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Simulation Night School 2014Glenn Whyte + Damon Tordini

Simulation Specialists

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Simulation Night School Agenda

Overview/SimulationXpress

The Analysis Process

Results and Result Interpretation

Intermission

Common Problems/Troubleshooting

SOLIDWORKS Flow Simulation

3

Computer Specs

HP EliteBook 8570w Laptop

Windows 7 Professional x64 Edition

Intel i7 3630QM (2.6 GHz)

4 computing cores

8 GB RAM

nVidia Quadro K1000M (2GB)

SOLIDWORKS 2014 SP4.0 x64

SSD Hard Drive

4

Overview of Simulation tools for everyone

Linear Static Stress Analysis

Simulation Xpress

5

Linear Static Stress AnalysisKey Assumptions:• Loads applied slowly, no inertia, no time-dependence etc.

• Dynamic analysis overcomes this assumption• Linear material behavior• Small deformations – constant stiffness matrix

• Nonlinear Analysis overcomes this assumption

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Matching Real-Life Results: Study Type

Linear Nonlinear

Static

Dynamic

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Stress/Strain Curves

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SOLIDWORKS SimulationXpressLimitations:• Linear static stress analysis on single-body parts.• Uniformly distributed force or pressure loading• Fixed-face restraints• Global control of mesh density• Result plots of Von Mises stress, displacement, and FOS• Single-factor optimization

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SOLIDWORKS Analysis Products

SOLIDWORKS Simulation Premium

SOLIDWORKS Simulation Professional

Static Frequency & Buckling Thermal Drop Test

FatigueMotion

Simulation Optimization PressureVessel

Flow Simulation

Electronic Cooling Module

HVAC Module

Nonlinear (static & dynamic)

Harmonic

RandomVibration

Time History

Composites Response Spectra

Sustainability

Plastics

Professional

Premium

Advanced

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Building the FEA Model

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Analysis Process and Considerations

Material Definition

Contact

Connectors

Fixtures

Loads

Meshing

Solving

Results/Post Processing

12

Materials Definition

• Start your mathematical problem with a strong base.

• Common area of mistakes in FEA problems

• The source for SOLIDWORKS material properties is Metals Handbook Desk Edition (2nd Edition), ASM International.

13

Custom Materials

•The default SOLIDWORKS material database cannot be modified. This is by design.

•When creating a custom material, it is recommended to copy an existing (similar) material, and modify.

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Elastic Modulus

Poisson’s Ratio

Yield Strength

Density

SOLIDWORKS Material Library

Required for Linear Static

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Meshing

Automatic Mesh Type Selection

Sheetmetal/Surfaces

Shell Mesh

Weldments

Beam

Everything Else

Solid Mesh

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Solid Elements•Basic shape is a tetrahedron

•High Quality (default) Solid Elements will have 10 nodes: 4 corner nodes and 6 mid-side nodes. Edges of HQ elements can better map curvilinear shapes.

•Draft Quality Solid Elements have 4 corner nodes and linear edges.

•For both cases, each node has three degrees of freedom, all translational.

Nodes

Draft High

Nodes 4 10

DOF per node

3 3

Total DOF 12 30

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Shell Elements•Used for thin geometry

•Basic shape is a triangle

•High quality (default) Shell elements have 6 nodes: 3 corner and 3 mid-side with 6 DOF per node (including rotational freedom). Can better map to curvilinear shapes.

•Draft quality Shell elements have 3 nodes (corners only), with 6 DOF per node. They remain linear through deformation.

Draft High

Nodes 3 6

DOF per node 6 6

Total DOF 18 36

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Element Quality Draft quality mesh will create an

analysis with the same fundamental mesh structure, but less nodes/DOFs

Stress results will likely not be accurate enough for final results

However, draft mesh is an excellent tool for model preparation or troubleshooting

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Why Use Shell Elements?•Any model could be meshed with Solid Elements. However, to get an adequate mesh for thin objects, the number of elements can become unmanageable. More DOF = Longer Solve Time!

1500 2000 2500 3000 35000

50000

100000

150000

200000

250000

300000

350000

Von Mises Stress

Deg

rees o

f Fre

ed

om

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Beam Elements

•Used for slender objects with a constant cross-sectional shape

• As of SOLIDWORKS 2011, tapered beams also supported

•Basic shape is a line element with two end points (nodes)• Each node has 6 degrees of freedom; 3 translations and 3

rotations.

