Bird Strike - Project - 2

Aim : To create the simulation of bird strike on the Aero Engine from the given FE model.

Requirements for this project : 

1. The blades should rotate at a constant velocity but the casing should remain stationary.
2. The cylindrical bird model should travel along its own axis and hit the blades.
3. Use elastic material for the bird(2000MPa) and the casing(200GPa). The material model for the blades is attached. The velocity of the engine blades and the birds can be chosen so that blade failure can be seen within a short span of time.
4. Follow a consistent numbering approach 100000+ for nodes, 500000+ for elements, and 1000+ for the parts. All other keywords should be numbered within 10000-19999 while following a range for each one. This guideline that the student is following should be included in the final submission.
5. The bird, casing, and the blades should be in different input files and there should be one main file referencing all the input files. The main file should contain only references. Control cards and boundary conditions should be there in another separate file. The reference includes path should be such that the folder can be copied anywhere and it is able to correctly reference all the files and run the simulation.
6. These two requirements are a must in a professional setting when dealing with large models and multiple people working with the same model simultaneously. 
7. Units used here (kg, mm, ms, kN, Gpa, KN-mm)
8. Density in kg/mm^3, Youngs modulus in Gpa, Sigy in Gpa

Methodology :

• The FE model consists of four parts that need to be separated and save partwise. The suitable material is created and saved in a sub-folder.
• 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.

 1. Import the keyword file:

 2.Material :

Bird :

• MAT_ELASTIC card material is selected and properties are assigned from the journal 
• The given properties are, Density-2.000 , Young's Modulus-2.000, Poisson Ratio-0.4700 e −6.

Blades :

• *MAT_24_Piecewise_Linear_plasticity card is given with properties of Aluminium, Density-2.713 , Young's Modulus-68.946999, Poisson Ratio-0.3300, Yield stress-0.0133600, Failure flag-0.2723, and Tangent modulus is given as Load curve ID by plastic strain rate behaviour.

 Casing :

•  MAT_ELASTIC card material is selected  nd the steel properties are assigned Density 8.000e-07 , Young's Modulus-210, Poisson Ratio-0.3300 e-6.

Hub :

• *MAT_24_Piecewise_Linear_plasticity card is given with properties of Aluminium, Density-2.713 , Young's Modulus-68.946999, Poisson Ratio-0.3300, Yield stress-0.0133600, Failure flag-0.2723, and Tangent modulus is given as Load curve ID by plastic strain rate behaviour. 

3. Section :

Section card is created individually upon the following FE models i.e., bird, blade, and engine casing with Element formulation of 16 (Fully integrated shell element modified for higher accuracy)

• Bird :

The thickness is assigned to be 15mm

• Blades :

The thickness is assigned to be 2 mm

• Casing :

The thickness is assigned to be 3 mm

• Hub :

The Element formulation is assigned to be 10 (point tetrahedron)

4.  Assign the part with respect to the material cards and section with proper Subsys.k after inserting the FE parts into a               single model file.

5. Create Contacts:

• Contacts are created using Part set, SSTYPE=3 & MSTYP=3
• Hence the blades should rotate according to the hub, *CONTACT_TIED_SURFACE_TO_SURFACE is used to tied the surfaces with the blade as a slave and hub as master.

• In order for the bird needs to hit the blade *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE is used as the bird as a slave and blade as a master

• Eventually, once the bird hits the blades the deformed blades not supposed to penetrate with each other. Here *CONTACT_AUTOMATIC_SINGLE_SURFACE is used.

6. Boundary Condition:

SPC

• Though the turbine engine case supposed to be fixed at the airplane wing.
• It has to be constrained in all the directions i.e, Translation and Rotation Initial Velocity

Initial Velocity:

• In this, we need to fix the casing and we need to give velocity to the blades.

Where we considered rpm as 5000

p=2π">ππNT/60 where p=0.5 rad/ms.

velocity =20 mm/ms

• Here the velocity of the bird is assigned to be VX=20 mm/ms along the X-axis translative direction.

Angular velocity

• 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=0.06 rad/ms, NX=1 (x-direction cosine)

7. Control

Termination time setup is 10 ms

Control Timestep card plays important role in reducing the runtime. We can have different combination of DT2MS and TSSFAC check the estimated runtime and percentage mass added during mass scaling. Here we will try to keep the percentage of mass added below 7% and reduce the runtime.

•  1st trial we done by keeping DT2MS = -2.0E-04 and TSSFAC=0.9 the runtime estimated is 1hrs 26 min but actual it took 10 min with 2.4% mass addition.
• 2nd trial we done by keeping DT2MS = -2.20E-04 and TSSFAC=0.9 the runtime estimated is 1hr 2 min but actual it took 5 min with 2.9% mass addition.
• 3rd trial we done by keeping DT2MS = -2.50E-04 and TSSFAC=0.9 the runtime estimated is 51 min but actual it took   3  min with 3.7% mass addition.(Acceptable)

 at    -2.00e-4

at  -2.20e-4

 at -2.50e-4

8. Database

Generally, the list of output request is specified with the Time interval between outputs DT= 0.05 ms for GLSTAT, MATSUM, NODOUT The frequency of the animation file is set to be Time interval between outputs DT= 0.10 ms

Energy plots :