Past GDIS™ Presentations

Laser welded blanks have been widely used to achieve lighter weight with improved structural integrity in automotive BIW structures. However, stamping of laser welded samples have many challenges, one of which is stretch-bending failure. In this study, an experimental methodology is developed to characterize the stretch-bendability of laser welded and monolithic steel blanks. Along with the stretch-bending strain limit criteria, a new global failure criteria is proposed in this study for comparison of stretch-bendability, which helps product design engineers to examine design limits and thus minimize the risk of stretch-bending failure during stamping processes. The results show that the stretch-bendability of the laser welded blanks are less affected by the R/t ratio (radius of the stretch-bending punch / blank thickness) compared to the monolithic blanks.

Increasing automotive requirements for improved corrosion life on frames and chassis components have created a challenge for OEMs and suppliers to improve corrosion resistance. To meet these requirements and improve corrosion resistance, many OEMs are requiring zinc-coated components. The zinc coating adds an additional degree of difficulty to welding as its low vaporization point leads to zinc vapor that can be trapped in the weld metal as porosity.
In response to the aforementioned issue, Lincoln Electric has developed a unique GMAW wire, SuperArc® XLS, that has a marked reduction in porosity compared to conventional GMAW wires on zinc coated steels. Its novel chemistry has shown distinct benefits for minimizing porosity, allowing welds to be made at increased speeds with fewer defects. When combined with a pulsed waveform, this complete process solution provides low spatter and increased process efficiency while maintaining a lower level of porosity when compared to traditional GMAW wires.
The proposed presentation for this conference is as follows: compare end-product porosity defect results and demonstrate the outgassing behavior of zinc vapor in the weld pool. The welding comparison was performed on automotive zinc-coated steels with SuperArc® XLS and standard GMAW wires.
For end-product comparison, X-ray analysis was performed to determine porosity on lap welds completed with constant weld settings and environmental conditions. For outgassing behavior, the movement of zinc vapor was observed via high-speed video of the weld pool surface and via high-speed in-situ X-ray video. This experiment suggested a three region model to discuss the evolution of zinc porosity in GMAW. The results from all testing showcased clear improvement in end-product porosity and markedly different zinc vapor behavior when using SuperArc® XLS compared to standard GMAW wires.

Press-Hardened Steels (PHS) are known to be used in the safety cage of the body-in-white structure of a car owing to their high strength from phase transformation during hot stamping. Resistance spot welding (RSW) of this steel produces a martensitic microstructure in the fusion zone that is brittle and shows minimal energy absorption capability during crash events. In this regard, in-situ post-weld heat treatment (PWHT) has been adopted as a means to improve the toughness of the fusion zone. In this study, in-situ tempering and recrystallization pulses were employed to modify the fusion zone microstructure and improve the energy absorption capability of PHS spot welds. The optimal tempering pulse schedule was obtained by measuring the average hardness of the FZ while the changes in grain size and aspect ratio were used to determine the optimum recrystallization pulse schedule. The results indicate tempering and recrystallization are effective to improve the joint mechanical properties, change the crack propagation path and failure mode after cross-tension test. Similarly, the fractography revealed that the PWHT welds failed in a ductile mode while the as-welded condition showed cleavage features indicating a brittle failure. A comparison between the effectiveness of both tempering and recrystallization will be discussed in this work with an emphasis on the changes in microstructure, joint properties and relevance to the industry in terms of applicability.

