S8-1 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation SECTION 8 INTERCOOLER STRUCTURE

S8-2 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation SECTION 8 INTERCOOLER STRUCTURE

S8-3 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Topics covered in this case study: u Creating 3D Geometry u Meshing 3D Geometry u Controlling the mesh in 3D u Nastran Solid Element Definitions u Post Processing the 3D analysis SECTION 8 INTERCOOLER STRUCTURE

S8-4 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Problem Description u We are tasked with analyzing an Intercooler Design. The Intercooler is pressurized and cooled by a fluid on the inner face of its thick wall. Hot fluid passes through holes running inside the wall. u For the initial analysis we will only consider the mechanical loading. We will consider the combined thermal loading in a later case. CASE STUDY: INTERCOOLER STRUCTURE

S8-5 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Intercooler – assumptions u We are going to simplify the analysis by assuming that a 30 degree segment is able to represent the full 360 degree structure. u We will set up constraint boundary conditions to achieve this. CASE STUDY: INTERCOOLER STRUCTURE

S8-6 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Analysis Objectives u Determine stress levels in the intercooler under pressure loading. The maximum stress must be below the yield stress of the intercooler material. CASE STUDY: INTERCOOLER STRUCTURE

S8-7 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Basic Intercooler Idealization u No cooling holes SIMPLIFIED INTERCOOLER STRUCTURE

S8-8 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Getting started on the Intercooler analysis u We will introduce the idea of Solid Geometry Creation. u The simple type of Solid Geometry in PATRAN is a Blue Solid. We will use this. SIMPLIFIED INTERCOOLER STRUCTURE

S8-9 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n A PATRAN Solid can be: u Blue - Parametric u White - Boundary Representation n In our case we will build a Parametric Solid (Blue) Vector function of three parametric variables (,, ) u Parametric solids are meshed with the IsoMesh (Mapped) mesher (Hex, Wedge, or Tet elements) SOLID GEOMETRY

S8-10 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Geometry Menu Create a local cylindrical Coordinate system - number 1 - to help in the construction Construct 2 points in this system at 100,0,0 and 130,0,0 CREATE GEOMETRY

S8-11 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Construct 2 curves by revolving the 2 points in the cylindrical coordinate system Note the Axis definition 1.3 and the angle definition CREATE GEOMETRY (cont.)

S8-12 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Construct a green surface from these two curves CREATE GEOMETRY (cont.)

S8-13 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Extrude the surface to form the geometric solid, using the local axis system CREATE GEOMETRY (cont.)

S8-14 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Use Isomesh and Hex8 Element Type This results in NASTRAN 8-Noded CHEXA Elements MESH THE GEOMETRY

S8-15 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation l Set up material Properties as before Steel: E = 209E9 = 0.3 l Then assign Physical Properties CREATE MATERIAL PROPERTIES

S8-16 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Element connectivity is defined on the NASTRAN CHEXA entry, looking at Element 1 in our intercooler: CHEXAEIDPIDG1G2G3G4G5G6 CHEXA G7G CHEXA CHEXA CHEXA bdf file extract ELEMENT CONNECTIVITY

S8-17 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation PSOLIDPIDMID1CORDMINSTRESSISOPFCTN PSOLID110 n Element physical property is defined on the NASTRAN PSOLID entry $ Elements and Element Properties for region : wall PSOLID bdf file extract ELEMENT PROPERTIES

S8-18 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation $ Material Record : steel $ Description of Material : Date: 26-Oct-00 Time: 14:47:56 MAT1* * n A snap shot of the NASTRAN input file for this problem shows how the connectivity entry, the property entry, and the material entry are linked together. ……… CHEXA $ Elements and Element Properties for region : wall PSOLID ELEMENT PROPERTIES (cont.)

S8-19 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n An interesting feature of the solid elements in Nastran, such as the CHEXA, is that each grid only has: u 3 translational Degrees of Freedom (DOFs) u No rotational DOFs n We must be very careful to account for this when we mix element types, or apply constraints to the solid type elements. SOLID ELEMENTS

S8-20 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation We want to apply theta direction constraints to the two cut faces of the segment. This will mean each face is free to slide radially. CREATE BOUNDARY CONDITIONS

S8-21 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Theta Direction Constraint on Theta = 0 Remember – only translational DOFs for solids CREATE BOUNDARY CONDITIONS (cont.)

S8-22 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Theta Direction Constraint on Theta = 30 CREATE BOUNDARY CONDITIONS (cont.)

S8-23 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Question - we have applied constraints on faces theta 0 and theta 30 u Are these sufficient to enable us to carry out the analysis? u Think about how these components of constraints map to the basic x y z system of the model and remember that ALL possible Degrees of Freedom need to be considered. CREATE BOUNDARY CONDITIONS (cont.)

