Residential garage doors are a type of overhead door that is lifted and lowered using the assistance of two coiled springs which are wound to balance the weight of the door. The springs allow less expensive lifting mechanisms to be in the garage door design.
There have been numerous cases in which overhead doors have fallen and injured people in the vicinity.
Fortunately, residential garage door springs often fail with the door in the down position because that is the position in which the spring bears the most stress.
When a metallic component fractures, two matching fracture surfaces are exposed and can be examined for features indicating the failure mode. Additionally, the microstructure of the metal can be examined for indications that manufacturing process played a role in the failure.
This failure is a great example showing features identified using typical metallurgical evaluation techniques.
Additionally, the sound created by these springs can be described as that of a metal snake approaching on the attack and, in this case, scared the bajesus (proximal damages??) out of the author when it occurred.