Steel E-Motive: Autonomous Vehicles That Only Steel Can Make Real

Steel E-Motive: Autonomous Vehicles That Only Steel Can Make Real

The Steel E-Motive program–commissioned by WorldAutoSteel in partnership with Ricardo plc–has developed the world’s first fully autonomous electric vehicle body structure concept purpose-fit for ride-sharing. This global steel industry initiative showcases the strength and durability of steel with an eye on playing a pivotal role in reaching net zero emissions targets.

Download the Steel E-Motive Engineering Report

Here, we break down the many benefits of the Steel E-Motive concept that only Advanced High-Strength Steel (AHSS) can enable.

Steel E-Motive Was Conceived as a Level 5 Autonomous Vehicle

The Steel E-Motive concept is designed to be a Level 5 autonomous vehicle, so it does not include any driver interfaces. The design features a spacious, airy cabin with rear-facing front-passenger seat configurations. The B-pillarless structure and unique battery system design offer easy ingress and egress.

Steel E-Motive Vehicle is shown in a brick paved area with greenery

The Steel E-Motive concept is designed to be a Level 5 autonomous vehicle.

Designed to Exceed Future Mobility Safety Standards

Modern Advanced High-Strength Steels innovations allow the Steel E-Motive autonomous vehicle to exceed current global high-speed crashworthiness standards. By using AHSS, the Steel E-Motive vehicle is the first to acknowledge compliance with NHTSA and IIHS safety standards publicly.

For example, the 4-passenger B-sized urban concept SEM1 introduced a new front-end passenger protection zone. This design features the small overlap Glance Beam, which forces the car to “glance” off the barrier and reduces passenger cabin intrusion. It also lowers the crash pulse and ultimately minimizes passenger injury. Advanced High-Strength Steels also offer strong battery protection and preserve door ring integrity in this autonomous vehicle.

The Evolution of Advanced High-Strength Steel

Over the past quarter century, vehicle concept projects have showcased the continuous advancement of steel. In 1998, global steelmakers introduced the Ultralight Steel Auto Body, which used one of the earliest forms of AHSS. This project demonstrated steel’s ability to reduce weight without compromising safety.

By 2010, we introduced the Future Steel Vehicle concept. Using 27 AHSS materials, the body structure design reduced mass by over 35%. Steel materials enable these massive reductions while allowing the design to meet global crash and durability requirements.

The Steel E-Motive concepts benefit from no fewer than 64 materials under the AHSS umbrella. The “infinite tunability” of AHSS allows product customization by designers and engineers to select exactly the right steel for every need and purpose in the vehicle.

Key Attributes of the Steel E-Motive Autonomous Vehicle

From lowering the carbon footprint to massively reducing weight, the Steel E-Motive vehicle offers first-of-its-kind benefits for future mobility made possible by AHSS.

Steel allows the vehicle to reduce weight without sacrificing strength. For example, 66% of the Steel E-Motive autonomous vehicle structures’ materials have an Ultimate Tensile Strength of at least 1,000 MPa, and these materials’ weighted average tensile strength is 1259 MPa.

By using 33% Press Hardened Steels and 11% 3rd Generation AHSS, the design includes complex geometries fully formed by hot and cold-stamped gigapascal steels.

In another example, 43% of the Steel E-Motive structure is fabricated from material-efficient processes such as press hardening, hydroforming, roll forming, and roll stamping. With these processes, the steel body design maximizes material utilization and minimizes scrap rate. This means less material is produced, lowering the structure’s carbon footprint. These achievements reduce manufacturing costs to support a profitable margin both for the vehicle manufacturer and the mobility service provider.

Using AHSS, the Steel E-Motive autonomous vehicle’s body structure mass is 25% lower than benchmark vehicles of a similar volumetric footprint. Additionally, Steel E-Motive realizes a 27% lower battery frame cost than a fully enclosed battery design, with 37% mass savings.

In conclusion, the Steel E-Motive program stands as a remarkable testament to the innovative potential of steel in shaping the future of mobility and autonomous vehicles. With its groundbreaking design, the Steel E-Motive concept paves the way for Level 5 autonomous electric vehicles prioritizing safety, sustainability, and efficiency.

Harnessing the unique attributes of AHSS, this global steel industry initiative also showcases the remarkable evolution of steel materials over the years. From Ultralight Steel Auto Body to Future Steel Vehicle, the journey of AHSS has been one of continuous improvement, leading to Steel E-Motive’s exceptional achievements in weight reduction, enhanced safety, and minimized environmental impact.

As we venture into an era of net-zero emissions and advanced mobility solutions, the Steel E-Motive concept proudly positions steel as a driving force in shaping a cleaner, safer, and more connected future. 

Download the Steel E-Motive Engineering Report

Die-Free Blanking of Class A Quality & Structural Parts

Die-Free Blanking of Class A Quality & Structural Parts

You’ll find this content as part of our page on Laser Blanking, but this month, we want to highlight it in our AHSS Insights blog.  We thank Schuler North America for contributing this insightful case study.

