Door Sag Analysis 1

[vanguard478]

Hi All,
In the vehicle door sag FE analysis(Abaqus), we add a gravity loading to the door assembly ( step-1), then a vertical load at the latch point(step-2), and finally a release the vertical load(gravity loading still there).
To calculate the permanent set due to gravity we subtract the vertical displacement observed in step-1 and step-3.
Now to check the effect the of vertical loading we subtract the vertical displacement observed in step-1 and step-2.
All the displacements are reported with the effect of gravity subtracted from the result. But in real scenario the effect of gravity will always be there.
So why do we subtract the contribution of gravity loading to check the effect of vertical loading? As in real life if a load(vertically) is exerted on the vehicle door the gravity is still acting and the effect will be a summation of both the loading.

 

[aerostress82]

Is the door in open or closed condition when you are doing this analysis? I'm guessing it would be completely open?

Spaceship!!


Aerospace Engineer, M.Sc. / Aircraft Stress Engineer with 7 years of experience
(United States)

 

[vanguard478]

The door is kept in open condition at different angles ( 15deg and sometimes higher)

 

[aerostress82]

Your vertical load should be somewhere around 250lb. So, it is probably a significantly larger moment inducing load than the door itself.
As you mentioned open condition, the reason to why they would be doing this is to evaluate only "the displacements created by the abuse loading".

The difference between step-1 and step-2 will give the maximum displacement of the door at the peak abuse loading point. (during its service life)
The difference between step-1 and step-3 will give you "the permanent displacements that the door structure went through" during this abuse loading. If you have a very small value (close to 0), then your abuse loading doesn't do any significant damage to the door assembly.

Also, at the end of these studies at 15-30-45-60 or so degrees, you will probably create a document regarding door's safe usage conditions. Let me know if any of the above isn't clear..

Spaceship!!
Aerospace Engineer, M.Sc. / Aircraft Stress Engineer