Past GDIS™ Presentations

As AK Steel’s NEXMET™ advanced high-strength steel (AHSS) products move from development to commercialization, significant progress is being made to move beyond lightweighting “concepts” to fully functional production intent prototypes that provide not only a “proof” of concept for mass savings, but also provide validation for the FEA models used to predict forming, springback and structural performance. As more of these concepts are proven, a knowledge base is generated to provide OEMs with answers to many nagging questions involving the manufacturing of parts with 3rd Generation AHSS. This knowledge base will allow OEM’s gain the confidence they need to make critical material decisions earlier in the design phase and thus, facilitate further use of AHSS. Several examples will be discussed that demonstrate not only the mass savings of these components but will also provide details of manufacturing.

Lightweighting is critical for reducing fuel consumption levels in future vehicles, and automotive OEMs are striving to use the latest generations of materials with high-strength/density ratios, particularly advanced high-strength steels (AHSS) with complex microstructures. It is well established that the deformation of steels is largely rate dependent; nevertheless, stamping and crash simulations are often performed using data obtained at quasi‐static rates(<~0.1s‐1), which fall below the deformation rates associated with stamping- operations(~0.1 ‐ 10s‐1), and far below the rates experienced during a crash event (~50 ‐ 500s‐1). This is primarily driven by the difficulty in getting experimental data at multi‐ and, rate dependence in many cases is considered insignificant to be accounted for, especially within a narrow window of forming simulations. While this might be acceptable for some steels, it is far from true for the majority of steel grades, particularly the latest generations of AHSS. In this work, detailed experiments are performed over multiple strain rates to fully characterize the flow behavior and fracture behaviors of different steels with various microstructures. The experimental results are used to extract quantitative comparisons between the different rates (in regards to hardening parameters, strength, ductility and fracture strains), and associating those with the different steel types and their micro structures. The differences in rate‐dependence among the investigated steels, and the relationships to the phases present in their microstructures, are discussed.

The need to produce lightweight vehicles has driven the automotive industry to use new advanced steel materials for the vehicle body structure, making the forming processes more challenging for manufacturing engineers. Capturing the behavior of metallic parts during crash events has become very important in determining the structural crashworthiness of vehicles. As the auto industry relies increasingly more on computer simulation for evaluation of crash performance, accurate prediction of material behavior in crash simulation has become a necessity.

The thinning and plastic deformation that occurs during the forming process can influence the energy absorption of a part. There are already established techniques to initialize numerical models for crash analysis using strain and thinning values obtained from forming simulation. Depending upon the amount of plastic strain and the state of stress, damage can also develop during the forming process. This damage may affect the location of failure and the load levels at which failure occurs during a crash event. This project extends the existing methods of initializing crashworthiness models to include damage. The project outlines two approaches of initialization and evaluates the reliability of each of these methods. The first method involves computing the damage directly during the stamping simulation by incorporating a damage law in the material model. This is the most reliable method but requires a change in the standard process of performing forming simulation. The second approach approximates damage using the thinning and plastic deformation computed from a standard incremental forming simulation. The laboratory-scale T-shape panels were formed at different forming depths to achieve different forming statuses, such as with and without necking on the up-front radius. The ex-situ digital image correlation was employed to map the true major and minor strain distribution for the formed T-shape panels, which was considered as a baseline to compare with the forming simulation results. Static crash tests were performed on the T-shape panels with and without necking to determine the crash performance experimentally. In addition, a real production part was also examined analytically to assess effect of forming damage on the crash performance of the part. This project documents direct comparison of the simulation and test results. The work highlights the need for accurate forming simulations at levels of plastic deformation beyond the necking point.

KEYWORDS: Advanced High Strength Steel, Crash, Forming, Damage, Safety

Current methodologies for the experimental and numerical fracture characterization of sheet materials for vehicle crash applications are built upon the identification of a failure locus in proportional loading conditions. These stress-state dependent fracture models require a comprehensive set of experimental tests such as uniaxial tensile and notched-tensile specimens that are analyzed using a fine mesh of solid elements due to the onset of localization where the stress state becomes triaxial and the strain path non-linear. Although commonly used, these test coupons and the inverse-approach to numerical characterization is time-consuming and expensive for automotive applications such as crash events of structural components. A lengthy and convoluted mesh regularization process is required to adapt the three-dimensional failure locus first to plane stress using shell elements and then to larger mesh sizes. Although good predictions can be obtained in the crash simulations, the final failure locus is effectively an exercise in numerical calibration where the numerical fracture strains may have little resemblance to the experimental fracture strains. With the rise of third generation advanced high strength steels (AHSS), an efficient methodology is required that is specifically tailored to industrial crash applications.

In the present study a comprehensive experimental and numerical investigation was performed using three DP980 steels to identify the appropriate test geometries for plane stress fracture characterization in proportional loading. Over ten different test geometries were considered including notched tensile tests, Nakazama domes, tight radius bending and biaxial stretching with miniature punches that promote a strain gradient that suppresses localization. It was observed that an experimental fracture locus can be identified in using only four simple tests that do not require inverse-numerical approaches. A simplified approach to mesh regularization was developed to adapt the experimental locus directly to plane stress models for crash applications. To evaluate the proposed methodology, quasi-static and dynamic axial crush and three-point bend tests were performed for the three DP980 steels using a simplified structural rail geometry. In each of the test cases, the predicted structural response was in very good agreement with the experimental results in terms of the force-displacement, crack locations and energy-absorption.