Production of Class A quality and structural parts without a blanking die is possible, even for high-volume serial production. Laser blanking enables flexible, cost-effective, and sustainable manufacturing and is capable of reaching 45 parts per minute.  DynamicFlow Technology (DFT) from Schuler provides highly productive, die-free blanking with lasers—directly from a continuously running steel coil. DFT combines the advantages of flexible laser cutting with the speed of conventional blanking.

 

Laser Blanking Lines at a Glance

Figure 1 – Laser blanking lines offer additional flexibility over conventional blanking approaches.

Laser blanking technology addresses market challenges such as frequent die changes, the need to increase capacity, and improving plant floor utilization, material utilization, and downstream processes.

 

LASER BLANKING ELIMINATES FREQUENT DIE CHANGES 

It is important to remember that there are no dies with laser blanking technology, and no dies mean no die changes. Overall Equipment Effectiveness (OEE) of up to 80% can be achieved with laser blanking technology. In fact, 4 to 6 million parts per year of various materials are produced with the help of DFT—including mild steel, high-strength steel, and advanced high-strength steel. Even processing press-hardening steels with an aluminum-silicon coating is possible with laser blanking.  Surface and cutting quality can be maintained over this spectrum of steel grades.  Laser blanking technology can even achieve effective small batch production of Class A outer body panels and structural parts typically up to 3mm thick.

 

LASER BLANKING INCREASES PLANT OUTPUT

Competitive high-speed and high-output results can be achieved in multiple ways with laser blanking technology. The above-ground coil-fed line, optimized for short setup time, can handle coils with material widths up to 2,150 mm, weighing up to 30 tons. The material transport is smooth and controlled, simplifying setup and leading to uninterrupted processing within the laser cell.

There are three highly dynamic and simultaneously moving laser cutting heads within the laser cell of these lines. These laser cutting heads cut the programmed blank contour from a continuously moving material coil. Cutting speeds can exceed 100 meters per minute. The material is protected against any process contamination throughout the cutting process by custom-designed cutting clearance and material transport. 

Figure 2 reveals the high-speed and high-output results for outer body parts. Each part is measured by improved output per minute and hour to achieve an OEE of 80%. Laser blanking lines can achieve up to 45 parts per minute and reduce costs per blank.

High productivity achieved with laser blanking

Figure 2: High productivity achieved with laser blanking  

 

LASER BLANKING IMPROVES MATERIAL UTILIZATION

Up to 90% of blank costs are determined by the material price. The most significant leverage would be to reduce scrap and save on materials. Schuler conducted research based on the production of 300,000 cars per year, at 350 kg per car and $1,000 USD per ton of steel to provide a realistic inside look at how much cost savings can be achieved with laser blanking. The result was $1 Million USD saved with just 1% of material savings. This is extremely significant as material costs keep increasing.

Laser blanking is the digital way to cut blanks. All that’s needed to create a blanking program is a drawing to be loaded and a material to be selected. The part-specific program can be created offline and modified at any time. It is designed to create optimal combinations of material utilization and output—resulting in a high level of flexibility that significantly reduces development time for optimal blanks while also allowing for need-based production. This makes production planning easier, and it also opens the door to continuous contour optimizations for the forming process. Additionally, laser cutting does not require any gaps between individual parts due to smart nesting capabilities that cannot be achieved in comparison to die nesting or flatbed laser nesting. The combined smart, flexible nesting functions unlock new potential for material savings. Manufacturers can optimize individual blanks and eliminate the separating strip or connection bridges. Scrap savings in the forming process can also be achieved as there are no geometric restrictions due to cutting dies, and manufacturers can continuously optimize or adapt parts.

Figure 3 showcases the comparison of die nesting (the two graphics on the left) versus a laser-optimized blank contour and material savings via smart, laser blanking line nesting (the two images on the right). 

Die nesting compared with laser-optimized blank contours highlighting potential

Figure 3: Die nesting (left) compared with laser-optimized blank contours highlighting potential material savings (right)

Overall, laser blanking lines can have an equivalent throughput to conventional blanking lines, but laser blanking lines can achieve up to 10% greater material utilization.

 

You can read the full Case Study, including how laser blanking reduces infrastructure costs and improves downstream processes here: Laser Blanking Case Study

 

Schuler will present laser blanking technology, along with a variety of digital tools that create the “Press Shop of the Future” at FABTECH Chicago 2023 (booth # D41306). Tiago Vasconcellos, Sales Director at Schuler North America, will present “How Smart is Your Press Shop?” during FABTECH’s Educational Conference. The presentation will use The Smart Press Shop, a newly formed joint venture between Porsche and Schuler, as an exemplary case study for smart manufacturing standards. Attendees will discover innovative and practical ways to incorporate digitalization into production and become a state-of-the-art stamping facility directly from Schuler. 