Nodes 2

DOF per node 6

Total DOF 12

Nodes

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Invalid for Beam Elements

•Beam elements support tapered beams, but cross-section can only shrink or grow proportionally

•For other invalid beams, see the help file article titled: “Invalid Tapered Beams”

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Contact

No Penetration Bonded

Virtual Wall Shrink Fit

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Contact/Gap Hierarchy

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Global Contact

•Bonded- Selected components or bodies behave as if they were welded during simulation (no relative translation or rotation).

•Allow Penetration – Selected components or bodies may pass through each other.

•No Penetration-Selected components or bodies do not penetrate each other during simulation. Surface to surface contact formulation is applied by default.

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Global Contact Limitations•Global contact will only be applied to faces/entities that are coincident at the start of the analysis.(2014 allows some non-touching faces in global contact, but have had limited success with this function)

•Mixed mesh types: global bonded contact does not always automatically create connections

•Solution: Local Contact Sets!

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Contact Tools and Tips

• Interference detection – “Treat coincidence as interference” does a great job of showing where parts are initially touching

• Contact Visualization Plot – New in SW2014, allows you to visualize what contact has been created, and what type.

• Solver-based contact visualization will show contact relationships between mesh elements.

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BoltsStandard or Counterbore

with Nut

Countersink with Nut

Standard or Counterbore Screw

Countersink Screw

Foundation Bolt

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Fixtures Used to represent how the given model is

attached to the rest of the world– Fixed on a Surface, Edge or Point– Free Sliding or Rotation

Helpful for reducing the size of the problem to a component level or subassembly level

Ensures the problem is in static equilibrium

Remove DOF in the model

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Degrees of Freedom• Objects in 3-D space have 6 degrees of freedom (DOF)

• In Cartesian coordinates, there are:• Three translational (x,y,z)• Three rotational (about x, about y, about z)

• In SOLIDWORKS Simulation, the conditions of the problem (fixtures, contact, mesh) determine how many total DOF exist

• More DOF means a more complex problem,requiring more computer resources

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Fixture Types

Standard

• Fixed Geometry• Roller/Slider• Fixed Hinge

Advanced

• Symmetry• Circular Symmetry• Use Reference Geometry• On Flat Faces• On Cylindrical Faces• On Spherical Faces• Bearing

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Fixtures PreviewTranslationRotation

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No Fixtures Preview?

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Loads

Standard

• Force• Torque• Pressure• Gravity• Centrifugal• Bearing Load• Temperature

Imported

• Flow Effects• Thermal

Effects

Other

• Remote Load• Remote Mass• Distributed

Mass

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Force vs. Pressure

Both are external loads intended to represent other components or environmental conditions acting upon your design.

Force Pressure

Defined in units of force (lbf, N) Defined in units of force per area (psi, N/m2)

Can be applied to faces, edges and vertices

Can only be applied to faces

Can be applied normal to face or in specified direction

Can be applied normal to face or in specified direction

Components can be defined in all 3 vectors (local x,y,z)

Can only be defined in one vector

By default, Force values are distributed across the selected geometry, while Pressure values are constant over the selected geometry

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Force vs. Pressure.Forces and Pressures can both represent the same load depending on how you define them!

100 lbf / 1 in2 = 100 psi

100 psi * 1 in2 = 100 lbf

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Remote Mass vs. Distributed Mass

Two differences:1. Remote mass adds stiffness to the model

as the component being replaced by the remote mass is considered to be attached by rigid bars.

2. The remote mass can have a non-uniform distribution whereas the distributed mass is always uniformly applied.

Please note: "Treat as remote mass" only considers mass…so be sure to define gravity!

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Mesh Creation Tools• Two mesh creation schemes – Standard and Curvature-Based

• Generally, Curvature-Based will create more elements, but better adapt to complex geometry

• Curvature-based mesher takes greater advantage of multi-core CPUs

Standard Curvature

Elements 109 258 70 752

Time to Mesh 33 seconds 9 seconds

Percentage of distorted elements

0.215 % 0.543 %

Mesh Control needed 133 faces 0 faces

• Mesh controls allow you to specify a smaller mesh resolution for specific vertices, edges, faces, bodies or components

38

Challenge Question: Mesh Options

•Which mesh options will give the most accurate result?•Which will be the quickest to solve?

Max Von Mises (psi) Time to (s)

Standard Mesher

Curvature-Based Mesher

Standard Mesher with Mesh Control

“True” Result

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Challenge Question: Mesh Options

•Which mesh options will give the most accurate result?•Which will be the quickest to solve?

