## General Mechanical

#### Spring simulation

Subscriber

I have a system with a spring inside a housing. The housing has a notch that fits the spring inside, and is slightly wider than the spring (front view). The depth of the notch is about half the spring diameter, so the spring sticks out about halfway (side view). The top and bottom of the spring contact the edges of the notch(top and bottom), which hold it in place. There is a second housing that goes over this, with a similar notch for the spring. This piece moves up and down, compressing the spring as it moves down. There is an issue with the springs bending up on the side of the housing. My thought was that this is happening because the notch in the housing is too wide, thus allowing the spring to sit in the housing at an angle, which eventually catches the wall and starts bending the spring.

I want to try to simulate this behavior to verify my theory, but I've never done any sort of spring simulation before and have no idea where to start. Any pointers on how to go about this?

Also, sorry if the description was incredibly confusing, I don't really have any pictures that I can attach.

• peteroznewman
Subscriber

sageblade, you could make a rough illustration using SpaceClaim, which you have used before.

To model the spring, create a helix curve and mesh that with beam elements with a circular beam cross section that matches the wire diameter used to make the spring. Since this is a compression spring, there are four ways the ends can be finished. Which end do you have?

Do the ends of the spring make contact with the flat bottom face of a blind hole?  Is that the "notch" you are talking about?

For closed ends, the curve has to transition between the helix angle of the body of the spring and the flat end of the spring. That is a bit more work in geometry editing.

That beam element based spring can make contact with the sides of the housing, including the edges of the holes where the spring is captured, and can be compressed when one housing moves toward the other.

Clearly, closed end springs are going to stay in a mostly straight line, while an Open non-ground spring is going to have an off-center force that creates a moment that will cause the spring center to bow to the side and make it more likely to catch the edges of the hole it sits in. This effect may depend on the angle around the spring circumference where the open ends terminate. Are they on the same or opposite sides of the spring diameter?

The is also the consideration of the buckling load of the spring.

Subscriber

I finally finished the modeling for this and tried to do a simulation, but it's not treating the spring like a spring. The outer housing gets pushed down, and it should push the spring with it, but the spring in the simulation won't compress. I've attached the file if you could check it out and offer some tips.

• peteroznewman
Subscriber

I have AIM Student 19.0 installed and I downloaded your wbpz file but it gives me an error when I try to open that file in AIM.
I know that you have AIM because when I tried to restore the archive in Workbench, it told me to use AIM.

I had a similar problem with another member's AIM archive.  Please try creating a zip file of the folder where this AIM project is saved. I mean the folder holding the container.wbpj file and the container_files folder then attach that zip file instead.  But only make the zip file after you have closed AIM.

Another method to get some information passed along is when SpaceClaim is open, use Model, Export and save the geometry to a file.  I created an AIM 19.0 project called block. See if you can open this in AIM.