Just ask Brett Longhurst, owner and managing director of Bremar Automotion, Melbourne, Australia. His company provides simulation, testing, validation and design optimization services to a range of customers across many industries, including motor sports. Specifically, the company is known for its roll cage validation and design capabilities.
Bremar Automotion has received approval from the Confederation of Australian Motor Sport (CAMS) – theNational Sporting Authority in Australia and an affiliate of t he Fédération Internationale de l’Automobile (FIA) – to certify motorsport roll cages using finite element analysis (FEA). This accreditation enables the company to independently approve roll cages for commercial use inAustralia and internationally.
Tracking Roll Cages
The governing bodies of various motorsports events keep close track of components,including roll cages. Companies that certify roll cages must create reports that are submitted to the governing bodies, logged and documented.
The governing bodies can then track who made the cage, its material composition and its compliance with the rules. If a vehicle is involved in an accident, the governing body can monitor whether any modifications or changes were made to the roll cage structure.
HyperWorks Virtual Wind Tunnel enables engineers to analyze a Speads RS10 sportscar to assess downforce and radiator airflow.
Simulation Confirms Physical Testing
Bremar Automotion, based in Melbourne, Australia, is among an elite group of companies that has been accredited by the Fédération Internationale de l’Automobile (FIA)and the Confederation of Australian Motor Sport (CAMS) to certify motorsport roll cages using finite-element analysis (FEA). It appears on the FIA’s Technical List No. 35.
To obtain the certification, the company was required to construct and test a full-size roll cage by applying the FIA’s specified roll cage loads to the structure. Destructive testing was required to confirm the accuracy of the computer modeling and to demonstrate competency to the FIA.
Bremar Automotion designed a mild steel roll cage for a vehicle weighing approximately 2,645 lbs (1,200 kg). They then affixed multiple sensors and strain gauges to it to measure deflection and strain at various locations. Per FIA criteria, the company applied a load in the order of 10T.
Once the FIA load criteria had been met, the company ran another test in which it applied the maximum allowable displacement of 50mm – which required a load well in excess of 20T.
Once testing of the roll cage structure was complete, tensile tests were performed on specimens of the roll cage tubing to determine suitable material properties for use in the computer models.
Bremar Automotion correlated results of physical testing of a vertical main hoop with FEA using Altair RADIOSS®. According to Bremar Automotion’s Managing Director Brett Longhurst, there was a close correlation between the physical structure and computer
Roll cages protect occupants from being injured in roll-over accidents that sometimes occur in the heat of competition. Roll cages vary in design, depending on the type of race car. For example, a roll cage for the Australian V8 Supercar Series – based around General Motors and Ford production cars – is very different from a roll cage built for off-road racing vehicles.
Depending upon the type of vehicle and race category, there are different requirements on which bars and types of reinforcement are based. “The roll cage regulations that we work to essentially depend on the vehicle weight,” says Longhurst. Other factors that affect product development include material strength stiffness,safety and cost.
He explains that the roll cage designs vary in material grade, and the grade of material governs the complexity of design. For instance, a roll cage made out of entry-level material is characterized by a lower strength. As a result, the roll cage is thicker and often constructed of more tubes, which generally lead to a heavier structure. A roll cage developed with a higher grade steel, such as chromoly, has a higher strength, so the tubes can be thinner to reduce weight. In some cases, more tubes may need to be added into parts of the structure to maintain the strength and stiffness.
“The factors affecting product development are always playing off each other and have conflicting impacts on the design,” says Longhurst.
When customers approach Bremar Automotion about developing a new roll cage, often the first step in product development is to perform a3D scan of the vehicle and/or its interior to determine where the roll cage will be placed. The Bremar team then packages specified vehicle sub-systems and components within a CAD model – including information on the driver and steering wheel, among others – and provides an initial roll cage design and tube sizing.
In some cases, a mock-up of the roll cage is created with plastic tubing to ensure that the driver can get into and out of the car and that the roll cage is not impeding the driver’s ability to steer and reach the gear stick. It’s often difficult to judge these ergonomic factors in CAD, so a physical mockup in the vehicle is often the simplest and most accurate way for the driver and team to confirm it meets the requirements.
Once the team is satisfied with the design, a drawing of the roll cage is submitted to CAMS or the governing body for the racing category. “Before we go through the process of doing the analysis and building the roll cage,” says Longhurst, “we want to get confirmation that it is actually compliant with the regulations. ”After the governing body approves the design, Bremar Automotion moves forward with simulation.
Three load cases need to be assessed for roll cage approval. There’s a vertical load case, where the static load pushes down on the roll cage structure from above. There’s a lateral load case that pushes on the side of the roll cage, and then there’s an offset load case on the front corner of the wind screen that pushes down on that front corner.
