Here ya go, I found a couple of threads on it.
https://www.backyardchickens.com/forum/viewtopic.php?id=61042
https://www.backyardchickens.com/forum/viewtopic.php?id=97062
I've read someplace that a person got some cracked eggs and just for grins covered the cracks with melted candle wax, (I think it was), to seal the cracks and went ahead and put them in the bator. I remember that at least one hatched.
You might search "incubating cracked eggs"??