About Schuler Group

Schuler offers customized cutting-edge technology in all areas of forming—from the networked press to press shop planning. In addition to presses, Schuler’s products include automation, dies, process know-how, and service for the entire metalworking industry. Schuler’s Digital Suite brings together solutions for networking forming technology and is continuously being developed to further improve line productivity and availability. Schuler customers include automotive manufacturers and suppliers, as well as companies in the forging, household appliance, and electrical industries. Schuler presses are minting coins for more than 180 countries. Founded in 1839 at the Göppingen, Germany headquarters, Schuler has approximately 5,000 employees at production sites in Europe, China and the Americas, as well as service companies in more than 40 countries. The company is part of the international technology group ANDRITZ.

Schuler’s global portfolio of world-renowned brands include BCN (Bliss Clearing Niagara) Technical Services, Müller Weingarten, Beutler, Umformtechnik Erfurt, SMG Pressen, Hydrap Pressen, Wilkins & Mitchell, Bêché, Spiertz Presses, Farina Presse, Liebergeld, Peltzer & Ehlers, Schleicher, and Sovema Group.

About Schuler North America

Schuler North America (Schuler), headquartered in Canton, Michigan, is the North American subsidiary of Schuler Group. Schuler provides new equipment, spare parts, and a portfolio of lifecycle services for all press systems—including preventative maintenance, press shop design and optimization, turnkey installations, retrofits for existing systems, and localized production and service. Schuler’s best-in-class position in the metalworking and materials industry serves automotive manufacturers and tier suppliers, as well as home appliance, electronics, forging, and other industries.

 

Roll Forming

Roll Forming

Roll Forming takes a flat sheet or strip and feeds it longitudinally through a mill containing several successive paired roller dies, each of which incrementally bend the strip into the desired final shape. The incremental approach can minimize strain localization and compensate for springback. Therefore, roll forming is well suited for generating many complex shapes from Advanced High-Strength Steels, especially from those grades with low total elongation such as martensitic steel. The following video, kindly provided by Shape Corp.S-104, highlights the process which can produce either open or closed (tubular) sections.

The number of pairs of rolls depends on the sheet metal grade, finished part complexity, and the design of the roll forming mill. A roll forming mill used for bumpers may have as many as 30 pairs of roller dies mounted on individually driven horizontal shafts.A-32

Roll forming is one of the few sheet metal forming processes requiring only one primary mode of deformation. Unlike most forming operations which have various combinations of forming modes, the roll forming process is nothing more than a carefully engineered series of bends. In roll forming, metal thickness does not change appreciably except for a slight thinning at the bend radii.

Roll forming is appropriate for applications requiring high-volume production of long lengths of complex sections held to tight dimensional tolerances. The continuous process involves coil feeding, roll forming and cutting to length. Notching, slotting, punching, embossing, and curving combine with contour roll forming to produce finished parts off the exit end of the roll forming mill. In fact, companies directly roll form automotive door beam impact bars to the appropriate sweep and only need to weld on mounting brackets prior to shipment to the vehicle assembly line.A-32 Figure 1 shows example automotive applications that are ideal for the roll forming process.

Figure 1: Body components that are ideally suited for roll-forming.

Figure 1: Body components that are ideally suited for roll-forming.

 

Roll forming can produce AHSS parts with:

  • Steels of all levels of mechanical properties and different microstructures.
  • Small radii depending on the thickness and mechanical properties of the steel.
  • Reduced number of forming stations compared with lower strength steel.

However, the high sheet-steel strength means that forces on the rollers and frames in the roll forming mill are higher. A rule of thumb says that the force is proportional to the strength and thickness squared. Therefore, structural strength ratings of the roll forming equipment must be checked to avoid bending of the shafts. The value of minimum internal radius of a roll formed component depends primarily on the thickness and the tensile strength of the steel (Figure 2).

Figure 2: Achievable minimum r/t values for bending and roll forming for different strength and types of steel.S-5

Figure 2: Achievable minimum r/t values for bending and roll forming for different strength and types of steel.S-5

 

As seen in Figure 2, roll forming allows smaller radii than a bending process. Figure 3 compares CR1150/1400-MS formed with air-bending and roll forming. Bending requires a minimum 3T radius, but roll forming can produce 1T bends.S-30

Figure 3: CR1150/1400-MS (2 mm thick) has a minimum bend radius of 3T, but can be roll formed to a 1T radius.S-30

Figure 3: CR1150/1400-MS (2 mm thick) has a minimum bend radius of 3T, but can be roll formed to a 1T radius.S-30

 

The main parameters having an influence on the springback are the radius of the component, the sheet thickness, and the strength of the steel. As expected, angular change increases for increased tensile strength and bend radius (Figure 4).

Figure 4: Angular change increases with increasing tensile strength and bend radii.A-4

Figure 4: Angular change increases with increasing tensile strength and bend radii.A-4

 

 

Figure 5 shows a profile made with the same tool setup for three steels at the same thickness having tensile strength ranging from 1000 MPa to 1400 MPa. Even with the large difference in strength, the springback is almost the same.

