There may be a sonic way to check crank but might take intact crank of same design to calibrate healthy base line spectrum. I am licensed to irradiate people through the bone and have done metal components to find steel ain't all that dense to x-ray in the 125,000 volt beam range and as the cracks are at the thinner places likely a good medical unit could get inside views by a series of tangent shots around cheeks and journals radius. Worse case to shoot through sideways were xxx+ 'large' women's pelvis. I swear I could sense a sizzle or smell so eventually quit it and sent out for imaging. Some kid put together his own portable unit in two hand carry tool boxes with like 60Kv potential. It would be a neat exotic service if someone DIY too but likely many services out there more cost effective. There is the X-ray image of Cdo's available but not making crank transparent. But its can be very hard to detect a fresh or failed to heal non inflamed bone fracture that is not displaced nor showing evidence of callus. So similar issue in metal cracks, only following the metal grain interfaces at the time. These metal grain fault acts as conducts for oxygen corrosion and piezo electric potentials from vibration of dissimilar grains which create what are called currents of corrosion - exactly same as lead battery voltage chemistry. They used to have free x-ray novelty floro units you'd stick hands or feet in, till they found out what that did not so long term later.
Its been joked about that very high voltage ignition coils generate ionizing rays near the one's junk.
So really only the traditional tried and proved method to run to failure will find it every time : (
Newer digital imagers are cheap in used equipment vendors which greatly cuts down on exposure power and increased resolution so might make this practical.
http://www.popsci.com/diy/article/2012- ... ay-machine
