Week - 3 Drop test Challenge

MOBILE PHONE DROP TEST

Objectives :

To perform a drop test for a mobile phone onto a steel platform.

Procedure :

The Military Drop test testing is for 26 times at 5ft, the drop is simplified.

1. Open the Drop_test.k file in LS-Dyna prepost.

2. Delete the red color 2D shell using edit elements option.

3. Create boundary conditions for the Rigid plate by constraining its nodes in all DOF using Create Entity command.

4. Create a Solid section using Keyword manager with Element formulation=1. Take unit system as g mm ms.

5. Create Material ID, 020-rigid and 024-piecewise linear elastic for rigid plate made of steel and Mobilephone respectively with appropriate values.

6. Create 2 part ID for rigid plate and Mobile phone and spectify respective Material ID using Keyword Manager.

7. Create initial velocity for the nodes on the cellphone 10

mm/ms.

8. Create a contact using Keyword Manager in Automatic Surface to Surface. Select the mobile phone part as slave and Rigid plate as Master.

9. Set Control> Termination to 0.0027 s.

10. Database > ASCII select GLSTAT , ELEOUT, RCFORC with DT 0.0001 and Database > Binary D3plot >DT 0.0001.

11. Save the Active Keyword file and Run from LS-Dyna Manager.

12. Open LS-Dyna Prepost and open the binary d3plot file.

13. Play the animation.

14. Using fringe components for post processing, Animation of Vonmisses stress.

15. Animation for effective plastic strain.

16. Using X-Y plots, Plot Energies graph.

The phone hits the rigid plate at 1.8E-3 s and the kinetic energy drops from 43E+3 J to 20E+3 J at 2E-3s and internal energy increases to 24E+3 J at 2E-3 s. Total Energy is at 43E+3 J but reduces to 38E+3J at 2E-3s and again comes back to 43E+3 J.

17. Plot Resultant force acting on Mobile phone(slave).

The maximum resultant force reaches upto 0.1E+6 N at 2.1E-3 s.

18. Plot Effective Plastic Strain at an element 6378.

At 0.21ms the the effective plastic strain increases to 0.24 units.

Effective plastic strain is a monotonically increasing scalar value which is calculated incrementally as a function of (Dp)ij, the plastic component of the rate of deformation tensor. In tensorial notation, this is expressed as...

epspl=integral over time of (depspl)=integral[sqrt(2/3(Dp)ij*(Dp)ij)]*dt

19. Plot Resultant velocity at a node 12331.

The velocity drops when phone hits the steel plate , from 10mm/ms to 5mm/ms at 2ms and again increases to 7mm/ms at end of simulation 2.7ms.

Link for droptest model : https://drive.google.com/drive/folders/1n-vEj8ITSktWlf7udMSAEYbBhwI855h3?usp=sharing

Conclusion :

1. The Material,initial velocity, boundary conditions and contacts are properly assigned.

2. The animation outputs for Vonmisses stress, Effective plastic strain are obtained by running the simulation.

3. Energy , resultant force , displacement graphs are plotted.