Max Von Mises (psi) Time (s)

Standard Mesher 2,354 4

Curvature-Based Mesher

2,557 14

Standard Mesher with Mesh Control

2,688 8

“True” Result 3,241

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SolvingFFEPlus – Uses an iterative approach to solve the equationsDirect Sparse – Directly solves the system of equations

Direct Sparse Large Problem DS FFEPlus

More efficient with No Penetration Contact

Similar to direct sparse with less memory load

More efficient with large problems, ie. >250k DOFs

Uses more RAM for larger problems, around 10x more than FFEPlus

Efficient for large problems, with good multi-core capability

Better equipped to utilize multiple cores

Better with significant differences in materials

41

Results and Result Interpretation

Result Quantities Available

Result Viewing Options

Failure Theories

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Result Quantities Available• Stress

• Stress in X, Y, Z• Shear stress about X, Y, Z• Principal Stresses - 1, 2, 3• Von Mises• Stress Intensity (P1-P3)• Energy Norm Error• Contact Pressure

• Displacement• Displacement in X, Y, Z, and resultant• Reaction Forces

• Strain• Strain in X, Y, Z, resultant• Shear Strain about X, Y, Z• Principal Strains• Strain Energy Density

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Result Plots Available• Contour Plots

• Section Clipping• Iso-Clipping• Probe• List Results

• Reaction Forces/Free body forces

• Options, Settings and Definitions• Now streamlined in 2014!

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Failure TheoriesFactor of safety plots can be viewed to show how the stresses related to different failure theories compare to failure limits.

• For ductile metals (and also other situations)• Von Mises

• Tresca (maximum shear stress)

• Von Mises is more commonly used, Tresca is more conservative

• For brittle materials – Mohr Coulomb Stress theory/internal friction

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Coming Soon to HawkWare Tools

Simulation Results Manager!

• Archive completed study results to save disk space

• Clean up results directories for easier sharing

Visit store.hawkridgesys.com for more information

46

Common Problems/Troubleshooting

Results Convergence

Matching Real-Life Results

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Mesh Convergence PracticesIn stress analysis the quality of the result is directly dependent on the quality of the mesh.

No stress result should be accepted as “correct” until you’ve proved that the mesh is adequate.

This is done by proving that the stress results are “converged”

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What is Convergence?

• All FEA analysis is based on the concept of discretization- breaking a model into individual pieces that can be calculated (meshing).

• This inherently adds error to results- convergence is the process of reducing mesh error

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Checking Strategies

Methods:

1. Manual Inspectiona) Run a Study > Refine Mesh > Review

Results (stress)b) Utilize Trend Tracker

2. Design Studya) Create a parameter linked to mesh

control or Global mesh sizeb) Manually specify sizes or use

Optimization

3. Adaptive Meshing

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Checking Convergence – Manual Inspection1. Run an analysis2. Increase mesh density (either globally or locally)3. Review key results4. Repeat until key results don’t change within an acceptable

tolerance

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Checking Convergence – Adaptive Meshing

•The h-Method• The concept of the h-method is to use smaller elements.

After running the study and estimating errors, the software automatically reduces the element size in appropriate areas.

•The p-Method• The concept of the p-method is to add more nodes and

increasing the order of the element in regions with high errors. After running analysis and estimating errors, the program increases the order of elements in regions where necessary.

Adaptive Finite Element Analysis

h-Adaptivity, p-Adaptivity

Refining the mesh (h-Adaptivity)

Changing the “order” of elements (p-Adaptivity)

1st order(Draft Quality)

2nd order(High Quality)

… 5th order

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Concentrations & Singularities

No Singularity Singularities

No sharp geometrical discontinuity and no concentrated load/fixture

Sharp geometrical discontinuity or concentrated load/fixture

Will converge when mesh is refined Will not converge with refinement

Converged stress value can be trusted Stress values cannot be trusted

•Stress concentrations are areas of high stress

• Stress singularities are a type of concentration that displays unrealistically high stress values due to mathematical phenomena (displacements are not affected)

• Singularities generally occur in sharp corners

54

Hawk Ridge Systems Knowledge Base

For more details on recommended procedures and the mathematics behind convergence, check out our guide at:

support.hawkridgesys.com/forums

55

Matching Real-Life Results

•What are the SOLIDWORKS Simulation results being compared to?

