Reply To: Different Stress-Strain Diagram of RC Beam

[John Doyle]

At the point in the load history, where force reaction is highest, can you post process any plastic strain?  If not, you might be seeing extrapolation of elastic stress and strain, from element integration points to nodes, just before yielding begins.  If that is the case, try turning off all extrapolation by adding an MAPDL command 'ERESX,no'  in the Environment Branch, to be executed just before the Solve.

Refining the mesh is putting element integration points closer to the outside surfaces and corner nodes.  This is generally a good thing, but perhaps you are propagating very localized yielding in tension, causing convergence instability. With regards to mesh refinement and local plasticity, it can often be a tradeoff between accuracy and convergence stability.  Also, sometimes switching to lower order elements with enhanced strain formulation, can help stabilize element distortion issues.