Bulge in MacBook Pro near Hard drive
This is the result of excess force squeezing the wrist pad against the internal components.

In your other question asking about heat stress is a no go. Aluminum doesn't weaken or deform that way in temperature ranges where plastic won't melt and batteries don't catch fire. The bulge in the other question is really compression bending the case inward and components sticking up. Think aluminum foil placed over one large ridged potato chip - press lightly with a finger and you will see the ridges below the foil.

Why not upload a picture if you have an example, or is this a hypothetical case?