Figure 5: Roll formed profile made with the same tool setup for three different steels. Bottom to Top: CR700/1000-DP, CR950/1200-MS, CR1150/1400-MS.S-5

Figure 5: Roll formed profile made with the same tool setup for three different steels. Bottom to Top: CR700/1000-DP, CR950/1200-MS, CR1150/1400-MS.S-5

 

Citation A-33 provides guidelines for roll forming High-Strength Steels:

  • Select the appropriate number of roll stands for the material being formed. Remember the higher the steel strength, the greater the number of stands required on the roll former.
  • Use the minimum allowable bend radius for the material in order to minimize springback.
  • Position holes away from the bend radius to help achieve desired tolerances.
  • Establish mechanical and dimensional tolerances for successful part production.
  • Use appropriate lubrication.
  • Use a suitable maintenance schedule for the roll forming line.
  • Anticipate end flare (a form of springback). End flare is caused by stresses that build up during the roll forming process.
  • Recognize that as a part is being swept (or reformed after roll forming), the compression of metal can cause sidewall buckling, which leads to fit-up problems.
  • Do not roll form with worn tooling, as the use of worn tools increases the severity of buckling.
  • Do not expect steels of similar yield strength from different steel sources to behave similarly.
  • Do not over-specify tolerances.

 

Guidelines specifically for the highest strength steelsA-33:

  • Depending on the grade, the minimum bend radius should be three to four times the thickness of the steel to avoid fracture.
  • Springback magnitude can range from ten degrees for 120X steel (120 ksi or 830 MPa minimum yield strength, 860 MPa minimum tensile strength) to 30 degrees for M220HT (CR1200/1500-MS) steel, as compared to one to three degrees for mild steel. Springback should be accounted for when designing the roll forming process.
  • Due to the higher springback, it is difficult to achieve reasonable tolerances on sections with large radii (radii greater than 20 times the thickness of the steel).
  • Rolls should be designed with a constant radius and an evenly distributed overbend from pass to pass.
  • About 50 percent more passes (compared to mild steel) are required when roll forming ultra high-strength steel. The number of passes required is affected by the number of profile bends, mechanical properties of the steel, section depth-to-steel thickness ratio, tolerance requirements, pre-punched holes and notches.
  • Due to the higher number of passes and higher material strength, the horsepower requirement for forming is increased.
  • Due to the higher material strength, the forming pressure is also higher. Larger shaft diameters should be considered. Thin, slender rolls should be avoided.
  • During roll forming, avoid undue permanent elongation of portions of the cross section that will be compressed during the sweeping process.

 

Roll forming is applicable to shapes other than long, narrow parts. For example, an automaker roll forms their pickup truck beds allowing them to minimize thinning and improve durability (Figure 6). Reduced press forces are another factor that can influence whether a company roll forms rather than stamps truck beds.

Figure 6: Roll Forming can replace stamping in certain applications.G-9

Figure 6: Roll Forming can replace stamping in certain applications.G-9

 

Traditional two-dimensional roll forming uses sequential roll stands to incrementally change flat sheets into the targeted shape having a consistent profile down the length. Advanced dynamic roll forming incorporates computer-controlled roll stands with multiple degrees of freedom that allow the finished profile to vary along its length, creating a three-dimensional profile. The same set of tools create different profiles by changing the position and movements of individual roll stands. In-line 3D profiling expands the number of applications where roll forming is a viable parts production option.

One such example are the 3D roll formed tubes made from 1700 MPa martensitic steel for A-pillar / roof rail applications in the 2020 Ford Explorer and 2020 Ford Escape (Figure 7).  Using this approach instead of hydroforming created smaller profiles resulting in improved driver visibility, more interior space, and better packaging of airbags. The strength-to-weight ratio improved by more than 50 percent, which led to an overall mass reduction of 2.8 to 4.5 kg per vehicle.S-104

Figure 7: 3D Roll Formed Profiles in 2020 Ford Vehicles using 1700 MPa martensitic steel.S-104

Figure 7: 3D Roll Formed Profiles in 2020 Ford Vehicles using 1700 MPa martensitic steel.S-104

 

In summary, roll forming can produce AHSS parts with steels of all levels of mechanical properties and different microstructures with a reduced R/T ratio versus conventional bending. All deformation occurs at a radius, so there is no sidewall curl risk and overbending works to control angular springback.

 

Roll Stamping

Traditional roll forming creates products with essentially uniform cross sections.  A newer technique called Roll Stamping enhances the ability to create shapes and features which are not in the rolling axis.

Using a patented processA-48, R-9, forming rolls with the part shape along the circumferential direction create the desired form, as shown in Figure 8.

Figure 7: Roll Stamping creates additional shapes and features beyond capabilities of traditional roll forming. (Reference 1)

Figure 8: Roll Stamping creates additional shapes and features beyond capabilities of traditional roll forming. A-48

 

This approach can be applied to a conventional roll forming line.  In the example of an automotive door impact beam, the W-shaped profile in the central section and the flat section which attaches to the door inner panel are formed at the same time, without the need for brackets or internal spot welds (Figure 9). Sharp corner curvatures are possible due to the incremental bending deformation inherent in the process.

