Lightening Up Through Topology Optimization

(Image: csi GmbH)

Although Altair describes itself as “a global technology company that provides software and cloud solutions in the areas of product development, high performance computing (HPC) and data intelligence,” many people in the auto industry (one of many industries that Altair works with) are probably familiar with the company not only through its products like HyperWorks, a suite of software tools that includes such things as OptiStruct—a tool for structural design and optimization, a package that helps with what achieving topology optimization—but because for the past seven years the company has been sponsoring a competition for OEMs and suppliers, the winners of which are those who have developed light-weight products through the use of innovative design, materials, engineering, and manufacturing approaches.

What’s interesting about the “Altair Enlighten Awards,”* which draws entries from around the world and which are presented at the Center for Automotive Research Management Briefing Seminars, is that this isn’t something that is predicated on the use of its products; the winners are based on selection criteria that go to the solution, which is a more mass-efficient design.

According to Altair’s Richard Yen, senior vice president, Strategic Solutions Team and Global Automotive Business, an objective is to provide recognition to those who are advancing the state of technology leading to the reduction of vehicle weight.* Yen says this is what Altair has long been promoting, so it is completely in line with its approach. He and his colleagues believe in the importance of lightweighting, so not only do they provide the digital tools that can help make that happen, they think it is important to celebrate those who are making this happen in the physical world.

BMW i8 soft-top attachment component is 3D printed with aluminum. Note the organic shape of the component, with more mass being located in areas where loads need to be accommodated. The component weighs less than an injection molded plastic part that would otherwise be used. (Image: BMW)

Given the move toward greater vehicular electrification, as well as regulations in major parts of the world aimed at reducing emissions or increasing fuel economy, manufacturers are being faced with the need to reduce mass. At that same time, however, there is no less a requirement for vehicles—and all that go into them—to provide ever-increasing levels of safety; whether it is the latest IIHS or Global NCAP testing regime, vehicles must be structurally sound and capable of protecting occupants. Once upon a time it may have been that vehicle manufacturers could just “beef up” their structures to address any evident deficiencies (which tended to mean that not only was there additional mass where needed but probably more than was essentially in other areas due to the nature of the part design), but with the objective toward lightweighting, that mass-add is no longer feasible.

Altair’s Anthony Norton, vice president, Americas, Technical Operations, says that a goal they’re pursuing in part design is “optimization,” which he says means “maintaining performance and attaining lower weight or maintaining weight and achieving higher performance.” Either way, it is a win.

One of the things that they recommend that designers and engineers do is, as Norton puts it, “use simulation up front to guide the design rather than using simulation as virtual testing after the design has been made.”

This approach, he explains, helps provide a deeper understanding of the design as they move forward rather than using the tools after the fact. To be sure either way there are benefits that are achieved; according to Yen, if there is an existing, non-optimized design to which topology optimization is applied the weight save is on the order of from 10 to 20%  But Norton emphasizes that learning about the design is really important. What’s more, he says, “Ordinarily when you design something, you partition it arbitrarily. But when you take a holistic view of the structure and apply optimization to it, you see where the material wants to be and you can decide which type of material needs to be where before you get into discussions of gauging or grade.” (This brings to mind Dr. W. Edward Deming’s Profound Knowledge, in a sense, in that it is important to understand a system, not just an individual aspect or element.)

“People say to put the materials in the right place,” says Yen. “But where is the right place?” That is the challenge that people face when designing a structure. “I think the hard part when designing a structure is that it is difficult for people to imagine where the loads are.” Which is why designing with topology optimization tools from the beginning is helpful. “Consider a seat,” Yen says. “There are many load cases associated with it.” These cases range from the simple act of someone sitting on the seat all the way to the loads associated with the vehicle getting into an accident.

“Typically,” Yen says, “when someone starts a design they start with styling.” But it is important to understand the structure that is beneath that exterior styling.

One of the typical consequences of applying topology optimization during design, practicing generative design, is that because it is about putting structure where it is needed and minimizing it where it isn’t, what have historically been fairly symmetrical designs give way to more organic shapes. Because these parts can look so different from the traditional approaches, Norton says that typical applications for the optimized parts are for things like brackets that are usually out of sight to the consumer. However, he says that some companies—and he mentions Harley-Davidson and Polaris Industries as examples—are actually using these forms as part of an overall design aesthetic, as the parts are truly visually distinctive.

