{"id":397704,"date":"2024-12-17T07:24:41","date_gmt":"2024-12-17T07:24:41","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/artificial-stresses-at-the-fixed-points-in-thermo-structural-analysis\/"},"modified":"2024-12-17T11:08:35","modified_gmt":"2024-12-17T11:08:35","slug":"artificial-stresses-at-the-fixed-points-in-thermo-structural-analysis","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/artificial-stresses-at-the-fixed-points-in-thermo-structural-analysis\/","title":{"rendered":"artificial stresses at the fixed points in thermo-structural analysis"},"content":{"rendered":"

<p><p>Hello,<\/p><p>div>I am working on a Thermo-structural analysis of a printed circuit heat exchanger (PCHE, it is a 50 stack HEx) model where I need to determine the appropriate thickness of the top plate. For simplification I’m just considering the top plate and the plate below it. The key loading conditions are:<\/div><div> <\/div><div>Maximum temperature: 535°C(both the bodies)<\/div><div>Pressure acting on the top plate(due to the fluid in the channels of the immediate below plate): 210 bar<\/div><div> <\/div><div> <\/div><div>To determine the stresses, I have attempted several boundary conditions:<\/div><div> <\/div><div>Fixing the side surfaces<\/div><div>Fixing the bottom surface (I understand this may be over-constraining the model)<\/div><div>Using remote displacement<\/div><div>Adding extensions to the side surfaces and fixing them<\/div><div> <\/div><div>Unfortunately, none of these approaches produced satisfactory results. <\/div><div>As a final attempt, I applied the 321 rule to constrain the model, allowing it to freely expand. While this approach resulted in zero thermal stress(which seems promising), I observed the following:<\/div><div> <\/div><div>Under pressure, the stress in most parts of the plate is below the yield point.<\/div><div>However, stress concentrations remain very high at the fixed points and their surroundings.<\/div><div>At this point, I am unsure if my current approach is correct or if there is a better way to define the boundary conditions to obtain realistic results. So my queries are as follows:<\/div><div>1)What type of restraining boundary condition is suitable for the analysis?<\/div><div>2)Is 3-2-1 principle the right approach?<\/div><div>3)Even when the 3-2-1 principle(if this is the correct approach) is used, it’s resulting in very high stresses at the fixed points. So what should be done to eliminate them?<\/div><div> <\/div><div>I am attaching few pictures of the geometry profile and the results obtained when the 3-2-1 rule was employed.<\/div><div> <\/div><div> <\/div><div>Could someone kindly provide insights on the correct boundary conditions for this type of simulation? Your guidance would be invaluable in resolving this issue.<\/div><div>Edit: the deformation and stress values are increasing with mesh refinement(even though the mesh is fine).<\/p><p>\"its<\/div><div>\"current<\/div><div>\"\"<\/div><div>\"\"<\/div><\/p><\/p><\/p>\n","protected":false},"template":"","class_list":["post-397704","topic","type-topic","status-publish","hentry","topic-tag-stress-singularity","topic-tag-unrealisticstress-1"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t