Past GDIS™ Presentations

Electric vehicles came to market demonstrating new technologies and new challenges for OEMs and their suppliers. A significant focus of current research and development has been related to the cells’ chemistry, which is improving at a fast pace. In addition to this, new requirements regarding safety and performance are demanded which causes the battery tray to constantly evolve. In this direction, Gestamp defines an innovative steel battery box solution, which can be applied in a wide range of electric vehicle segments.

Four basic requirements have been established for this revolutionary system: High energy capacity, stampings with high formability, simplified assembly process and high safety performance. These four pillars were used to develop the first cell-to-pack concept. The cross members were deleted, allowing more space for additional cells. The enclosures were redesigned taking advantage of extra deep drawing steel alloys. The joining technologies were selected taking into account the process energy input to decrease final distortion and improve final assembly quality.

The new Gestamp steel battery box design achieved an energy storage increase of 15% using the same exterior packaging. Components have simple geometries with a high degree of manufacturability. The body and battery housing work as a holistic system resulting in a high crash performance, lighter weight solution.

With the rapid growth of electric vehicle (EV) market, overall battery safety becomes more and more important. One of the most challenging tasks is to minimize the intrusion to battery enclosure during the crash under side impact load. Rocker and rocker reinforcement are critical for the strength of the local periphery area to absorb lateral load. In this study, a vertical stacked-up steel tube design (CVST) is proposed for the rocker reinforcement, using steel grades of 1500 and 1200 MPa. Its performance is evaluated against a comparable aluminum extrusion design. With mass parity, the CVST design achieves better performance in peak force in three points bending analysis. Its advantages in cost of the simple steel tube design as well as the greenhouse gas emissions versus extruded aluminum solutions are assessed.

Ideal proportional loading conditions with linear strain paths are rarely encountered in automotive forming and fracture applications. Despite this, the majority of forming and fracture models such as forming limit curves and phenomenological fracture surfaces have been proposed under the assumption of linear strain paths. In the present study, the influence of nonlinear strain paths on the fracture behavior of DP1180 automotive steel was experimentally investigated. The DP1180 was subjected to bilinear strain histories with the first path being proportional in-plane stretching in uniaxial, plane strain and equal-biaxial conditions. Fracture coupons were then extracted and tested for the second loading stage from shear to biaxial tension. The experimental data was then used to evaluate popular phenomenological fracture modes used in industry and academia such as the Johnson-Cook and GISSMO damage models. It is shown that phenomenological fracture models that employ strain-based damage indicators can result in significant errors in non-linear strain paths. An alternate modelling approach is proposed by defining a stress-based “fracture potential” that can be calibrated with proportional test data and does require a phenomenological damage model for non-linear loading. Finally, recommendations and best-practices are discussed to minimize the testing required to characterize the constitutive and fracture behavior for crash applications.

OEMs are rapidly moving toward electrification of their vehicle fleets. This powertrain transition from internal-combustion engine (ICE) to battery electric vehicles (BEV) present a significant opportunity for steel, particularly with battery enclosures. While many OEMs actively consider steel battery enclosures for smaller mass-market vehicles, they have tended to use aluminum enclosures for larger platforms. The preference for aluminum may be attributed to the need for lightweighting, non-availability of efficient steel designs for benchmarking, short program times for detailed design, and lack of lightweight designs being developed and promoted by tier suppliers.
ArcelorMittal has developed a family of steel battery enclosure solutions to address the specific and varied needs of our automotive customers. These solutions combine innovative design along with the judicious use of the steel grades available from ArcelorMittal. Some options include:

1. Module cooling via an external steel cooling structure attached to the bottom of the tray.
2. Cold stamped and roll formed concepts that take advantage of 1300Y1500T steel grades to maximize weight reduction.
3. A concept with a single piece, press hardenable steel (PHS) inner structure to minimize part count.

All solutions are engineered to meet commonly specified OEM requirements for side crush and natural frequency. Manufacturing and assembly feasibility assessments are undertaken for all designs to ensure the viability of the solutions.

Automotive manufacturers are moving rapidly towards producing battery electric vehicles (BEV) in an effort towards a clean and sustainable future. Electrification introduces flexibility into vehicle architecture by adapting to an updated powertrain while reimagining the vehicle structure.

