 ## General Mechanical

Topics relate to Mechanical Enterprise, Motion, Additive Print and more

• grotstein
Subscriber
I am modelling a beam using beam elements and a rectangular tube cross-section in ANSYS Mechanical.nUsing the beam tool, I can extract a maximum bending stress, which is the maximum stress around either the internal Y or the Z axis, depending on which stress is higher. The same is true for the minimum bending stress.nHowever, I would like to calculate the sum of the stresses around Y and Z, because in one corner of the cross-section there is an constructive addition of these two stresses, which leads to a higher stress than the one indicated in maximum bending stress. I am able to work around this by exporting the bending moments and calculating the stress using the section modulus. Is there a way to do this calculation directly in Mechanical?n
• 1shan
Ansys Employee
nThe maximum bending stress included stress calculated from moments in all directions not just x or y. If you are interested in how the stress varies at a particular cross section I would recommend using solid elements to model your beam and view results at a particular cross section. Do check this video https://www.youtube.com/watch?v=_04tFkcaqXwnRegardsnIshann
• grotstein
Subscriber
Dear Ishan,nthanks for answering and the video link! I have seen it beforeand it explains the pitfall with maximum bending stress quite well at 3:16. nHowever, this only shows the one-dimensional case: The force and the bending is only in z direction (I can't see excatly which direction in the video, let's assume z for the sake of argument). If you add a smaller force in the y direction, creating an additional, smaller bending stress around the other axis, the value reported in maximum bending stress does not change (!). It only reports the maximum of the two bending stresses. This is also consistent with the manual (Mechanical -> Using Results -> Structural Results -> Beam Tool): nMinimum Bending Stress: From any bending loads a bending moment in both the local Y and Z directions will arise. This leads to the following four bending stresses: Y bending stress on top/bottom and Z bending stress on top/bottom. Minimum Bending Stress is the minimum of these four bending stresses.nMaximum Bending Stress: The maximum of the four bending stresses described under Minimum Bending Stress.nI am interested in the maximum sum of y and z direction stresses. I think it is not sensible to report only the maximum in one direction: if the bending stresses are of similar magnitude, the reported result may only be half of the true stress, which can be very dangerous if the part is critical.nCertainly, using the solid element model would be one solution, but it is costly in computation time and I am trying to learn about beam elements in ANSYS.nBest,nGregorn 