2 Replies Latest reply on Mar 31, 2015 2:27 PM by Jared Conway

    Bonded versus no penetration w/ bolted connectors

    Aaron Hayden

      I have been working the past few days on a study of a pivoting door. The shaft is supported by 4 pillow block bearings. The counterweight at each end is cantilevered on the shaft with a slip fit and held in place with keys and setscrews. There is a crank arm at each end mounted with a slip fit on the shaft between the bearings again using keys and setscrews. There are five "arms" also mounted on the shaft in similar fashion that the door panels will bolt to. There are bolted ribs between the arms. Most everything is low carbon steel with the exception of the door panel plates are 1/2" 6061-T651/6511 and the shaft will likely be 1144 TG&P. The door is too wide for a single sheet of aluminum, so there are two plates side by side. I am applying only gravity. I added bearing fixtures to represent the pillow blocks and fixed the clevis pin holes of the crank arms. I first ran the study with everything bonded. Peak stress was in the shaft at around 20-30 ksi depending on how I setup the study and mesh. The max deflection was where you would expect it at the middle of the door panel away from the pivot shaft. With bonded the max deflection I get is around .375-.400" depending on the study setup and mesh.

       

      It seems to me that using globally bonded will make the door panel more rigid that in really is. There are numerous bolts in this design, but I would think that the panel will be more flexile than if it was a welded construction. Late yesterday I set the aluminum panels to no penetration and used bolted connectors. I now get a max deflection of around .937" and a max stress in or near that location of 9.5 million psi. The arms and ribs are currently still bonded to each other, which I think they should be set to no penetration as well. I am trying to do this study in steps so that I can identify and resolve issues as I go.

       

      Will globally bonded make the door far more rigid as I suspect? What is the best practice to setup a bolted construction like this to get realistic results (and hopefully not take days upon days to accomplish)?

       

      Thanks,

      Aaron

       

       

      Pivoting door.JPG

        • Re: Bonded versus no penetration w/ bolted connectors
          Aaron Hayden

          I think I figured out my high stress issue. I had set the aluminum plates to no penetration to the ribs and arms as well as each other. The issue I believe was that when I created the contact sets I selected both the large surface of the aluminum plate where it mates with the ribs/arms as well as the narrow surface where it adjoins the neighboring aluminum plate. I believe since I used one contact set for both conditions this confused the simulation and it still bonded the narrow surfaces of the two aluminum plates to each other. In essence, I think it was treating them as one plate, but calculating a tremendous bending stress where they meet. I removed the narrow surface where the plates meet from the original contact sets and added a separate no penetration contact between the two plates. Now my stresses seem much more realistic.

          • Re: Bonded versus no penetration w/ bolted connectors
            Jared Conway

            step 1, run this with bonded. get some understanding of how the system is working.

            step 2, if you don't need bolt forces, don't use bolt connectors. just use a pin or bond maybe the edges. with the bond you'll use no pen between the faces. with the pin you would also use no pen.

             

            i would also recommend using symmetry here.