OEMs are moving towards high volume production of BEVs. Alternative materials like aluminum, magnesium and composites are good choices for low volumes but are not ideal for high production volumes. For managing economics of scale, cost optimization is critical. To optimize investment, OEMs are simplifying assembly by reducing assembly steps using so-called mega structures. Our steel laser welded Multi Part Integration™ (MPI) concepts are excellent solutions to meet these challenges.

Laser welded blank (LWB) technology is a proven solution enabling performance improvement, part consolidation, and weight optimization in vehicles. Additionally, cost improvement, modularity, and sustainable steel use make LWBs an ideal solution to battery electric vehicles (BEV) architectural challenges.

ArcelorMittal Tailored Blanks (AMTB) will showcase our next generation of MPI battery pack concept in steel that enable re-designing of the vehicle architecture surrounding the passenger and battery space. Our design concept enables cell-to-body integration, which can make the battery pack modular with a reduced part count by potentially eliminating the floor and provide additional rigidity to the cabin space. The concept has been developed to provide an answer to the sealing challenges that OEMs face when it comes to a modular battery pack. An upper and lower LWB clam shell design helps seal the battery modules while managing crash loads using press hardened steel.

Our presentation intends to make a strong case for steel-based architectures using MPI designs which are key enablers in weight reduction, cost improvement, performance optimization and reducing assembly complexity, cost and time while improving sustainability of future BEV designs.

As the automotive sector moves further into electrification, overall vehicle mass increases due to battery content and long-range expectations. The IIHS 2.0 Side Impact event is of particular interest, as the impact barrier’s mass and speed has increased. The body structure must manage higher levels of energy, ensuring vehicle crash worthiness, occupant safety and battery integrity.

Gestamp utilizes extreme-size stamping strategies to address higher impact energy levels. Benefits include part count reduction, reduced vehicle build time/complexity, green steel attributes and recyclability. Gestamp uses a holistic approach to vehicle energy management, addressing the impact event in stages with the body structure. Although all impact events are critical, the side impact is one Gestamp has a great deal of experience with, providing many innovative solutions. Gestamp’s focus today is how to best use the steel door Ring and sill/rocker structure to manage the IIHS 2.0 Side Impact event, while protecting the occupant and battery enclosure.

Gestamp’s OLPB Door Ring and Wave Rocker innovations offer a high strength low-cost solution to the energy management challenge. The OLPB Door Ring, comprised of spot-welded blanks prior to hot stamping, offers (~7-10%) cost savings over traditional architectures while reducing mass, part count and plant complexity. The Steel Wave Rocker is made from either Press Hard or Hydroformed Steel, and absorbs maximum energy in a compact environment to prevent intrusion into the battery enclosure.

Design and manufacturing of modern electric vehicle (EV) battery trays currently don’t follow a uniform standard and features a variety of different requirements, materials and joining technologies.
While one design is based on extruded aluminum profiles, other models use higher-strength steel alloys. Some battery boxes can be replaced frequently for recharging; others remain in the vehicle for the long term. In any case, the connection between the battery tray and the car body is not only exposed to mechanical stresses with every movement, but must also be corrosion-resistant over the long term and waterproof even under cyclic loads.
This presentation illustrates the requirements for fasteners, particularly in the application of battery trays, and how their performance can be proven and verified. The relevant simulation, testing and measurement methods are explained and presented with practical examples of different designs made from extruded profiles and higher-strength steels.

Sumitomo Heavy Industries developed a new press forming technology Steel Tube Air Forming (STAF) for forming Body-in-White (BIW) parts such as A-pillar reinf., bumper reinf., side frame and so on. The concept of STAF is concentrated on maximum weight reduction and reduction of manufacturing cost with a single process. In the STAF process, a steel tube is processed through “a single step” in the tooling of press machinery. A steel tube is jouel heated (high-speed), air-formed and hardened.

STAF-formed parts have characteristic appearance with optimally designed flanges, TS over 1500 MPa, and continuously varied closed cross-section structure. First of all, STAF-formed parts can significantly improve basic performance against conventional hot-stamped parts due to its closed and flanged geometry. Sumitomo can expect weight reduction by around 30%. More than anything, the most unique part of the process is forming various flanges, which can integrate surrounding parts into STAF, improve joining and enhance performance. STAF’s flanges dramatically reduces part count, thereby reducing manufacturing costs and tooling investments. Furthermore, we puts a compact jouel heating device into practical use, replacing the conventional large heating furnace. The heating process will bring not only super power-saving but significantly reduces CO2 emissions from equipment.

As described above, STAF is the latest technology that can drastically improve performance and reduce weight and manufacturing costs.