S8-24 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Answer – The translational constraints in the theta 0 and theta 30 planes map to constraints in the x and y directions only of the basic coordinate system. These constraints can take out translational movement in basic system x and y. They will also take out rotations of the structure about the basic system x y and z axes by providing couples. They will not constrain the model in basic system z – or indeed the local cylindrical z which maps directly. So we must add a z direction constraint. As we are not loading in the z (axial) direction then we can choose just one grid as a datum. If we wanted to load in the z direction we would need to consider an appropriate constraint set: u either build in the base or top u or apply a reflective symmetry constraint CREATE BOUNDARY CONDITIONS (cont.)

S8-25 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation We specify a Node by using the FEM filter The z translation of the basic Coord system is constrained CREATE BOUNDARY CONDITIONS (cont.)

S8-26 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation $ Displacement Constraints of Load Set : plane1_th SPC $ Displacement Constraints of Load Set : plane2_th SPC $ Displacement Constraints of Load Set : datum_z SPC n A snap shot of the NASTRAN input file for this problem showing the three defined constraint regions CREATE BOUNDARY CONDITIONS (cont.)

S8-27 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation $ Nodes of the Entire Model GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID GRID n If we look at a sample of the GRID data for those grids in the constrained faces, we see the Analysis Coordinate System has been automatically set to 1 for each grid. n It is essential that each grid preserves this Analysis Coordinate System in any further PATRAN modelling, otherwise the sense of the constraint is corrupted. CREATE BOUNDARY CONDITIONS (cont.)

S8-28 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation The constraints are verified using a Marker Plot CREATE BOUNDARY CONDITIONS (cont.)

S8-29 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation The pressure of N/m 2 is applied to the inside face CREATE LOADS

S8-30 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Select linear static analysis PERFORM ANALYSIS

S8-31 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Status window reports job progress PERFORM ANALYSIS (cont.)

S8-32 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n After NASTRAN completes the analysis, we are now ready to read the results back into PATRAN. Solver ACCESS RESULTS

S8-33 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n The.xdb file is attached ready to view the results for post processing. n We will look at the deformed shape – to confirm correct boundary conditions. n And we will look at the stresses to check the magnitude and sense of the loading. ACCESS RESULTS (cont.)

S8-34 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation The correct radial nature of the deformation is shown by a top view with the deformed shape shown as outline dashed PLOT RESULTS

S8-35 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation The radial and hoop stresses can be checked by looking at stresses relative to the local cylindrical system no. 1 hoop radial PLOT RESULTS (cont.)

S8-36 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation hoop radial PLOT RESULTS (cont.)

S8-37 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n We can look at radial and/or hoop stresses in a similar manner by setting up the vector controls. n Define everything relative to the local coordinate system 1. n Switch off the option to plot on the deformed shape. n Root the base of the vector. n And choose either of the xx or yy vector components to plot. PLOT RESULTS (cont.)

S8-38 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation PLOT RESULTS (cont.)

S8-39 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation PLOT RESULTS (cont.)

S8-40 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Basic Intercooler Idealization u No cooling holes u Alternative Construction: l Create 2D shells l Extrude those 2D shells l No solid geometry created BASIC INTERCOOLER

S8-41 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Alternative Construction – sweeping: u Create the base surface as before. u Mesh this base surface using 2D shell elements. u Sweep the 2D mesh to form a 3D mesh. u Delete the 2D elements. u This is a powerful technique, but not often feasible in complex solid geometry. BASIC INTERCOOLER (cont.)

S8-42 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Construct a green surface as before CREATE GEOMETRY

S8-43 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Construct a mesh of quads on the base surface MESH THE SURFACE

S8-44 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Construct the solid elements by sweeping the shells The vector and distance are defined on the main form The number of solid elements are defined under mesh control SWEEP THE ELEMENTS

S8-45 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Clean up the model by deleting the shell elements An easy way to do this is by a general element delete command, but using the entity selection icon to only pick 4-noded shells SWEEP THE ELEMENTS (cont.)

S8-46 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n The model creation and analysis are as before except: u There is no Patran geometry associated with the solid elements. u This means we have to apply loads and boundary conditions to the FEM. u We have to apply the Element Physical properties directly to the group of solid elements. SWEEP THE ELEMENTS (cont.)

