Drop test Simulation of a mobile

Aim

• To setup a keyword file for the simulation of drop test for a mobile phone from mesh file
• To simulate the drop test and understand the results obtained

Case setup

The mesh of the mobile in close proximity of ground is shown below.

Here, the rigid plate acts as the ground.

 The model is in millimeter scale. So we use kg-mm-ms as the unit system for the simulation.

Material:

The material properties of both mobile and plate should be defined in the material card

1.Plate is defined as a rigid material with appripriate properties as shown

Also, the plate is constrained in translation and rotation about z-axis.

The young's modulus and density values are given higher than those of mobile material.

2.Mobile is defined as an elastic material

Section:

1.Plate is defined as Shell section with a thickness of 1 mm.

2.Mobile is defined as Solid section, both with default element formulation.

Part:

Here, we match the part with respective section and material ids for both plate and mobile

Set:

1.Node set

We need to define a node set for all the nodes in mobile in order to give a velocity to it.

2.Segment set

Segment set of entire plate and bottom surface of the mobile are created for usage in contact keyword.

Initial_Velocity:

An initial velocity of 10 mm/ms in -ve 'Z' direction is given to the nodeset of mobile.

Contact:

The contact between mobile and plate is defined as an automatic surface to surface contact with mobile as slave and rigid plate as master as shown below

Here the segment sets of mobile bottom surface and rigid plate are used for contact definition.

Control_Termination:

Termination time of the simulation is set as 4 ms as the impact occurs at around 2 ms.

Database:

1. Ascii 

The following ascii outputs are enabled with time interval of 0.01ms

Glstat - Global statistics

Matsum - Material energies

Rcforc - Resultant interface forces

Sleout - Sliding energies

2. Binary D3PLOT

The same time interval is used to output the d3plot file which is the output file used for animation, fringe component, etc.

Keyword_ID & Title are set to the model to make it ready for the simulation.

Results

Von-mises stress:

• Von-mises stress of 0.04 GPa is observed just after the impact of mobile with rigid plate
• Since the material of mobile has a youngs modulus of 50 GPa and the stresses induced are much lesser it does not yield in these conditions

Global Energy:(Glstat)

• The total energy of the system is constant and is the sum of all internal, kinetic and sliding enegies at all times as shown in the plot
• The kinetic energy of 5.5 J is converted at the impact to internal and sliding energies
• Sliding energy goes down to zero as soon as the mobile rebounds off of the surface of plate

Material Energy:(Matsum)

• Mobile material energy gives same plots as that of the global energy
• Plate material energy plots are close to zero as it is defined as a rigid body as shown below

Sliding Energy:

• The sliding energy of mobile (slave) reached 1 J at the contact
• Both master and friction energies are close to zero