Past GDIS™ Presentations

Nearly all vehicles produced have front subframes, also referred to as engine cradles in front engine vehicles, which are considered a part of the vehicle suspension. Significant effort has been invested into reducing the mass of engine cradle assemblies. Many aluminum and aluminum/steel hybrid engine cradles are currently in production and carbon fiber prototypes have even been developed. Mass optimized steel engine cradles, on the other hand, receive less attention. Advanced high-strength steels (AHSS) are rarely used since engine cradles are primarily stiffness driven assemblies, and lightweighting manufacturing technologies, such as tailored blanks, are rarely employed. This presentation will take a closer look at mass reduction methods for optimized steel engine cradle designs and propose new lightweight steel designs with corresponding mass and cost estimates.

Use of press hardened parts in Body-In-White (BIW) structures has evolved in recent years to encompass wide range of part complexity, size and mechanical properties. In addition, the number of components per vehicle has also increased pushing demand for more capital investments. Suppliers of press hardened parts need to accommodate these changes while staying competitive. Advanced design of heat treatment furnace has to offer a unique furnace design that provides flexibility to handle future part sizes minimizes down time to increase line utilization and offers a unique solution to produce tailor tempered parts for crash performance.
This paper presents advanced innovative design of continuous roller furnace. These types of furnaces are generally used in hot forming lines. Design is focused on optimal heating layout, modern drives of rollers, new design and other items respecting the optimal technological and technical aspects. Also the technological functions like the dew point temperature regulation, oxygen rate regulation. All results are based on the theoretical background of heat and mass transfer, con-firmed by numerical Finite Element Method (FEM) analysis. Based on the long-time experiences with manufacturing and development of the machinery for the automotive industry, new roller furnaces were designed using modern methods including the FEM analyses for numerical simulations of heating processes and heating power distribution. The numerical solution of many mathematical problems involves the combination of external and internal conditions and different technological processes.

This presentation will summarize work of the Auto/Steel Partnership (A/SP) projects, Gas Metal Arc Welding (GMAW) of Advanced High Strength Steel (AHSS). This project is focused on the development and validation of 3rd Gen GMAW process for AHSS for use by the automakers. The Project Team identified (3) different AHSS grades for evaluation. Two GI coated materials were welded using gas metal arc welding techniques and the welds produced were tested using X-ray and quasi-static lap shear tensile tests. The other non-coated steels were welded using different fillers to evaluate differences in filler strength materials. Micro-hardness and metallurgical examinations were conducted to evaluate the welds. Lap tensile shear coupons for coated and uncoated steels were tested to determine tensile shear strength, fracture locations, and other weld metallurgical properties.
In general for 3rd Gen AHSS, coated steel is susceptible to Liquid Metal Embrittlement (LME). Based on observation, there is no concern under current welding procedures.

This presentation will summarize work of the Auto/Steel Partnership (A/SP) projects, gas metal arc welding (GMAW) of advanced high-strength steel (AHSS). This project is focused on the development and validation of 3rd Gen GMAW process for AHSS for use by the automakers. The project team identified (3) different AHSS grades for evaluation. Two GI coated materials were welded using GMAW techniques and the welds produced were tested using X-ray and quasi-static lap shear tensile tests. The other non-coated steels were welded using different fillers to evaluate differences in filler strength materials. Micro-hardness and metallurgical examinations were conducted to evaluate the welds. Lap tensile shear coupons for coated and uncoated steels were tested to determine tensile shear strength, fracture locations, and other weld metallurgical properties.

In general for 3rd Gen AHSS, coated steel is susceptible to liquid metal embrittlement (LME). Based on observation, there is no concern under current welding procedures.

This presentation describes a new method called generalized stress parameter (GSP) to predict fatigue life of gas metal arc weld joints (GMAW). GSP is based on the structural stress and the stress intensity factor and is based on a modified version of the Maddox equation. The structural stress accounts for the effect of global weldment geometry and the stress intensity factor captures the local effect of the weld angle and weld toe radius. Stress versus fatigue life (S-N) curve is developed using GSP and fatigue test results of various specimen configurations, material grades and thickness combinations. The developed S-N curve along with the GSP approach is used to predict the GMAW’s fatigue life of an actual OEM’s production control arm link subjected to variable amplitude loading. Laboratory tests of the above component subject to the same variable loading history are conducted. Comparison of the analysis results based on GSP and the test results revealed excellent correlation.

