What is Formula SAE?

Formula SAE is an international competition put on by the Society of Automotive Engineers which challenges students to design, build and test a formula-style racecar. Virginia Tech competes along with 120 schools every May.  The Formula SAE competition is for SAE student members to conceive, design, fabricate, and compete with small formula-style racing cars. The cars are built with a team effort over a period of about one year and are taken to the annual competition for judging and comparison with approximately 120 other vehicles from colleges and universities throughout the world. SIMULIA is proud to sponsor the Virginia Tech team with a free Academic Research Suite.¹ 

Virginia Tech Formula SAE Team 

We asked the Virginia Tech SAE team to tell us about their design efforts of the VT 2017 combustion car (VTM17c) in two use case scenarios. They are using SIMULIA products centered on Abaqus analyses to explore the response of the components and assemblies, preliminary and detailed design, as well as virtual test and test support.  The two examples are highlighted below.   

Please describe your project. Why does this workflow need to be analyzed?

Combustion Car (VTM17c) Carbon-Fiber Monocoque Chassis:

The carbon-fiber monocoque chassis has undergone three design stages.  The design refinements have moved from concept validation and detailed design/analysis to the task of establishing stiffness allowables.  The VTM17c carbon-fiber monocoque chassis explored a design refinement this year to retain the torsional and bending stiffness of the VTM16c chassis design while reducing weight, improving the stiffness-to-weight ratio.

Combustion Car (VTM17c) Driveline Component Halfshafts:

The most significant design change in driveline rotating components this year is for the halfshafts.  The end connection for the shafts and tri-pod bearing is polygon shaped rather than splined, as in past designs (see Figure 1).  The purpose of the redesign of the halfshafts is to reduce the wall thickness as well as to change the end connection from splines to a polygon connection.  After analyzing the new design with a classical mechanical design approach, Abaqus was used to determine the stresses in the tripod bearings and halfshaft using contact modeling.  The redesign reduced the stress concentration factor from 2.4 to 1.4 and the thinner wall thickness for the shafts reduces the rotating mass by about one pound.

Describe how you executed the simulations.

Combustion Car (VTM17c) Carbon-Fiber Monocoque Chassis:

• The monocoque chassis analysis relies heavily on the use of composites.
• 3-D continuum and shell elements are used to model the carbon-fiber layups and well as the honeycomb core.
• Elastic displacement constraints, and contact interactions are developed for hard-point mounting to the composite chassis.
• Abaqus Quasi-Static General analysis is typically performed.
• Linear Perturbation-Frequency analysis will be used to predict the chassis natural frequencies.

Combustion Car (VTM17c) Driveline Component Halfshafts:

• 3-D continuum elements are used to represent the halfshaft and the tripod bearings. Extensive use of partitioning is performed to control the meshing.
• Elastic displacement constraints, and many contact interactions are developed to represent the tripod connection such that proper representation of stress concentrations can be developed.
• Abaqus Quasi-Static General analysis is performed.

Were there any key technical challenges you faced along the way? How did you solve them?

Key Challenges Carbon-Fiber Monocoque Chassis:

• Effective material characterization. The material coupons were laid up and cured.  Mechanical testing was performed in a load frame.  Material test coupons included different carbon-fiber layups and ply counts as well as carbon-fiber with honeycomb core as shown in the figure below.
• Material ply and orientation layup on the 3-D model of the chassis. The solution was develop a manual procedure which established local coordinate systems to apply the different layup schedules.
• Abaqus models of the virtual test were developed to correlate the material characterization data with the material model.

Key Challenges Halfshaft Model with Tripod Bearings:

• Meshing requirements were resolved by effective partitioning of the halfshaft and tripod bearing parts.
• Resolving the interaction conditions for constraints and contact. The assembly model requires the use of a 3-D contact model with loads transferred through discrete rigid bodies.
  • The contact model was resolved with surface-to-surface contact using the penalty function approach with contact surfaces developed with the use of cell partitions. The contact pairs included the halfshaft and tripod bearing surfaces, as well as each of the tripod bearing lobe and discrete rigid roller surfaces.
  • The moment applied to the tripod bearing was simulated using discrete rigid bodies modeling the rollers in contact with the lobes of the tripod bearing. An equivalent moment was generated by applying concentrated forces to each of the discrete rigid rollers.
  • The contact was modeled at just one end of the halfshaft, with the polygonal surface at the opposite end of the halfshaft being assigned fixed constraints to simulate symmetry.

What were the advantages of using simulation in your project?

Developing expertise for simulation along with fundamental knowledge of the problem domain is required to contribute to the design of products or solutions which advance the state of the art.  Simulation models are developed to be operated on, the model itself is the not the end objective.  The objective is to develop models with the fidelity required to support decision making studies for validation, design, sensitivity, failure mode exploration, and optimization.

The advantage of using simulation cost and time savings alone is important.  However, the primary advantage of simulation with validated, operational models is the development of professional experience and understanding, resulting in more informed decision making.  The exploration of the problem/design being studied results in understanding and experience that may be intractable to obtain through physical test.

Why did you choose Abaqus over other simulation products?

We have been using Abaqus with Virginia Tech FSAE for nearly ten (10) years.  We have been teaching finite element analysis to undergraduate students with Abaqus for over 10 years.

Do you feel that learning simulation skills in University will provide your students with an advantage in their career? Please explain.

Yes, the fact that the FSAE team have been developing finite element and other simulation expertise over the years, is one of the more prominent reasons why the team does very well in the design event at competition.  It is another important reason why employers and program sponsors hire our FSAE students, many of these companies are among the largest Abaqus customers.

Is there anything else we should know about this project?

There are other simulation and analysis studies used throughout the FSAE program at Virginia Tech.  Nominally those projects are associated with design studies for structural and driveline problems.

To find out more about the Virginia Tech team, follow them on social media! 

¹VT Motorsports Website: http://www.vtmotorsports.com 

Facebook Page: http://www.facebook.com/VTMotorsports

Interested in a SIMULIA Academic sponsorship? Apply now and give your engineering team the winning edge!