Figure 8: A roll stamped door beam formed on a conventional roll forming line eliminates the need for welding brackets at the edges. (Reference 2)

Figure 9: A roll stamped door part formed on a conventional roll forming line eliminates the need for welding brackets at the edges.R-9

A global automaker used this method to replace a three-piece door impact beam made with a 2.0 mm PHS-CR1500T-MB press hardened steel tube requiring 2 end brackets formed from 1.4 mm CR-500Y780T-DP to attach it to the door frame. The new approach, with a one-piece roll stamped 1.0 mm CR900Y1180T-CP complex phase steel impact beam, resulted in a 10% weight savings and 20% cost savings.K-58 This technique started in mass production on a Korean sedan in 2017, a Korean SUV in 2020, and a European SUV in 2021.K-58

Figure 10: Some Roll Stamping Automotive Applications (Citation D)

Figure 10: Some Roll Stamping Automotive Applications.K-58

High Strain Rate Testing

High Strain Rate Testing

Dynamic tensile testing of sheet steels is becoming more important due to the need for more optimized vehicle crashworthiness analysis in the automotive industry. Positive strain rate sensitivity (strength increases with strain rate) as an example, offers a potential for improved energy absorption during a crash event. New systems have been developed in recent years to meet the increasing demand for dynamic testing.

Three important points collectively highlight the need for high-speed testing:

  • Tensile properties and fracture behavior change with strain rate.
  • Conventional tensile tests using standard dogbone shapes take on the order of 1 to 2 minutes depending on the grade.
  • An entire automotive crash takes on the order of 100 milliseconds, with deformation rates 10,000 to 100,000 faster than conventional testing speeds.

Characterizing the response during high-speed testing provides critical information used in crash simulations, but these tests often require upgraded equipment and procedures. Conventional tensile testing equipment may lack the ability to reach the required speeds (on the order of 20 m/s). Sensors for load and displacement must acquire accurate data during tests which take just a few milliseconds.

Higher speed tensile and fracture characterization also aids in predicting the properties of stamped parts, as deformation rates in stamping are 100 to 1,000 times higher than most testing rates.

Steel alloys possess positive strain rate sensitivity, or m-value, meaning that strength increases with strain rate. This has benefits related to improved crash energy absorption.

Characterizing this response requires use of robust testing equipment and practices appropriate for the targeted strain rate. Some techniques involve a tensile or compressive Split Hopkinson (Kolsky) Bar, a drop tower or impact system, or a high-speed servo-hydraulic system. Historically, no guidelines were available as to the testing method, specimen dimensions, measurement devices, and other important issues which are critical to the quality of testing results. As a result, data from different laboratories were often not comparable. A WorldAutoSteel committee evaluated various procedures, conducted several round-robins, and developed a recommended procedure, which evolved into what are now both parts of ISO 26203, linked below.

Published standards addressing tensile testing at high strain rates include:

The specific response as a function of strain rate is grade dependent. Some grades get stronger and more ductile as the strain rate increases (left image in Figure 1), while other grades see primarily a strength increase (right image in Figure 1). Increases are not linear or consistent with strain rate, so simply scaling the response from conventional quasi-static testing does not work well. Strain hardening (n-value) also changes with speed in some grades, as suggested by the different slopes in the right image of Figure 1. Accurate crash models must also consider how strain rate sensitivity impacts bake hardenability and the magnitude of the TRIP effect, both of which are further complicated by the strain levels in the part from stamping.

Figure 1: Two steels with different strength/ductility response to increasing strain rate.A-7

Figure 1: Two steels with different strength/ductility response to increasing strain rate.A-7

 

 

 

Benefits of Tailored Products in Automotive Body Construction

Benefits of Tailored Products in Automotive Body Construction

Key materials characteristics for formed parts include strength, thickness, and corrosion protection. Tailored products provide opportunities to place these attributes where they are most needed for part function, and remove weight that does not contribute to part performance.

Figure 1 highlights some of the areas within the body structure where companies have considered transitioning to welded tailored blanks. Other tailored products may be suitable in other areas.

Figure 8: Applications suited for tailor welded blanks.A-31

Figure 1: Applications suited for welded tailored blanks.A-31

 

Tailored products offer numerous advantages over the conventional approach involving the stamping and assembly of individual monolithic blanks which have a single grade, thickness, and coating, including:

Improved materials utilization

  • Certain parts, like door rings, window frames, and door inner panels, have large cutout areas contributing to engineered scrap. Converting these to welded tailored blanks allows for optimized nesting of the individual components. Figure 2 presents an example of optimized nesting associated with body side aperture designs using a tailor welded blank. Reduced blank width requirements may allow for additional suppliers or use of master coils yielding slit mults. In the other extreme, blank dimensions larger than rolling mill capabilities are now feasible.

