Posted by Rick Denney on February 05, 2001 at 14:08:14:
In Reply to: Re: Re: Re: Re: Re: thin vs thick metal horns posted by CK on February 05, 2001 at 12:19:07:
Now, I'm no materials science expert, but I am a civil engineer licensed by the state to design things with this stuff, and I see aluminum used in all sorts of applications where age-hardening would be a dangerous phenomenon, such as airplanes and bicycles. Aluminum used in bicycles has been tested over periods of years with no measurable change in either modulus of elasticity, yield strength, or any of several workability measures. There is a change in brittleness caused by loading cycles that stress aluminum to a high percentage of its yield strength, but that is work-hardening, not age-hardening. But that fatigue is a much greater issue with aluminum than it is with brass. There is a myth among non-technical cyclists that bicycles get soft over time, though this has never been demonstrated other than in new bike sales literature.
I do seem to recall hearing someone mention that brass does self-anneal over time, though this would be more like "age-softening" than "age-hardening."
Rather than just disagreeing, can you add to the body of knowledge by explaining yourself? I'm willing to admit that my statement was too broad in this context, but I want to know why and to what extent.
Now, you repair dudes: Have you ever said to yourself, "This horn is really, really old and will therefore be harder to de-dent than a new one."?
Rick "let's add, not subtract" Denney