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how to measure force?

N

nza0104

Member
Hi! :)

I'm new to Alibre.

I have a rotating rod with an input torque at one end and would like to measure the force at the other end when it hits the ground. How can I this? As far I know, only position/velocity/ acceleration graphs can be obtained by right clicking the rod and choosing dynamic measure. There's no option for force or torque there...

Does anybody know how to do this? :?:

Thanks a lot.
 
dmckee101

dmckee101

Alibre Super User
Why wouldn't you calculate this? Other than the neat outputs. (I like those! :D )
Assuming the rod is fixed at one end and rotating like a spoke:
Moment, M, applied to the rod, divided by the length of the rod, gives the reaction force when the rod impacts.

So for example: a one diameter inch rod, 3 feet long, given a moment of 300 lbf*ft will exert a force of 100 lbf at the end of the rod.

If you are looking at the stress that occurs you will have to consider the section modulus of the rod.
 
W

wathavy4

Alibre Super User
Dennis, you're right.
Ancient time, I calculated displacement after I applied 2tons to my structure.
I double checked if it's right by manually calculated.
They both showed the same value.
And I was happy. :mrgreen:
 
I

IKRAJ

Member
In this problem you are applying a known TORQUE to the part.
However, if you were to apply a "prescribed motion" to a part you can also calculate the forces.
Once the prescribed motion is applied and the assembly analyzed with Alibre-Motion you can get the desired data to calculate said force.
Dynamic Measurements calculates the Acceleration.
Once you know the Maximum Acceleration and Mass of the part you can do your calculations.

F= MA : Force = Mass X Acceleration :D
 
N

nza0104

Member
thanks guys...

actually i have a 7 bar linkages mechanism that can rotate freely with springs at 2 of the joints. i would to check/verify whether my hand calculation is correct by using alibre... i think, yes, i can try to get the acceleration from dynamic measurement and multiply it wih the mass as ikraj said...

thank u so much :)
 
dmckee101

dmckee101

Alibre Super User
WOW :shock: You really simplified that description didn't you! I can see why you would want the computer analysis as well.
Reminds me of when my wife said she's had a little project for me and it turned out to be pouring a concrete pad and building a shed!
 
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