WORKSHOP 3 EQUIVALENCE AND VERIFY THE HYBRID MESH

WS3-2 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation

WS3-3 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Model Description The hybrid microcircuit is monolithic: all material interfaces have negligible resistance to heat transfer. Hence, there are no contact resistances modeled in the structure and the entire model is materially continuous. In this exercise you will identify any incongruities, cracks, in the finite element mesh and equivalence to eliminate them. You will examine the completed mesh with quantitative verification tools. You will evaluate the mesh element aspect ratio, taper, and skewness. These are generally useful in qualitatively assessing the accuracy of results and identifying problem areas for convergence to a solution.

WS3-4 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Objectives In this exercise you will equivalence the 3D Hybrid Microcircuit model mesh. You will sample the finite element verification functions to examine the aspect ratio, skew ness, and taper of the mesh elements. Exercise Overview 1. Open the existing database named microcircuit.db. 2. Use Finite Element/Verify/Element Boundaries to identify any cracks which remain as artifacts from the geometry creation and meshing process. 3. Equivalence/All/Tolerance Cube to eliminate duplicate nodes and eliminate cracks in the mesh. 4. Verify/Hex/Aspect to identify elements with aspect ratios greater than Verify/Hex/Face Skew to identify elements with face skew angles greater than 110 degrees. 6. Verify/Hex/Face Taper to identify elements with highly tapered faces. 7. Quit MSC.Patran.

WS3-5 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Step 1: Open an Existing Database Open the existing database a.Select File from the Menu Bar b.Select Open from the drop down menu c.Select the name microcircuit.db. d.Click OK. a b c

WS3-6 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Step 2: Identify Cracks in Mesh Identify any cracks which remain as artifacts from the geometry creation and meshing process. a. Select Finite Elements. b. Verify/Element/Boundaries c. Select Apply. d. Display should now appear as shown. a b c

WS3-7 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Step 3: Equivalence The Mesh Nodes Equivalence nodes to eliminate duplicate nodes and eliminate cracks in the mesh. a. Equivalence/All/ Tolerance Cube. b. Select Apply. c. Verify/Element/ Boundaries. (reexamine mesh boundaries after equivalencing.) d. Select Apply. e. Your model should now appear as shown. c d Note: The nodes bounding the interior cracks will be circled in the display and the command line will indicate that a number of nodes were deleted. a b

WS3-8 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Note: MSC.Patran Thermal is reliable in converging to a solution even with elements of relatively high aspect ratios. However it is up to the analyst to decide whether too large a gradient is resolved across the long dimension of a high aspect ratio element. If this is so then resolving the mesh to a lower aspect ratio in that area will yield more accuracy. Step 4: Evaluate Element Aspect Ratios Identify elements with aspect ratios greater than 3.0 a. Finite Elements. b. Verify/Hex/Aspect. c. Change the Aspect Ratio to 3.0 d. Apply. (Since Paver mesh was used results may vary.) e. Now Select Plot Failed Elements Only. f. Apply. g. If geometry obstructs view of hex elements use Display: Plot/Erase and select Erase under Posted Entities/ Geometry. a b c d e

WS3-9 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Step 5: Evaluate Element Face Identify elements with face skew angles greater than 110 degrees. a. Finite Elements. b. Verify/Hex/Face Skew. c. Change the face skew angle to d. Apply e. Select Plot Failed Elements Only. f. Apply. a b c d e Note: The finite element formulation of an R-C network in MSC.Patran Thermal has been developed to provide a higher order accuracy to the resultant temperature distribution than is available with the traditional lumped mass/element centroid technique. Hence, even meshes with skewed elements yield results which do not contain artifacts of the mesh geometry.

WS3-10 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Step 6: Evaluate Element Face Taper Identify elements with highly tapered faces. a. Finite Elements. b. Verify/Hex/Face Taper. c. Change Face Taper to d. Apply. e. Select Plot Failed Elements. f. Apply. a b c d e Note: The verification functions in MSC. Patran provide a tool for quantifying the geometric quality of a finite element mesh. The criteria which determine the performance of the mesh in a numerical analysis remain the province of the analyst and his or her experience with the particular analysis.

WS3-11 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation Step 7: Quit MSC.Patran Quit MSC. Patran a. Select File form the Menu Bar. b. Select Quit from the drop down menu. a b

WS3-12 PAT312, Workshop 3, December 2006 Copyright 2007 MSC.Software Corporation