Advanced High Strength Steels (AHSS) and New Generation Steels (Gen3), with their unique combination of durability, ductility, and strength, are enabling automakers to meet increasing vehicle weight, safety and performance targets. One of the biggest challenges with these materials is simulating the spot weld separation under impact loading. The Auto/Steel Partnership (A/SP) in collaboration with The University of Waterloo, have developed advanced testing and modeling methods to predict spot weld separation under dynamic loading modes. Novel test methods have been developed to characterize the mechanical properties of the spot welds, which includes the weld nugget, base material and the different components of the heat affected zone (the coarse-grained region above Ac3, the region between Ac3 and Ac1, and region below Ac1). Mini-tensile and mini-shear coupons were extracted from welded coupons for the weld nugget and base metal properties, and HAZ regions. Five test configurations were employed to characterize the plasticity and failure properties of the spot welds, which were uniaxial tensile, shear, notch tension, central hole, and V-bend. To validate the mini-coupon results, larger test coupons were produced using a Gleeble unit to reproduce the representative microstructures of each three HAZ regions. The characterized material properties of the Gleeble produced coupons were compared with the mini-coupons extracted from welded coupons. The mechanical properties were used as input parameters for finite element (FE) simulations. Multiple weld modeling strategies were studied in this project. A meso-scale detailed spot model with a fine FEA mesh was developed to simulate the coupon response to load paths based on microhardness data and the constitutive properties generated from coupon tests. A large-scale industry modeling method was used to study different spot weld failure modes. The next phase of work includes dynamic welded component testing, which is a critical validation step for predicted spot weld energy absorption and strength. Two different dynamic tests are planned for component level validation using CAIMAN Mode 1 and Mode 3 testing.

Third-generation ultra-high strength steels (3G-AHSS) have shown great potential for use in automotive body structures to improve vehicle safety during crash scenarios while simultaneously offering significant light-weighting opportunities. Characterization of material mechanical performance and resistance spot weld joining methods have been completed and must be modeled in CAE simulation software to assist with implementing these materials into automotive structures. Continuous improvement of the weld fracture models used in simulation lead to better prediction of vehicle impacts and helps optimize vehicle design when implementing 3G-AHSS materials. In this work, an optimized single spot-welding schedule was used to weld KS-II single spot weld test samples. The spot welding was optimized to generate a nugget size that matches the electrode face diameter and a nugget size that matches the minimum weld size specified per the AWS D8.9 standard. A unique method of data analysis is employed to improve the simulation boundary conditions and achieve better calibration. The same welding schedule was then used to join structural components with multiple spot weld used in the Caiman Mode I and Caiman Mode III experiments. The Caiman components were tested via quasi-static and dynamic loading conditions. Various common weld material models were calibrated over a range of loading conditions by using the KS-II single spot weld test. The calibrated single spot weld models are then implemented into the component level multi-spot weld CAE model. The simulation accuracy of these weld material models is validated against the experimental data, with a particular focus on the post-weld failure unloading response as weld failure propagates throughout the test component. The results of these weld material model simulation validations highlight that although the peak force of the experiments can be well captured, accurately prediction of the total absorbed energy is an on-going challenge and may indicate a limitation of the current modelling practices. Other material models for joining with finer control over failure behavior are examined as possible alternatives.

This paper discusses a high efficiency 2-cell cross-section roll formed profile in 22MnB5 steel that is subsequently hot formed using the well known Accra® process to result in a front bumper beam with low mass and high performance. Manufacturing and material challenges for the complex blank are discussed. Section optimizations are also reviewed, including corner radii that are tighter than commonly achieved with ultra high-strength steel (UHSS) to achieve higher performance than current state of the art. Hot forming the section to include aggressive and variable section sweeps not normally achievable in UHSS provides for a drop-in replacement of a current production extruded and stretch bent Aluminum bumper. The final assembly is shown to meet similar performance requirements with a very small mass penalty (primarily driven by the drop-in requirement) and a significant cost savings for an upcoming North American OEM SUV mid-cycle enhancement.

The ladder frame used in PU/SUV is a key component for aspects of vehicle performance such as rough road durability and robustness. At the same time, meeting CAFE regulation and achieving carbon neutrality calls for further weight reduction. Our next generation frame installed in new PU/SUV models adopts an integrated differential thickness structure using new curved (non-linear) tailor welded blanks technology featuring high productivity and reliability. Small radius curved welding enables more efficient reinforcement using steels with larger variation in thickness and material composition, resulting in a weight reduction of approximately 14kg compared to the current structure that welds the reinforcement plate on the main body.