Bremar creates FEA models of the structure, applies the three load cases, ensures that the design meets the criteria for acceptance and then submits a report. If the roll cage doesn’t meet the regulations, they can easily alter the models by thickening a tube or placing a bar in a different orientation.
Once the design has been approved, the roll cage is built by the customer or manufacturer. If there are changes made during the build process, Bremar Automotion revises its simulation models and does another round of FEA to ensure that the final as-built structure is still compliant with all the requirements.
The Road to Innovation
There are times when a team wants to use materials that are not specified in the CAMS rule book or would like to add or remove bars from the roll cage design. This is where simulation shines.
According to Longhurst, FEA studies enable Bremar to optimize tube thickness or use different tube sizes and material grades at different places within the roll cage to achieve innovative designs that also adhere to regulations. “In many cases,” he says,“the goal is to minimize the mass of the roll cage while getting maximum strength and stiffness.”
Of course, cost, weight and safety are all part of the iterative process, and Bremar Automotion balances these factors in pursuit of innovative designs. “Once we have a model,” says Longhurst, “we can quite easily change the material property and see its effect on the design – or change the wall thickness and have a look at how the strength varies compared to the weight.
”What’s more, Bremar Automotion uses simulation to automate optimization. Longhurst notes, “We can set the roll cage design up and say, ‘Tell us which thicknesses are best in the appropriate areas to maximize the stiffness or the strength of the roll cage.’ At the end of the day, it boils down to being able to easily assess those designs and make changes to them within the FEA environment – and then assess which designs are going to meet all those different factors in the way that we want them to.”
The Efficiency Factor
To help improve efficiency in product development, Bremar Automotion has automated part of its roll cage design process. For example, the company has created a spreadsheet that includes the dimensions and sizes of roll cages. Customers receive the spreadsheet and are asked to fill it out.
The spreadsheet is then used to drive development of the CAD models. Longhurst explains that the spreadsheet automatically updates the parametric 3D CAD models of the roll cages based on the dimensions specified in the spreadsheet. “That has saved us a lot of time and allows us to perform assessments a lot quicker,” he says.
Assessments are also performed quickly, thanks to Bremar Automotion’s use of the Altair HyperWorks® suite. For example, the company uses HyperMesh® to create 2D shell meshes of the actual tube surfaces, rather than a1D representation of the tube centerlines. This approach shows localized effects occurring at a roll cage joint, where one tube meets another. “This would be difficult to do in other software,”says Longhurst.
In addition, Altair RADIOSS® enables Bremar Automotion to perform crash analyses, studying how roll cages handle different impacts. The nonlinear code is well suited for structural and material deformation applications that can occur in racing.
Longhurst says, “We use as much of the Altair software as we can, from OptiStruct® and RADIOSS to MotionView®and MotionSolve®. As a small business,we can’t afford to purchase multiple CAE packages to do different types of analyses. For us, the partnership with Altair enables us to have one licensing environment and one software environment to cover all our CAE needs. It’s a huge benefit for us, both economically and from an efficiency standpoint. All the codes talk to each other, and all the types of analyses we need to do can interact with each other, if needed.
”Longhurst believes that the application of simulation and other technology has contributed to advances in the racing industry. The time and cost required to perform physical testing can be prohibitive. However, simulation enables customers and companies like Bremar Automotion to optimize and validate their designs before ever making a physical part, providing efficiency gains in terms of development time and money.
“As a small business,we can’t afford to purchase multiple CAE packages to do different types of analyses. For us, the partnership with Altair enables us to have one licensing environment and one software environment to cover all our CAE needs.”
– Brett Longhurst, managing director, Bremar Automotion
What’s more, simulation demonstrates that the products perform as predicted. Longhurst says, “That gives us additional confidence that we can use simulation to develop and validate designs – and that our simulation methods are providing accurate results.”
Pushing the Boundaries
With more than 15 years of experience in the industry, Bremar Automotion has seen simulation capabilities advance over the years. “When we started our company,” Longhurst says, “we were performing more basic analysis. Now, I feel we’re really pushing the boundaries of what can be achieved with simulation.”
The company, for example, is now conducting virtual wind tunnel testing. They perform external aerodynamic analysis on vehicles and aerodynamic components using HyperWorks Virtual Wind Tunnel™. And, it is using Altair AcuSolve® to perform fluid flow analysis on engine manifolds and brake ducts, among other components.
Many smaller companies, including racing organizations, may not have access to leading-edge technology. BremarAutomotion provides the technology and services that bring these customers up to speed, making them current in the way they’re operating, designing, developing and manufacturing their products.
Longhurst concludes: “I think it’s a real strength, and one of our differentiators, that we can bring such a broad range of technology into these businesses, whether they are motorsport businesses or others. It allows the use of simulation and these modern design and manufacturing techniques – and allows customers to implement them.”
To learn more about Altair solutions for the motorsports industry, visit www.altair.com/motorsport.