One of the driving principals of automotive engineering today is improving fuel efficiency thereby reducing carbon emissions. Many strategies have been implemented concurrently by the automotive OEMS such as improved aerodynamics and adopting alternative powertrains but the most widely implemented practice involves reducing vehicle mass. More than ever, innovative designs and light-weight materials are playing a significant role in enabling the engineering teams to design competitive vehicles that do not compromise performance. While offering various degrees of mass saving compared with traditional materials, rarely do these innovations integrate seamlessly into longstanding manufacturing and design practices. There are often headwinds associated with implementing new technologies. Examples of headwinds include complex manufacturing and assembly processes, additional equipment, new fastening schemes or unproven CAE modeling techniques.

MSC Smart Steel® is a new multilayer steel laminate engineered as a direct substitute for vehicle body parts stamped from low carbon steel. While offering up to a 35% mass save compared with same thickness standard steel, MSC Smart Steel® is produced as a coil, stamped in typical dies, spot welded with existing equipment and processed through standard electro-coat and paint systems – essentially minimal disruption to existing manufacturing systems. This is the first ever spot weldable low-density composite laminate to be used in a body application.

Following a five-year collaborative effort between Material Sciences Corporation and a strategic customer, MSC Smart Steel® is now validated for vehicle implementation and is going into production on multiple 2019 global platforms.

In support of a scientific foundation for the predictive design of composition and processing of quench and partition (Q&P) martensite/austenite TRIP steels, theory of coupled diffusional/displacive transformation is experimentally calibrated to control austenite carbon content and its associated mechanical stability. The calibrations are based on highly accurate experimental measurements using electron microscopy, high- energy x-ray diffraction and 3D atom probe tomography to quantify the amount and carbon content of retained austenite as a function of Q&P treatment. Varying the initial quench temperature to vary the initial retained austenite amount, it is demonstrated that carbon partitioning is affected by the direction of motion of the interface, favoring greater C partitioning for BCC->FCC motion. The variation in partition temperature is shown to have the maximum effect the austenite carbon content and its stability. The influence of processing parameters and alloy composition on the final Q&P microstructural characteristics are predicted via the developed mechanistic models and validated with a new series of experimental alloys. The effect of change in the microstructural features (phase composition, phase stability) on the mechanical properties would be discussed.

Since our first application of inline robotic laser cutting on the 2019 RAM 1500 hot stamped door ring, the industry is now focused on next generation advancements in overall equipment effectiveness. New process innovations combined with robust automation solutions allow for next generation door ring laser cutting machines to have increased performance, throughput, part to part quality and process robustness. We will explore the current obstacles of laser cutting in relation to upstream and downstream processes such as the blank trimming, furnace variables, hot forming press, die changes, and touch base on theoretical solutions to overcome these process variables. There are many laser cutting avenues that compliment other value added trim processes such as near net shape, in-die trim and predeveloped holes. Finding the right balance will ensure industry best practices are used in future light weight cost effective hot stamp door ring solutions.

Steel content for automotive applications represent the fundamental building blocks that OEMs and their tier 1’s suppliers continue to rely on to meet the evolving needs of the North American auto landscape. Advanced grades of steel show no signs of slowing down with innovation in its production, forming, and applications within the vehicle. The Ducker Study builds on several past iterations to determine current content (demand Pounds per Vehicle) by grade of steel for all NA produced light vehicles as well as scenario based forecasts for materials thru 2025.

There is a growing need to efficiently and accurately characterize next generation advanced high-strength steels (AHSS) for virtual prototyping and to predict the response of automotive structural components in crash events. The focus of the present study is to consider two next generation steels of 980 and 1180 MPa strength to develop the experimental test methodology to characterize and predict the material behavior for forming and crash applications. Advances have been made in the determination of the hardening response to large strains and to predict the formability and fracture curves in stress states ranging from shear to biaxial tension with an emphasis on plane strain bending. This project is a collaboration with SMDI and Honda Research Americas and will detail the fracture characterization and methodology used in the virtual design and tooling try-outs for a full-scale 3rd Gen B-pillar for a mid-size SUV.

Three failures can be found on drawn parts in the stamping productions. One is the necking and split on the walls of the drawn part that can be predicted with the Forming Limit Diagram (FLD), another one is the necking at the tangent point of a drawn part radius that is controlled by the material n value. These two failures are all caused by the material plastic instability. The third one is the fractures of advanced high-strength steel (AHSS) on part radii when the materials are subjected to an excessive bending under tension load. The failure criterion has yet to be developed to control the issues in stamping productions. In the current study, the fracture limits of four grades of AHSS, i.e. DP590, DP780, DP980 and DP1180, were studied with a simulative 90 degree stretch bending tests and various tool radii (from 1.0mm to 14.0mm). The DIC equipment was used to measure the surface strains and determine the fracture limits. On the basis of test results, the failure criterion has been developed for the four AHSS grades in terms of the permissible tensile strains of materials when they are on different tooling radii (R/t).

