Past GDIS Presentations
Past GDIS Presentations
Jill Fuel discussed the 2022 Honda Civic (North American Car of the Year).
Jason Lyman and Weston Lawson discussed the 2021 Nissan Rogue.
Steel E-Motive: Development of advanced high-strength steel (AHHS) body structure for a new, fully autonomous Mobility as a Service (MaaS) vehicle.
Autonomous vehicle technologies opens up the possibilities for a significant growth in MaaS and ride sharing transportation. This paper details the development of a new body structure design for a Level 5 fully autonomous vehicle, using the latest Advanced High-Strength Steel grades and fabrication processes. The vehicle concept was created within the Steel E-Motive project, a collaboration between WorldAutoSteel and Ricardo. The vehicle has been designed with the new mode of transport in mind, with a strong focus on the user, the fleet operator and the vehicle’s operating environment. A change from human to fully autonomous vehicles removes the requirement for driver interfaces and controls and enables occupants to be seated in unconventional locations and orientations. Legislative requirements such as driver vision and obscuration are also removed, which opens up further freedoms such as the ability to place structure in existing glazed areas. These freedoms have enabled the creation of a unique and spacious transportation environment, whilst being compact in size and agile around city center. The vehicle is designed to be compliant with global high-speed crash and safety requirements and with occupants positioned in unique positions and orientations, a revised approach to the crash load management and occupant protection is required. This paper details the design of the Steel E-motive vehicle and body structure, the steel grades and technologies used and the performance achieved.
Kate Namola discussed Toyota Motor NA’s weldability investigation of 3rd Gen AHSS for automotive manufacturing. Presentation not available.
Most automotive companies have public-facing goals to improve the sustainability performance of their companies and products due to drivers from government, investors, non-profits organizations, and customers. For example, Ford has a goal of becoming “carbon neutral globally by 2050” [1]. GM’s vision is “zero crashes, zero emissions and zero congestion” and has a published goal to “Strive for at least 50% sustainable material content in our vehicles by 2030” [2]. Companies increasingly recognize that meeting their goals will entail assessing and reducing the impacts of their supply chains, including the production of automotive materials, like steel, aluminum, and plastics. However, given that the sustainability movement and associated frameworks are rapidly evolving, they may not know where to start or focus. Furthermore, there can be confusion around emerging sustainability topics, like decarbonization, Scope 1, 2, and 3 greenhouse gas emissions, Science-based Targets, net zero, carbon neutrality, and life cycle assessment. This presentation strives to provide clarity about key sustainability concepts, trends relevant to the automotive market, and the role of material suppliers. As steel is the largest share by weight in today’s vehicles, the steel industry has a key role to play in an automotive company’s strategy. The American steel industry has been striving to reduce impacts for decades and is actively working on strategies to not only reduce its own impacts, but also to further improve the environmental performance of steel products. This presentation will also provide details on the American steel industry’s sustainability performance and the path ahead on sustainability.
[1] https://corporate.ford.com/microsites/fordtrends/sustaining-sustainability.html
[2] https://www.gmsustainability.com/esg-management/goals-and-progress.html
For 30 years, TWB has been expanding technology and capability to meet the growing demands for lightweighting and improved crashworthiness. Starting in 1992, the first tailored blanks produced were common grades, only changing the thicknesses across the blanks, these components were doors and bodysides, driven by requirements on material savings and part consolidation.
Over time, with customers and regulations demanding safer and more fuel-efficient vehicles, many advancements in material grades, joining and manufacturing processes have occurred. The presentation will focus on the newest developments in tailor welded blanks and how they advance the adoption of advanced high-strength steel (AHSS).
