Constraining and Applying Loads in Pro/M

[slamdfullsize]

The company I work for is looking to simulate what can be considered a 'shock' load on a plate. What I have is a plate of steel, roughly 12"x12"x1.75" that rolls along a track. the track is not smooth and at certain point (ie intersection) within the track, the plate will drop slightly (0.004"). We have a plate that is being tested now in our shop with load sensors and have determined that the highest force expeirenced during this drop is roughly 4000 lbs.

What I am trying to do is to simulate what happens as the plate moves through the interesction at the time of the drop. So the leading edge would experience a load of 4000 lbs being applied upward, while, due to a free body diagram, the trailing edge would experince and simlar force in the opposite direction.

How can I constrain the model to allow it to 'rotate' as it experiences this sudden force?

 

[Twoballcane]

If I was doing it, I would not apply a force load, but an acceleration load (Gs) to the plate. The force load tends to go in the directin you want, but acceleration will load the plate so a natural rotation at the pivot point will occure. Applying force per area is more of a situation like haveing sand on top of the plate. That is my opinion.

For ProM, you would want to constrain the side surface of the plate. Constrain so that the surface does not go side to side, but free to go up and down and back and forth. For the rotation, fix rotation for roll and yaw, but keep pitch free to rotate.



Tobalcane
"If you avoid failure, you also avoid success."

 

[slamdfullsize]

so i have placed a 'gravity' load on the ucs of the model. (9.81 m/s^2 going down and our acceleration rate of the horiztonal movement). now when i go into the analysis and create a new dynamic analysis, it doesnt give me an option to choose what loads i want to use, only constraints. does Mechanica automatically use all loads associated with the model?

 

[Twoballcane]

Well first a correction on my part. Constrain all sides in all directions, but keep the rotation the same.

Let’s start at the beginning. For any kind of shock analysis you have to get the shock profile and this is usually in the form of a time domain (Gs vs time). Lets say you get 10gs with a half period of .005 sec, so this works out to be 1/(2*.005)=100Hz. So your load will be 10gs at 100Hz. If your plate has a Fn of 100Hz your plate will have deflections with a load of 10gs plus amplification (this is more scope you may have to research your self), but lets say your “best” case is 10gs. You will have to multiply your gravity by 10 and put that in as your gravity load. For me it would be 10 x 384 in/sec^2 which is 3840 in/sec^2. Now in ProM, you do a "Static Analysis" and gravity is your load set. Run the file and you will get the deflections and stress (this is at full response of the shock) which from there you can determine if the plate can handle the shock load.

Dynamic Analysis is a different animal where you will need a profile to simulate the shock / vibe.


Tobalcane
"If you avoid failure, you also avoid success."