Drop Test Simulation

Objective:

In this report, I will conduct a drop test simulation of a cellphone against a steel made plate.

Model Setup:

The unit system used is g/mm/ms.

1. Material:

- 001-ELASTIC for the cellphone: Mass is chosen to be 174 grams --> density is 0.0015820 g/mm^3. Young\'s Modulus is chosen to be 30000 MPa. Poission ratio is 0.3.

- 020-RIGID for the ground. Material is chosen to be steel with the following properties: density is 0.0078300 g/mm^3. Young\'s Modulus is chosen to be 200000 MPa. Poission ratio is 0.3.

I set the boundary condition for the ground to be fixed by setting CMO = 1, CON1 = 7 (constrained x, y, and z displacements), CON2 = 7 (constrained x, y, and z rotations).

2. Section: Both the cellphone and the ground are solid elements with ELFORM = 1 (constant stress solid element).

3. Initial Velocity: Suppose the cellphone is dropped from height of 1.5m, the velocity at the time of touching the ground is `v=√2gh=√(2×9.81×1.5)≅5.42 m/s`.

4. Contact: The contact between the cellphone and the ground is chosen to be CONTACT_AUTOMATIC_NODES_TO_SURFACE.

5. Control: Control cards to be set up are:

- ENERGY

- HOURGLASS

- TERMINATION: endtime = 1 ms

- TIMESTEP

6. Output Database: Database cards to be set up are:

- ASCII_option: ELOUT, GLSTAT, MATSUM, NCFORC, RCFORC, SECFORC, SLEOUT.

- BINARY_D3PLOT

- CROSS_SECTION_SET: to get stress results for solid element in the specified cross section and defined SECFORC in ASCII.

- EXTENT_BINARY: to get some more output of the strain and stress results displayed in the fringe component heat map.

- HISTORY_SOLID: to get ELOUT results defined in ASCII

Results:

- Von Mises stress at impact:

The maximum Von Mises stress is around 45.9 MPa.

- Contact force:

We can see from the graph that the impact occurs at around 0.2 ms when the contact force between the cellphone and the ground reaches around 28000 N.

- Global Energy plot:

We can see from the graph that the conservation of energy is satisfied. When the impact occurs at around 0.2 ms, the kinetic energy drops to 0 as and the energy is transferred to internal energy and sliding energy due to contact.

After the point of impact, the cellphone rebounds and the kinetic energy is rising again along with the decrease in internal and sliding energies.