Week - 8 Mass Scaling
Introduction-
Mass scaling- the concept of mass scaling is used to reduce the Computational time for solving a simulation by adding non physical mass.
we can initiate mass scaling in ls dyna by CONTROL_TIMESTEP card, by means of Dt2ms and Tssfac(time step scaling factor)
Objective-
the Aim is to solve the fiven k file which takes large computational time by mass scaling henceforth reducing the computational time by ensuring the stability of mass scaling
TSSFAC- timestep scale factor is scale factor for computed time step its defualt is 0.9. it does not effect mass scaling
DT2MS- it is timestep for mass-scaled solution. if DT2MS is negative is mass is added only to those elements whose timestep is less than DT2MS, othersmasses are same
if DT2MS is positive mass is added only to those elements whose timestep is less than DT2MS, mass is reduced for elements whose mass is more than DT2MS.
if stablity is less,then TSSFAC is reduced.
In implict analysis mas scaling hass no effect
Procedure-
Explicit analysis
-first the given k file is solved in launch manager
this simulation is done without mass scaling
estimated time is 26 hrs 29 mins(95353 sec)
(TSSFAC=0.9) DT2MS=-1e-05
this simulation is done with mass scaling
estimated time is 25 hrs 47 mins(92878 sec)
(TSSFAC=0.9) DT2MS=-2e-05
this simulation is done with mass scaling
estimated time is 29 hrs 55 mins(107738 sec)
(TSSFAC=0.9) DT2MS=-3e-05
this simulation is done with mass scaling
estimated time is 35 hrs 46 mins(128790 sec)
(TSSFAC=0.9) DT2MS=-4e-05
this simulation is done with mass scaling
estimated time is 22 hrs 42 mins(81732 sec)
(TSSFAC=0.9) DT2MS=-5e-05
this simulation is done with mass scaling
estimated time is 26 hrs 56 mins(96969 sec)
added mass- 3.75E+02
Percentage Increase-1.3179E-03
(TSSFAC=0.9) DT2MS=-6e-05
this simulation is done with mass scaling
estimated time is 14 hrs 52 mins(53535 sec)
added mass- 6.46E+03
Percentage Increase-2.2726E-02
(TSSFAC=0.9) DT2MS=-7e-05
this simulation is done with mass scaling
estimated time is 21 hrs 24 mins(77056 sec)
added mass- 4.06E+04
Percentage Increase-1.4296E-01
(TSSFAC=0.9) DT2MS=-8e-05
this simulation is done with mass scaling
estimated time is 17 hrs 2 mins(61363 sec)
added mass- 2.4003E+05
Percentage Increase-8.4355E-01
(TSSFAC=0.9) DT2MS=-9e-05
this simulation is done with mass scaling
estimated time is 11 hrs 47 mins(42424 sec)
added mass- 7.808E+05
Percentage Increase-2.744E-00
(TSSFAC=0.9) DT2MS=-10e-05
this simulation is done with mass scaling
estimated time is 12 hrs 57 mins(46666 sec)
added mass- 1.8277E+06
Percentage Increase- 6.4233E-00
(TSSFAC=0.9) DT2MS=-11e-05
this simulation is done with mass scaling
estimated time is 1 hrs 18 mins(4738 sec)
added mass- 3.0878E+09
Percentage Increase- 1.0852E+04
this cannot be considered because of percentage increase
CONCLUSION-
DT2MS is decresed upto 19 however all values are neither given in table nor in bar, by mass scaling estimated time or computational time is decreased but percentage added is increased, even decreasing Dt2ms we may get less computational time but we may also not get accurate data due to instability caused due to more percentage increase. mass scaling must be done basing on percentage increase by above case asin DT2MS=-11E-05 the percentage increase is very high so the model faces instability.