Welcome to a new Tutorial about FEM Workbench in Freecad You will see how to use two different materials in a FE-Analysis The blue part is made of plastic and is fixed on both sides The profile is made of steel and has a tensile load on the upper surface I'm using a development snapshot of FreeCAD 0.18 First Part: modelling the geometry Second Part: Defining of materials and constraints & meshing of the geometry Third Part: Two ways of Post-Processing Let's start... Choose Part Design Workbnch new document, new body, new sketch on xy-plane right click and choose polyline follow the screen and double right click to terminate polyline click on the blue script and press delete button to remove conflicting errors of the sketch 5 degrees of freedom which have to be eliminated... make the two lines equal in length make them equal too... make them equal too two degrees of freedom left over define vertical length of 3 mm define horizontal length of 30 mm sketch is green, i.e. sketch is fully defined, click close pad the sketch with 20 mm in both directions, i.e. choose symmetric to plane choose model tab and create a new body to proceed modelling the plastic block create a new sketch on xy-plane right click and choose rectangle define vertical length of 30 mm define horizontal length of 50 mm two degrees of freedom left over define vertical length of 15 mm define horizontal length of 22,5 mm sketch is green, i.e. fully defined, click close pad the sketch with 30 mm symmetric to the xy-plane the two bodies have to be made into one in order to enable the meshing process in a FE-Analysis let's try different ways of unification... (including wrong ways) choose Part Workbench create a simple copy of the steel profile select the plastic part, pess ctrl-key and select the copy of the steel part press the cut-button (it's a boolean operation) select the remaining steel part und press space bar, i.e. hide the steel part now you can see the result of the former cut operation press space bar to show the steel profile let's start with the first way of unification of the two bodies select both bodies an press and make a fusion (boolean opertion) very good, only one body in the model tree. Let's have a look inside the body choose clipping plane, activate z-direction and be aware that the inner conture of the steel part has vanished i.e. this way of unification doesn't work for a FE-Analysis with two materials close clipping menu, select the fusion and press delete-key to undo the fuse-operation let's try another way of unification (also not expedient for a FE-Analysis) select both bodies and make a compound of them very good, only one body in the model tree let's have a look inside the body using transparency (right click on the body and choose appearance) the steel part has not vanished, so let's try a meshing process... choose FEM-Workbench select the body, click on gmsh-mesher and click apply to start the meshing process there is a mesh, but not a good one it's a non-conformal mesh, i.e. the two parts (steel & plastic) don't share the same nodes because there are two faces in the geometry which havn't been unificated using a compound to unify the two bodies click cancel to close the meshing menu and delete the mesh with delete-key choose Part-Workbench select the compound and press delete-key to remove the compound let's start with a truely working way of unification, promised... :) select both bodies and click on boolean fragments click on boolean fragments in the model tree and click the icon Analyze Geometry (another way to look inside a geometry) open the menu Shape Conent Two compounds (not good, can be a problem during meshing), no compound (would be good, only one face between different parts of a geometry) close Analyze Geometry and choose the Data Tab on the bottom left side of the screen change the mode of Boolean Fragments from Standart to CompSolid use the tool Analyze Geometry... There is a CompSolid (good), but one Compound is still left over (will be removed as well) select Boolean Fragments in the model tree and use the tool Compound Filter to remove the remaining Compound use Analyze Geometry again to inspect the result using Comound Filter No Compound, one Compsolid, two Solids and 20 Faces... let's count the numer of faces (controll if there are doubled faces lying on each other) click on model tab, appearance, choose transparency and active "Selectable = false" in order not highlighting faces with the mouse go back Tabs and count the number of faces (there are 20!) 20 faces, i.e. between steel and plastic is only one face, i.e. a conformal meshing process is possible Bottom line, to unify a set of bodies for a FE-Analysis with multiple materials use Boolean Fragment with the mode CompSolid let's start FEM choosing the FEM Workbench start a FE-Analysis creating a new Container let's start creating constraints... create fixed Constraints (body can't move in the 3d space) Problem! go back to Model-Tab and click "Selectable = True" so you can highlight faces... follow the screen... create a load with 500 Newton... let's create user defined materials won't use the standard materials, I'm going to define my own ones... open the material editor and enter your material properties (mechanical, thermal etc.) Youngs Modulus: 210 GPa & Poisson Ratio: 0,3 make sure to activate a Solid for your just created material and not a Face/Edge click Add and click the steel profile... be aware the "Solid1" has been selected Same procedure: new material, material editor (E-Modul = 1,2 GPa & Poisson Ratio = 0,38) and select the plastic body (be aware: Solid2) let's start meshing the geometry... click on Compound Filter and Gmsh-Mesher define max. element size = 4 mm don't click Apply (would start meshing) but ok in order to create a lokal mesh refinement right click on the mesh and have a look on the mesh info: the mesh is empty (meshing not started with apply) activate the mesh in the model tree and click on FEM Mesh Region define a local mesh refinement with 1 mm. Let's start to assing the refinement to inner faces of the steel part inner faces can't be selected, so the plastic part have to be hiden click on model tab and hide the Compound Filter and show only the steel body (using space bar) go back the the Task Panel and select the faces of interest for a mesh refinement make sure to hide the steel body and make the Compound Filter visible again double click on the empty mesh and click apply to start meshing (about 6 seconds on my machine...) the created mesh will be hidden by default, so make it visible using the space bar... let's have a look inside the mesh to inspect the local mesh refinement... Data Tab: Max Faces Show Inner, add 000 (strange thing in Freecad...) select Wireframe... Show Inner = true now you can see the mesh refinement (could of black lines within the body) you can use clipping to inspect the mesh on regions of interest.... I just admire the mesh... Sum up: constrains are crated, materials are defined and geometry is meshed. Let's start the solver... double click on the CalculiX Solver, write the solver input file and start the solver after it is written on my machine, the solver will run about 50 seconds... solver run has finished in 54 seconds without any error, close the menu... First way of Posprocessing: select the results in the model tree and click on the results icon...
