Till now we have seen static structural analysis before. If you have not seen those posts, you can check them out here. In this post, we are going to add a bit of a twist and perform dynamic analysis using Radioss.
So let’s start by understanding what it is Dynamic Analysis.
What is Dynamic Analysis?
Dynamic analysis is the analysis of bodies under motion, that is when they are moving. In this tutorial, we are going to simulate a bird crash into an aircraft windshield. We will be using SPH elements to represent bird.
So the question arises what are SPH elements?
What are SPH Elements?
SPH stands for Smooth Particle Hydrodynamics. These are basically very soft particles that dissociate on crashing with a higher-density object.
Performing SPH Analysis
For this tutorial, we will use a surface to represent the windshield of an airplane and an ellipsoid with a flat face to represent a bird. We will be fixing the sides of the windshield and applying an initial velocity to the bird component.
Meshed Model
I have meshed the windshield of the airplane using 2D quad elements and the bird component with SPH elements.
For meshing the bird component with the SPH element we can go to 1D -> SPH and then select the surface, pitch, and material density to create the SPH elements as shown in the image below.
Boundary Condition
We will create a load collector named fixed to constrain the windshield in space. For fixing this windshield we will create a set of nodes on the circumference of the windshield. We can do this by right-clicking on the white-browser area and then going to create -> Set, in the Solver browser, we will name this set as nodes.
If the Solver browser is not visible, you can go to view -> browsers -> Hypermesh and then select the Solver browser.
We will constrain all the degrees of freedom of the windshield as shown in the image below.
Next, we will create a load collector for the velocity of the bird component. For this again we need to create a set containing all the SPH elements. We can do this by right-clicking on the white-browser area and then going to create -> Set, in the Solver browser, we will name this set as bird.
We will assign a velocity of 50000 mm/s in the negative Z direction to the bird set as shown in the image below.
Next, we will create a TSTEP load collector named Tstep. We can do this by right-clicking on the white-browser area and then going to Create -> Load Collectors. We need to select the card image as TSTEP. We will put N as 100 and DT as 0.2.
Next, we need to create a TLOAD1 load collector. We can do this by right-clicking on the white-browser area and then going to Create -> Load Collectors. We need to select the card image as TLOAD1. Select the DAREA load collector in the ExciteID field, Type as LOAD, and TableD1 load collector in the TID field.
Analysis Setup
Now we will create material and property for the Windshield and Bird component.
We can create material by right-clicking on the white browser area and then going to Create -> Mat -> Law 27_Plas_Brit. We will name this material as Glass as shown in the images below.
We will create the material for the bird component by right-clicking on the white browser area and then going to Create -> Mat -> Law 6_Hyd_Visc. We will name this material as Bird as shown in the images below.
Next, we need to create a property for the Windshield. For this, we can again go to the white browser area and then right-click on the white browser area and then go to Create -> Prop -> SHELL. We will name this property as Glass as shown in the image below.
Next, we will assign these materials and properties to the respective components as shown in the image below.
Kindly note that the property for the Bird component automatically gets created when we create the SPH elements.
Now before starting the analysis, we need to add some solver cards for the smooth running of the solver. We will create Run, Anim, TFILE, and Mon cards.
We will also create the output cards to extract the results for the contact and the parts as shown in the image below.
Performing Analysis
Now we have everything in place. We will perform the analysis. For this we can go to Analysis -> Optistruct select the run options as ‘Analysis’ and then click on Radioss as shown in the image below.
Output
After you click on Optistruct a pop-up window will appear showing the progress of the run as shown in the image below.
After the run is complete we can click on Results to view the results in Hyperview as shown in the image below.
You can also refer to the below video for more clarity.
This is all for this post. I’ll see you all in the next post. Don’t forget to follow my Facebook and Instagram Pages for regular updates. Until then, keep learning.