Week - 8 Mass Scaling
AIM: -
To run a file using mass scaling reduces the running time of the model. And run the same file in implicit and explicit.
PROCEDURE: -
Since DTMS and TSSFAC are the important parameters in the *CONTROL_TIMESTEP card that transforms the timestep and the runtime of the simulation
In order to that, we could change these values in each iteration to obtain an optimized runtime with a stable solution and to make sure mass scaling accomplishes 8%
CASE 01 EXPLICIT ANALYSIS WITH MASS SCALE
Import the file
Import the given FE model usually as the keyword parameter consists of a set of keywords demanded.
DTINIT - Initial time step size (Default)
TSSFAC - Scale factor for computed time step
DT2MS - Time step size for mass scaled solution
Iterations 1: DT2MS: -3.5E-5 & TSSFAC: 0.9
From the above image, the computation time is 22 hrs 21 mins. As a result, there is no mass added with given DT2MS of -3.500e−05, this can be varied by changing the values of DT2MS and TSSFAC.
Iterations 2: DT2MS: -3.5E-5 & TSSFAC: 0.7
From the above image, the computation time is increased by 1 hrs 58 mins by 24 hrs 19 mins, as a change in TSSFAC=0.7 leads to a rise in timing However, we can see that the mass-scale factor still pertains to zero factor.
Iterations 3: DT2MS: -6.5E-5 & TSSFAC: 0.9
From the above image, the computation time for is decreased rapidly from 24 hrs 19 mins to 12 hrs 41 mins, there is a considerable decrease in computation time.
However, mass added with a default value of TSSFAC=0.9, DT2MS of −6.500e−05 with a percentage of mass increase in 5.7852E-2.
Since the added mass exceeds the limit, the energy values also vary considerably. Values need to increase.
Iterations 4: DT2MS: -6.5E-4 & TSSFAC: 0.9
From the above image, the computation time for is decreased rapidly from 12 hrs 41 mins to 1 hrs 25 mins, there is a considerable decrease in computation time.
However, mass added with a default value of TSSFAC=0.9, DT2MS of −6.500e−04 with a percentage of mass increase in 3.7311E+03.
Since the added mass exceeds the limit, the energy values also vary considerably. Values need to be reduced.
Iterations 5: DT2MS: -1.5E-4 & TSSFAC: 0.9
From the above image, the computation time for is decreased rapidly from 1 hrs 25 mins to 6 hrs 10mins, there is a considerable increase in computation time.
However, mass added with a default value of TSSFAC=0.9, DT2MS of −1.500e−04 with a percentage of mass increase in 1.1432E+02.
Since the added mass exceeding the limit, the energy values also vary considerably. Values need to be reduced slightly.
Iterations 6: DT2MS: -1.1E-4 & TSSFAC: 0.9
From the above image, the computation time for is Increased rapidly from 6 hrs 10 mins to 9 hrs 47mins, there is a considerable increase in computation time.
However, mass added with a default value of TSSFAC=0.9, DT2MS of −1.100e−04 with a percentage of mass increase in 2.0393E+01.
Since the added mass exceeding the limit, the energy values also vary considerably. Values need to be reduced slightly.
Iterations 7: DT2MS: -1.01E-4 & TSSFAC: 0.9
From the above image, the computation time for is decreased from 9 hrs 47 mins to 8 hrs 10mins, there is a considerable increase in computation time.
However, mass added with a default value of TSSFAC=0.9, DT2MS of −1.0100e−04 with a percentage of mass increase in 6.9297E+00.
Since the added mass exceeding the limit, the energy values also vary considerably. Values need to be reduced slightly.
Iterations 8: DT2MS: -1.029E-4 & TSSFAC: 0.9
From the above image, the computation time for is increased rapidly from 8 hrs 10 mins to 10 hrs 47 mins, there is a considerable increase in computation time.
After many iterations, TSSFAC=0.9, DT2MS of −1.029e−04 attains the percentage of mass around 8.005E+00.
The mass scaling can be done by changing the TSSFAC values, The TSSFAC values will generally range between 0.5 to 0.9
DT2MS | MASS PERCENTAGE | COMPUTATION TIME |
-3.5E-5 | 0 | 22 Hrs 21 Mins |
-3.5E-5 | 0 | 24 Hrs 19 Mins |
-6.5E-5 | 5.7852E-2 | 12 Hrs 41 Mins |
-6.5E-5 | 3.731E+3 | 1 Hrs 25 Mins |
-1.5E-4 | 1.1432E+2 | 6 Hrs 10 Mins |
-1.1E-4 | 2.039E+1 | 9 Hrs 47 Mins |
-1.01E-4 | 6.929E0 | 8 Hrs 10 Mins |
-1.029E-4 | 8.005E0 | 10 Hrs 47 Mins |
CASE 02 EXPLICIT ANALYSIS WITHOUT MASS SCALE
From the above image, the computation time is about 19 hrs 57 mins, there is a considerable higher computational time
CASE 03 IMPLICIT ANALYSIS
Generally in LS pre-post, the solver practices an Explicit method for all the FE models. In order to perform an Implicit method, the solver requires the following keywords to switch from Explicit to Implicit analysis.
Control_Implicit_Auto
Control_Implicit_General
Control_Implicit_Solution
Control_Implicit_Solver
The run time is not given at start of simulation but at the end of termination and it is of 2 sec.
NOTE: LS-DYNA FILE is too big to upload in website. So, I shared the google drive link to download.
Download link : https://drive.google.com/drive/folders/1hRMXZYYzwVvq0n6yNQwRbiE-uzHgaW3W?usp=sharing