Pretension in a bolted joint
Pretension in a bolted joint
(OP)
Hello everybody. I am trying to analyse a bolted joint and i have defined pretension to the bolts. But i see that the pretension section shrinks and the bolt head has negative stresses even though the preload is a tensile load which i didnt understand why. I have defined pretension in step 1 using cload and in the second step i have applied the external load using cload,op=new and i have also used boundary,fixed in the second step. is this right or am i missing somethin? looking forward for your reply. Thanks.
Kota





RE: Pretension in a bolted joint
The bolt head will be in compression generally as it is being loaded by a tensile load acting downwards, and an upward load from the object surface. These two forces apply compression.
corus
RE: Pretension in a bolted joint
and also i had one more question. To check the bolt load i check the contact force since i have defined contact between the upper bolt surface and the upper plate hole and the lower bolt surface and the lower bolt hole. But is this contact force what i get is the force exerted by the slave on the master. 'cause i have defined the bolt as the slave and i am getting the contact force for the upper bolt surface negative( which means the force is acting downards according to the co-ord system i have chosen)..Thanks for ur help. i really appreciate it.
Kota
RE: Pretension in a bolted joint
If you don't believe the results then simply look at the deformed shape of the surface underneath the bolt head. This should show a compressed surface.
Another way of checking the bolt load is to look at the stresses in the bolt shaft. Multiply the average stress by the area.
corus
RE: Pretension in a bolted joint
RE: Pretension in a bolted joint
here are the details:
CFT(BOLT)----1122 LBS
CFT(JOINT)----1122 LBS
EXTERNAL LOAD-- 100 LBS(TENSILE)
AVERAGING METHOD(BOLT SHAFT)--1222 LBS
I always thought in reality the bolt load shld increae and the joint load shld decrease.if i follow the averaging method then it proves my above thought.But if i juss go for the CFT values then both bolt and joint load is decreasing.Do u know why this could be happening? or should i juss go for the averaging method considering the bolt shaft and not the bolt head to get the bolt load and consider the CFT value for the joint load. do u think its reasonable. looking forward for your reply. Thanks.