Week - 3 Drop test Challenge

Objective:

To create a complete simulation file for the given .K file to perform drop test simulation of a mobile phone with a rigid plate

Procedure:

case setup & Execution:

1. The given Drop_test_onlymesh.k is imported into LSPP

2. The File Only Consists of the nodes and elements of the Mobile phone and the plate. the shell elements present in the model is deleted.

3. The Unit system Followed here is kg, mm, ms

4. To perform the simulation we need to specify Material, section, initial velocity and boundary conditions and output request for the given model which are as follows:

Assigining the material:

• We need to assign material for both rigid plate and mobile phones separately,For The Phone Aluminium alloy material is selected from the Database Survey. Mostly the Mobile Phones are made of plastic, silicon, aluminium..etc. since the Material of the Plate is Rigid Subsequent material Aluminium alloy is Selected for the Phone.
• For assigining the material the following steps are followed Keyword manager `rarr`All `rarr`Mat `rarr` Select the material card, here different material properties like mass density, youngs modulus, poisson's ratio and other recommended values are given
• For the rigid plate a rigid material is taken Mat_20_Rigid card With properties of steel assigned
• For the mobile phone Mat_24_Piecewise_Linear_Plasticity card with properties of aluminium alloy assigned.

Section creation:

• Since we deleted the shell section at the begining now only solid section is needed to be defined by selecting Keyword manager `rarr`All `rarr`Section `rarr`Solid
• Here the solid selection with element formulation 2 is defined

Specifying section and materials to their respective part ID's

• For creating the part Keyword manager `rarr`model `rarr` part is used , then the respective section and materials for the mobile phone and rigid plate is assigned to them respectively

Boundary conditions:

• Since the plate needed to be fixed during the simulation we need to assign boundary condition to it by selecting four nodes at each corners of the plate
• The following steps are followed to give boundary condition to the rigid plate Create entity `rarr`Boundary `rarr`Spc `rarr`create
• Here spc ( Single Point Constrain ) is used because we needed to constrain only four separate nodes at each corners of the plate
• here all the DOF's are set to 1 which implies that its moved is locked both rotationally and translationally in all direction.

Initial velocity:

• Initial velocity is defined to the phone by Keyword manager `rarr`New `rarr` Initial `rarr` Velocity
• Since the distance between the plate and mobile phone is 20 mm so the velocity V= `sqrt(2gh)`is used
• The velocity is found out to be 5.94 mm/ms , since the phone has to drop along the negative Z axis `V_z`= -5.94 mm/ms is given by selecting all the nodes in the mobile phone part.

Contact interface:

• Now contact interface needed to be defined between the plate and the mobile phone by Keyword manager `rarr` Contact `rarr` Automatic surface to surface`rarr`
• All other parameters are set to default values.

Control cards :

• Control cards such as control energy which is used to specify the control of hourglass energy and control termination which controls the termination of the end time of simulation are specified here
• Keyword manager `rarr`All`rarr` control `rarr` Energy/Termination command is used to define control energy and control termination

Output request:

• Generally output resquest are specified to view the results of the simulation which is done by the following commands
• Keyword manager `rarr`All`rarr` Database`rarr` ASCII_option from which GLSTAT and RCFORC option is selected with DT= 0.5 ms
• GLSTAT is defined with DT=0.5 ms which gives the output of energies such as Internal energies, kinetic energy & other types of energies where as RCFORC defines the forces due to the contact between the rigid plate and the phone
• Keyword Manager `rarr`Database `rarr` Binary D3plot `rarr` DT 0.5, this command prints the output at the end of each 0.5 ms

5. Run the simulation

• The keyword is saved in a separate folder and it is opened in Ls-Dyna manager

6. After Running the Simulation Open the Binary D3plot file in Ls Dyna pre-post.

Von-misses stress:

From the Gif, we can see that there is no Impact till 3.3s After that The phone Bounces at 3.9s

The Maximum Stress acted on the element is 3.441e-02gpa at 3.4498 sec in the element6 6076

Strain Rate:

here the maximum strain rate acchieved is 9.9432e-10 at node 6076

Graph:

Energy graph:

• There is no impact till 3ms After 3 ms we can see Deflection in Both Kinetic energy and Internal energy
• As we can see the Internal energy produced By the Rigid Plate is Almost the same as the Kinetic energy
• The Total energy is remaining constant Throughout the process, The law of conservation of energy is satisfied.

Hourglass energy graph:

• Here we can notice that there is no hourglass energy is formed in this simulation since the plot remains almost remains zero throughout the simulation.

Conclusion:

Keyword file for the complete simulation is created from the given raw data file which contains only the nodes and elements of the two parts included keywords like material, initial velocity, section, boundary conditions, controls, database, and contact are properly assigned to create a basic solver deck to simulate a drop test. The study of mobile drop tests is been carried out and outputs for Vonmisses stress, Effective plastic strain is obtained by running the simulation, and energy, resultant force, strain graphs are also plotted.