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## How to model a gravity load

Hi All,

OK, here's the senario. i have a door hanging by one hinge, the top hinge. Obviously gravity will act on teh door, and pull the door downwards & inward (so that the door's CoG falls under the load point (or close to it)). I'd like to see how the door hangs, and more importantly, how the hinge deforms, what the stresses are on the hinge. I'll assume I will get major deformations & stress at this constrained point!

I've modeled the hinge as a single block with a hole (the hinge rotational hole, the 'pin'). The door is a seperate peice, constrained to it. I've added a 'pin' displacement contraint the pin hole, and I've added a 'gravity' load.

I fee there should be a way to tell Creo not to include the door in the meshing routine, but use its CoG & Material as the load (under gravity).. And I shdou get a returned displacement plot of the hinge all deformed & stressed, not how much the bottom of the door has swung under teh hinge.. (I can't seem to find this lesson!)

thanks!

4 REPLIES 4

## Re: How to model a gravity load

Are you trying to account for inertial forces too?

## Re: How to model a gravity load

I'm not entirely clear on the scenario you're trying to model, and there is a couple different way you can do this; which is more appropriate depends on the specifics of your system and the results you're after. I can't tell you what the most appropriate method is without a more detailed look at what you're trying to model.

That being said, you can do the following:

1. Define the material for the door prt file (File -> Prepare -> Model Properties -> Material).
2. Measure the Mass Properties to obtain the location of the center of mass and total mass (Analysis -> Mass Properties). The location of the center of mass will be relative to the coordinate system you select, and you need to select a CS that doesn't depend on the geometry of the door as we'll be suppressing it later.
3. Create a datum point (Offset of Coordinate System is the easiest for this) that coincides with the center of mass location you previously calculated. Make sure the CS you use is the same as the one you used for your Mass Properties measurement.
4. In Simulate, go to the Refine Model tab and select Mass. Select the datum point you previously created and enter in the mass value you measure.
5. Under the Refine Model tab, go to Weighted Link. Change the Independent Side to whatever reference you want to "connect" the mass point to. Select the datum point with your mass point for the Dependent Side.
6. Suppress the geometry for the door.

## Re: How to model a gravity load

Shaun, that look like the right direction!

## Re: How to model a gravity load

Thanks all,

Yes, i'm playign around with Simulate. The books & lessons only show you a few ideas, and they pretty much walk you thru the exapmples. I wanted to try somethign on my own. I figured a stressed hinge woud be an easy thing to do (as I look at my boss' office door!) My thought was, it the bottom hinge failed (lost the pin) how would the top hinge get stressed? So, a standard 'door', hanging off the top hinge, and is free to move as it wishes(just gravity, no side loads or other 'obstacles' [door frame!]). A single knuckle hinge instead of the usual 3 or 5 knuckles. That one knuckle is constrained (pinned) the to the door frame. How much woudl it twist? where is the most stress observed?

The main idea was how to get a load not on the hinge, but outside the bounderies of the part. And, have just the hinge modeled / meshed / incused in the calcs.

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