comments:
Yes, people are saying they often hold for a few months or even a year or two before they fail. That's 100% consistent with it being the terminal that connects the wire to the device. There are lots of examples of other types of bad contacts that fail after similar amounts of time. A good example of that is the notorious backstab terminals on 5-15 receptacles. Another example of that is aluminum wire in the screw terminals. There's a terrific book about that that combines good storytelling and deep technical expertise. There are lots of ways that a bad connection can gradually get worse, until it much more rapidly gets worse. They include but are not limited to: Thermal cycling, in which the deformation caused by thermal expansion gradually loosens a connection. Creep, in which materials gradually deform under stress, accelerated by higher temperatures. Oxidation, in which metals that are exposed to air build a layer of oxide that has higher resistivity than the bare metal. This of course happens more rapidly at high temperature. Good connections have a region of contact where the copper has deformed to match the surface it is in contact with over some significant area, making a tight enough contact that gas is excluded and oxidation does not occur. Yes, tons more people have used the cheap outlets then have had fires. The fire is not guaranteed but is just a bad risk. That's 100% consistent with the story I'm telling. Similarly tons more people have used backstabs than have have them fail and yet they continue to fail regularly. Your confidence from photos that it's always the blade contacts is not good data for two reasons. One is the you are partially extrapolating from 120 volt outlets, where failure due to worn blade contacts is more common. You also seem to be surprisingly unaware of how many of those are actually from backstab connections, which brings me to the other reason that that's not good data, would you actually mention yourself, which is that the metal inside the receptacle conduct heat between the different parts. A typical photo from the outside will show melting around one of the slots. However, you need to find examples where people have also provided a photo after opening it up. That's why I talk about the center of the radius of destruction. Yes, there is melting as far out as the slot but you have to look at the whole region of that damage and see where the center of it is. And that is right at that contact. Have you ever been up close and personal with Leviton 279-s00 receptacle? If you haven't, they are quite inexpensive, and if you want to talk knowledgeable about this problem, it's worth getting one and trying connecting wires to the terminals yourself and seeing just how bad they are.
When the industry is also the regulator, this type of crap happens. Here’s an interesting read on how UL messed a lot of things up in the past as well: https://a.co/d/0bKjjeTc