S8-47 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Typical Menu selections are therefore: Creating Physical Properties: Pick the elements directly Use the selection icon to help pick only solid elements CREATE ELEMENT PROPERTIES

S8-48 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Hidden Line Pick Creating displacement constraints: Pick the FEM Filter Use the hidden line picking option Use the polygon picking option to capture the correct region Polygon Pick CREATE BOUNDARY CONDITIONS

S8-49 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Advanced Intercooler Idealization u Introduce cooling holes u Alternative Construction: l Create 2D shells l Extrude those 2D shells l No solid geometry created DETAILED INTERCOOLER

S8-50 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Alternative Construction - sweeping u Create the base surface as before including hole. u Mesh this base surface using 2D shell elements. u Sweep the 2D mesh to form a 3D mesh. u Delete the 2D elements. DETAILED INTERCOOLER (cont.)

S8-51 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Create the two start curves as before Then create the mid points CREATE GEOMETRY

S8-52 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Create the center point of the circle CREATE GEOMETRY (cont.)

S8-53 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Create the center circle using 2D Arc Angles Method (R=5) Then close the outer boundary with two curves Then chain the outer boundary using autochain Then create the trimmed surface CREATE GEOMETRY (cont.)

S8-54 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation The 2D base mesh is constructed in the same way as the rib in case study 4 Concentric circles are made from the center ring, using a local cylindrical axis system These are mesh seeded Then the surface is paver meshed MESH THE SURFACE

S8-55 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Construct the solid elements by sweeping the shells as before The vector and distance are defined on the main form The number of solid elements are defined under mesh control SWEEP THE ELEMENTS

S8-56 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Now apply materials, properties, loads and boundary conditions as before, but without using geometry to assist. u We must use the FEM filter and carefully pick the surface grids for the displacement constraints. u Similarly, the internal pressure load is applied to the solid element faces. LOADS AND BOUNDARY CONDITIONS

S8-57 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Theta Direction Constraint on Theta = 0 Remember – only translational DOFs for solids LOADS AND BOUNDARY CONDITIONS (cont.)

S8-58 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Theta Direction Constraint on Theta = 30 LOADS AND BOUNDARY CONDITIONS (cont.)

S8-59 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Alternative Construction – Advanced Solid u Create the base surface as before including hole. u Copy the base surface to the top. u Create the other bounding surfaces. u Form the Boundary-Representation (B-Rep) Advanced Solid. u Tet-Mesh the Solid. ALTERNATIVE METHOD

S8-60 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Non-Parametric Solids (White) u Non-parametric solids have only a surface representation inside PATRAN. u Boundary representation (B-Rep) solids can be created. u CAD solids are normally accessed as B-Rep solids and can be meshed using the Auto Tet Mesh algorithm. Solid Automatic Tet Mesh ALTERNATIVE METHOD (cont.)

S8-61 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation The base surface is created as before as a trimmed surface CREATE GEOMETRY

S8-62 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation The base surface is translated to form the top surface CREATE GEOMETRY (cont.)

S8-63 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation The other 5 surfaces are created (including the hole) These are simple green surfaces CREATE GEOMETRY (cont.)

S8-64 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Now we have the b-rep solid complete CREATE GEOMETRY (cont.)

S8-65 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Another way to create the solid is to extrude the base surface directly CREATE GEOMETRY (cont.)

S8-66 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation Mesh the solid using TET10 Topology Use Global Edge of 2 MESH THE SOLID

S8-67 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Summary of Patran Solids PATRAN SOLIDS

S8-68 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Commonly used solid elements: u PENTA (6-15 nodes) u HEXA (8-20 nodes) u TETRA (4-10 nodes) Note - any or all mid-side nodes may be deleted NASTRAN SOLID ELEMENTS

S8-69 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n HEXA - u Recommended for general use. Accuracy degrades when element is skewed and used in a situation where bending behavior is dominant. In most modeling situations, it has superior performance to the other 3D elements. PENTA - u Commonly used to model transition. This element is designed to behave well as a reasonable thin shell element. If the triangular faces are not on the exposed surfaces of the shell, excessive stiffness results. TETRA - u Frequently used by automatic mesh generators. The 4- noded TETRA is not recommended for modeling. The 10- noded TETRA elements will provide much better accuracy. NASTRAN SOLID ELEMENTS (cont.)

S8-70 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation n Hex versus Tet Meshing u Convenience and speed of Tet Meshing in a non 2 ½ D case u Control and Quality of Hex Meshing MESHING METHODS SUMMARY

S8-71 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation EXERCISE Perform Workshop 9A 2 1/2 D Clamp – Sweep Mesher in your exercise workbook. Perform Workshop 9B 2 1/2 D Clamp – Iso Mesher in your exercise workbook.

S8-72 NAS120, Section 8, May 2006 Copyright 2006 MSC.Software Corporation