Past GDIS Presentations
Past GDIS Presentations
Mark Mikolaiczik discussed Ford’s 2021 Mustang Mach-E.
Youngtaeck Kim discussed General Motors’ 2021 Chevrolet Trailblazer.
Jeff McCormick discussed General Motors’ 2021 Cadillac Escalade.
Mobility Service providers seek to provide transportation services in densely populated cities that meet customers’ needs for comfort, reliability, safety, and connectivity. Future mobility will be defined by unique powertrains, technologies and architectures that ensure these attributes are met – but there are materials challenges in these designs. Fleet owners must offer products and solutions that also deliver a profitable business model, and the supply chain must deliver on these needs.
This presentation will share details of our newest vehicle program, Steel E-Motive, where we are exploring steel solutions to address Mobility as a Service (MaaS) challenges for fully autonomous and connected electric vehicles. The presentation will showcase the vehicle technical specifications and expectations for steel innovations.
Jeremy Lucas discussed Honda’s 2021 Acura TLX.
There is a growing need to efficiently and accurately characterize next generation advanced high-strength steels (AHSS) 3rd Gen for virtual prototyping and to predict the response of automotive structural components in crash events. The focus of the present study is to consider several 3rd Gen steels of 980 and 1180 MPa strength to develop the experimental test methodologies to efficiently and accurately characterize the material behavior for forming and crash applications. To provide a performance benchmark for the proposed CAE methodology, the geometry, tooling and forming process for a full-size B-pillar for a mid-size SUV were virtually designed in collaboration with Bowman Precision Tooling and Honda R&D Americas. The tooling was then fabricated and the B-pillar forming trials were successful for both 980 and 1180 3rd Gen AHSS with springback after trimming accurately predicted. Assessment of the forming process using a conventional FLC for the 1180 3rd Gen was found to be overly conservative and erroneously predicted significant splitting that did not occur in the forming trials.
Niobium microalloying was originally introduced to dual-phase (DP) steels for the improvement of local and global formability balance through microstructural refinement. Recently developed TRIP-assisted DP steel variants contain retained austenite for enhanced work hardening and provide increased ductility and global formability. Niobium microalloying of these newly developed PD variants, in addition to well-known effects of microstructural refinement, produces a non-trivial strength increment through dispersion of nanometer-sized carbide precipitates in the steel matrix. This study investigates both the microstructural evolution and progress of niobium precipitation during industrial processing of a TRIP-assisted DP 980 steel in which an intermediate batch annealing process is employed to optimize precipitate influence on recrystallization kinetics. Remarkable reductions in structural heterogeneity are observed between the hot rolled and final products. These observations are interpreted considering the solubility and precipitation kinetics of niobium. Pronounced refinement of the cold rolled and annealed TRIP-assisted DP microstructure is observed due to a strong recrystallization delay of the cold rolled ferrite matrix by niobium carbide precipitates in the final annealing cycle. The influences of associated microstructural characteristics on strength and formability are elucidated.
The VDA 238-100 tight-radius bend test provides excellent plane-strain conditions for fracture characterization and has proven to be valuable for material ranking and selection for forming and crash applications where material folding is paramount for energy absorption. The custom inverted V-Bend test frame at the University of Waterloo facilitates full-field DIC strain measurements and thus provides failure strains for calibration of fracture models in addition to the conventional bend angle. The VDA specification recommends the use of a load threshold for unique identification of material failure that has been found to systematically underpredict the performance of many grades of automotive steel. Three simple alternative methodologies for fracture detection are proposed based upon: the bending moment, nominal principal stress, and the strain rate for a range of representative automotive steels. The novel fracture detection methodologies were evaluated for seven automotive steels with strength levels from 270 to 1500 MPa that included hot-stamped, third generation advanced high strength, dual phase, and mild steels. The proposed metrics for fracture detection can be readily implemented using the current test data available in the VDA test to efficiently and accurately characterize bend performance for forming and crash.
