Challenge

Week - 8 Mass Scaling

MASS SCALING IN LS-DYNA

Aim: To use the mass scaling techniques in explicit and implicit to reduce the run time of the simulation and compare the runtime.

Given Model:

Procedure:

1. Run the simulation without mass scaling.

In this case, the default values of tssfac = 0.9 and dt = -3.500e-05. dt is less than 0, which indicates that mass is added to the element to increase the time step for faster simulation.
Now run the simulation and check for the estimated clock time.

2. Run the simulation with mass scaling.

Now the value of dt changed gradually until the until the percentage increase in mass is around is 8%.
Now the tssfac will remain same and dt is changed to -7.5e-05 and run the analysis and check for added mass and estimated clock time.

The simulation is estimated to run for 29hrs and percentage add in mass is around 0.3%. So we can further try to increase the dt.
Now we run the simulation with dt value of -9.5e-5 and run the analysis and check for added mass and estimated clock time.

Simulation is estimated to run for 22hrs and percentage add in mass is around 4%. So we can further try to increase the dt.
Now change the dt value to -1e-4 and run the simulation.

Simulation is estimated to run for 21hrs and percentage add in mass is around 6.4%. So we can further try to increase the dt.
Now change the dt value to -1.015e-4 and run the simulation.

Simulation is estimated to run for 19hrs and percentage add in mass is around 7%. So we can further try to increase the dt.
Now change the dt value to -1.025e-4 and run the simulation.

Simulation is estimated to run for 19hrs and percentage add in mass is around 7%. So we can further try to increase the dt.
Now change the dt value to -1.03e-4 and run the simulation.

Simulation is estimated to run for 22hrs and percentage add in mass is around 8%. Percentage add in mass has reached to max.

Now we try to change the scaling factor (Tssfac) with dt value of -1.025e-4 to avoid the instability.

Tssfac = 0.8 and dt = -1.025e-4

Tssfac = 0.7 and dt = -1.025e-4

Tssfac = 0.6 and dt = -1.025e-4

Implicit simulation.

The same file with dt = -3.5e-5 is run in implicit by adding implicit_auto, implicit_general and implicit solver cards are added.

The implicit analysis automatically adjust the dt and the total time taken to complete the simulation is 24minutes.

Conclusion: The technique of mass scaling is carried out in the above simulation in explicit and implict analysis.

Ship work like this
in your own course.