AISI’s Hesham Ezzat discussed the role of steel in future mobility.

NEXMET® 1000 is a commercialized 3rd Generation AHSS innovatively developed by AK Steel. With significantly improved elongation at higher ultimate tensile strength, NEXMET® 1000 offers OEM customers a promising solution for the lightweighting goals. To demonstrate stamping formability with NEXMET® 1000, a systematic experimental analysis was conducted to generate the forming limit curves at various thicknesses. The formability was then verified with finite element simulations and through actual component stamping. Edge stretchability and its sensitivity to hole punching configurations (punch profile, cutting clearance, etc.) was evaluated with both in-plane and out-of-plane hole expansion tests. In order to understand deformation induced plasticity phenomena in NEXMET® 1000, neutron diffraction and 3D digital image correlation (DIC) techniques were utilized to measure the evolution of constituent phase transformation at different stain paths.

The continuing expansion in the application and use of advanced high-strength steels (AHSS) in automotive vehicle structures requires increased attention relative to engineering, design and manufacturing to effectively take advantage of the superior performance characteristics of these steels. Additionally, the needs for both local and global formability must be properly balanced for efficient component manufacturing along with the added consideration of in-vehicle structural performance. It has become increasingly evident that the focus on a select group of mechanical properties and manufacturing performance metrics, e.g., yield strength, tensile strength, elongation, n-value, FLD, etc., has proven inadequate for an increasing number of applications. This talk will examine the continued development direction of selected advanced steel classes, namely press hardened steel and multi-phase steels, with a focus on property optimization via microalloying techniques and associated process strategies. Novel grade classifications with improved properties for applications are proposed for adoption within the global automotive industry.

April Bagley discussed Stellantis’ (formerly FCA) 2019 Jeep Wrangler.

AISI’s Brandie Sebastian discussed the life cycle assessment (LCA) GHG consequences of lightweighting with aluminum over advanced high-strength steel (AHSS).

The 3rd Gen advanced high-strength steels (AHSS) combine excellent strength and formability that can lead to a weight savings of between 10 and 20% in a vehicle, compared to existing Dual Phase (DP) grades. Because of their superior properties, 3rd Gen AHSS grades can absorb more energy during crash events and deform in a controlled manner while using lesser steel. At the same time, it can be used to stamp parts that otherwise would be difficult to form with conventional high strength steels. These properties make 3rd Gen AHSS ideal for use on many structural parts of the Body-in-White (BIW) such as front rail and B-pillars. However, weldability of 3rd Gen AHSS has been an important matter of discussion within the automotive industry. While, robust joining capability is crucial for any crash application with these grades, it is also important to note that these materials are compatible with the existing welding technology used for current grades in the industry.

ArcelorMittal has studied different product design parameter to deliver HF980 GI with superior weldability and minimum susceptibility to surface cracking during conventional welding. Four different welding types of resistance spot-welding (RSW), laser welding, MIG brazing and gas metal arc welding (GMAW) have been examined with no signs of surface cracks in critical zone.

Spot weld joint behavior of HF980 GI using hat shaped parts subjected to axial crush impact loading is presented in the paper. Data for different test scenarios including the effect of section geometry, part thickness, weld schedule, paint baking and weld pitch on overall joint strength and part behavior under crash loading is presented. The presentation also demonstrates the importance of different variables to be aware of when designing structural parts on a BIW with 3rd Gen steels.

The AHSS Chassis Corrosion team has completed corrosion testing on welded coupons and test specimens to evaluate various corrosion protection coatings over a 15 year simulated environment. A test procedure was developed to evaluate the corrosion in welds, crevices and exposure to gravelometer and poultice using methods consistent with procedures at FCA, Ford and General Motors.

In an effort to improve corrosion protection on chassis components which are using more thinner, higher strength steel grades, this project was designed to compare different coating for their effectiveness. The project also included the testing of weathering steels to determine whether chemistry changes in the steel substrate can be effective in reducing corrosion over a vehicle’s lifetime.

The results of this testing showed that certain coatings performed well in reducing corrosion over baseline e-coated specimens, and also showed that sample preparation can have a significant effect on improving corrosion resistance.

This presentation will show the results of the welded coupon testing, which is similar to the results attained on the “biscuit tin” test specimens tested over a 15-year simulated environment. It will also recommend potential future testing that could provide additional corrosion protection opportunities in chassis applications as well as for body structures.