Today, welded blanks in light duty frames have allowed for the cost-effective utilization of AHSS to meet crash energy management and performance goals, while offering a lighter weight alternative. New unique welded blank applications have been applied in battery electric vehicles to enable efficient steel designs. AHSS grades account for many of the welded blanks produced today, commonly joined to other AHSS grades or HSLA grades. Recent work has been completed to demonstrate future welded blank applications can include 3rd Gen steels. And finally, the HotWire+ process is now in production, which eliminates the ablation requirement when welding AlSi coated PHS.
The past 30 years of TWB have been full of milestone developments providing increased value to the OEM and the customer, the next years are projected to be as full of innovation as the last, with TWB positioned to provide tailor welded solutions for the vehicles of the future.
OEMs are challenged with securing the battery cells/modules (energy storage) within the BEV in a safe and cost-efficient manner. The energy storage components must be protected from a multitude of crash and impact scenarios as well as extreme environmental exposure and do so in a cost and package efficient manner. KATCON, a Leading Global Tier 1 Supplier of Automotive Exhaust System Components, recognized the opportunities and threats that the emerging BEV market presents. Together with their partner, Forward Engineering, the team set out to develop a new family of Cost Effective, Flexible, Scalable HV Battery Enclosure Solutions.
In this presentation, the team will share the results of this fast-track development process. Starting with a clean sheet of paper and the latest and most stringent OEM Technical and Global Regulatory Requirements, the team has developed a Multi Material HV Battery Enclosure (MMBE) design which is lighter and more cost effective than incumbent aluminum designs. Key to the outstanding crash performance and cost effectiveness of this new MMBE design was the smart application of a variety of high-performance Advanced and Ultra High Strength Steel Alloys and cost-efficient forming technologies. The team from ArcelorMittal played an important role in alloy selection as well as joining and forming technologies. This innovative design outperforms the incumbent design at a projected 26% mass savings and 14-16% cost savings.
The development of the 3rd Generation of advanced high-strength steels (AHSS) has opened new avenues for the product design of automotive lightweight components but the methodologies to fully exploit their superior mechanical properties have been lagging behind. The traditional in-plane forming limit curve (FLC) remains the standard engineering tool for formability assessment and leads to an overly conservative product design. The present study provides insight into the effect of tool contact pressure in three-point bend simulations that served for the development of a novel instability framework to capture the delay in material localization. It is demonstrated that both the magnitude and the boundary condition of how the contact pressure is applied governs the formability gain. An analytical-numerical stretch-bend model was developed which successfully captures the increase in the forming limit strains studied in Marciniak, Nakazima, stretch-bend and V-bend tests of a 3rd Gen AHSS with a nominal tensile strength of 1180 MPa. Application to a structural B-Pillar technology demonstrator correlates well with the forming trials and identifies false positives which were erroneously flagged for splitting when relying on the conventional FLC.
Note: This talk is part of to the AISI Automotive Program Project
Advanced high-strength steel (AHSS) is often illustrated in the Steel Strength-Ductility Diagram. Both academia and industry frequently refer to such a diagram to not only concisely categorize the evolving AHSS generations but also to direct the future development objectives. Nevertheless, with various new AHSS developed in recent years, the diagram is considered too simplified to represent the sophisticated tensile properties of these AHSS in the practical applications: that is, the experimental data are typically characterized at a quasi-static uniaxial strain rate at room temperature. The present work focuses on investigating how the temperature and strain rate affect the tensile properties of AHSS and correspondingly shift their distributions in the diagram. The target AHSS includes two dual phase (DP) steels, two quenched and partitioned (Q&P) steels and two austenitic steels. The results illustrate in the diagram how diverse the temperature and strain-rate dependencies of different AHSS can be. Concisely, with the temperature rising by either the external or the adiabatic heating, the Q&P and DP steels exhibit their tensile properties varying from a valley to a peak, while the two austenitic steels behave monotonic property trajectories towards two different directions. Furthermore, behind every turning of the property trajectories, there are multiple instantaneous effects, either favoring or opposing, acting together to determine how the materials behave at that moment. Particularly, the Q&P steels can be affected by the evolving thermal softening, dynamic strain aging, and transformation-induced plasticity (TRIP) effects during different temperature and strain rate ranges. Further understanding of the inter-relationship between strain rate, temperature, and material behavior, including the TRIP-effect reactivation, offer future paths to further optimization of AHSS designs for automotive applications.
