Week - 3 Drop test Challenge

                                                            DROP TEST SIMULATION USING LS-DYNA

                                                                                    WEEK-3

Aim: To Create drop test simulation using LS-DYNA

Objective: 

• To create material for different parts
• To create section for solid and shell elements.
• Assigning material and section ID to parts.
• Create Boundary conditions.
• Create Contact between phone and plate
• Assigning initial velocity to phone
• Control simulation time, recording animation, plots etc.

Procedure:

1.Import: Import (.k) file as shown below. Go tofile >> open >> LS-DYNA keyword file. 

• These are the Keywords present in the imported model.

2.Creating Boundary:In order to run a simulation, we need certain boundary conditions such as constraints and initial parameters such as velocity etc.

• First create two different node set ID’s. One NSID consists of all elements of plate which is used as (SPC) Single Point Contraint and the other NSID is to represent set of all phone elements which are later given initial-Velocity

• Now, create a boundary SPC and select NSID and then apply.

3. Material Creation: 

• Every part is made up of a material. We should create the material properties accordingly and assign those materials to their respective parts.
• We are using kg-mm-ms unit system, all the data which is input should be in same unit system.
• Create material for a plate which is rigid Model and Part>MAT(all)>020_rigid plate . and for phone here considered as aluminium (024_picewise_linear_plasticity).

4.Section Keyword:  

• In order to define the type of element i.e., shell, or solid, we must define the section keyword.
• Section is created using Model >> Part >> section(all) >> shell. Here we should give thickness and type of element formulation here is not important because all nodes are fixed in all directions, therefore no element undergoes displacement

 5 Assigning Material and section:

• After creating Material and section we can assign those to the parts by directly using Model >> Part. Check the part list and each part has the option to select for Section ID and MATID.

6.Initial velocity: 

• In order to move the phone against the plate we must assign initial velocity of 10 mm/ms in negative z- direction. Select the node set and input velocity in which direction it should move as shown below.

7.Create Contact: 

• Impact will take place between phone and plate, only if there is a contact defined between them or else phone will go through through plate. 
• All phone element nodes are taken as slave and all plate element nodes are taken as master nodes.

8.Control setup:

• In LS-DYNA prepost, *CONTROL_TERMINATION card is used for defining the simulation time.
• Simulation is set to run for 5ms, this is the rate at which the phone drops to ground.

• Control Hourglass keyword is the defined as unusual deformation occurs without strain.

9.Output Request: 

• BINARY3DPLOT - The complete state dump interval as given in *DATABASE_BINARY_D3PLOT serves as the time step to be used in the material model driver run.
• ASCII option consists of different outputs. I have selected some of them
• ELOUT - This latter option will output all integration point data or extrapolated data to the connectivity nodes in a file call elout.
• GLSTAT - Read the energy like KE, PE, IE
• MATSUM - Every material part energy due to deformation
• RCFORCE - contact force between plate and phone
• SLEOUT - gives us Sliding force due to contact 
• SPCFORCE - Single point contact force.

 10. Solving the setup:

• The model is checked for any errors before solving using model checker. After all the errors are cleared, the drop test setup is saved and is ready to run in LS DYNA manager for solving the scenario.   

• The saved keyword file is selected as input to run in LS-RUN. Normal termination of the run is achieved and is ready to analyse for post processing.

11.Post Processing:

• Input the d3plot file and we can see all the output results which we have given earlier.
• Animation and plots can be seen and saved easily using LS-PrePost

• Initially we can say that the velocity is maximum therefore kinetic energy is also maximum. But during the impact kinetic energy is absorbed by the part and it decreases, simultaneously internal energy increases (in the middle).
• After impacting with the rigid body, it rebounces back with the same velocity, ie., K.E increases and I.E decreases

• We can see that the phone body i.e., slave energy increases to a maximum at the time of impact and reaches below master energy after the impact but the rigid body i.e., master nodes energy remains constant during the entire simulation. 

Conclusion: Drop test simulation is successfully performed using LS-DYNA. All the objectives are fulfilled and results are recorded.