Advanced Thermal, Stress, Fatigue, and Vibration Workflow (Class MA 7422-P)

Transcription

1 Advanced Thermal, Stress, Fatigue, and Vibration Workflow (Class MA 7422-P) Bruno Fairy CAE & Rendering Technical Specialist Parker Hannifin James Herzing Technical Consultant Autodesk

2 Class Summary Autodesk Simulation Multiphysics class covering: Basics of Finite Element Analysis (FEA) Thermal analysis Fatigue analysis Shock/vibration analysis Drop analysis 3D Hydrodynamic transient analysis Plastic deformation analysis

3 Learning Objectives At the end of this class, you will be able to: Prepare simulation model in Autodesk Inventor Fusion Set up a thermal analysis Optimise your model using the Fatigue Wizard Set up vibration/shock analysis Set up analysis with 3D hydrodynamic elements Set up plastic material characteristics

4 Basics of FEA

5 Basics of FEA Static Analysis Deformation is the first output to be calculated according to: Or {Force} = [Stiffness] * {Deformation} {F} = [K] * {d} (or {x}) Therefore: {d} = [K] -1 * {F} FEA packages will generate [K] based on geometry and properties of FE model.

6 Basics of FEA Static Analysis (continued) {F} [K] [K] -1 {d} (or {x}) = Vector of applied forces (specified by User) = System stiffness matrix = Inverse of [K] = Displacements vector From the displacements vector, FEA packages will calculate: Element forces Reaction forces Strains Element stresses

7 Basics of FEA Modal Analysis If subjected to a disturbance, a system/structure will tend to vibrate at particular frequencies called natural frequencies. A Modal Analysis will calculate the natural frequencies of a system according to the following equation: Or [Mass] * {Acceleration} + [Stiffness] * {Deformation} = {0} [M] * {d } + [K] * {d} = {0} In a Modal Analysis no applied loads are used and the structure has no damping properties.

8 Basics of FEA Modal Analysis (continued) [K] = System stiffness matrix [M] = Structure Mass matrix {d} = Displacements vector FEA packages will generate [K] & [M] based on geometry and properties of FE model. Due to the absence of applied loads, displacements will always be normalised to a Unit Value and the parameter of importance will be the natural frequency. Dynamic Shock or Vibration analyses will use results from Modal Analysis to calculate a system s overall response to a given excitation input.

9 Basics of FEA Modal Analysis (continued) Tacoma Narrows Bridge: A very good example of the deadly potential of operating at/near natural frequencies.

10 Basics of FEA Dynamic Analysis Dynamic Analysis is the next step to Modal Analysis. Dynamic Analysis is used for simulating a structure s response subjected to loads varying with frequency or time. A Dynamic Analysis will calculate a structure s dynamic response according to the following equation: Or [Mass] * {Acceleration} + [Damping] * {Velocity} + [Stiffness] * {Deformation} = {Force} [M] * {d } + [C] * {d } + [K] * {d} = {F}

11 Basics of FEA Linear vs Non Linear Analysis In general terms, the following equation of motion: Or [Mass] * {Acceleration} + [Damping] * {Velocity} + [Stiffness] * {Deformation} = {Force} [M] * {d } + [C] * {d } + [K] * {d} = {F} Defines: - A) Linear Analysis: If [M], [C], [K] are constant -but {F} can be varying-. - B) Non Linear Analysis: If at least one parameter ([M], [C], [K]) is not constant.

12 Steady-State Heat Transfer Analysis

13 Setting up thermal analysis Thermal Analysis (from Autodesk Simulation Help file) Calculates the temperature and heat fluxes of components after infinite time (steady state) or defined time (transient). Examples: structures (furnaces, insulating wall), electrical components.

14 Setting up thermal analysis Thermal Analysis (from Autodesk Simulation Help file) The stress caused by the temperature is calculated from the difference between the applied temperature(s) and the Stress Free Reference Temperature. The effect of this temperature difference depends on the Thermal Coefficient of Expansion defined in the Material Specification dialog box.

15 Thermal Analysis Setup Thermal Loads: Controlled Temperature Convection Heat Source Internal Heat Generation Initial Temperature Radiation Body-to-Body Radiation *Note: You can also analyze fluid convection if you have the fluid domain modeled

16 Design Workflow and Results From the concept, determine the necessary level of detail for the CAD model. The model must be meshed in the thermal analysis first, so nodes match in all following analyses Temperature profile stored in a ds.to file for use in stress analysis Concept CAD Model Mesh Result

17 Thermal Stress Analysis

18 Thermal Stress Loading Analysis Parameters: Gravity Thermal Browse to.to file from design scenario 1 to apply temperature profile to assembly Loads and Boundary Conditions: Pressure in the Container Fixed Boundary Conditions

19 Thermal Stress Results Results Evaluation: von Mises Stress Displacement Localized Stress Due to Thermal Load Nozzle Support Legs Fatigue Concerns in Support Legs *Note: Remember to define a stress free reference temperature in the Element Definition to avoid erroneously high stress values!!!

20 Fatigue Analysis

21 Fatigue Analysis Fatigue Analysis Steps: 1. Fatigue Life Calculations Strain Based Stress Based 2. Material Entry 3. Stress Concentrations/Surface Finish 4. Load Curve 5. Analysis Output/ Desired Life Cycles 6. Analysis 7. Results

22 Linear Dynamics

23 Linear dynamics Random Vibration (from Autodesk Simulation Help file) Generated in vehicles from motors, road conditions, etc Combination of many frequencies. Has a certain random nature. Random vibration (modal superposition) analysis determines how the structure of an object or a supported object reacts to constant, random vibration. The random nature of vibrations will require a statistical approach of the problem

24 Linear dynamics Random Vibration (from Autodesk Simulation Help file) Random vibration (modal superposition) analysis uses input from linear natural frequency (modal) analysis and power spectral density (PSD) curves. They are representations of vibration frequencies and energy in a statistical form.

