Bird Strike - Project - 2

Aim-

• To perform and simulate the non-linear case of Birdstrike in Aero-engine using explicit analysis in LS-Dyna.

Objective-

• The FE model consists of 4 parts that need to be separated and save part-wise. The suitable material is created and saved in a subfolder.
• The node number, element number, and part number are assigned as mentioned above. Also, to conclude the final simulation create the main file with the *include file and run the explicit simulation using mass scaling.

Theory-

• Bird strikes pose a significant threat to aircraft structures, as contact with a bird while in flight can cause significant structural damage. 
• For more than 30 years, computational approaches have been used to design birdproof structures, and they have proven to be a cost-effective alternative to costly physical certification testing with live birds. 
• The bird behaves as a soft body and flows over the target structure in a fluidlike way at the velocities of interest, with the high deformations of the spreading material being a substantial problem for finite element simulations.

Procedure-

Case setup

• The given keyword file BIRD_STRIKE  consists of nodes and elements for all the four parts collectively i.e, Engine casing, Blade, Hub, and Blade

• Separate the given parts by assigning the keywords file. Those parts are distributed and saved .k keyword file, by deleteing other parts and saving it.
• Firstly we will renumber the parts and then proceed to save the models seperately.

 

Bird

Blades

Casing   

                                                                                                                

Hub

Note-For this FE model the unit system followed here will be Kg, mm, ms.

• Now we will take each part seperatley and create the material card and section cards accordingly.

1. Bird Model-

• As per data given in project problem statement that we have to use elastic mat card with E value as 2000MPa, so we will so the same.

• Now we will create the section card for the bird model.

• After this we will assign this to parts.

 

2. Casing Model-

• As per data given in project problem statement that we have to use elastic mat card with E value as 2000GPa, so we will so the same.

• Now section card will be created with shell section.

• Now assign all things to pats.

3. Blades Model-

• As per data given in project problem statement that we have given a material type which we have to use for blade, so we will use same material card with piecewise linear plasticity_024, and also assign a curve for same.

• Now weill define a curve as per given in the mat card and assign it to the model mat card.

• Again we will assign the given inputs to the part.

4. Hub Model-

• Here we will create mat_piece wise linear plasticity_024 mat card.

• As it has tetra mesh we have to create a solid section card for it.

• Now finally we wil ssign this to part.

• Now we will close all files and create a new include file and browse and recall all save seperate model .k files.

 

• Now we have to create contacts between the parts one by one.
• firstly we will create contact tied surface to surface between hub and blade where hub is master and blade is slave.

• Now second contact is between blades and bird, where bird is master and blades are slave.

• Now third contact is between blades and casing, where casing is master and blades are slave.

• Now fourth contact is between bird and casing, where casing is master and bird are slave.

 

• Finally we have to create the singlre surface contact for blades only.
• Eventually, once the bird hits the blades the deformed blades not supposed to penetrate with each other.

• Now we have to create the boundy condition for running the simulation.
• So casing is not going to rotate we will provide SPC set boundary to it & contrain it in all directions.

 

• The average velocity of the bird travels from the references is observed to be approximately 20 to 80 mm/ms.
• Here the velocity of the bird is assigned to be VX=70 mm/ms along the X-axis translative direction.

• The angular velocity of the blades is roughly around an average speed of around 3000 to 20000 RPM.
• Considering 5000 rpm and convert it to radiant. From which angular velocity OMEGA=0.5 rad/ms, NX=1 (x-direction cosine).

• we have to define control termination card, For that go to Model and part> Keyword manager> All> Control> Termination, Provide the End time is 5 ms.

• Control Time step card is also defined with experimenting the percentage mass scale to be upto 8%.

• Now we will create the database file.
• BINARY_D3PLOT -  It defines the frequency at which the animation file is to be created and is set to 0.1ms 
• Now we will create the ASCII files.

    The output request in ASCII format, The following keyword are activated

1. GLSTAT- Global Data
2. MATSUM- Material Energies and
3. NODOUT- Nodal point data

• Now we will check the model and then head for simulation.

• Since there is no error we can proceed further to save and run the keyword file.

• As simulation ended with Normal Termination. Therefore, the model is simulated successfully.
• Now we can open this files one by one using LS-post processor.

Results & Plots-

Effective Stress (V-M)-

Effective plastic strain-

Plots-

• In this Explicit Analysis, when the bird hits the blade at a velocity of 70kmph. The Internal energy increases and kinetic energy decreases due to the impact on the blades.
• There is no hourglass formation due to full integration ELFORM-16 is used the total energy of the system remains constant throughout the simulation.
• Hence we can notice that the plot satisfies the law of conservation of energy.

Conclusion-

• All the components are following a consistent number pattern for each element, node, and part as followed in many Industries.
• All the files such as for component, BC's, contact, control, database are included in the Main file. The BC and load conditions are mimicking the real-world scenario.
• For Mass-scaling, the % mass added is 8% which accepted value. From the energy plot, we can observe that total energy is constant over the simulation which represents the simulation runs well(1st check).
• The max V-M stress produced in the fan blade is 0.1261 Gpa at nearly 2.6ms of simulation The max strain developed is 0.2723 at 0.3 ms of simulation and remains constant over the simulation.

Animations-

Effective Stress (V-M)-

Effective plastic strain-