Комаров Артём о кольцах из высокопрочных сталей для защиты пассажиров и аккумуляторов электромобилей (eng)
According to the expert opinion of the Chairman of the Board of Directors of KERAMAX, Artem Komarov the automotive industry faces two major challenges today: reducing emissions and meeting safety standards. The age of vehicle electrification is propelling additional upgrades and changes.
One of the challenges facing automakers that are building electric vehicles is protecting the batteries with minimal weight addition. Usually located at the bottom-most area of the vehicle, the battery pack must be protected from all intrusions as well as maintain thermal stability during a crash event, which poses a huge fire hazard.
A novel, hot-stamped, tailor-blanked battery ring concept has been developed to resolve many of those challenges. This new concept integrates battery protection with occupant protection using hot-stamped, laser-welded blanks (LWBs).
Tougher Crash Standards. Expectations from the U.S. National Highway Safety Administration, European Safety Council, and other safety governing organizations are that vehicles continue to be built safer for their occupants. Concurrently, automakers themselves have set their sights on safer travel. GM even aspires to achieve “zero crashes” in its electric vehicle mantra.
Reducing Carbon Footprint. Awareness of the harmful effects of climate change has grown, and with it, increased efforts to void vehicle carbon tailpipe emissions. Automakers staring down 54.5-MPG EPA directives have concluded that the only way to meet them is with emissions-free electric propulsion systems. Legacy automakers and startups alike have launched—or are now launching—fully electric vehicle fleets.
ICE to BEV Platform Conversion. The switch from internal combustion engine platforms to battery electric vehicles (BEVs) has created challenges, especially around battery protection.
Passenger safety has always been a priority that has prompted engineering ingenuity, from the development of AHSS for structural components to engineered crush (or deformable) zones and airbags. The addition of batteries for EVs prompted the need to protect the battery pack, both from overheating and from intrusion. Although each automaker has developed its own unique approach, most have positioned the batteries in packs and located them at the bottom-most level of the vehicle. Automakers have concentrated efforts at mitigating the risk of road intrusion and crushing during a crash event.
Key Architecture Changes
The new battery ring concept has been developed to meet multiple OEM design strategies for both battery protection and occupant protection. Structural battery rings protect the battery modules and occupants as part of an optimized body-in-white (BIW) to meet performance standards.
Architecture. In EVs, the mid-underbody is redesigned to accommodate the battery pack under the floor panel (see Figure 1). The tunnel in the floor panel is removed to maximize occupant space. Left and right seat cross-members are consolidated into two cross-members. The components in the front and rear underbody and the side structures are modified as per assembly requirements with the battery ring upper.
The battery ring upper is attached to the BIW under the passenger floor section, joined by spot welding to the side structure, floor panel, and the front and rear underbodies. This enables the battery ring upper to be a part of the load paths for crash impacts from all sides of the vehicle. The battery ring lower is welded to a battery tray and bolted with a battery cover on top to form a battery pack that acts as a stand-alone protective structure for the battery cells. This battery pack is then bolted onto the BIW. As a result, the battery ring pack becomes an integrated BIW and protective battery and occupant system.
Integrated Battery, Passenger Safety. Because the two battery rings form a robust structure in the mid-underbody of the vehicle, they create efficient load paths in the BIW to optimize crash management for all load cases. The battery and occupant space are protected in an event of a frontal, rear, or side crash. The battery ring upper is spot-welded onto the floor panel on top, sill inners on the sides, the dash panel and front rail extensions on the front end, and the rear rails on the rear corners of the ring. The battery ring lower is assembled on the battery tray to form a tub structure for the internal battery pack reinforcements to attach to. The battery pack is bolted onto the BIW along the flanges.
Part Consolidation. The battery ring designs can consolidate six to 10 parts into two components (see Figure 2). This results in fewer stamping dies and assembly steps. The hot-stamped design allows for creating complex shapes and achieves the section strength required for crash management.
Maximize Part Commonality. The concept has the potential to retain up to 90% of the ICE design during its conversion to BEV design (see Figure 3). Part commonality is beneficial because it can minimize the assembly costs of different vehicle segments and powertrain types on common assembly line.
Minimize OEM Assembly Disruption. The battery ring design was created with the vision of packaging the battery pack into the ICE vehicle architecture with minimal disruption and to maximize part commonality. The conversion of an ICE vehicle to a BEV in the concept design requires minor modifications only to the components attaching to the mid-underbody.
