CAF - Fordypningsmodul - Inventor

CAF  

Fordypningsmodul - Specialisation Module

Since my choice for course of study is mecanic (MEK), I decided to take the CAF Modul exploring the Stress and Dynamic Analysis in Inventor.


 First in the list is to make a Workplan for approval.

Once the Workplan is approved, the tutorials are downloaded and the work really starts.
It is important to have familiarity with the ribbon user interface and the Quick Access Toolbar as well with the use of the model browser and context menus.

DAY 1 Stress Analysis Tutorials

Part Model and Stress Analysis

   -Create a simulation for modal analysis.

    -Override the model material with a different material.

    -Specify constraints.

    -Run the simulation.

    -View and interpret the results.

Assembly Stress Analysis

Now that you have completed this tutorial, you have a basic understanding of the typical workflow in the stress analysis environment. This workflow includes:

• Creating a simulation.
• Excluding components not needed for the simulation.
• Assigning materials as overrides of the existing material.
• Adding constraints and loads, sometimes called boundary conditions.
• Adding contact conditions.
• Generating meshes.
• Running the simulation.
• Viewing and interpreting the results.

Assembly Modal Analysis

In this tutorial you performed a structural frequency (modal analysis) analysis with the goal of finding natural mode shapes and frequencies of vibration. The steps performed included:

• Create a modal simulation.
• Use Manual Contacts to establish the correct relationship between components.
• Exclude components, or use a Design View Representation to remove components from the simulation.
• Override materials
• Add constraints
• Manually add contacts
• Specify mesh parameters
• Run the simulation
• View the results 

FEA Assembly Optimization

In this tutorial, you learned to:

• Create a simulation.
• Specify materials, constraints, and forces.
• Specify parametric dimensions and generate configurations.
• View different configurations as 3D color plots and XY plots.

Stress Analysis Contacts

In this tutorial, you created two simulations. In completing each simulation, you learned how to:

• Copy an existing simulation to make new ones.
• Define manual Contacts.
• Modify automatic contacts.
• Add local mesh controls.
• Display design constraints in the parametric table.
• Use multi-select to change component visibility.
• Use Copy / Paste for material overrides.

DAY 2 Frame Analysis Tutorials
Frame Analysis

Now you have a basic understanding of the typical workflow in the frame analysis environment. This workflow includes:

• Creating a simulation.
• Assigning materials as overrides of the existing material.
• Adding constraints and loads, sometimes called boundary conditions.
• Running a simulation.
• Viewing the results.

Frame Analysis Results

Now you have an understanding of the tools you can use to view and interpret results of frame analysis. You know how to:

• Display and edit diagrams.
• View beam detail.
• Adjust displacement display.
• Display maximal and minimal values in the graphics window.
• Animate results.
• Generate report.

Frame Analysis Connections

Now you have a basic understanding of how to work with a connection in frame analysis. You learned how to:

• Create a simulation.
• Change direction of Gravity.
• Add custom nodes.
• Assign rigid links.
• Set the degrees of freedom of rigid links.
• Assign releases.
• Run a simulation.
• Viewing and interpreting the results.

 

Modal Type of Frame Analysis

In this tutorial, you performed a structural frequency (modal analysis) analysis with the goal of finding natural mode shapes and frequencies of vibration. The steps performed include:

• Create a modal simulation.
• Change simulation properties.
• Exclude components from simulation.
• Run a simulation.
• View the results.
• Create an animation of results.

DAY 3 Dynamic Simulation Tutorials
Dynamic Simulation - Part 1

You can also export load conditions at any simulation motion state to Stress Analysis. In Stress Analysis, you can see, from a structural point of view, how parts respond to dynamic loads at any point in the assembly's range of motion.

In this tutorial, the skills you learned include:

• Understanding basic differences between the Dynamic Simulation application and the regular assembly environment.
• Having the software automatically convert relevant assembly constraints to Dynamic Simulation standard joints.
• Use Color Mobile Groups to distinguish component relationships.
• Manually creating rolling, 2D contact, and Spring joint types.
• Defining joint properties.
• Imposing motion on a joint and defining gravity.
• Using Output graphers.
• Running a dynamic simulation to see how joints, loads, and component structures interact as a moving, dynamic mechanism.

Dynamic Simulation - Part 2

Here they showed how to:

• Add the saw blade subassembly.
• Add various joints.
• Impose motion, friction, and retained degrees of freedom in subassemblies.
• Add traces.
• Publish a simulation animation using Inventor Studio.

Assembly Motion and Loads

Here they showed a general idea of how to link a cam and valve, how to create a spring device, and how to use the Output Grapher to view simulation results.

• Create a spring.
• Create a 2D Contact joint.
• Impose a motion.
• Simulate dynamic motion.
• View the simulation results.
• Export the simulation results to Microsoft Excel.

FEA using Motion Loads

Here they showed how to:

• Generate motion loads for a selected part.
• Access and use those loads within Stress Analysis.
• Generate reports of analysis results.