25 Linear dynamics Shock (from Autodesk Simulation Help file) Part of Response Spectrum Linear Analysis. Calculate the maximum displacements and stresses due to a spectrum-type load: Examples: structures subjected to earthquakes, blast and shock loads, etc Response spectrum (modal superpositon) uses the results from a modal analysis.

26 Modal and Response Spectrum A modal analysis needs to be run before any other dynamic analysis For natural frequencies that take into account other loads, Modal with Load Stiffening needs run The only loading necessary for response spectrum is pointing to the modal results and Input Spectrum This analysis will act as if an earthquake is acting on the structure

27 Mechanical Event Simulation Drop Test

28 MES Drop Test Setup Steps for a drop test: An impact plane can be generated to avoid the need to model the ground For a drop test, a short duration and high capture rate help *Tip: Defining an initial velocity instead of analyzing the entire drop saves a lot of time!!! In this case, gravity is not necessary.

29 Material Models and Results Since this part will yield, a new material model should be defined. von Mises with Isotropic Hardening von Mises Curve with Isotropic Hardening In the results, if you don t change material models, your stress will be unrealistically high For high strain models, changing the analysis formulation to Updated Lagrangian helps convergence

30 Preparing a model in Autodesk Inventor Fusion

31 Preparing a model in Autodesk Inventor Fusion What is Autodesk Inventor Fusion? Direct/Parametric modeling tool History free (no parent/child relationship) Ideal for preparing models for CAE (defeaturing, etc ) without affecting the master model

32 Preparing a model in Autodesk Inventor Fusion Preparation work Import Inventor model into Fusion Defeature as required (holes, external radii, chamfers, etc ) Modify geometry (anticipate mid-surface meshing, merge components, etc ) Rename parts as required Launch Autodesk Simulation

33 Setting up an analysis with 3D hydrodynamics elements

34 Setting up an analysis with 3D Hydrodynamics elements Hydrodynamic elements Used to simulate (mechanical) interaction of fluids with solids Inertia of moving fluids taken into account Behaviour similar to jelly

35 Setting up an analysis with 3D Hydrodynamics elements Preparation work Defeature Meshing: Specify element type for parts (brick, 3D hydrodynamic, etc ) Specify mesh parameters for parts (solid, mid-plane), either as Model or Part settings Mesh model Apply mesh refinement as required Check element parameters (large displacement, element thickness for mid plane Material: elements, etc ) Apply material to parts (steel, water, etc ) Contact: Apply contact between parts (surfaces in preference) Specify surface contact parameters

36 Setting up an analysis with 3D Hydrodynamics elements Preparation work Loads: Apply required loads (gravity, forced displacement, etc ) Simulation parameters: Define convergence parameters as required Run: Specify number of (time) steps and duration of simulation

37 Preparing a model in Autodesk Inventor Fusion Inventor Model

38 Preparing a model in Autodesk Inventor Fusion Defeaturing parts

39 Preparing a model in Autodesk Inventor Fusion Adding fluid component

40 Preparing a model in Autodesk Inventor Fusion Renaming components and cutting model along symmetry plane

41 Preparing a model in Autodesk Inventor Fusion Offset fluid to half plate thickness (to prepare for Simulation midplane meshing)

42 Preparing a model in Autodesk Inventor Fusion Boolean of handles and reservoir (to prepare for Simulation midplane meshing)

43 Preparing a model in Autodesk Inventor Fusion Adjust handles to correct depth (to prepare for Simulation midplane meshing)

44 Preparing a model in Autodesk Simulation Multiphysics Meshing and mesh refinement

45 Preparing a model in Autodesk Simulation Multiphysics Setting up contacts and tolerances

46 Preparing a model in Autodesk Simulation Multiphysics Setting up Boundary Conditions and Loads

47 Preparing a model in Autodesk Simulation Multiphysics Materials and Simulation settings

48 Preparing a model in Autodesk Simulation Multiphysics Meshing and mesh refinement

49 Preparing a model in Autodesk Simulation Multiphysics Results

50 Setting up Plastic materials for MES

51 Setting up plastic materials for MES Material properties Typical material curve shows 2 characteristics: Elastic behaviour Plastic behaviour (Source: Metallurgyfordummies.com) (Source: Wikimedia.org)

52 Setting up plastic materials for MES Material properties Typical FEA analysis will assume: Linear analysis Elastic materials (E=constant) Stress levels remain below materials Yield Strength σ yield (Source: Wikimedia.org)

53 Setting up plastic materials for MES Material properties (from Autodesk Simulation Help file) Plastic deformation: When elastic material loaded past its yield strength. Typical plastic material characteristic: Elastic region of the stress versus strain has a slope equal to the modulus of elasticity Plastic region of the stress versus strain has a slope equal to the strain hardening modulus. (Source: Simulation Help file)

54 Preparing a model in Autodesk Inventor Fusion Inventor Model

55 Preparing a model in Autodesk Simulation Multiphysics Meshing and mesh refinement

56 Preparing a model in Autodesk Simulation Multiphysics Setting up Boundary Conditions and Loads

57 Preparing a model in Autodesk Simulation Multiphysics Materials and element definition

58 Preparing a model in Autodesk Simulation Multiphysics Simulation settings

59 Preparing a model in Autodesk Simulation Multiphysics Setting up contacts and tolerances

60 Preparing a model in Autodesk Simulation Multiphysics Results

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