Elimination of reinforcement parts and reduced manufacturing infrastructure requirements

  • In areas needing additional thickness for stiffness or crash performance, conventional approaches require stamping both the primary part and an additional smaller reinforcement and then spot welding the two parts together. The tailored product directly incorporates the required strength and thickness. Compared with a tailored product, the conventional approach requires twice the stamping time and dunnage, creates inventory, and adds the spot welding operation. Tolerance and fit-up issues appear when joining two formed parts, since their individual springback characteristics must be accommodated.

Part consolidation

  • Similar to the benefits of eliminating reinforcements, tailored products may combine the function of what would otherwise be multiple distinct parts which would need to be joined.

Weight savings

  • Conventional approaches to body-in-white construction requires individual parts to have flat weld flanges to facilitate spot welding. Combining multiple parts into a tailored product removes the need for weld flanges, and their associated weight.

Improved NVH, safety, and build quality

  • Joining formed parts is more challenging than joining flat blanks first and then stamping. Tailored products have better dimensional integrity. Elimination of spot welds leads to a reduction in Noise, Vibration, and Harshness (NVH). A continuous weld line in tailored products means a more efficient load path.

Enhanced engineering flexibility

  • Using tailored products provides the ability to add sectional strength in precise locations to optimize body structure performance.

Easily integrated with advanced manufacturing technologies for additional savings

  • Tailored products incorporated into hot stamping or hydroforming applications magnify the advantages described here, and open up additional benefits.

 

Figure 9: Nesting optimization dramatically reduces engineered scrap.A-31

Figure 2: Nesting optimization dramatically reduces engineered scrap.A-31

 

To learn more about the different types of Tailored products, read the full article here.

TEASER!:  A future post will highlight how these tailored products are applied to press hardening steels to create a single component having strength levels tuned to the needs of each segment of the body structure. Stay tuned!

More Reveals of the Steel E-Motive Autonomous Vehicle Demonstration

More Reveals of the Steel E-Motive Autonomous Vehicle Demonstration

WorldAutoSteel has a 30-year legacy of steel demonstration all the way back to the Ultra-Light Steel Auto Body (ULSAB), whose engineering report is still being downloaded from our worldautosteel.org site today. The one you may remember best is the FutureSteelVehicle (FSV), results of which we launched in 2011. FSV demonstrated steel innovation for not only Battery Electric vehicles (BEV) but also Fuel Cell vehicles (FCV). Steel E-Motive is the sixth of our global steel industry programs.

So Why Mobility as a Service?

The Automotive sector is undergoing the most rapid change in 40 years. This transformation shifts our thinking – from the movement of vehicles to the efficient movement of people and goods. Over the past eight years, we have conducted extensive research into global trends such as urbanization, transport emissions reduction, as well as the waning interest in vehicle ownership among the young and old. This is especially prevalent in megacities characterized by pollution, congestion, limited parking and enormous ownership costs. Our research concluded that mobility as a service (MaaS) will grow exponentially in high population areas and would place a significant challenge on vehicle design and manufacturing. Therefore, we needed to make sure we as an industry were active and visible in providing STEEL solutions in this new market place.

Steel E-Motive will demonstrate the benefits of steel, linking the properties of the material to the required architectures and attributes for MaaS vehicles.

This program will demonstrate the benefits of steel, linking the properties of the material to the required architectures and attributes for MaaS vehicles. It connects us with original equipment manufacturers (OEMs) and future mobility providers (FMPs), reinforcing steel’s advantages in strength, durability, sustainability and affordability.

An autonomous BEV structure aligns perfectly with steel’s best attributes, however most new concepts trial alternative materials. The global steel industry is investing significantly in product and fabrication development to continually prepare for the next challenge. High Strength and Advanced High-Strength Steel (AHSS) portfolios have grown from the 11 highlighted in the ULSAB program, to more than 60 grades available for use in designing and optimizing Steel E-Motive’s autonomous BEV architecture. Third Generation AHSS (3rd Gen AHSS) will have a prominent role in Steel E-Motive’s body-in-white, taking strength levels ever higher while improving manufacturability. And our industry continues to evolve Press Hardened Steels (PHS) with strength levels upwards of 2000 MPa.

Finally, efficient fabrication processes such as roll stamping, press hardening, and hydroforming use less steel and therefore contribute lower vehicle production emissions. These are the details being highlighted in Steel E-Motive, where we hope to demonstrate that only Steel can make it Real.

Steel E-Motive: A game changing, world first?

Many OEM’s and mobility service providers follow the typical vehicle development process where they adapt an existing vehicle structure to the new vehicle requirements. We don’t have that in Steel E-Motive We believe Steel E-Motive is one of the world’s firsts.

  • The first for a Level 5 autonomous vehicle that is compliant with global high-speed crash requirements.
  • The first autonomous vehicle to be a conventional high-volume stamped steel body construction, creating an affordable platform for the mobility service provider.
  • First to offer a competitive, robust, and sustainable MaaS solution.

For engineers, being first is very exciting but a little nerve wracking – there are no benchmarks out there. There is less to “hang on to.”  We’re on our own. Target setting is more challenging; we are the benchmark. Time will tell if we make it to the automotive hall of fame.