The Auto/Steel Partnership (A/SP) stamping team has been working to better understand advanced high-strength steel (AHSS) and 3rd Gen AHSS material behavior and improve AHSS forming models to predict the forming tonnages more accurately for these steels. The mass reductions, particularly in the automotive Body-In-White (BIW) structure, continue to dominate the list of vehicle electrification enablers. The combination of high-strength and high-ductility of the 3rd Gen AHSS are ideal for vehicle component and assembly lightweighting. Understanding the forming nuances of stamping these steels will facilitate the design and manufacture of lightweight components that enable automakers to achieve electric vehicle range, emissions, and performance targets.
The A/SP stamping team has been working to better understand AHSS and 3rd Gen AHSS material behavior and improve AHSS forming models to predict the forming tonnages more accurately for these steels. The team recently completed the second phase of this work, which focused on assessing applied press tonnage through the complete press stroke of a pseudo-automotive component. The components were stamped using a Nidec/Minster servo press and a Martinrea die, which is an extended hat section with an in-die spring-back control feature called an “S-Corner.” In prior work, it was shown that forming simulations accurately predicted press tonnage up to the point of die closure, but the simulations did not include the work done after die closure to obtain desired dimensional quality. This work will demonstrate that: a) the S-corner is an effective spring-back countermeasure, b) will highlight the effects of adding energy to the part without increasing the press force by delaying the time the press/die system is in dwell, c) show an ideal press geometry, as well as the stamping cross section and d) justify further work to improve press tonnage prediction.

This presentation will summarize work of the Auto/Steel Partnership (A/SP) project, Die Wear Testing – Phase II using 1180 GI & EG coated sheet steel. This project is focused on obtaining new knowledge by comparing/calibration test results with die wear simulated sliding energy calculations, as well as relationship of wear vs. sliding energy density of 3rd Gen advanced high-strength steel (AHSS) stampings. The team utilizes a die wear sliding tabletop tester to do a series of experimental test on 3rd Gen ultra high-strength steel (UHSS) of galvanized iron (GI) and electro galvanized (EG) coated steel sheets to continue improvement of forming die material, surface treatment, lubricant and coating. Cast Caldie with/without ionitride and physical vapor deposition (PVD) Ionbond 90 coating. The team will examine through optical microscopy, scanning electron microscope (SEM), weight measurements any wear and/or surface build up upon the die wear pin and any damage on either the sheet and/or the pin. The collection of friction data and integrated sliding energy for each testing case will be process.

On cold formed applications Mubea is currently using micro-alloyed advanced high-strength steel (AHSS) to produce blanks and formed parts with variable gauges. With the general idea to close the gap in the TRB material portfolio between the maximum strength cold form material (CR500 TRB) and press hardened steel (PHS) applications, Mubea TRB developed the material families MTS (Mubea Tailor Softened) and MTH (Mubea Tailor Hardened).
Both new developments offer tailored mechanical properties in cold formed structural parts to satisfy the local performance requirements of the vehicle with reduced process cost.
The main characteristic of MTS material is to have two strength levels beside different gauges in one part. By choosing gauges with low rolling reductions the slightly elevated raw material mech. properties can be used to have higher strength areas with high thickness in the part. At the same time the thinner gauges will have a lower strength compared to the higher gauge area. This can be used to design intrusion beams with cold form material without the high cost of the hot forming process.
In case of the MTH material the higher strength is being achieved by increasing the mechanical properties to the higher strength level (yield and tensile strength) using cold rolling and the mechanism of “dislocation hardening” in defined borders. Different to the already establish TRB process for cold formed material, we are starting with a much lower (less expensive) material grade compared to the reference and we are omitting the annealing process. Both aspects are the main driver to achieve a cost reduction compared to the baseline material and contribute to CO2 reduction in the production process as well as in the vehicle use phase. Material cards for MTS and MTH material were developed for forming simulation as well as for crash simulation including failure.

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.