8 Replies Latest reply on Jan 6, 2014 1:36 PM by Karan Lingerkar

    Stresses at Top surface of the shell?

    Karan Lingerkar

      Hello,

      How do I calculate the stresses at the top surface of the shell?

      Do I use an offset to the top surface (as shown in the attached) which will generate the mesh at the top surface of the part (rather then mid surface of the part which is default) and then use the results on the top surface?

        • Re: Stresses at Top surface of the shell?
          Jared Conway

          rmb on your stress plot and choose to plot the stress on the top shell vs the bottom or vice versa. results are shown on the mid surface or whatever surface you select for your shell but the results come from the top or bottom respectively.

            • Re: Stresses at Top surface of the shell?
              Karan Lingerkar

              999.png

              Hello Jared, Do you mean selecting the "Top shell face" or the "Bottom shell face" in the drop down menu (shown in the image) will show the results on the TOP SIDE (A) or BOTTOM SIDE (B) of the part respectively?

               

              444.png

              Also does selecting the "Bending" from the drop down menu show the bending stresses on the entire part (not specific to any surface?)

                  • Re: Stresses at Top surface of the shell?
                    Karan Lingerkar

                    Thank you Jared for the clarification....

                     

                    Speaking about the offset option for shells.........The link below says that mesh will be created on the TOP SIDE of the part.....right?

                     

                    http://help.solidworks.com/2012/English/SolidWorks/cworks/c_Offsets_for_Shells.htm

                     

                    If this is the case, should my max stress results using the

                     

                    1) Offset option and top surface (in shell definition) or

                    2) Using default mesh in the middle surface and selecting "TOP SHELL FACE" in the drop down menu in the stress polt

                     

                    should create same results? Right?

                      • Re: Stresses at Top surface of the shell?
                        Jared Conway

                        hi karanm offset is a slightly complicated subject

                         

                        why are you trying to use the offset option?

                         

                        what i would recommend is you take a step back and get handle on top and bottom shell results first and then worry about offset

                         

                        what i mean is make a surface at the midplane, run the analysis, get an understanding of how top and bottom results and bending and membrane results work.

                         

                        then you can start playing with offset to understand how the selection of the offset, the direction of the shell, all influence your results and what is the top and bottom..etc.

                         

                        but in the end, the inherent assumption in shells is that the parts are very thin and that the selction of the shell face should ave little effect on the results.

                         

                        if you are asking these questions because something is "wrong" with your results, i would suggest leading with that question.

                          • Re: Stresses at Top surface of the shell?
                            Karan Lingerkar

                            I tried to play with a lot of cases to understand the shell results with top and bottom. (not offset). I think I now understand how this work....reading and analyzing results..

                             

                            I find very little or unclear explanation about using shell offset in solidworks. The issue is how to analyse results when we use offset?

                            Are offsets only used for composite layered structure with many layers? Is it not used in my simple case? Is there a good article to explain this? I know SW2013 has much better options now "3D rendering" etc....but we are using SW2012.....

                              • Re: Stresses at Top surface of the shell?
                                Jared Conway

                                offset is used when you want to add slightly more accuracy to your analysis

                                 

                                when you use a shell, the analysis is done assuming that what you have selected is the mid-plane of the part

                                if you use sheetmetal, this is done automatically, or if you make the midplane yourself, it is done automatically

                                 

                                but sometimes you choose the inside or outside faces of a part to define the shell. so the mid plane is 0.5 thickness away

                                this is where offset comes in

                                 

                                nothing has really changed between the versions on this (well except since the addition of being able to define the offset a few versions ago) and really comes down to making selections.

                                 

                                like i said previously, unless you have a very very very thick shell, it is unlikely to make much of a difference in the results. we've covered this in our one-on-one mentoring sessions for customers that primarily deal with shells but the basics are taught in a standard simulation training class as well. there are lots of articles about it in the solidworks KB and also in the forum. i think there was one recently where we discussed using the render 3d shell option to confirm your selections.