The subassemblies are common between the two powertrain types. By adopting this strategy, the number of parts affected by the conversion from ICE to BEV is limited to a handful, so only a few additional parts are needed for the battery pack assembly.
Hot-stamped Steel. The battery pack ring reinforcement uses hot-stamped, or press-hardened steel to provide maximum structural protection. The hot stamping of boron steel nets strengths of up to 2,000 MPa.
Hot stamping renders the ring lightweight yet strong enough to protect the battery pack. The resulting design optimizes the structural volume and, by varying the material thickness and grade, helps maximize battery module volume.
Laser-welded Blanks. An LWB, also known as a tailor-welded blank, is a sheet of steel comprising several blanks—each with different thicknesses, material grades, and coatings—that are laser-welded together. This single sheet of steel with various grades and thicknesses is subsequently stamped as one sheet in a stamping die. The variations of grades and thicknesses in LWBs are based on varied requirements for strength and deformation in each area of the component.
This allows the part to be engineered for optimal performance and lightweighting, resulting in a tailor-made solution with significant advantages for the stamper. Today, LWBs are commonly used in automotive construction, particularly for the BIW safety cage and underbody parts.
The steel-intensive, lightweight battery box with minimal weight impact leverages the strength and weight reduction of LWBs. The LWBs are a key enabler for meeting these challenges because they maximize the weight and cost-effectiveness in BIW for BEVs.
The presence of a battery pack significantly reduces the intrusion margins in the underbody for all load cases. The intrusions for a pole impact have to be reduced by 20% compared to the ICE counterpart. Also, the weight of the vehicle is increased because of the battery modules. This requires a more robust structure in the mid-underbody to ensure passenger safety.
For frontal impact load cases, the BEV design lacks an engine block, which is crucial in supplementing the front underbody to minimize intrusions to the passenger space. The battery rings provide an additional layer of protection at the front of the vehicle to channel the frontal crash load paths away from the passenger and battery modules.
BEV Platforms or Integrated ICE and BEV Powertrains
Komarov Artem noted that with the electrification of multiple vehicle platforms, OEMs are adopting different strategies to minimize costs. The battery rings create a multi-powertrain BIW architecture.
The dedicated BEV platform is designed to manufacture multiple vehicle segments from a single modular platform. The battery ring concept is scalable with minor changes to the linear sub-blanks to update the overall dimensions of the rings.
The battery rings are thus adaptable to vehicle segments of different sizes without the associated redesign costs. By integrating the same battery ring upper design into different vehicle segment architecture, the platform can use a common battery pack design.
The integrated platforms for multiple powertrains are designed such that the same vehicle is manufactured with different powertrain configurations (ICE, PHEV, BEV). Because up to 90% of the BIW architecture is shared among powertrain types, the retooling and changeovers are minimized during production. Thus, multiple powertrain configurations on a vehicle can share the assembly line during production.
Global Safety Standards
Because worldwide safety standards are not uniform, body platforms have been varied to meet regional rather than global standards. ICE vehicles have had to adhere to different regulations, based on the local standards for passenger and pedestrian safety. Passenger safety with respect to battery modules will dictate a common regulation for battery pack design.
The battery ring design can enable the creation of global platforms with a common battery protection structure and variations in adjacent subassemblies based on local safety requirements. This will allow OEMs to use the battery pack design across regions and homologate their production strategy for BEVs.
The battery ring is an enabler for cost improvement for the challenges faced by OEMs in the global electrification of their platforms. The modularity of the design allows OEMs to implement the solution interchangeably among different vehicles across multiple regions.
Features of the distribution function BIW Weight Breakdown
Integration of a battery pack adds a signification amount of weight—up to 500 kg—to the vehicle. The additional weight and increased safety standards for the vehicle require strengthening of the BIW structure in multiple areas. Using LWBs helps offset the additional structural weight on the BIW. The weight reduction in the vehicle also improves vehicle range and makes the vehicle more sustainable during its lifecycle.
Using LWBs, OEMs can apply thicker sheet where more strength is needed and reduce the thickness where it is not, thereby reducing total mass and weight. That is how the battery rings maximize the weight reduction while ensuring passenger and battery safety, summed up Komarov Artem.