Linear Static Analysis of a Cantilever Beam

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Section 1 - What Will You Learn in This Tutorial?

In this tutorial we will learn how to simulate the effects of a 100 kN/m^2 force on a simple 3D steel cantilever beam.  We will analyse the displacement and stress in the beam.

You will learn:

  • The Basic Simulation Workflow in OnScale Designer
  • How to set up a 3D model
  • How to create a simple geometry
  • How to perform static analysis
  • How to display and post-process your results
What is Static Analysis?: Static Analysis is the most simple type of analysis in that it assumes that your system does not depend on time (i.e. your applied load does not vary with time e.g. force load). The opposite of this is Dynamic Analysis.

Section 2- Model Definition

model_def.png

Characteristics of the model:

Model:

Steel Beam of Dimensions 100 mm x 20 mm x 10 mm

Mesh Size:

1 mm

Simulation Iterations (Conjugate Gradient Method):

1000 iterations

Output Results:

-Time History of Z Displacement at [100,10,9.9]

-Data Snapshot of Z Displacement 

-Data Snapshot of Stress XX

Material Data:

Name Mild Steel, Generic
Code Name steel
Density 7,900 kg.m-3
Bulk Velocity 5,900 ms-1
Shear Velocity 3,200 ms-1

Section 3 - Why This Simulation?

In real life, steel beams are used in many different structures. It is important to be able to simulate the strain and displacement of these beams when forces are applied to them to ensure they do not buckle.

In this simulation we will apply a 100 kN/m^2 force to the top end of a beam while fixing the opposite end and observe the deformation of the beam.

Section 4 - Step by Step Tutorial in Video

Here's the tutorial recorded in video:

 

The procedure is detailed in text after that: 

Section 5 - The Simulation Process:

Let's go through the step by step tutorial and see how to simulate this Simple Beam in OnScale!

Note: You can click on the images in the tutorial to make them bigger.

Step 1 - Create a New Project

Open up OnScale in Designer Mode. The first step is to create a new project.

  1. Click New Project to open the New Project dialogue
  2. Enter Model Name
  3. Change working units to mm 
  4. Click ... to choose a directory to save the project to
  5. Click OK to create the project.
newprjct.png
 

Step 2 - Add the Materials from the Material DB

The second step is to add the material steel to the project materials to be used for the beam.

  1. Click Project Materials icon to open the Material Database
  2. Expand the 'Metal' materials dropdown 
  3. Add steel (double click to add the material)
  4. Select Done
mats.png
 

Step 3 - Create the Beam Geometry

We will make use of the geometric primitives to build the beam. This beam is going to be a 100x20x10 mm cuboid so the cuboid primitive shape can be used. Click on the cuboid primitive in the application's ribbon to create this shape.

  1. Set the Material property of primitive_1 to 'steel'
  2. Set the X End (mm) property to 100
  3. Set the Y End (mm) property to 20
  4. Set the Z End (mm) property to 10
  5. Right click in the workspace and select Reset View to snap the view to the geometry
prim1.png
 

Note:You can also assign materials by right clicking the part in the Model Tree and selecting Assign Material...

Step 4 - Define a Static Function

The next step is to add a static forcing function of value 100 kN/m^2.

  1. Expand Forcing Functions in the Model Tree
  2. Click '+' to open the Static Function dialogue
  3. Set Amplitude to 100,000
static.png
 

Step 5 - Choose The Right Mesh Size

It is time to set up the meshing of the model. Since this beam is a simple structure we can mesh coarsely.

  1. Expand Model and Mesh in the Model Tree
  2. Select Configuration
  3. Set Mesh Definition to Coarse
Important: The size of the grid is absolutely critical to get accurate results. It is generally advised to do a "Mesh Convergence" Analysis to select the most appropriate mesh size for your model. Because a Mesh which is too coarse will give you bad results and Mesh which is too fine will increase computation time. "Mesh Convergence" Analysis is done by changing the mesh size from coarse to fine and observing the results which are of interest. This makes it easy to spot where the results start to converge to a stable "accurate" value. Mesh Convergence Studies can be done easily using OnScale as all of these simulations can be run in parallel on the Cloud! 

Step 6 - Create The Force Load

We will now apply a 100 kN force load to the tip of the beam acting in the Z direction. First we must create the load.

  1. Expand Boundary Conditions in the Model Tree
  2. Click '+' to open the load dialogue
  3. Set Creation Mode to be Geometry Interface
  4. Set Geometry to primitive_1
  5. Set Interfacing Item to side_6 (zmax)
  6. Select Create Load
load.png

Change the properties of the load

Now that our load has been defined, we can set it's properties.

  1. Ensure Boundary Conditions is expanded in the Model Tree
  2. Select load_1
  3. Set Load Type to Force
  4. Set Forcing Function to staticfunc_1
  5. Expand Scale
  6. Set Z Scale to -1
  7. Expand Interface Definition
  8. Expand Minimum 
  9. Set X Minimum to 90
  10. Expand Maximum 
  11. Set X Maximum to 100
  12. Set Y Maximum to 20
  13. Set Z Maximum to 10
editload.png
 
Note: Force loads adds a force to the part of the model. They must be defined using; the name of the forcing function to use, the scale factors which represent the magnitude and direction of the force, interface definition which describes which material interface the load has to be applied to.