The purpose of this study is to investigate the effects of both steel gauge and punch radius on the bend performance metrics in three point bending. Current sharp-radius bend test methodologies, e.g., VDA238-100, will be evaluated and compared to proposed bend test variants to determine testing parameters that provide maximum test result delineation for crashworthiness evaluation. Results of focus will be peak load, bending angle at peak load, pre- and post-peak energy absorption, and total energy absorption. Additionally, the effects of steel gauge on the above-mentioned properties will be evaluated to determine expected variation for specification development. Correlation to component level testing may be performed as a secondary task to verify applicability of sharp radius three-point bending for crashworthiness evaluation.
3rd Gen advanced high-strength steel (AHSS) are extensively considered for usage in Body-In-White (BIW) with lower thickness to reduce the vehicle weight and increase fuel efficiency. To improve strength and ductility in 3rd Gen. AHSS, the materials design concept can be different from Gen 1 and Gen 2 AHSS. Hence, it is necessary for the automotive industry to evaluate these materials properly for manufacturing. Resistance spot welding (RSW) continues to be a major joining process in BIW, and that is common for 3rd Gen AHSS as well.
Liquid metal embrittlement (LME) has been recognized as one of phenomena sometimes observed during welding. However, LME depends on several factors, but not only materials design but also welding condition and industrial noise factor. In Auto/Steel Partnership (A/SP), it has been aimed to understand LME behavior using Gleeble to find the proper temperature and deformation is required to form LME. A/SP has conducted a deep investigation to develop a procedure Gleeble procedure and analyzing of data for LME susceptibility level. In continuity of this effort, A/SP has developed a more lab based RSW protocol for LME evaluation which can be used for LME level evaluation of 3rd Gen AHSS. In meantime, to minimizing LME through welding parameters, the effect of different welding parameters is investigated.
To complete the loop for fully understanding the post-weld performance of 3rd Gen. AHSS in design, A/SP also investigate on weld performance during quasi-static and dynamic, through different type of mechanical tests, and a short overview will be presented.
Resistance spot welding (RSW) is the most common joining process in car body manufacturing and is frequently used to join components made of advanced high-strength steels (AHSS). These steels are typically applied with a zinc coating to improve their resistance against corrosion. During the RSW-process liquefied zinc can infiltrate the grain boundaries of the steel substrate, causing a phenomenon referred to as liquid metal embrittlement (LME). In cases where LME is especially severe, joint performance might be affected; therefore, prevention or mitigation of LME is desirable.
This study investigates methods suitable for the practical avoidance of liquid metal embrittlement during the resistance spot welding of AHSS. At first, the effect of an electrode geometry variation is investigated by utilizing a progressively elongated weld time. Occurring effects are analyzed in detail and correlated with a FE-simulation to generate a better understanding of the mechanisms causing LME in RSW. The importance of adapted hold-times depending on the welding boundary conditions is shown and the general effect of excessive energy input by high weld currents and elongated weld times is discussed. Finally, the robustness of the proposed methods is validated in a more complex welding scenario.
With the ever increasing application of 3rd Gen advanced high-strength steels (AHSS) in the automotive industry, springback control is becoming a very important issue that affects the dimensional accuracy of the stamped panels. A lab-scale die with combination beads (stake beads combined with draw beads) has been manufactured, funded by Auto/Steel Partnership (A/SP), to investigate stamping springback control and reduction. This is done by engineering a combination of draw beads on the binder during draw process together with stake beads on the punch during post-stretching. The finished panel is a U-channel. The investigation is conducted using a next generation AHSS with various bead combinations and depth. Correlations with FEA modeling are conducted using AutoForm which incorporates material models of yield surface and work hardening derived from internal tests. AutoForm Sigma is used to optimize the die actions and bead conditions. It is also used to assist identifying the dominant setup parameters and key material properties in controlling springback.
