6 Replies Latest reply on Nov 14, 2018 2:59 AM by Michael Kuhn

    Wave spring - deformation / constraints virtual wall

    Michael Kuhn

      Hello!
      I´d like to calculate the reaction force due to a given deflection of a wave spring.

      The spring is held between to planar faces and stays there while compression.
      There is clearance between the bore diameter and the outer diameter of the spring.


      The Geometry:

       

      How i model it: (i´d like to know if there is a better way)

       

      (3 bodies - upper and lower "wall" rigid)

       

      My thoughts on the constraints:
      On the bottom of the spring i´ll use a virtual wall constraint - so the spring can lift/tilt of the surface freely but can not penetrate it.
      But how do i model the top deflection without using a 2nd body (like shown in the image above)?

      • the contact area changes
      • tilt/lift possible

       

      Thanks in advance,

      Michael

        • Re: Wave spring - deformation / constraints virtual wall
          Michael Kuhn

          I am still working on this problem *push*

          • Re: Wave spring - deformation / constraints virtual wall
            Sameer Qureshi

            Hi Michael,

             

            From what I understand, a virtual wall would be adequate to use on the bottom supporting surface to simplify the simulation and still provide the relative constraints for the lower portion of the model and not allow penetration. For the reasons you mentioned above, you would require some form of second body/surface to contact the wave spring and compress it as the contact area the force is applied over varies as the spring contorts and twists out of plane when compressed. If you're running a static analysis you have to remember the loads are considered to be applied slowly and remain constant in there direction of application.

             

            To allow some twist out of plane, you could could try splitting the top face of the spring and applying point displacements/forces at three points that coincide with where the 'peaks' of your wave spring are. Or you could modify the geometry of the top body so it is only in contact in the necessary area of the spring. However this then defeats the purpose of having the spring 'sandwiched' between two planar faces and being held there as the planar faces would limit the 'out of plane' motion when contact occurred between the two - so I'm not sure if this works for you.

             

            Personally I think the setup you have works well enough and only if you are getting excessive displacements and strains/materials are non-linear would I consider switching to a NL analysis to tackle this problem as the NL solver can re-evaluate the loading direction (can enable this in the properties) and stiffness of the model at each iteration.

             

            Looks okay to me!

             

            Thanks,

             

            Sameer

            • Re: Wave spring - deformation / constraints virtual wall
              Bence Rivasz

              Hi Michael,

               

              even your setup and simulation is successful, there is a high chanse that it wont give the same result as a real life measure (it shows far less reaction force):

              Almost all of these spring-washer-thingies (but also the ones made from wire) after the heat threatment have a process called "Scragging" :

              During this process the part will be squeezd (sometimes until it will be absolutely flat). That couses plastic deformation in the material and completely changes the load/displacement curve of the Spring.