Step 7 - Define the Boundary Conditions 

We need to set the boundary conditions so that one side of the beam is fixed.

  1. Click Domain Boundaries in the Model Tree
  2. Expand X Minimum
  3. Set X Minimum to Fixed
  4. Expand X Maximum
  5. Set X Maximum to Free
  6. Expand Y Minimum
  7. Set Y Minimum to Free
  8. Expand Y Maximum
  9. Set Y Maximum to Free
  10. Expand Z Minimum
  11. Set Z Minimum to Free
  12. Expand Z Maximum
  13. Set Z Maximum to Free
boun.png
 

Step 8 - Define the Type of Analysis 

We will now choose to do a static analysis on the beam.

  1. Click Analysis 
  2. Change Analysis Type to Static
analysis.png

Note: The Static Analysis Solver in OnScale uses a conjugate gradients method to solve the finite element problem. This method converges with iterations which do not represent a time-step. Make sure that the maximum number of iterations is sufficient to get accurate converged results.

Why do I have iterations for a Static Analysis? Solving a static problem is equivalent to performing a simple matrix inversion, but here in OnScale we’re using a conjugate gradient method, which solves it iteratively. You can search for ‘stat’ in the software documentation for more details.

Step 9 - Define the Simulation Output Results

We will now define 3 outputs, a time history of the displacement at the tip of the beam, the Z displacement of the beam and the stress in the beam.

Output Result 1 : Time History Graph of Displacement at (100,10,9.9)

  1. Click '+' to create a new output
  2. Set Output Type to Time History
  3. Set Array Type to Displacement
  4. Set Array Component to Z
  5. Expand Location
  6. Set X Location to 100
  7. Set Y Location to 10
  8. Set Z Location to 9.9
out1.png
 

Output Result 2 : Data Snapshot of Z Displacement 

  1. Click '+' to create a new output
  2. Set Output Type to Data Snapshot
  3. Set Array Type to Displacement
  4. Set Array Component to Z
out2.png
 

Output Result 3 : Data Snapshot of XX Stress 

  1. Set Output Type to Data Snapshot
  2. Set Array Type to Stress
  3. Set Array Component to XX
out3.png

Note: In OnScale, you have to define which results you want to see out of this model before it is run. This is done mainly to decrease the amount of memory required and only output what is required and this also decreases the amount of data that is required to be downloaded from the cloud, so choose wisely what you want to get from your model!

Step 10 - Run the Simulation on the Cloud

At this point the model is completely set up and it can now be run on the cloud.

  1. Click Run on Cloud 
  2. Select Estimate 
  3. Select Run
roc.png

How does the "Estimator" works? The Estimator, like its name indicates, performs one step of the simulation and provides an estimation of the Model Solve Time. This estimation is done with complex algorithms and a lot of simulation experience. This then allows the user to choose how many Cores they wish to use for the simulation. More Cores will speed up the completion time of your model.

What are Core Hours? A Core-Hour is a measurement of computational time. In OnScale, if you run one CPU for one hour, that's one Core-Hour. If you run 1000 CPUs for 1 hour, then that's 1000 Core-Hours. More details here.

How to Get the Simulation Results?

Once the simulation has finished, the results are available in your storage to download.

  1. Click the Storage icon to open the cloud storage
  2. Select your job from the dropdown menu
  3. Expand the simulation folder
  4. CTRL + select the flxdato & flxhst file, right click and select Download Selection

 

download.png

Choose an appropriate save location and close the cloud storage.

Step 11 - Check the Simulation Results

Switch to the Post Processor 

Click this icon to access the Post Processor to analyse simulation results

ppswitch.png

Note: Post Processor is a mode in OnScale where you can review and process results calculated during simulations.

Open Results 

  1. Click File Explorer
  2. Select the folder icon and choose the directory you saved your results to
  3. Double click the history file to open the field history results
  4. Double click the data out file to open the time data results
fileex.png
 

Plot Time History (Z Displacement at Tip of Beam)

Note: Time Histories are output types which allow users to monitor the results at a specific point in a model.

  1. Double click 'zdsp' to plot displacement time history
  2. Set Plot Title to 'Z Displacement at Tip of Beam '
  3. Set X-Axis Label to 'Iterations'
  4. Set Y-Axis Label to 'Displacement (m)'
timehist.png
 

Plot Data Snapshots

Important: Snapshot results are the way in OnScale to obtain the full model data at every node or element at a snapshot in time.

Stress

  1. Double click 'sgxx'
  2. Select Deformed Plot icon
  3. Reorientate axis to XZ
stress.png
 

Z Displacement

  1. Expand 'Dspl'
  2. Double click 'z'
  3. Select Deformed Plot icon
zdsp.png
 

Section 6 - Try for yourself 

Now that we have introduced you to the tutorial, try have a play around with some of the settings, add some other outputs, or use this model as a starting point of your own.

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