It's the stresses in the bolt, not the forces acting on the side of it, that
matter. Specifically, torquing down on a bolt is the equivalent of
stretching it until it holds two things together. The torquing causes the
threads to act against each other so as to place the bolt in tension (as
opposed to compression).

For correlating torque to the axial load it produces, one finds somewhat
crude estimates like that given at the bottom of
http://www.engineersedge.com/torque.htm . But of course, this formula will
require tweaking depending on conditions. E.g. fine thread vs. coarse
thread.

Anyway, it's really about 200 ft-lbs. divided over the six edges of the
roughly 1.7/2 cm (= about .33 inch = about 0.028 foot) radius bolt head (for
a 91 Civic, for one), anyway. (This Civic's pulley bolt has a 17 mm head and
14 mm nominal diameter.) So something like 200/6/(0.028) = about 1200 pounds
is applied to each bolt head edge. Key word being "edge." Then one has to
think about what it means to "apply" this force to the whole edge. It's
distributed over the surface of the edge, for one thing. If one took 1200
lbs. and set it on a bar of steel with a cross-sectional area of about 1/8
inch by 1/8 inch = 1/64 inch (conservative for this back-of-the-envelope
calculation), the stress would still be only 1200*64 = 77000 psi, far below
the yield strength of typical steels. And it's not being applied
perpendicularly to each face, but more in shear, besides.

Which mating surfaces?

If the above is supposed to relate to your earlier calculation, then I think
there's a conceptual error here.

I have doubts that a cold bolt-pulley-crankshaft assembly would hold up to a
hand application of 300 ft-lbs. of tightening torque. 'Cause crude
estimators like the one I cite above indicate this would produce in the
neighborhood of 300(12)/(.2*.55) = 32700 lbs. of axial load in the bolt, or
32700 / (Pi r^2) = about 137,000 psi of tensile stress in the bolt, which is
mighty close to the yield strength (~ 130,000 to 150,000) of many steels.
This is too close for engineering comfort.

Which is why I am led to believe galling, aggravated by extreme heat cycling
and the high loads of that pulley working on an initially pretty tight bolt,
plays at least some role and possibly all of it.

I am unconvinced by this theory.

1) If microscopic ratchet teeth are created to cause the bolt to
self-tighten, wouldn't they be destroyed when the god-awful tight bolt is
broken loose? The bolt at least should be specified as a "use once" item,
regardless of how the mating threads in the crank fare.

2) In order to tighten, the bolt will have to move with respect to the
pulley. That means the washer must have similar ratcheting action, and on a
similar microscopic level to allow the ratchet to occur with miniscule
motion. That means if the washer is less than pristine and is reused the
bolt won't self-tighten.

3) The forces are downright outrageous. In round numbers, if the washer
diameter is 1/2 inch and the bolt thread diameter is 1/4 inch, to tighten
past the 200 ft-lb mark the bolt head has to experience 5000 pounds force
from one side to the other, or 10000 pounds force on one side relative to
the center. The equivalent force on the thread is double that.

4) If there is significant motion of the pulley relative to the crank, the
mating surfaces will wallow out. We see it often enough with splined drive
axles that are insufficiently torqued.

Altogether, it doesn't add up. Torsional forces between the pulley and crank
must act unidirectionally on the bolt, with several tons of force being
transferred through both sides of the washer and without damaging the pulley
or crank mating surfaces, with enough movement to materially tighten the
bolt. The theorized ratchet mechanism has to operate on a microscopic basis,
not be damaged in removal, and to allow effortless unthreading when the bolt
is broken loose. It must work over a wide range of lubrication, including a
penetrant oil film or being cleaned with brake cleaner. I'm glad I haven't
been asked to design something like that, particularly if I could just
specify tightening to a different torque in the first place.

Mike

http://square.cjb.cc/bolts.htm

  "Self Tightening Bolts theory.
  Warning: this page is only a theory, not a fact."

That's a good description.

Could someone please explain what self-tightening and
self-locking bolts are and give examples. The author may
have the latter in mind.

  "Figure 4.1 This picture explains the great inertia and
  centrifugal force"

  "When ever there is a difference in inertial force (as
  pointed out with the arrows) the pulley will move. Not
  180-ft-lb torque can hold the pulley still."

I wonder what this is about.