Concern about RBE3 - Printable Version +- MYSTRAN Forum (https://www.mystran.com/forums) +-- Forum: MYSTRAN (https://www.mystran.com/forums/forumdisplay.php?fid=4) +--- Forum: MYSTRAN (https://www.mystran.com/forums/forumdisplay.php?fid=5) +--- Thread: Concern about RBE3 (/showthread.php?tid=105) |
Concern about RBE3 - Victor - 01-25-2024 I'm trying to implement my own RBE3 according to the Mystran manual and I've noticed something that looks like a familiar type of wrong behavior. I'm not really sure if it is wrong or not or if Mystran also behaves this way. I haven't used Mystran before but I'd like see what other people think of it before setting up Mystran and learning how to define a model. In my implementation, when I apply a moment load about the x axis, it causes the correct moment about x but also another moment about the y axis as shown in the attached picture. Note that the independent nodes are on an inclined face, not in a plane normal to the applied moment. If you've used RBE3 before, would you expect this beam to bend as well as twist? I'm suspicious of this because CalculiX has a similar issue with its moment loads on beams which are internally converted to MPCs similar to an RBE3. RE: Concern about RBE3 - Victor - 01-25-2024 I've made a simpler example and solved with Mystran. It's a single CHEXA element supported on one face (grids 1,2,3,4) by SPCs and with a moment about Z applied to the opposite face (grids 5,6,7,8) via RBE3 from a separate grid 9. Input file: Code: SOL STATICS Here's the solution for reaction forces on the SPC nodes (T1-T3) and my hand calculated moments about the 3 axes due to those forces (Moment X, Moment Y, Moment Z): Code: GRID COORD T1 T2 T3 Moment X Moment Y Moment Z The total reaction moment about Z (-1.000000E+05) is the opposite of the applied moment which looks correct. However, there's also a reaction moment about Y (-1.000000E+04) which I think should be zero. It doesn't balance with the applied moment. Any thoughts? RE: Concern about RBE3 - Admin - 01-25-2024 Gotcha...we use this forum sometimes for general info and some static links and such. But all of the action is on Discord. |