`1980s refrigerator shelf failures`

Used as opening example of how naïve material substitution (metal → plastic shelving) creates new stress concentrations at dissimilar-material joints. Holman teaches it as a thermal-expansion-mismatch failure.

One of the main material substitution issues that happened years ago was when they switched from metal shelving to plastic shelving. What they initially did was say, all right, we're going to mold this out of plastic and stick it in, and it'll save us a ton of weight. One of the things here is that when you're working with a system, you can't just look at one property or one particular aspect of the system. You have to look at everything as a whole and how it interacts.