DAY 4 Mechanical Design Tutorials
Shafts

Here they showed how to use the Shaft Component Generator:

• Start a Shaft Generator.
• Configure a shaft.
• Specify loads and supports.
• Specify load values.
• Insert a shaft.
• Edit a shaft.

Spur Gears Connections

Here they showed how to:

• Start a Spur Gears connection.
• Set calculation options.
• Place components.
• Perform the calculation.
• Set file names.

Bearings

Here they showed how to:

• Select bearings from the Content Center according to specific criteria.
• Set bearing parameters.
• Insert bearings.

Lynda Tutorial
Fundamentals of Stress Analysis Tools in Inventor Professional.
A very interesting video that shows the basics of how works the Stress Analysis Tools in Inventor.

Gear Box Modeling

Now that all the theory and tutorial have been completed, I started work on my own design.
I defined my model as a 2 stage gearbox with a 1:9 ratio, that could be used to couple a small motor.
These are the starting parameters:

Input torque: 20Nm
Output torque: 180Nm
Gear width: 20mm
module: 6
stage 1 ratio: 1:3 (gears of 20 and 60 teeth)
stage 2 ratio: 1:3 (gears of 20 and 60 teeth)
Shaft 1 minimum diameter: 18mm
Shaft 2 minimum diameter: 25mm
Shaft 3 minimum diameter: 28mm 

My proposed excersice is as follows:
1. Model a gearbox with a simple geometry with the above parameters. 
2. Perform Dynamic and Stress analysis on the model.
3. With the results do an initial design iteration to optimize the weigth of the gearbox by removing material where the analysis shows small levels of stress.  

 
DAY 5 3D Modeling

The first elemets for 3D modelling are the shafts and the gears.

The gears are modeled with constant thickness and with as few features as possible.

 To have a simple design, the shaft will be supported on standard bearings secured by retaining rings, and connected to the gears by keys.
The element selection was made by browising the Content Center and also from the options that the Design Accelerator gave me.

The next step is to design a simple housing that fits the shafts and gears with two identical halfs and is connected together with standard bolts and nuts.

Here is a view of the complete assembly. The upper housing is not shown for clarity.

DAY 6 - Drawings

 Drawings for the complete assembly and the parts that I have designed are now made.

 DAY 7 - Stress and Dynamic Analysis

A basic dynamic analysis is made on the model, having as input the defined 20Nm of torque. The position of the teeth for gears 1, 3 and 4 are plotted. 

The results show the different ratios of the gearbox, as well as the way in which it accelerates due to the torque. 

 Here is a video of the dynamic simulation: https://youtu.be/HTJWqvgrHV4

 For the stress analysis, a locked rotor situation is analized where both the input and the output shafts have an equivalent moment so there is no rotation.

 Here is a video of the stress analysis: https://youtu.be/lZx-BVKKSFw

 The stress analysis shows small levels of stress on the gears and on the second shaft. On the picture above the scale has been modified to show a short range of values so that it is possible to see where the gears are loaded.

The way forward is to remove some material from the gears on the areas that are not part of the teeth or the hub, and also to make the second shaft hollow.

Day 7-8  3D Modeling - Optimization

The weight optimazation is made on the gears by reducing the thickness on the areas that are not part of the teeth or the hub, and also holes are added.

 The second shaft is made hollow.

And also the housing is modified to have a thinner wall. 

Here is a view of the optimized gearbox 

Day 8-9  Drawings - Optimization

Stress and Dynamic Analysis - Optimization

 The dynamic analysis is updated for the new geometries.

 Here is the video of the simulation: https://youtu.be/GqnxxTUa1tE

The stress analysis is also run to get the results for the new geometry.

Here is the video of the stress simulation: https://youtu.be/qg23MfzUbho


Day 10 - Results

As stated on the exercise description, the optimization of the model is centered on its weight. Here are the results for both cases:

Original case
Total weight: 50.5 kg
Maximum stress (Von Mises):  169 MPa
Minimum safety factor: 1.22

Optimized case
Total weight: 24.5 kg
Maximum stress (von Misses): 203.6 MPa
Minimum safety factor: 1.01

Conclusion for the exercise:

A weight reduction of 51.5% (26kg) was achieved by removing material form the less stressed elements. This is a significant reduction. The structural integrity is confirmed by the stress analysis.


Conclusion for CAF Module project.

Overall I am very pleased with the project. The tutorials followed on this module were sufficient to understand the use of the design and analysis tools. Although I would change the order in the plan to start with the Lynda video, since it give a nice overview of the analysis tools. 

For the 3D modeling I kept the design simple, and most likely some elements would need modification to comply with engineering design criteria, but for this exercise I think the model had a good balance of detail and simplicity. The use of the gear and shaft generating tools, as well as the Content Center made a big impact on the time spent designing.

Performing the dynamic analysis was straigth forward, but achieving results that were easy to interpert took some trials. 

The Stress analysis took also some trials to achieve proper constraints and to ajust the results' scale to meaningfull values.

Inventor is a very interesting program, and I like it more and more as I learn more from it. It was a good choice to use the CAF module to learn the Analysis tools and hopefully I can find a final project that is somehow related.

Video presentation: https://youtu.be/Daihp8qhioQ

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