Learning Forum

[BenjaminStarling]

The opposite direction of the forces is not caused by the difference in coordinate systems. APDL and Mechanical take care of the directions when requesting results. You can specify any arbitrary coordinate system for the elements and you will get the same result. nThe reason they are opposite is because the ENFO result is representative of internal force, you can plot ENFOVECTORS scoped to the whole body, and see the internal force at each element, including the discontinuity between elements. FVECTORS is representative of applied external forces, when scoping FVECTORS to a body, there is no result through the domain, only at locations where boundary conditions are applied. Internal force and externally applied forces are equal and opposite by definition, although FEM does not guarantee that they are exactly equal in magnitude.nQuadratic elements can have differing stiffness at the corner and midside nodes. Because you applied a displacement constraint this results in the two different magnitudes at corner and midside nodes. If you apply a force boundary condition, you should see a similar F result at both, with slightly different displacements. The most interesting example of this is quadratic solid elements, which have negative stiffness at their corner nodes.n