Verification of Baja and FSAE Loading Using MotionSolve

Christopher_Fadanelli

Overview

CHALLENGE  

 

Assessing load cases on Baja and FSAE Vehicle’s. 

 

PREFACE  

 

As an engineering student participating in BAJA and FSAE competitions, you face significant challenges in learning on the job designing, testing, and refining a complete competition vehicle. This often means countless late nights spent troubleshooting and overcoming unexpected issues that inevitably happen with a new design. Key concerns include optimizing vehicle performance, balancing weight distribution, ensuring safety, and meeting competition regulations. Good simulation software can help ease some of these concerns by allowing designs to be vetted carefully in a low-cost, no-risk virtual environment- resulting in an optimized, competitive design the first-time metal is cut and assembled!

Altair MotionSolve, a multibody dynamics (MBD) software toolset, provides a comprehensive vehicle library that simplifies the design process and allows for advanced simulation of vehicle dynamics. MBD offers a deeper analysis of kinematics & compliance and allows 3D calculation of internal loads between moving parts under real operating conditions. This includes capturing dynamic effects, which kinematics tools like Optimum G may not fully account for. While a lumped parameter 1D tool like Carsim is good for vehicle dynamics, 3D MBD tools like MotionSolve offer the ultimate advantage in ending up with a competitive and weight-optimized of FSAE/Baja chassis using a streamlined set of models.

 

 

INTRODUCTION  

 

It is crucial to verify the loads acting on the suspension components, particularly under various static load cases. For example, consider the loads acting on the tie rod when the vehicle is braking or in an extreme scenario where the wheel experiences a 3G vertical force due to a road obstacle. Understanding these forces helps determine whether the components can withstand such load scenarios. Ensuring the durability and reliability of these parts under different conditions is vital for the overall safety and performance of the vehicle. It is preferred to validate the Kinematics and Compliance of the vehicle first before assessing loading scenarios.

In this example, a static load analysis will be activated onto the vehicle and crucial load case scenarios will be applied either from the wheel center or the tire contact patch. Load scenarios that OEMs will apply to the vehicle include the 1-2-3 loading method. 1G of lateral load applied to the tire contact patch to simulate left and right turning of the vehicle. Longitudinal force of 2G acting upon the tire contact patch to simulate a braking scenario. The vertical force of 3G acting upon the wheel patch to replicate an extreme bump scenario to calculate the fatigue of the components. Other important scenarios include a load of 1G acting upon the wheel center to replicate the vehicle resting. A reverse 1G load acting longitudinally on the wheel patch to simulate reverse braking. In addition, a vertical load of non-synchronous 2G acting upon the tire patch to replicate the vehicle rolling over on each side. 

 

Pre-Requisite

SOFTWARE REQUIREMENTS: 

1. 1. Operating System: Windows
   2. MotionView (2023 or newer)
   3. MotionSolve (2023 or newer)
   4. Workable knowledge of MotionView and Vehicle Modeling preferred.
   5. Access to Baja FSAE Library

Model Definition

1. Front_Baja Zip File (refer to attachments).

Usage/Installation Instructions

Modeling Steps:

1. Load in the Front_Baja.mdl
2. With the Baja_FSAE_Library loaded in (refer to KB0124791), access the event wizard and load in a Static Load Analysis into the model.                                                   
3. Accept all defaults for the analysis from the pop-up windows.
4. In the analysis, navigate to the Loadcases Forms. In the Entity Editor select Form.
5. In the pop-up window, a table will appear. To expand the table, select the button marker “…”.                                 
6. Configure the table to correspond to the loadcase table shown below.
   1. Select Add to incorporate new entries.
   2. Make sure the LoadCase number is properly defined.
   3. Update the Location to either be the left and right wheel center or tire patch.
   4. Update the loading direction.
   5. Verify the multiplier. For example, a load of 3G will have the multiplier value set to 3.
   6. Copy and paste the Value expression into new entries.
   7. Set the amount of time steps to 10.                                                                                   
7. Add force outputs in the model for the crucial suspension components (or you can create a single force output that captures the forces acting on all the bodies).                                                                                             
8. Save and run the model.
9. Once simulation is complete, the forces can be plotted in HyperGraph and the force vectors can be animated in HyperView.
10. To Export the max peak loads from each loadcase, Load export can be utilized.
11. Access the Load Export Tool
12. In the pop up window, select open and insert the .meta file from the previous run. Then select the requested bodies.
13. For the time selection, the peak value will occur at the first second of the LoadCase (duration of 2 seconds). Either input the timesteps manually or import the timesteps from a csv file.                                                                                 
14. In the Load Export tool, apply the TimeStep’s and export as a tabular summary or as a FEA loadcase file.                                 

RESULTS  

Upon completing the simulation, the force vectors can be visualized in HyperView, providing an excellent overview of the vehicle's motion under load and the primary directions of forces acting on its components.

Additionally, peak forces can be exported using the Load Export feature. These results can be compiled into a text summary file for selected components or exported as an FEA loadcase, which can then be imported into an OptiStruct or Nastran study for further analysis. 

 

Post-Requisite

CONCLUSION

In this example, we embarked on an exploration to determine the maximum forces that suspension components could experience under various load cases, which are critical for qualifying the vehicle's durability. Verifying these forces is essential to ensure that the suspension system can withstand real-world stresses, preventing potential failures and enhancing overall vehicle safety and performance. By accurately understanding these forces, engineers can make informed design decisions, optimize component strength, and improve the longevity of the vehicle.