Simulation Justification - Research
- Kimberly Liu
ASC Regulations and Guidelines
Analysis Method
Section F.3.3 Analysis states that “analyzes may be in the form of computer modelling (such as finite-element analysis) or empirical testing of the actual vehicle or its components.
5G Impact Loads
A schematic of required analysis cases is given in Figure 1.
Front, rear, side and rollover impact must be validated with minimum impact loads of 5G (G is the total gross mass of the vehicle including the driver and ballast).
(“Rollover analysis must address loads at a minimum vertical and two increments between horizontal and vertical”)
Static Structural vs Explicit Dynamics
Static Analysis Justification
MS12 and MS 14 have mainly used static structural for simulations
Based on some research, explicit dynamics is more commonly used for vehicle collision simulations.
Why was static analysis chosen over dynamic analysis for chassis collision simulations?
Static analysis was chosen because based on the way ASC regulations were worded.
A load of 5G is specified which lends itself to static analysis.
For this reason, static is the best way to pass the regulations (and used more commonly amongst teams).
NHTSA (National Highway Traffic Safety Administration) specifies a speed into a barrier
this is why dynamic analysis is more commonly used for vehicle simulations (outside of ASC)
However, a dynamic simulation would be a good way to double-check the chassis design
there just hasn’t been enough time to do this in the past
if a dynamic simulation can be fully justified, this can be a good way to get the chassis to pass simulations
Static vs Dynamic Analysis
STATIC
system being simulated does not depend on time, loads are constant
can be used when things are moving slowly
does not consider inertia
deformation is negligible
DYNAMICS
involves time (speed, varying loads)
considers inertia due to acceleration
used for impacts, considers vibrations and deformation
https://enterfea.com/difference-between-static-and-dynamic-analysis/
“Often times, you will just increase the impact loads with a “dynamic factor” and then analyzed them in a static way.”
This is similar to a safety factor however, these values can range from 1.5 -10.
Relevant Ansys Simulation Confluence Pages
Beam Elements Justification
This page provides justification for the use of beam elements.
In summary, using beam elements allows us to save computational time by simplifying the mesh of the chassis tubes while retaining the validity of the simulation.
ANSYS - Beam Elements (Only for Spaceframe chassis)
This page is a guide to using beam elements in Ansys.
“Beam elements is a powerful tool within ANSYS Workbench that converts a complicated tube/bar structure into a set of "beams" for analysis. This simplifies the mathematical model by treating each member of the part as a simple beam under load, and greatly decreases solve times. Note that beam elements is best suited for space-frame structures, like a vehicle chassis.”
MS 14 Simulation Cases
The 13 simulation cases are outlined here.
MS12 Simulation Log
This page contains all relevant simulation data and design iterations of the MS12 Chassis.
Ansys Guides
Guides for Static Structural Analysis, ACP, Beam elements and Beam and shell elements can be found here.