In sheet metal forming simulations, a material card refers to a data-file that has, at minimum, information about hardening curve, yield locus, and fracture criteria. Depending on the requirements, a material card may have information about strain rate sensitivity, unloading modulus variation, the transient Bauschinger effect and permanent softening (as described by Yoshida and Uemori), and edge crack sensitivity. In addition to the “material card”, more information about the process can be included in the simulation: friction between the sheet and the tool as a function of sliding velocity, pressure, temperature; press kinematics, elastic deflection of the tooling and the press.
Each additional data-set will require time and expense. In this paper, the authors introduce “multi-level” material cards for different phases of sheet metal forming process developments. The idea is proven with stamping experiments using a 3rd Generation Advanced High-Strength Steel (AHSS).
The goal of this study is to understand the performance of additively manufactured (AM) die inserts in stamping applications. Stamping of 50,000 symmetrical U-bend parts made from 1 mm thick Dual Phase 980 sheet steel was performed in a progressive die with one side of the tool fabricated from Maraging Steel AM material and the other side fabricated from conventional D2 tool steel. The additive manufactured material was fabricated using laser powder bed fusion with Maraging Steel powder. All tested inserts were coated with IB90 PVD coating.
Both inserts produced quality stampings, with no significant visual artifacts. Likewise, no significant scratches were found on either insert. On the D2 side more hairlike flow lines were visible, but no deeper scratches. The D2 insert has more wear in the area close to the die entry radius, which resulted in shallow scratches on the samples’ surface.
The AM insert has deeper and wider scratches in the general contact zone (horizontal surface of the insert), but produced samples having better surface quality since this insert has less wear in the area close to the die entry radius. These results indicate that AM produced inserts have strong potential to be employed in die components for stamping of High Strength Steels.
Liquid metal embrittlement (LME) cracking during resistance spot welding (RSW) is a challenge restricting the application of zinc coated 3rd Gen AHSS in automotive structural components. From a production perspective, the potential for LME cracking in a spot weld has two related aspects, first is the steel’s susceptibility to LME cracking and the second is whether LME will manifest during RSW. The Auto/Steel Partnership (A/SP) has developed a test methodology to assess the LME susceptibility of steels using a production-like RSW process, which addresses both aspects. The Rapid LME test is low-cost rapid test that is useful in quickly determining the risk of LME cracking in homogeneous and heterogenous multi-steel stackups. To validate the effectiveness and repeatability of the Rapid LME Test, A/SP applied the test to 12 carefully chosen steel stack-ups comprised of homogenous and heterogeneous 3rd Gen AHSS and mild steel. The results showed that the cracking severity rating from the Rapid LME Test in homogeneous joints is a good indicator for the cracking severity in heterogeneous joints. However, it was found that in the heterogenous stack-ups, the fixed weld schedule used in the Rapid LME Test was not able to produce weld nuggets that met the general acceptance criteria for meaningful cracking severity comparison, due to the large materials resistivity and thickness differences. A new supplementary method to Rapid LME Test, called Weld Lobe LME Test, was developed to evaluate the cracking severity in heterogenous joints. The more production-representative weld schedules adopted by Weld Lobe LME Test was found to effectively differentiate the cracking severity in heterogenous joints. To thoroughly assess a material’s LME cracking susceptibility in both homogeneous and heterogenous joining conditions, a combination of Rapid LME and Weld Lobe LME tests is recommended. As their characterization methods of cracking severity are essentially identical, future work of this project will focus on establishing recommended crack acceptance criteria.