We are producing concepts for two BEVs based on a single modular platform.  SEM1 (Figure 1) is a front-wheel drive short wheelbase urban version for inter-city travel for four passengers. It has a compact design and vehicle footprint, comparable in footprint to a European B/C segment size. SEM2 (Figure 2) is an all-wheel drive, long wheelbase extra urban version designed to carry up to six passengers. It has an adaptable interior volume that can result in additional luggage capacity compared to SEM1.

Figure 1: SEM1 Vehicle Specifications

Figure 1: SEM1 Vehicle Specifications  (© WorldAutoSteel 2022)

 

Figure 2: SEM2 Vehicle Specifications

Figure 2: SEM2 Vehicle Specifications (© WorldAutoSteel 2022)

 

Body in White Steel Usage

Steel E-Motive benefits from a broad portfolio of steel grades and fabrication process, as identified by our member steel experts. The design is nearly finalized, and material selections are being evaluated against various performance targets with the representative structure shown in Figure 3 with high PHS usage at this stage in the design (as of May 2022). This is mainly driven by the safety requirements. Steel E-Motive BIW steel and steel technologies include:

  • Right steel grade in the right place
  • Significant proportion of >1500MPa grades, primarily for occupant and battery intrusion zones
  • Mixture of stamped, roll formed, roll stamped, press hardened steel and hydroformed parts
  • Spotweld, laser weld and structural adhesive

Figure 3: Steel E-Motive’s Body-in-White Steel usage as of May 2022. (© WorldAutoSteel 2022)

 

At the Core of the Steel E-Motive Concept Is an Innovative Battery Design

Figure 4 shows Steel E-Motive’s battery frame design’s construction:

  • Battery modules and cooling plates are mounted to an AHSS carrier frame (off-line).
  • The carrier frame is mounted to the body structure (in general assembly).
  • The BIW floor acts as the top cover and provides sealing.
  • The AHSS bottom cover plate provides impact protection.

This design provides significant cost and weight savings, as well as improved NVH. This extremely efficient package does not compromise safety and enables a flat floor with a lower step-in height.

Figure 4:  Steel E-Motive Battery package assembly. (© WorldAutoSteel 2022)

 

Competitive Body Stiffness with an Open B-Pillarless Body Structure

With clean sheet design, and generally less package constraints in a Level 5 vehicle, our design teams have had more freedom to engineer and optimize the crash and stiffness structural loadpaths. We used topology, optimization, and Virtual Reality tools to determine the most efficient structural loadpaths (Figure 5). The results informed the joint designs and enabled optimization of the joining and structural adhesives. These steps and the advantage of steel’s high modulus resulted in impressive performance.

Figure 4: Topology Load Path Optimization

Figure 5: Topology Load Path Optimization. (© WorldAutoSteel 2022)

 

The approach for achieving body stiffness was as follows. Results are shown in Figure 6 following.

  • Topology load path optimization
  • Appropriate section size, profiles, part integration and flange / joint design
  • Strut towers integrated with key body members, such as A-pillars, vertical dash brace
  • Contribution from structural battery frame and battery cover closing, roof structure trusses
  • Rigidly connected front and rear subframes
  • Optimized joining and use of structural adhesives
  • Capitalizing on the Inherent high modulus of steel

Figure 6: SEM Torsional Rigidity animation. (© WorldAutoSteel 2022)
Static torsional stiffness 38,000Nm/deg
Global trimmed BIW modes >28Hz
Local attachment static stiffness ten times bushing stiffness

Front Crash Structure Engineered to Balance the Requirements of 56kph USNCAP FFB, IIHS ODB, IIHS SORB and EuroNCAP MPDB Load cases

One of the most challenging aspects of the Steel E-Motive program has been achieving the front crash performance that minimizes occupant injury. The challenge has been compounded by the overall compact size of the vehicle and the short front overhang dimensions, meaning less space to manage and balance the required crush energy with intrusion resistance.

For the IIHS 25% Small Overlap test, we worked from the outset to achieve a barrier “glance off.” The goal is to deflect the vehicle off the barrier by the time the barrier reaches the hinge pillar. This results in a reduced amount of vehicle kinetic energy converted to crush energy. The vehicle continues after the impact with some onward velocity and kinetic energy. This strategy results in reduced intrusion to the passenger compartment and a much lower vehicle pulse (below 20g), which translates into lower occupant injury. We are very excited by this outcome, as in our benchmarking we have not seen many (if any) vehicles of this size managing to achieve a glance off for this test. Figures 7 and the bullets following provide a look at the results.

