Strut/shock absorber modelling

[flyforever85]

I have to model a 3-legs landing gear. One of the leg is a strut, designed to take only compressive loads and acts as shock absorbed. I don't really care at this stage of the stresses within the strut. I do care of the loads that this strut will transfer to the structure.

What's the best way to model it? I'm try to use a connector with translation available and I'm trying to set 2 different length (fully extended/fully retracted) but with no success. At the 2 extremities the strut doesn't transfer bending (it' pinned).

I can post a pic if it helps.

Thanks!

 

[FEA way]

Connector is the best option here but it needs to be defined correctly. You can even add connector actuation feature. Variety of available connector behaviors will allow you to include elasticity, damping and even damage/failure. If you share a picture I will try to advise you how to apply connector to your model (possibly AXIAL or CYLINDRICAL in this case). In general I recommend the use of Connector Builder. It makes the process faster and easier. Just remember to request force output for connector sets.

 

[flyforever85]

The design is very similar to the one below so you have an idea of a real image (the rear landing gear)

https://en.wikipedia.org/wiki/Piase...:Piasecki_HRP-1G_US_Coast_Guard_in_flight.jpg

This is the actual model (well, part of it).

https://files.engineering.com/getfi...28ef-4402-baf3-b19248cecc39&file=Picture1.tif

The landing is composed by 3 legs, the purple, the orange and the connector which should be the piston. Referring to the coordinate system, I need the piston to be able to move only along x and rotate and its ends only around y axis. to be more real, the piston should have a max extension of 20 in and a minimum of 20 (stroke is 5 in)

 

[FEA way]

So you need U1,UR1 and UR2 motions free and the rest blocked, right ? This will require the use of AXIAL + ROTATION. Such combination will give you the following motions: U1,UR1,UR2,UR3. You can eliminate this one unnecessary rotation (UR3) using connector stop/lock feature.

 

[flyforever85]

Actually I need only U1 and UR2. I'm not sure how to use lock

 

[FEA way]

To use connector lock you have to specify COMPONENT (in which lock criterion will be awaited) and LOCK (component of motion which will be locked). So for example if you set force criterion and specify COMPONENT=3 and LOCK=4 then fourth component will be locked when given force occurs in third component (local 3-direction). However there's also another way - you can define multiple connector elements in parallel (acting between the same nodes).

 

[flyforever85]

I understood all the functions, but I can't figure out how to tell ABAQUS that I don't want to lock a specific direction based on another condition/criteria. I want that to happen all the times. I tried by defining a very large force interval but it seems it doesn't work.

 

[FEA way]

Instead of force criterion you can set the limit on relative position (in this case angle). You will have to define very low values (around zero) so that the CORM is locked from the beginning. But I think that parallel connectors may be a better way to do it.