Phone Drop test using LS-Dyna

AIM:

To perform a drop test in the given LS-Dyna model and plot the results and contour obtained.

PROCEDURE:

1. Open LS-Dyna program manager>>Start LS-PrePost>>Import the given model.

2. There are 3 parts shown in the figure below. The parts are renamed as per convenience.

3. Go to Part>>Select Shell Elements>>Delete>>Accept the selection.

4. Go to Keyboard Manager>>All>>MAT>>Assign suitable material for phone and rigid wall. For phone and rigid wall the material assigned is aluminium 7075 and concrete. The properties are given below:

Concrete:

Density: 2.4e-09 `<a href="undefined" target="_blank">g</a>/(mm)^3`, Young's Modulus: 41000 MPa, Poisson's Ratio: 0.21

Aluminium 7075 alloy:

Density: 2.81e-09 `g/(mm)^3`, Young's Modulus: 71700 MPa, Poisson's Ratio: 0.33, Tangent Modulus: 71.69 MPa, Yield Stress: 500 MPa

5. Go to Create Entity>>Set Data>>*SET_NODE>>Select Pick By Part>>Assign two sets for phone and rigid wall>>Apply.

6. Go to Create Entity>>Set Data>>*SET_SEGM>>Create>>Select Pick By Part>>Assign two sets for phone and rigid wall>>Apply.

7. Go to Create Entity>>Boundary>>Spc>>Create>>Select Pick By Part>>Pick the rigid wall>>Arrest all DOF's>>Apply.

8. Go to Keyword Manager>>All>>Initial Velocity>>Select the phone node set>>Give velocity in z-axis. This is shown in the figure below.

9. Go to Keyword Manager>>All>>Section>>Solid>>Define a solid section as shown in the figure below.

10. Go to Keyword Manager>>All>>Select Phone as Slave and rigid wall as Master>>Accept.

11. Go to Keyword Manager>>All>>Control>>Termination. Give a termination time of 0.01 seconds. This time might change after analysing the simulation results. This is because only a small time after the impact is needed for analysing the results.

12. Go to Keyword Manager>>All>>Database>>BINARY_D3PLOT>>Give a timstep 0.0005 seconds.

13. Go to Keyword Manager>>All>>Database>>ASCII_Option>>Give the necessary output parameters with a necessary time step.

14. Go to Keyword Manager>>Model Check>>Keyword Check>>Ensure that no errors are present in the keywords.

15. After completing the model check, save the keyword with .k extension. Go to LS-Dyna Manager and run the model.

RESULTS AND DISCUSSIONS:

Open LS-PrePost>>File>>Open>>LS-Dyna Binary Plot. Open the necessary d3plot file and load the results.

 The following energy plots are obtained.

From the above plot, it can be inferred that the total energy remains constant over the time period. Due to fall of phone with an initial velocity, the kinetic energy of the phone is transformed to rise in internal energy of the phone due to its impact in the rigid wall. Also, to achieve a more realistic energy plot, the yield stress value of mobile is reduced. This causes an increase in plastic strain value of the phone. This is shown in the figure below.

As explained above, the plastic strain in the lowermost element of mobile phone increases at time 0.0015 seconds. This is the time in which the phone touches the ground and the impact is started. This effective plastic strain contour shown below.

The Von-Mises stress contour is shown in the figure below.

As shown in the above stress contour, the stresses starts to generate when the phone impacts the ground. These stresses propagate through the phone as shock waves which can be seen after the impact. 

Therefore, drop test is simulated using LS-Dyna and the necessary contours are obtained in post processing.

Drive Link: https://drive.google.com/file/d/19M8o7oWDOKqUrggfy3tQ7q66USqVmO__/view?usp=sharing