5 Replies Latest reply on Nov 16, 2007 12:33 AM by Valentin Leung

    Plastic deformation and Living hinge

    Valentin Leung
      Okay, a simple question, I need to make some FEA on some plastic parts, the problem is the presence of living hinge.
      For those who don't know what is a living hinge, on a plastic part, sometimes, you will see a area so thin that it acts like a hinge. In this area, the deformation is a plastic deformation, so the material does not tear.
      Right now, I have made a simulation of my model, but the living hinge does not work (it's just too hard), does someone has already manage to simulate living hinge?
      Thanks
        • Plastic deformation and Living hinge
          Vince Adams
          Hi Valentin, I apologize if this is a silly question but I have to ask before we proceed... did you model this with nonlinear material properties? Are you trying to model the initial flexure of the living hinge or are you trying to evaluate the response of the system with a previously flexed living hinge? These are important points.

          Let me know...

          Vince
            • Plastic deformation and Living hinge
              Valentin Leung
              I am using nonlinear solver, but I am using the common PP of the material library. Right now, from my boss'analysis, the results are coherent with the initial flexure of the hinge (the hinge does not want to be fold... ), but I want to simulate the response of the system with this hinge previously flexed so that it acts more like a hinge. This way, I can see deformation on the rest of the body.

              Thanks for your help.
            • Plastic deformation and Living hinge
              Valentin Leung
              Vince?
              Any things in your mind that would help me?

              Thanks in advance

              Val
                • Plastic deformation and Living hinge
                  Vince Adams
                  Hi Val, two suggestions come to mind, use the true SS curve with plasticity to fold the hinge past yield where it becomes in essence perfectly plastic and then, using the load/time curves in the nonlinear set up, apply your operating loads once the plastic hinge has reached zero stiffness. This is the hard (yet cool) way.

                  Another option is to assume that the areas that have gone perfectly plastic stay that way and model, using a multi-body part, the areas that have lost stiffness as a different material. You'll need to play with your properties to match some physical sample but in the end, this could be more efficient.

                  Beyond that, I'd need some time with the application.

                  Good luck!!

                  Vince
                • Plastic deformation and Living hinge
                  Valentin Leung
                  Thanks Vince,
                  I tried to play with a PP material with a much lower elastic modulus but it's still too hard and if I lower it more, it refuses to load the simulation.

                  Plastic is a little new to me as I was using FEA on steel structures before... I need to get some work on plasticity now.

                  Thanks anyway.
                  Val