snap-hook fit with angular deformation

[hamph1337]

Hi,

Currently I'm facing a problem of what I thought would be a rather simple setup with a snap fit design.
However I face some difficulties regarding the boundary conditions as I think it's important to get the snap to have a rotational displacement.

First of all: what is the proper way to do this? As for now I have a remote displacement on the edge of the part and just telling it to deform along the Y axis, which will be a linear deformation.

Secondly, (and this problem could be caused by my linear/bad remote displacement BC) when the part gets deformed the reaction force from the edge/snap tends to bend the upper surface. In reality this is where you will have your thumb and force the surface flat - this will ofcourse affect the stress/strain in the snap fit. How do I model a BC that mimics the support on the top part?
The surface still have to be able to deform downwards to the edge because of the movement, but be locked (stay straight) in when the snap wants to bend it. Can I add another cordinate system that follows the deformation somehow?

Thanks and please just ask if you dont understand my problem..

 

[scheah]

Could you add another body to represent the thumb; have thumb actuate the part via contacts?


Best regards,
Sze Kwan (Jason) Cheah

 

[hamph1337]

Hi Jason,

Hmm yes possible.. so you mean adding a "thumb" / plate on top of the snap geometry with a connection?
Won't these BCs collide with the remote displacement?
If the two geometries are connected with bonded/no seperation.

I'm starting to realize more and more that the original problem is in my first remote displacement which is presing it straight down the Y axis.
Anyone know how to make it rotate (around my cylindrical support axis) by a certain amount of degrees?

 

[scheah]

so you mean adding a "thumb" / plate on top of the snap geometry with a connection?

Yup

Won't these BCs collide with the remote displacement? If the two geometries are connected with bonded/no seperation.

The "thumb" would replace your original remote displacement. The contacts between them will be frictional.

Anyone know how to make it rotate (around my cylindrical support axis) by a certain amount of degrees?

In Ansys remote displacement, you could specify the "Location" which it is to rotate about.


Best regards,
Sze Kwan (Jason) Cheah

 

[mronlinetutor]

To model point B for partial fixity would be a contact problem. You have to insert a pin in the hole in the x-direction at point B and specific the amount of friction between the pin and the latch. Not all software supports contact. Also it seems from the model that the latch doesn't have a tight fit. That is the latch doesn't lock when point C is pressed down completely. You have to modify the dimensions of your prototype.

disclaimer: all calculations and comments must be checked by senior engineers before they are taken to be good.

 

[hamph1337]

To model point B for partial fixity would be a contact problem. You have to insert a pin in the hole in the x-direction at point B and specific the amount of friction between the pin and the latch. Not all software supports contact.

I though I handled this by the cylindrical support BC ? I understand I miss the friction but it's of minor importance for the U-hook on the snap-fit I think.. I'm using ANSYS Mechanical 18 so it supports contacts, even though it can be a mess xD

 

[scheah]

I'm using ANSYS Mechanical 18 so it supports contacts, even though it can be a mess xD

Can you elaborate on the contact mess?


Best regards,
Sze Kwan (Jason) Cheah