When selecting a material what would you take into consideration more, tensile strength or yield strength?

Background: Given an example of a failed part, what material properties would you consider? Think about the use cases of the designed part.

Yield strength is typically more important. Yield strength corresponds to the amount of load that can be subjected to the part before plastic deformation. Tensile strength (UTS) corresponds to the amount of load a material can take before necking begins. You’d want to design a part around the yield strength because it would be pretty bad if you had a part start plastically deforming in the middle of its lifecycle.

I’ve never really taken UTS into consideration when designing parts because UTS is irrelevant in my application. I’m sure there would be some applications where UTS is considered more though, can anyone think of some example applications?

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The only thing I can think of is when plastic deformation is required for the utility of the product to be met. I’m thinking of those glowsticks that you bend to operate; I know the underlying principle is based on chemistry so IDK how much the plastic deformation plays into it but at least its a good visual indicator that you’ve initiated the chemical process.

In construction sometimes some plastic deformation is acceptable. Also for some materials it is desirable that there’s a significant margin between YS and UTS so failure isn’t as sudden and dangerous.