Laser welded blanks (LWB) have been successfully applied in automotive applications for over 30 years to save weight, reduce cost, consolidate parts, manage crash energy and improve material utilization. Over the last decade, advanced high-strength steels (AHSS) have become commonplace in LWB applications. Dual phase (DP), TRIP, and Multi Phase AHSS steels with tensile strengths up to 1180 MPa are used today in production applications. A 3rd Gen of AHSS will soon be added for their excellent balance of strength and global formability. However, the traditional methods that were originally developed to predict formability of a LWB with conventional steels may not be sufficient to accurately predict formability of a LWB with AHSS. Depending upon the steel chemistry, steel making process and the welding process, AHSS welds may exhibit softening in the heat affected zone or a reduction in ductility. Thus, a new approach to consider these properties in the finite element (FE) model may be needed. In this study, 3rd Gen LWBs were evaluated. To investigate the unique formability characteristics of the LWB, several standard mechanical tests, such as micro-hardness testing and various tension tests under uniaxial, plane-strain, and equi-biaxial conditions were conducted utilizing a digital image correlation (DIC) system. Under equi-biaxial conditions, the 3rd Gen LWB primarily fractures perpendicular across the weld seam, rather than in the parent metal, showcasing a robust welding process. The DIC system was successfully used to characterize the local ductility limit of the weld material. This information can be implemented in FE simulations of the LWB material to predict formability in the weld area. Also, FE simulations with different element types (shell, solid and hybrid) concluded that the weld section and properties should be considered for accurate fracture prediction. These preliminary results will lead to the development of a practice that can be beneficial for the automotive and steel industry to use in characterizing the formability limit of the LWB materials, simulating of stamping of the LWB materials and optimizing the laser weld parameters to improve local
Diode lasers are used in automotive body-in-white (BIW) assembly for more than 20 years. Today, the state of the art method for joining galvanized steel sheets in automotive BIW production is brazing with diode lasers. Due to the introduction of hot-dip galvanized materials through various OEM’ s the well-established brazing process with a single spot started to provide insufficient results. In order to maintain its customer base Laserline had to develop a new solution that would satisfy the quality requirements of the manufacturer. A specific optical module was introduced to target this challenge.
Multi-spot modules make tailor-made spot geometries possible and improve critical joining processes. Since 2016, these modules have been used in series production and have continuously been further developed. Triple-spot modules for brazing hot-galvanized sheets have been used in automobile production worldwide for more than two years now. This was followed by the use of a spot-in-spot module for the optimization of critical welding processes. Automated modules were introduced, and currently a new model has been added: a spot-in-spot module for asymmetric seams that was specifically developed for fillet welds and tailored welded blanks.
This presentation will explore the technology of multi spot modules, their different beam shaping and adjustment capabilities and how it reflects in brazing and welding applications of steel.
To evaluate various weld repair processes and to provide joint test data for use by OEM’s to update approved body repair strategies for coated and uncoated 3rd Gen advanced high-strength steels (AHSS).
This presentation reviews how digital image correlation (DIC) technology has set the metal forming industry up for a game changing revolution in the amount and nature of information that can be gleaned from material testing. The presentation will focus on the benefits of using DIC for the measurement and analysis of the common uniaxial tension test under monotonic loading conditions, providing literally orders of magnitude more information, including new information that not available without DIC.
The expanded and new types of information that DIC enables includes 1) measurement of the stress strain relation and evolution of R Value to strains far beyond maximum load, 2) detection of the onset of localized necking, 3) measurement of the degree of material homogeneity of all of its properties, 4) measurement of the degradation of the elastic modulus with strain, 5) ability to decouple strain and strain-rate effects on the stress-strain behavior, from a single monotonically loaded specimen, without employing jump tests, and 6) the determination of a realistic lower bound for the fracture limit strain and its dependence on strain path.
