Paul,
I sell titanium for a living, in fact I sell a lot of titanium chainplates. The reality is that like with most materials titanium has trade offs that must be engineered to get the best out of it. However because it is different than many metals there are a few realities that get blown way out of proportion. And frankly a helicopter pilot is not likelythebest source of information.
To be clear there are a number of types of brittleness, and like there are a lot of engineering types of strength.
The first one, and where Ti gets is reputation for brittleness is expressed as a percentage. It is measured by the yield/tensile strength. For Grade 5 titanium Ti rates at 92%. Meaning the yield strength is a huge percentage of its tensile strength. 316 stainless for instance is 39%, and 6061 aluminium is 44%.
So by this measure titanium is very brittle. However when you look at the numbers.... Grade 5 titanium has a yield strength of 128,000psi and a tensile of 138,000. The 6061 aluminium has a yield of 8,000psi and a tensile of 18,000. Note that the difference between these numbers is the same. 10,000psi.
Another type of brittleness refers to how for a metal will deform before it breaks. In this measure, and one normally considered more important for chainplates, titanium far surpasses other metals, which is why the best springs are made from titanium. Just think of the memory shape sunglasses. You can literly tie them into knots, and they will spring back to shape. It is this ability to return to bend and return to shape that allows titanium to absorb shock loads that would crack other materials.
That being said there are some fair concerns with titanium usage.
The first is do you design based on the old materials tensile or yield strength?
Second, if you reduce thickness to far because the material allows for it, have you left enough thickness for the pins?
Certainly as a salesman my opinions maybe suspect, so if you have any specific questions I will be happy to back up opinion with engineering references.
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