Inge,

I will risk myself and through in some confusion.

How did you realize you had this problem, in the first place? Are you sure it could produce failures?

Now the slippery teritory, since it's been years since I took my materials stress class: if I remember well, the stress class we had was based on several hypoteses and one of them was the homogeneous material. So the von Mise's I have studied was based on the same material all over the place. Here you deal with one alloy for the ball, one alloy for the top attachment and another alloy for the bottom attachment. Maybe this alters the stress distribution?

Are the whiskers you see mono crystals? In order for you to repeatedly get them, it is obvious you have the same stress, at the same place, every time. Maybe you have a Sn starvation at the equator due to migration towards the joined zones. Then you might have different stress distributions on the various zones due to different alloys. And on top of it, the creep. Wouldn't the whiskers a result of the creep?

If you think I am losing it, just have me recall the message.

Regards,

Ioan

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