-Hand calculations? -Experimental results?-Other software?

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Hand Calculation Example

Stress/Strain calculation used to evaluate deformation of tank wall under pressure

Formula predicts 0.485in, SOLIDWORKS predicts 0.501in for a single plate.

However, once you add the other 3 walls, displacement is 0.19inThe 3d case is closer to fixed support than simple support.

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Matching Real-Life Results: Conditions

•Are you comparing to physical tests, or real-world usage?

•Do you have a document that explains the experiment setup?

•What materials are being used? Do the mechanical properties of your material match that which is found in the SOLIDWORKS material database?

•How realistic are your restraints/fixtures?

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Matching Real-Life Results: Loads

•Are you running the correct study? A static load of value x may cause an object to react much different than an impact load of value x.

•Are there other factors that you are omitting in your analysis?

• Gravity• Friction• Damping

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Matching Real-Life Results: Study Type

Linear Nonlinear

Static SOLIDWORKS Premium Simulation Premium

Dynamic Simulation Premium Simulation Premium

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Where is error introduced?

5% 10% 65% 20%

<1%

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How to have confidence in results?

Validation examples

NAFEMS is an independent, not-for-profit organization that sets and maintains standards in computer-aided engineering analysis and, specifically, finite element analysis (FEA).

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Matching Real-Life Results

• Remember: when using FEA, the end goal should not always be to duplicate real world results.

• Garbage in, garbage out

• Significant value can come when using it to get relative results (Trend studies, design decisions).

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SOLIDWORKS Flow Simulation

What is Flow Simulation?

• Embedded CFD (Computational Fluid Dynamics) analysis tool inside SOLIDWORKS

• Evaluate designs for optimum flow rates, temperatures, aerodynamics, and more

• Piping Systems• Electronics Cooling• Heat Exchangers• Transportation

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Flow Simulation Procedure

Geometry Prep

Wizard

Boundary Conditions

Materials/Heat Sources/etc.

Goals

Solving

Results/Post Processing

66

Flow Simulation: Geometry Prep

•Simplify Geometry- not mandatory, but usually smart

•Internal or External analysis?

•Check Solid/Fluid Volume• Use Leak Tracker

67

Flow Simulation: Boundary Conditions

•Important mainly for internal analyses

•Establish where fluid enters or leaves the model

• Flow Openings: known inlet or outlet condition

• Pressure openings: ?

•Applied to lids• Always select inside face(s)

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Flow Simulation: Materials/Heat Sources/Etc.

•Important mainly for simulations with Heat Conduction in Solids enabled.

•Many optional conditions: Two Resistor Components*, Perforated Plates, Printed Circuit Boards*

•Typical properties to enter:• Thermal Conductivity, W/m2-K• Heat Power, W• No. of PCB layers

•Note: materials in Flow Simulation are different than in SOLIDWORKS Material library!

*Requires Electronics Cooling Add-on

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CircuitWorks and Flow SimulationNew for 2014: Import the following ECAD properties from CircuitWorks to Flow Simulation:

• Heat Sources • Conductivity• Dielectric and Conductor Density• Specific Heat• Printed Circuit Board properties with the Electronic Cooling Module

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Flow Simulation: Goals & Solving

•Goals allow easy checking of key results both during and after the simulation

• Verify what you’re trying to measure: average vs. bulk average

•Ensure a certain level of accuracy in the solver- “convergence”

•Solver can be run on local machine, or on network- will use all available CPU cores

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Flow Simulation: Results

•Both numerical and visual results are available to evaluate design

Typical workflow: 1. Check if requirements are met via Goals, surface

parameters, etc.1. Max CPU Temp? Pressure Drop?

2. Use Cut Plots, Surface Plots, Flow Trajectories to see why, and how design should be modified.

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Hawk Ridge Online Training

• 8 current Simulation course offerings via GoToMeeting

• Visit www.hawkridgesys.com/training for more information

73

Simulation Services

► One-On-One MentoringAs an extension to our classroom training, Mentoring provides customized training on applying SOLIDWORKS Simulation tools to your specific engineering problem.

► Analysis ConsultingLeverage the engineering and analysis expertise, experience and resources of our team to execute your analysis.

► HRS Simulation Services Credit25% of your simulation services fees can be applied to new SOLIDWORKS Simulation software license purchases.

► ContactYour Hawk Ridge Systems contact or Jared Conway, Simulation Services Manager (jared@hawkridgesys.com, 650-230-7006).

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