Resistance spot welds experience complex loading conditions in vehicle crash events. Performing mechanical tests considering a range of loading modes on spot-welded connections can help to better understand the relationship between failure characteristics and common spot weld performance indices such as strength and energy absorption capability. In this study, the mechanical performance and failure behavior of resistance spot welds from two grades of third generation advanced high strength steels (3G-AHSS), designated 3G-980 and 3G-1180, were evaluated by performing KS-II mechanical tests which impose combined/mixed loading on the joints. A novel triangulation technique coupled with digital image correlation was developed for more accurate tracking of local nugget locations during the tests which improved the accuracy of the energy absorption calculations. It was shown that propagation of the cracks into the fusion zone of the 3G-1180 spot welds restricts their capability to absorb energy via deformation of the nugget in the tensile direction, especially within tensile-dominated loading orientations. Correlation of spot weld failure modes and absorbed energy values revealed that full nugget pullout failures exhibited superior energy dissipation value during failure and are favored over partial pullout failures with low plug ratios.
The automotive industry worldwide is undergoing a radical transformation with a pivot away from the Internal combustion engine (ICE) towards battery-electric-vehicles (BEV) to address the carbon reduction and sustainability initiatives. Existing assembly lines are being retooled and also brand-new assembly lines installed at a hectic pace. Multiple powertrain configurations (ICE, Hybrid, PHEV, BEV) coupled with modular platforms and sustainability initiatives requires re-imagining and rethinking the car body structures and assembly process.
Laser welded blank (LWB) technology for Press Hardened Steels (PHS-LWB) is a proven solution enabling performance improvement, part consolidation, material optimization, and weight reduction in vehicles. Also, it reduces the carbon footprint in all stages of vehicle life cycle assessment (LCA).
AMTB in collaboration with our R&D will showcase our innovative PHS-LWB design concepts called Mega-Part or Multi-Part Integration (MPI). Through this presentation, we will demonstrate how implementing MPI designs will help OEMs reduce the overall carbon footprint, reduce assembly time and cost, amplifying the traditional benefits of implementing PHS-LWBs. Our MPI designs have been validated to meet performance for crash and stiffness and evaluated for manufacturing feasibility using our virtual CAE models. We have also computed CO2 savings and assembly benefits.
Our presentation intends to make a strong case for OEMs to study MPI designs for future vehicle design architectures. PHS-LWBs are key enablers in promoting steel versus alternative materials, reducing assembly complexity, cost and time while improving sustainability of future vehicle designs.
Distinct microstructures with unique mechanical properties are produced upon resistance spot welding (RSW) of advanced high strength steels (AHSS). To understand how RSW deform and fail when loaded, it is crucial to characterize the mechanical properties of RSW sub-regions, the fusion zone (FZ) and heat-affected zones (HAZ), as the local mechanical properties of these regions can influence the global failure response of vehicle structure assemblies. In this study, a novel experimental procedure was developed to characterize the local properties of RSW sub-regions by fabricating sub-sized tensile (mini-tensile) and mini-shear specimens directly from the spot weld. While the FZ properties were extracted from the mini-shear test, the mini-tensile specimens were utilized to attain HAZ properties using the digital image correlation (DIC) technique. To expand the validity of the findings, different grades of AHSS, including Gen3-980, Gen3-1180, and Press hardened steel (PHS-1500) with ultimate tensile strengths of 980 MPa, 1180 MPa, and 1500 MPa, respectively, were considered. The results showed strain localization occurred in the soft microstructure, while limited deformation occurred in microstructures with hard phases, such as the super-critical HAZ and FZ. The local stress-strain response was then compared to the common hardness scaling approach, which approximates the FZ’s local properties and different HAZ regions. The stress-strain response of the investigated BM is scaled by applying a proportional scale based on the hardness ratio. The equivalent stress-strain of the FZ and HAZ obtained by the new procedure was compared to the hardness scaled stress-strain data. The results showed the mechanical properties of the sub-zones of the welds might only be calculated using the hardness scaling approach if the microstructures across the weld result in a consistent strain hardening rate in all sub-zone.