This leads to a question about how topology optimization works with additive manufacturing, the process that allows shapes to be manufactured that would otherwise be practically impossible (more or less) to achieve with conventional processes. Not surprisingly, Norton says “additive manufacturing makes a fantastic marriage with topology optimization.”

But ironically, he admits that during the past 20 years that they’ve been working with topology optimization at Altair they’ve been working on the ways and means to achieve the forms with conventional means like extrusion and stamping.
 

Case Study: #ULTRALEICHTBAUSITZ

“It is a seat that’s completely rethought,” says Stefan Herrmann, project leader, Integration/Development, New Technologies at csi GmbH (csi-online.de), an engineering company that specializes in the development of lightweight structures and components for exteriors and interiors, one of three companies that launched the #ULTRALEICHTBAUSITZ, or #ULTRALIGHTWEIGHTSEAT, feasibility study, with the other two being Alba tooling & engineering GmbH, which focuses on the development of processing systems for producing plastics components, and Automotive Management Consulting (AMC), which concentrates on the development, commercialization and industrialization of lightweight construction solutions.

The elements of the seat that was developed using technologies ranging from topology optimization to 3D printing to advanced materials. (Image: csi GmbH)

Herrmann says that there were several drivers behind the program. Among them are new technologies—like 3D printing—and new requirements from electric and, potentially, autonomous vehicles.

What the three companies did—with support from companies including 3D|Core GmbH & Co. KG, a manufacturer of structural reinforcing foam cores; Covestro , a polymer company; Hofmann-IHR Moglichmachiner, a specialist in 3D printing; and LBK, which worked with the xFX process—was design, engineer and prototype a vehicle seat that has a total mass of 10 kg. Putting that into context, Herrmann says that the mass of a comparatively light seat in series production is on the order of 16 to 18 kg; a light aftermarket seat is 12 kg; and a very low-mass bucket seat—a carbon fiber shell with a minimum of cushion—is from 7 to 8 kg. The objective of the #ULTRALEICHTBAUSITZ program was to create a seat that would actually be comfortable and light.

The frame was produced with the xFX in 3D process. The “x,” Herrmann explains, signifies that various different types of fibers can be used in this composite material—from glass to hemp. The fibers are specifically oriented to accommodate the loads. This 3D winding process was deployed to produce frame elements that are both light and strong. “You only use as much material as you need,” he says.

Not only was the objective to make a light seat through the use of advanced technologies—ranging from software to materials to methods—but to make one that is aesthetically pleasing. (Images: csi GMBH)

The nodes are 3D printed with steel where there are high loads and aluminum where the demands aren’t as severe. The cushions under the climatex fabric (an eco-friendly material that has good thermal properties that eliminate the need for a ventilation system for the seat) is a 3D printed TPU. The back side of the seat is made with the 3D|CORE foam core material that exhibits high shear modulus and compression modulus characteristics. In addition to which, Herrmann says that they wanted the seat to have good aesthetic properties, which the foam core contributes to.

The entire seat was produced in a seven-month period. Herrman says that were the seat to go into series production, there would certainly be process changes. He points out that throughout the development, there was focus on manufacturing processes and materials so presumably, the transfer from this prototype to production would benefit from the attention to product and process detail.

FOOTNOTE:

*The 2019 winners are:

• Full vehicle, low-volume production: Ferrari Portofino (80 kg lighter and 35% stiffer than the outgoing California T)
• Full vehicle, high-production: Jeep Wrangler (92 kg lighter than previous generation)
• Module: ZF knee airbag with a 30% weight reduction and 20% size reduction compared to previous design
• Enabling: Materials Sciences for MSC Smart Steel, a multilayer steel laminate that is spot weldable
• Future of lightweighting: #ULTRALIGHTWEIGHTSEAT, a rethink of car seat design and engineering developed by Alba tooling & engineering, Automotive Management Consulting GmbH, and csi entwicklungstechnik GmbH, a feasibility study for a seat that has a mass of 10 kg