Interesting Question...

[danny_p]

turbos run at etreemly high rpm so  there for the centripedal force trying to rip the inpellers apart must be really something and the exhaust side gets quite toasty.   and even the shaft between the inpellers has to transmit quite an amazing amount of power,  id don't think they stress the oil that much as the rotating parts arn't heavy and the core is often water cooled as well. so i would say the exhaust inpeller of a turbo is most stressed but there again there made of some fandango alloys so are they actualy that stressed compared to what they will take.

apparently the cams, tappets give oil the most stick in a modern high outpute diesel due to the shear forces it experiances when the cams trying to open the valve's against the pressure in the cylinder ( on a vag diesle anyway )

the most stressed part may well be engine dependant, on a rover fourum i bet the general consencus would be the headgasket was most stressed

[Diamond Hell]

I'm kind of on this page as well.

And there I am - playin' to the crowd....

[clipperjay]

The balance crank shaft, oposite rotational forces means alot of stress
Could be talking Bo*locks though... 

[Agreeable Slick]

turbos run at etreemly high rpm so  there for the centripedal force trying to rip the inpellers apart must be really something and the exhaust side gets quite toasty.   and even the shaft between the inpellers has to transmit quite an amazing amount of power,  id don't think they stress the oil that much as the rotating parts arn't heavy and the core is often water cooled as well. so i would say the exhaust inpeller of a turbo is most stressed but there again there made of some fandango alloys so are they actualy that stressed compared to what they will take.

apparently the cams, tappets give oil the most stick in a modern high outpute diesel due to the shear forces it experiances when the cams trying to open the valve's against the pressure in the cylinder ( on a vag diesle anyway )

the most stressed part may well be engine dependant, on a rover fourum i bet the general consencus would be the headgasket was most stressed

This is what I mean. It doesn't state that there is a turbo present, but then there could be. It's quite a nice open question, so technically if you can justify what you are saying about each component mentioned in this thread then you could argue that you are not wrong.

Turbo speed ranges are quite rightly massive, 70,000-300,000rpm last time I checked. They are also made of very exotic alloys as you mention, i.e. titanium, and alloys of that. Even ceramics in some cases.