Week - 8 Mass Scaling
Aim:
1.For the use of mass scaling we have to run the runtime of a model and also ensure the stability of mass scaling.
2.We have to reduce the runtime required for running the analysis of the given model by using of mass scaling technique and
stability has to be completely intact.
3.Plot a histogram for camparing the runtime with mass scaling trails.
4.To optimize both the DT and TSSFAC parameters.
5.To run the same model by using of the implicit solver with required changes and compare both implicit and explicit runtime.
Note: The hard limit on mass scaling is 8%.
Procedure:
1.Import the given .k file model into the LS-Dyna software.Here in it we can observed that all keycards are specified to the given model.
2.Now we have to perform the mass scaling technique.To do that we use time step keycard for various mass scaling timesteps.
3.In order to find out the perfect mass scaling value which is under the 8% we need to do it in trail and error method.
Trail 1:For this trail we are not using any timestep key card because we want to know how much time is going to be taken to complete the
simulation.
From the above results fig we noticed that the solving time is huge for this simulation,to reduce that we need to find out the exact mass sacling
value or dt2ms value.
Trail 2:Now for the second trail we are running the simulation with the given default values of timestep card and the dt2ms and tssfac values are
-3.5E-05 and 0.9.
For the given default values in timestep values we are not getting the perfect required time so now we are started by decreasing the dt 2ms value
to find the perfect mass scaling which is under the 8 percentage.
Trail 3:For this trail we are not changing the values in timestep keycard except the given default dt 2ms value we are changing in into the value
of -3.0E-05.
Here also by changing the dt 2ms values we notice that there is no change in the simulation time and it is still hugeand we are not getting the
percentage increase.
Trail 4:For this trail the dt 2ms value is changed to -2.5E-05.
Trail 5:For this trail the dt 2ms value is changed to -2.0E-05.
Trail 6:For this trail the dt 2ms value is changed to -1.5E-05.
After changing the number of values of decreasing the dt2ms values still we are not getting the perfect mass scaling.so now we are going to
increase the dt2ms value.
Trail 7:Now from here the dt2ms value is going to be increased until we get the mass percentage as 8%. Here dt2ms value is -4.0E-05.
Trail 8:Here the dt2ms value is -5.0E-05.
As we noticed here that mass percentage starts to increase at 0.01% for this trail andd the problem is that time is still huge.
Trail 9:Here the dt2ms value is -6.0E-05.
Trail 10:Here the dt2ms value is -7.0E-05.
Trail 11:Here the dt2ms value is -7.8E-05.
Here we can noticed that the mass percentage is(6.27%) which is close to the 8% and problem time is reducing.
Trail 12:For this trail the dt2ms value is -1.0E-04.
Here we can notice that the mass percentage is very close to 8% so we need to be increase the small values in dt2ms values.
Trail 13:For this trail the dt2ms value is -1.5E-04.
Here the percentage of mass is 100% which is more than we need and now we can consider that dt2ms value is must be lessthan -1.5e-04 and
greater than the -1.0E-04.
Trail 14: For this trail the value is 1.03E-04.
Finally for this dt2ms value we got the mass percentage of 8% and now the problem is with the time,we have to reduce to 20hrs.
4.Now we need to check for the same dt2ms value but different tssfac value as 0.8,0.7,0.6.
As we can notice that the tssfac value is reduced then there is rise in the problem time.
5.Now we have to compare the both explicit and impliciit analysis,above all trails are in the explicit analysis.
To do that add some keycards in the implicit analysis like implicit auto,implicit general,implicit solver and implicit solution.
Now we have the implicit cards and run the file in the LS Run with the two different dt2ms values as 3.50E-05 which is default value and
-1.0248E-05 which gives the mass percentage of 8%.
The runtime required to complete the simulation for DT2MS = -3.5E-5 is 31 mins 02 sec and for DT2MS = -1.0289E-4 is 31 mins 08
sec. The percentage increase in mass is not reported.
RESULTS AND DISCUSSION:
Explicit Analysis:
From the histigram we can see that dt2ms value is affecting the run time of the sover and highest run time is occured at the default value -3.5E
05 and least occured at the -1.5E-05.
Conclusion :
Thus we have find out the dt2ms or mass scaling value for 8% with the help of trail and error method and we have plotted the graph for dt2ms
and Runtime.