what is the tension in a bolt when snug tigh

huangyhg

what is the tension in a bolt when "snug tight"?
i need to calculate the tension in a bolt due to torsion when the bolt is tightened to "snug tight". is there any formulae or codes (australian) that states this?
edit: i need this information to input into a finite element model.
hand tight plus 3/4 of a turn.
mike mccann
mmc engineering
tension is generally treated as zero at snug tight condition.
here is the microsoft excel formula for tension at snug tight.
=rand()*breakingload
snug tight is defined as the maximum torque exerted by hand using the standard spud wrench that ironworkers use.
mike... you've described a slip critical torque for a standard grip... (i think), i don't have my charts with me... but more than snug.
dik
from... guide to design criteria for bolted and riveted joints by kulak et al...
experience with the one full turn method indicated that it was impractical to use finger or hand tightness as a reliable point for starting the one turn. because of out-offlatness, thread imperfections, and dirt accumulation, it was difficult and time consuming to determine the hand-tight position. bethlehem steel corporation
developed a modified 鈥渢urn-of-nut鈥?method, using the aar studies and additional tests of their own.4.16, 4.17 this method called for running the nut up to a snug position using an impact wrench rather than the fingertight ondition. from the snug position the nut was given an additional 陆 or 戮 turn, depending on the length of the bolt. the snug condition was defined as the point at which the wrench
started to impact. this occurred when the turning of the nut was resisted by friction between the face of the nut and the surface of the steel. snug-tightening the bolts induces small clamping forces in the bolts. in general, at the snug-tight condition the bolt clamping forces can vary considerably because elongations are still within the elastic range. this is illustrated in fig. 4.18 where the range of bolt clamping force and bolt elongation at the snug tight condition is shown for 7/8 in. dia. a325 bolts installed in an a440 steel test joint. the average clamping force at the snugtight condition was equal to about 26 kip. the bolts in this test joint were snug tightened by means of an impact wrench. this modified turn-of-nut method was
eventually incorporated into the 1960 specification of the council.
for bolts equal to or greater than about 戮 in. dia., snug position provided by an impact wrench is approximately equal to the tightness attained by the full effort of a man using an ordinary spud wrench. for longer or larger diameter bolts, the force produced by this snug load will be less than that for the 鈥渟tandard鈥?case, and for shorter or smaller diameter bolts it will be more. these differences are accommodated in the specification by prescribing the same definition of snug tight...
dik
the rcsc specification for structural joints using astm a325 or a490 bolts, section 8.1 defines snug tight as follows:
"the snug-tightened condition is the tightness that is attained with a few impacts of an impact wrench or the full effort of an ironworker using an ordinary spud wrench to bring the connected plies into firm contact."
that being said, at the snug tight condition the tension in the bolts within a given connection will vary from one bolt to another.  the tension will also vary from one joint type to the next and depending on the sequence that the various plies are erected for a given joint type.
but don't let all of this variation get you down.  i usually place more value in the quantifiable portion of the rcsc definition - the full force of an ironworker (say 100# to 150#) using an ordinary spud wrench (16in - 18in long).  on the low end you're looking at 133 ft-lbs and at the high end  you have 225 ft-lbs of torque.
the translation of torque to tension varies widely (surprise surprise) with bolt lubrication, thread type and condition, bolt diameter, bolt length and fastener part (bolt and nut) lot.
hope this helps.
tim
mike... i found the data:
bolt grip <= to 4 times bolt diameter 1/3 turn
bolt grip <= to 8 times bolt diameter 1/2 turn
bolt grip <= to 12 times bolt diameter 2/3 turn
dik
as tgattie says, snug-tight is defined as the full effort of a bloke using a proper spud wrench.
if you want to convert this torque into tension you can use these formulas:
thank you all for your help