Doesn’t that depend on the MTBF ? Do aluminium pistons last as long as steel pistons ? Possibly not, but they last for thousands of cycles if they are designed correctly. Not wanting to start a huge discussion on it, I’m just drawn to query absolute statements in order to understand if they are true, or just perceived wisdom.
Cyclic-loading refers to a load that is applied, then removed, then applied, then removed, etc for many cycles. Elastic deformation is a necessary part of that.
The reason you should never buy cyclically-loaded parts made out of aluminum is that aluminum has a face-centered cubic unit cell structure. Materials with FCC unit cell structures cannot be designed for infinite life like body-centered cubic materials (like steel) can be. A steel spring clip can theoretically be designed for infinite cycles without fracture (or at least upwards 10^9 cycles which might as well be infinite).
"S-N curve" and "Endurance Limit" are helpful Google-able terms
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I’m just asking questions. Andrew came up with a technical reason for not choosing specific materials in certain situations. I’d have been OK with “don’t buy it, because it breaks”. The technical answer was more intriguing. I would now disregard a product with that material and a cyclic element.