Figure 7: IIHS 25% Small Overlap test. (© WorldAutoSteel 2022)

  • IIHS “good” rating achieved (based on predicted intrusions).
  • Our strategy for IIHS Small Overlap test was to achieve a “glance off” the barrier, which is a significant challenge given the vehicle’s short front overhang.
  • Front suspension engineered to detach on impact. This is important for achieving glance off.
  • Glance off results in some continued onward vehicle velocity after the impact.
  • This results in reduced crush energy, lower vehicle pulse and intrusions = enhanced occupant protection

 

Figure 8 points out features of the front crash structure. Most of the crush energy in FFB and ODB is absorbed by conventional longitudinal mid-rails, which are made of cold stamped, tailor welded blank Dual Phase steels. The plan view angle of the longitudinals has been optimized to provide load reaction early in the SORB event while remaining largely inside of the SORB barrier.

Front crash structure engineered to balance the requirements of 56kph USNCAP FFB, IIHS ODB, IIHS SORB and EuroNCAP MPDB load cases.

Figure 8: Front crash structure engineered to balance the requirements of 56kph USNCAP FFB, IIHS ODB, IIHS SORB and EuroNCAP MPDB load cases. (© WorldAutoSteel 2022)

 

Following in Figures 9 and 10 are animations of the FFB results:

Figure 9: USNCAP 56kph Rigid Barrier – Top View. (© WorldAutoSteel 2022)
Figure 10:  USNCAP 56kph Rigid Barrier – Side View. (© WorldAutoSteel 2022)

 

MaaS vehicles will need to accommodate quick ingress and egress as well as provide comfort and safety for the occupants. Consequently, we have flipped the front occupant around to a rear facing configuration and provided a B-Pillarless wide door aperture to enable comfortable and quick access for passengers. This changes the approach required for occupant protection in a front crash. Effectively we are dealing with a high-speed rear impact situation for the occupant. Current rear impact tests cover lower speed rear end shunts. Figure 11 notes the key points and challenges that Steel E-Motive is designed to meet.

Different approach and considerations are required for the protection of rear facing front occupants. We are effectively dealing with a high speed rear impact event

Figure 11: Different approach and considerations are required for the protection of rear facing front occupants. We are effectively addressing a high-speed rear impact event.  (© WorldAutoSteel 2022)

 

Side Crash Structure Consists of Absorption and Intrusion Prevention Zones, Compensating for Large Body Aperture

The side structure includes roll-stamped martensitic door waist rail beams and a one-piece Tailor Welded Blank, Press Hardened Steel door ring outer. A- and C-pillars in line with occupants provide good side impact protection. (You can learn more about the door design in our May blog).

In the section AA schematic in Figure 12 the TRIP690 hydroformed tube interlocking door B-pillar is shown (wrapped over the rocker and cantrail). The load travels through the side impact crush “hex” beam, which is a two-piece roll formed DP590 component.

SIDE CRASH STRUCTURE CONSISTS OF ABSORPTION AND INTRUSION PREVENTION ZONES, COMPENSATING FOR LARGE BODY APERTURE

Figure 12: Side crash structure consists of absorption and intrusion prevention zones, compensating for large body aperture. (© WorldAutoSteel 2022)

 

 

Steel E-Motive Design Demonstrates Good Side Crashworthiness and Good Levels of Occupant and Battery Protection

In addition to occupant protection tests, additional side impact load cases have been simulated to ensure optimal battery protection. The design maintains a less than 30 mm clearance to the battery.

In reviewing the design according to IIHS standards and based on the predicted intrusions, we are confident this vehicle would achieve an IIHS “good” rating.  See Figures 13 and 14 following:

Figure 13: USNCAP 32kph side pole (battery protection). (© WorldAutoSteel 2022)
In addition to occupant protection test, additional side pole load cases to ensure battery protection
>30mm clearance to battery maintained

 

Figure 14: IIHS 60kph side barrier II (occupant protection). (© WorldAutoSteel 2022)
IIHS “good” rating (based on predicted intrusions).

 

Total Cost of Ownership: Vehicle and Body Is Designed for Conventional Fabrication and Assembly Processes

The Steel E-Motive body has been designed with low cost in mind to provide the foundation for a lower total cost of ownership for fleet owners. The steel body design is optimized to maximize material utilization and minimize scrap rate. Steel E-Motive is suitable for >250,000 units/year production and is compatible with existing global automotive manufacturing facilities using conventional press and fabrication tools. We are also using Life Cycle Assessment as an integral part of the engineering process to ensure that Steel E-Motive is responsible for the lowest possible emissions throughout its entire life cycle. We will report on environmental performance and sustainability as a part of our final results.

Steel E-Motive Key Outcomes

The Steel E-Motive program is delivering an exciting futuristic vehicle, optimized from the ground up for autonomous MaaS application. We are addressing key challenges through careful design, application of simulation tools and efficient use of the latest Advanced High-Strength Steels and fabrication processes. Steel’s inherent characteristics of low production emissions, lightweighting capabilities for mass efficiency, infinite recyclability and product durability underscores its suitability as an integral part of stakeholder strategies to offer sustainable mobility solutions, today and in the future.

Be sure to follow us on our journey as we enter our final months of design, engineering and reporting by subscribing at the Steel E-Motive website. We welcome your questions about this program using the Comment box below.

 

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