6 Replies Latest reply on Apr 26, 2014 2:08 AM by Jared Conway

    Can shear stress be trusted?

    Chad Schmidt
    Chad Schmidt Mar 6, 2009 12:58 PM
      Something seems really off when looking at a shear stress plot. Example: When viewing shear stress as a vector the vectors are all over place. Forgive me if I'm wrong but these vectors actually have direction and magnitude. The thing that bothers me is the direction is determined by the setting of the type of plot. Suppose I pick TXZ. I would expect all vectors to be collinear to the YZ plane and also parallel with the Z axis. So If viewed these vectors from perpendicular to the Z axis I should see nothing but a bunch of arrows pointing directly at me or directly away from me.
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        • Can shear stress be trusted?
          Chad Schmidt
          Chad Schmidt Mar 6, 2009 2:10 PM (in response to Chad Schmidt)
          This is gettin worse! I looked at the vectors on a normal X plot and none of the vectors line up with the X direction. Can someone please explain to me what I'm not understanding here?
          • Can shear stress be trusted?
            1-DEXHLY Mar 6, 2009 6:38 PM (in response to Chad Schmidt)
            Would you please upload your file?
            It is the only way to check. Few times I had a similar problem doing structural analysis on frames (using weldments in SW). Check with a Free Body Diagram if the information given out are the same.
            • Can shear stress be trusted?
              1-I7AP5K Mar 6, 2009 10:38 PM (in response to Chad Schmidt)
              Hi Chad,

              Maybe I've misunderstood something, so please correct me if I'm wrong.

              You're working on the YZ plane and we select Y as being horizontal for the sake of discussion and Z is vertical. Your vectors are collinear (coplanar ?) with the plane and parallel to Z (vertical). If you're viewing this arrangement from a position perpendicular to Z, you must be at either +X or -X. Doesn't that mean that your vectors should be pointing either straight up or straight down (+Z or -Z)?
              • Re: Can shear stress be trusted?
                Keith Frankie
                Keith Frankie Apr 25, 2014 3:48 PM (in response to Chad Schmidt)

                I was confused about this also.  I sent SW an example file and recieved the following logical explination:

                 

                Thank you for contacting SolidWorks Technical Support. My understanding of how the vectors are plotted for shear stress is that SOLIDWORKS points them in directions perpendicular to the shear stress directions.

                So for TXY=TYX, the shear stress pair you noted, are in the Y-direction (YZ plane) and X-direction (XZ) plane. Therefore, to represent these shear directions, it shows the vector in the third direction perpendicular to the two, which is the Z direction. Similar TXZ=TZX will be plotted in the Y direction, and TYZ=TZY will be plotted in the X direction.

                • Re: Can shear stress be trusted?
                  Jared Conway
                  Jared Conway Apr 26, 2014 2:08 AM (in response to Chad Schmidt)

                  To get your head wrapped around it , I would recommend generating a model with a known result and posting some screenshots of the results and what you expect. I suspect it is as noted above that your expectations aren't matching what is done.