which could in turn affect how it vibrates in certain modes. If the material is so soft that it is microscopically plastic when vibrated, it could damp that vibration, but it seems to me that it would fatique quickly and fall apart if that was the case.

Standing it on the bell should not have any effect on this--unless the instrument is set down with enough force to cause the brass to yield, the stress imposed by standing on its bell is probably less than the stresses resulting from vibration, though that is a supposition.

Rick "who doesn't think resting a horn gently on its bell is abuse" Denney


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