The unprecedented amount and new information that DIC enables is there for the taking from each and every specimen loaded in uniaxial tension under monotonic loading conditions. Examples of these benefits will be demonstrated for uniaxial tension tests on DP 980 and a DP 1180 steels that were selected for use in the Numisheet 2021 Benchmark Study.
This study introduces a new testing method to evaluate edge formability by emulating production conditions. Production representative conditions include varied shear clearances, a stamping part design other than a simple round hole or straight edge, varied edge shearing speeds with the mechanical press, and applicable forming strain rates during the test procedure. Edge formability of dual-phase (DP) 780 steel from six different steel suppliers was evaluated using the newly developed stamping test using a 300-ton servo press as well as the ISO standard hole expansion testing and the half-specimen dome testing. The edge formability of advanced high-strength steel (AHSS) is significantly influenced by the plastic strain accumulated during the shearing operation. The work-hardening on the sheared edge was quantified with hardness measurements and advanced measurement tools. The concept of Shearing Induced Damage (SID) is introduced to compare the different levels of work hardening and damage on the sheared edges of six different DP780 materials resulting from shearing and punching operations. The SID trends of six DP780 materials show good correlations in both lab-scale testing and stamping results. One of the DP780 steels displayed consistently better performance, while several other DP780 steels showed poor performance in both lab-scale testing methods and stamping testing. Most DP780 steels showed similar formability performance with the machined edge condition for all three different testing methods. Upon shearing, however, the local formability of three of the DP780 steel is significantly reduced, and this results in an earlier onset of edge cracking compared to the best performing DP780 steel in this study. The newly developed testing method is very effective to correlate the lab-scaled standard test data with the edge cracking of the industrial-scale stamping.
OEMs worldwide have announced plans to roll out Battery Electric Vehicles (BEV) in this decade. Depending on regions and market penetration, various OEMs have announced dedicated BEV platforms or updated Internal Combustion Engine (ICE) powertrains to accommodate BEV powertrains. In addition, many OEMs have also announced plans for mild hybrids which would have both ICE and BEV powertrains.
Worldwide standards on battery and occupant protection are not uniform and no clear guidelines are available on how to best integrate the two requirements in future body platforms. Furthermore, many OEMs have scaled back investments on new platform and body assembly updates to funnel their investments to new BEV powertrain developments.
Arcelor Mittal Tailored Blanks (AMTB) Product Development group has developed a novel concept of integrated battery and occupant protection Body-in-White (BIW) concept that showcases way forward for many OEMs. This concept integrates BEV powertrains to ICE body architectures with minimal modifications. Our concepts have intensive use of Press Hardened Steel with Laser Welded or Tailored Blanks in key structural parts to develop an optimized BIW that is lightweight and protects the battery pack while maximizing battery module volume. This is accomplished by a novel central concept of floor ring assembly, optimized front, rear and side crash load paths, and strategic use of press hardened steel and tailored blanks to optimize the weight, cost and performance of the structure.
Concepts from overall dimensions and crash load paths were benchmarked against some recent ICEs and their EV variants that went into serial production in the last two years. Validation of the concept was done using advanced full body crash and stiffness analysis for all major scenarios that would satisfy the most stringent requirements in every region. In addition, the battery box was fully validated for standalone load cases in key regions. In addition, additional load cases were also proposed and evaluated specially to consider new crash modes for battery protection. Forming analysis and weight-cost optimization was also done to ensure manufacturing feasibility of all modified structural parts. Lastly assembly sequence and minimum impact to body assembly sequence was also ensured while ensuring serviceability concepts for battery and body.
Considering above, we see a strong case for steel to remain a material of choice for cost, weight and performance requirements. Tailored Blanks further enhances the position of steel especially with press hardened steel applications. While many OEMs have integrated battery boxes made in alternate materials, steel continues to be a material that could be the way forward, especially if the occupant and battery crash protection are integrated as this concept study demonstrates to maximize value, performance and weight in vehicle architecture.
If you have feedback about the GDIS past presentation tool, please email Sarah Burns at sburns@steel.org.