Learning Forum

[peteroznewman]

nThanks for the link to another video. The point he and I agree on is that if stress at a bolted joint is critical, it should be represented using solids for the nut and bolt, not idealized beams and constraint equations. nI can give you an example where Rigid behavior will produce results that are closer to the results from a solid bolt head than a Deformable behavior on a Beam connection. The example is two plates made of plastic or any material that is hundreds or thousands of times softer than a steel bolt. In that case, a Rigid behavior of the bolt head provides a stress field in the plastic that is closer to the solid bolt head than the Deformable behavior, which will pull the edges of the hole down way too much.nYes, Deformable is like RBE3 from Nastran. I recommend you use the upper half of the hole in the blue plate as the scope for the Mobile connection to the Beam. That will represent the stiffness of the threads more accurately than scoping to an edge on solid elements, which will be too flexible.nThe length of the bolt that can stretch is somewhat excessive in your threaded bolt on the right because you moved the top up by 2/3 of the bolt head and the bottom goes all the way to the end of the threads. In reality, the length of bolt shank available for stretching is only the thickness of the black block. You would get a more accurate representation of the flexibility of the bolt by locating the top beam vertex at the bottom of the head and the bottom vertex at the top of the blue block. Most of the load is carried by the first two threads, so you could have the beam go a little lower than the top of the blue block.nWhen there is a nut and bolt in two clearance holes, then the length available to stretch the bolt is the sum of the thickness of the two plates and that is correctly represented in the beam in the hole on the left.n