Hot forming steel is being widely used in the e-automotive industry. It offers high strength and ensures an efficient lightweight concept. However, due to its coating alloys and mechanical properties the thermal or mechanical integration of fastening elements in thin-wall, and at the same time, ultra high-strength (UHS) components present a manufacturing challenge. In a research project carried out by the University of Paderborn, Germany, the feasibility of mechanical joining of a fastening element during the hot forming process was successfully demonstrated (maybe this should be demonstrated). This approach was then identified to improve the manufacturing process efficiency eliminating welding problems, eliminating the need of laser cutting, and decreasing riveting challenges. Based on the results of the research, further investigations were carried out by PROFIL to widen the application range of this method and test other types of functional elements under serial production conditions. Regarding its mechanical properties, the element-sheet joint was tested under various loading scenarios. The hardness of both the panel and the elements as well as the coating of the elements were evaluated at the end of the process. Cyclic load tests were carried out in different conditions to determine the susceptibility of the innovative element-panel joint to cracks. Together with customers, a reliable In-Die solution for serial production was investigated as well. Finally, this technology widens the range of elements to be used in combination with this PHS components to include for example an optimized solid pierce rivet.
Advanced high-strength steels (AHSS) are a proven enabler to lightweighting automotive body structures, but these steels can pose forming challenges due to their high strength and complex microstructures. One frequent challenge is having sufficient press tonnage to obtain desired component shape and dimensions, often requiring time consuming and expensive process development. This is especially problematic if forming tonnage approaches or exceeds press capacity.
The Auto/Steel Partnership (A/SP) Stamping Team has been working to better understand the AHSS and 3rd Gen AHSS material behavior and improve AHSS forming models to more accurately predict forming tonnages for these steels. The team recently completed the first phase of work on a project titled, “3rd Gen AHSS Press Tonnage”, which has been evaluating the accuracy of press tonnage predictions of state-of-the-art forming simulations for an open channel “Automotive-Like” panel using three different grades of AHSS and 3rd Gen AHSS. The predicted tonnages for all three steels were compared against measured tonnages in die trials, which revealed several interesting gaps in press tonnage simulations.
The first gap is in the definition of press tonnage, or more specifically, at what stage of the forming process should press tonnage be measured? The second gap, which is related to the first, should press tonnage be related to the quality of the product; the ability of the process to achieve desired part shape and dimensions? A third gap was defining how press tonnage was assessed; e.g. ram tonnage, the tonnage at all four corners, off-center tonnage, etc. This presentation will provide an overview of the lessons learned and the team’s modified approach to improving press tonnage modeling and simulation.
Accuracy in the virtual design of the forming process is critical to promote the adoption of 3rd Gen advanced high-strength steel (AHSS) into a lightweight vehicle architecture with enhanced crash performance. To leverage the superior formability of 3rd Gen AHSS relative to conventional AHSS, advanced material characterization techniques should be used to consider the complex hardening response that influences springback and press tonnage along with the dynamic forming limits that account for bending, contact pressure and non-linear strain paths. To this end, three 3rd Gen AHSS steel grades with a nominal strength level of 980 MPa and 1180 MPa were characterized at the coupon level and used to develop a numerical toolkit using the latest capabilities in AutoForm® and applied to design of a B-pillar technology demonstrator. An extensive experimental test campaign entailing forming trials, 3-D part scans, and impact tests were undertaken to critically evaluate the models using different calibration strategies. Guidelines and best practices on experimental techniques and modeling strategies which could successfully capture springback in the formed parts and subsequent crash performance are proposed. Note: This talk is related to the AISI Automotive Program project and a collaboration with AutoForm.
If you have feedback about the GDIS past presentation tool, please email Sarah Burns at sburns@steel.org.