7 Replies Latest reply on Sep 19, 2011 9:37 PM by Karan Lingerkar

    Non-Linear Analysis

    Karan Lingerkar

      I have the stress strain curve for Radel material and I am trying to do some FEA stress analysis using the non-linear properties of the material. I know you have an option to input the stress strain curve for the material when you select the option Non-linear (see attached). When I do this and run the FEA again I still get exactly the same numbers. My understanding is that it is not considering the stress strain curve which I input in the material properties.

       

      Also when I go the simulation mode in solidworks and try to input the material properties in the materials section (in simulation mode) I dont get the option to solve non-linear problem in that mode? see attached

       

      Can someone help?

        • Re: Non-Linear Analysis
          Kevin De Smet

          I am not very knowledgeable in Plastics, but try to use Von Mises Plasticity or a Hyperelastic material model type.

          • Re: Non-Linear Analysis
            Paul Kellner

            Karen,

             

            First of all looking at the Radel Non-Linear.bmp screen shot there are no non-linear properties defined for that plastic.

            Second, the same is true in the material properties window.bmp screen shot.

            I am not sure what you entered for non-linear stress strain curve, but I will remind you that it is time and temperature dependent for any plastic.

             

            When facing a problem like this it is sometimes helpful to do a test case. A test case might involve a simple model, like say a test dogbone and material properties defined from scratch. You first run the problem with linear elastic properties and then you do another run and define non-linear properties with a stress strain curve and a time curve. Any non-linear run needs a time curve to define how the loads are applied as it is inherent in a non-linear analysis that you probably won't have the part return to the same shape it started in when the loads are removed if you get into the non-linear portion of the material curve.

             

            Just my 2 cents.

             

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              • Re: Non-Linear Analysis
                Karan Lingerkar

                Paul

                stress strain for radel.bmp

                Column A- Is a measure of % strain

                Column B- Is a measure of Stress in N/m2.

                I defined a stress-strain curve for Radel. However I have not defined any other curves like variation of CLTE, poissons ratio and density with temperature. Do you still need to define that, and are you saying we need to make a physical test to determine those curves? I do not have much experience with Non-Linear Plastic FEA. Also how/where do you define a time curve in solidworks window for Non-L Analysis. Thanks!

                  • Re: Non-Linear Analysis
                    Paul Kellner

                    I believe that definition of the time curve is done in the feature tree towards the top and then referenced when you create the non-linear run. The help might point you specifically to what you need.

                     

                    You might want to consider both the tensile and compressive regimes for your material curve as they are usually different in plastic.

                     

                    Plastics creep. So a proper analysis requires a knowledge of how long the load is applied and the rate of loading. Plastic behavior is also highly temperature dependent. If you are doing something critical in the non-linear area a material test or two would be mighty advisable.

                     

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                    • Re: Non-Linear Analysis
                      Jerry Steiger

                      Karan,

                       

                      Did you get the help you needed? I've been too tied up with work to follow the forums for the last couple of months and am just catching up. Since I'm not using Simulation yet, I left this forum till the last.

                       

                      It looks to me like you have input a material that is only 1% as stiff as Radel R-5800. Notice that your first column has no units. I believe that means it wants 0.002352 for the first value, not 0.2352%. When I multiply .002352 times 2300 MPa, I get 5.4 MPa for the stress, which is pretty close to your 4.9998.

                       

                      I haven't tried putting in non-linear material properties in SW Simulation, but I know it is generally pretty painful to get the right values in Ansys. I don't think I was ever able to generate the compression-tension curve that Paul suggested.

                       

                      Jerry Steiger