Just watched an Air Crash Investigation episode in which the investigators studying the wreckage say that a certain bolt shearing off during flight caused the crash. How can they tell that the broken bolt was during flight and not because of the crash?
In: 71
The key thing will be inspection of the fracture surface of the bolt. This is literally the face left behind where the bolt snapped.
A bolt that snapped in a single overload event will have a very “clean” surface because the break is very recent (there hasn’t been time for it to corrode). Even if inspected much later, the corrosion and colour will be the same across the broken face.
A bolt that has fatigued will have a colour gradient across it – darkest where the crack originated, as that’s been exposed to the elements the longest, and then very clean at the bit which snapped off once the bolt was weakened.
A bolt that’s had some kind of stress-corrosion cracking or other chemical attack will look slightly different again.
Most failures like the one you’re describing will be from fatigue. A failure caused during a crash will be a single overload event.
Latest Answers