Speed vs. Stability: The Art of Using Mass Scaling in Quasi-Static & Dynamic Analysis
Jun 05,2025
In today’s fast-paced product development environment, engineers and analysts are constantly seeking ways to optimize simulation time without much compromising accuracy. One of the powerful techniques available inSIMULIA 3DEXPERIENCEis Mass Scaling. This blog explores what mass scaling is, how it works, and how you can effectively use it to reduce simulation time in your finite element analyses with real case study example.
What is Mass Scaling?
Mass Scaling is a numerical technique used in explicit dynamic simulations to artificially increase the mass of elements in a model. The goal is to increase the stable time increment of the analysis without significantly affecting the accuracy of the results.
In explicit dynamics, the time increment is controlled by the smallest element size and material properties. For large models with fine meshes, this can lead to extremely small-time steps, increasing simulation time significantly. Mass scaling helps by increasing the smallest allowable time increment, hence reducing the total number of time steps needed.
When to Use Mass Scaling?
Mass scaling is most effective and appropriate in the following situations:
Crashworthiness simulations
Drop tests and impact analyses
Metal forming or high-speed manufacturing simulations
Large assembly simulations with local fine meshes
It’s important to ensure that the artificial mass does not significantly distort the physics of the problem. Therefore, it should be applied carefully and validated with benchmarks or experimental data when possible.
What is Stable Time Increment?
Stable time increment (Delta T) is basically ratio of smallest characteristic length (Lc) of any element in the model and speed of sound (C) in the material
Overall, in mass scaling, density increase, that decrease the speed of sound in material & which ultimately increase the stable time increment value, this helps to speed up the simulation.
Less element size leads to small Lc, which leads to small stable time increment, which increases the overall simulation time, CAE Analyst need to take care about time & should wisely choose element size.
Case Study – Mass Scaling
Here we have performed the few case studies with different stable time increment and compare the reduction of Simulation run time, Stress & Ratio of Kinetic Energy/Internal Energy, Physical behaviour.
How To Decide Time Period for Any Quasi-Static & Dynamic Analysis?
Each structure has natural frequency, first step is to find the natural frequency of given structure, here we found first natural frequency of structure is 8.38 Hz. Next step is calculating the time period, which is inverse of frequency, time period is 0.119 second, this time period is still short, we have use 3 times the current time period for reduce the dynamic effect but as per some source on internet, 10 times the natural time period should use to avoid the dynamic effect. Anyways, we have taken 0.4 seconds time period for crushing analysis.
Case 1 – No Mass Scaling
In case 1, we have not used the mass scaling, we interested to check stable time increment calculated by SIMULIA 3DEXPERIENCE, & what time takes to solve analysis
As mentioned above, SIMULIA 3DEXPERIENCE calculated stable time increment 2.4e-6 seconds, which suggests that we have different Lc size than theoretical value.
It is visible that wall time is 3243 seconds which is equivalent to 54 minutes. This showcase that without mass scaling, simulation takes 54 minutes to solve the problem.
Case 2 – Mass Scaling_1
Here we have use target time increment value which is nothing but theoretical stable time increment value 3.39e-6 seconds.
It is visible that with this target time increment, analysis has taken 2958 seconds which is equivalent to 49 minutes.
Case 3 – Mass Scaling_2
Here we have use target time increment value which is 6e-6 seconds
It is visible that with this target time increment, analysis has taken 1685 seconds which is equivalent to 28 minutes.
Case 4 – Mass Scaling_3
Here we have use target time increment value which is 9e-6 seconds
It is visible that with this target time increment, analysis has taken 1066 seconds which is equivalent to 18 minutes.
Internal Energy (IE), Kinetic Energy (KE) Plots & KE/IE Ratio
Case 2 – Mass Scaling 1 KE/IE Ratio: 1.14 %
Case 3 – Mass Scaling 2KE/IE Ratio: 2.17 %
Case 4 – Mass Scaling 3KE/IE Ratio: 3.38 %
It is visible in all cases that KE is lower than IE and KE/IE ratio is less than 5 %, which is falls under acceptable limit.
Results – Comparison
Physical Behavior at 0.3 seconds
Summary & Conclusion
Stress (MPa)
% Stress Diff.
KE/IE Ratio (%)
Run Time (min)
No Mass Scaling
1466
54
Mass Scaling 1
1381
5.8
1.14
49
Mass Scaling 2
1212
17.3
2.16
28
Mass Scaling 3
1412
3.8
3.38
18
In conclusion, Mass Scaling 3 emerges as the most effective option. It shows the lowest stress deviation at 3.8%, maintains a KE/IE ratio of 3.38% well within the acceptable limit and achieves the shortest runtime of just 18 minutes. This makes it an optimized choice for faster simulations without compromising accuracy. However, it’s essential to verify that the simulated physical behaviour aligns with experimental results. If discrepancies exist, other mass scaling cases should be evaluated to identify the best match for future simulations of similar designs and analyses.
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