5 Replies Latest reply on Jan 6, 2016 10:28 AM by Janko Stellaard

    fully reversed vs zero based

    Dustin Meyer

      Hello, doing some play with the fatigue feature.

       

      Im having some issues with the loading events, ive done the static (looks good), and ive done a fatigue fully reversed (looks good). When i do a zero based, it doesn't find any change in results, ie it is showing as nothing is happening (its one solid color).

       

      (attached)

       

      Thanks,

        • Re: fully reversed vs zero based
          Janko Stellaard

          Because in both cases you use a SN curve based on R = -1 in the material properties, so you end up with the same result.

           

          Janko Stellaard

          Cadmes BV

          The Netherlands

            • Re: fully reversed vs zero based
              Dustin Meyer

              Please explain what you mean, or maybe i didnt ask the question properly...? haha

               

               

              Wouldn't you want to keep the same ratio's, between the different tests? im keeping everything else the same, and then only changing the loading event.

               

              Granted, the results from the zero loading will differ greatly from the rev loading.... but it should still show something?

               

              zero.JPGrev.JPG

                • Re: fully reversed vs zero based
                  Janko Stellaard

                  The SN curve in the material properties also will be different for R=0 and R=-1

                   

                  You have to define both, and the software will linearly interpolate between the curves if a different ratio R is selected. For example R= -0.5.

                   

                  I don't understand why you mark your answer as correct, because it didn't answer your own question.

                    • Re: fully reversed vs zero based
                      Dustin Meyer

                      So  trying to change this R value, and it wont let me.. ive copied a new material from the standard database. The R value it is greyed out.. when i do change it to zero and try to save, it reverts back to -1 the next time i open it.


                      I made quick video to explain..

                       

                      Recording #13 - YouTube

                       

                      I also tried defining a new curve, and it will also not save..

                        • Re: fully reversed vs zero based
                          Janko Stellaard

                          Step by step:

                           

                          1. edit material by selecting 'Apply/Edit Fatigue Data'  (it will automatically select the material from initial static study)
                          2. select under define: curve-0
                          3. give a ratio R under 'Stress Ratio (R)'
                          4. fill the table with the SN curve values you have for the above selected ratio (R)
                          5. press apply
                          6. repeat step 2 for a different ratio (R)
                          7. repeat step 3 for a different ratio (R) than before
                          8. repeat step 4 for selected ratio (R) under step 7
                          9. press apply

                           

                          Now you have 2 SN-curves defined. Every ratio (R) has it's SN-curve now. The software can now either select the appropriate SN-curve that suits the selected Loading Ratio defined in the study properties under 'Event'.

                           

                          If the selected loading ratio defined under event is different than the 2 ratio's (R) with a defined SN-curve, it will now linearly interpolate between those 2 curves.

                           

                          For example if you have a curve defined for R=0 and R=-1, but your event is based on R=-0.5, it will use those 2 existing curves to define a curve for your R=-0.5 event.

                           

                          Hope this makes it clear.

                           

                          Janko Stellaard

                          Cadmes BV

                          The Netherlands