Keywords: GISSMO, Crashworthiness, DP980, Mesh Regularization

Tailor rolled products are frequently used in the automotive industry as a lightweight solution to meet continuously increasing requirements in crash performance, stiffness, and CAFE standards.

This presentation details the utilization of Tailor Rolled Blanks (TRB ®) for Body-in-White (BIW) automotive parts. Through the flexible rolling process, it is possible to roll different thicknesses into sheets of steel with harmonious transitions. Due to this ability to set a proper material thickness at a specific location of the part, a simple substitution of a monolithic part by a TRB ® part leads to an attractive weight savings. However, when a part design is optimized for TRB ®, the advantages of weight reduction, part integration, and functional improvement can increase significantly.

The applications that will be discussed are tailor rolled products in rear rails with hot formed material, and front rails and crash boxes with cold formed material.

On a part like the rear rail with a complex geometry and “S” bends in different directions, the nesting is often a challenge in combination with the optimized thickness run. When developing a tailor rolled solution for this application the biggest influencing factor is material utilization, which directly influences the production feasibility and cost of the part.

Development on the front rails is concentrated on flexibly rolled cold formed material. Through the utilization of advanced high-strength micro alloyed steels, TRB ® can compete with dual phase steel solutions for similar applications. Since energy absorption during the front impact is the main requirement on the front rail, TRB ® technology is suitable to tune the deformation behavior by having different gauges along the length of the part as well as integration of reinforcements.

The crash boxes need to absorb the energy for the low speed crash test to protect the front rails from damage. At the same time, they introduce the load during the ODB front crash to the front rail. With TRB ® technology it is possible to have a long transition zone between two gauges of constant thickness, so the energy absorption is controllable by gauge and transition zone length to achieve the optimal deformation behavior. Because of this, the cross section can be more compact to release packaging space for powertrain components within the limited space of the front end.

The demand for products with better performance has always been a concern for the automotive industry. With the development of less polluting and more efficient products, automakers are looking for lighter components that maintains at least the same level of quality for its main functions. The updates and new technologies in the Agricultural and Commercial vehicle business are growing faster and the customer requires an accelerated development for their components. Therefore, it is necessary to ensure the final product quality within a shorter time-to-market process.

Increasing the product performance requires more engineering time and a longer period in the whole development process due to several attempts aiming the project targets. Most of its delay is caused by the lack of assertiveness, which takes time to define the best profile for weight and stiffness to get it approved on durability tests. This causes sort of a loop inside the development process.

This study aims to show how Maxion Wheels uses the Finite Element Method tools to validate the project and simulate the process. Shortening this optimization loop and together with multi-processor supercomputers, as part of its innovation initiative, reducing up to 26% the time-to-market and how does the company manufacture the lightest products in each market nowadays. The FEA optimizations tools brings to Maxion a virtual environment for solving project variables and also the possibilities to feedback the model with field and test data acquisition. It considers infinite possibilities for several boundary conditions at the same time in a single matrix, covering all the customer needs and guaranteeing at the end a 30% better fatigue life performance and 6% lighter wheels.

This computing-aimed method together with the product and manufacturing know-how can reduce significantly the development time and increase the efficiency of defining a final profile with better performance.

Kurtis Horner discussed Honda’s strategic steel application in the Acura NSX space frame.

This presentation will summarize work in two Auto/Steel Partnership (A/SP) projects, gas metal arc welding (GMAW) of advanced high-strength steel (AHSS) and improved fatigue of GMAW. The first project was focused on the development and validation of a generic brazing and GMAW approval process for AHSS for use by the automakers. The project team identified four different AHSS grades for evaluation. Two steels 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 two steels were welded and brazed 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 the second project, the project team developed a bending test for lap shear coupons and conducted bending fatigue testing of select AHSS to establish baseline fatigue properties of GMAW. The results of the testing will be presented followed by a discussion on the advantages and disadvantages of the bending fatigue test setup and future work to optimize bending weld fatigue.

Joe Riggsby discussed Honda’s 2019 Acura RDX world’s first inner and outer door ring system.

Over the past two decades the hot press forming, or press-hardening of steel (PHS) has become an important technology enabler for meeting today’s safety requirements. Its ability to do this while at the same time lightweighting body structures has been its advantage. The widely used steel grade for hot forming is the boron-added steel 22MnB5 (0.22%C-1.2%Mn), achieving nominal strengths of approximately 1.5GPa.

Future fuel economy and safety regulation increases are demanding even more aggressive vehicle mass reductions without jeopardizing cost targets. New applications and technologies with tailored strengths and novel production methods are needed.

This presentation shares the development and accomplishments of a one-piece hot stamped door ring and novel laser cutting methods on the 2018 Ram 1500 Pickup Truck.

The elevated strength of advanced high-strength steels (AHSS) leads to great challenges for the sheet metal processing, one of which is hole punching operation. A comprehensive study was conducted to investigate the tool shape and punching configuration effects on force reduction, hole dimensional accuracy, edge qualities, etc. Three grades of AHSS (DP1180, DP980 and DP590) were tested using flat, conical and rooftop shaped punch respectively with three cutting clearances for each material. The punching force coefficient is calculated based on the experimental measured data, and it indicates a negative correlation with the material strength. The punching force was significantly reduced benefited from progressive cutting mechanism introduced by rooftop punch but such punch shape can lead to dimensional inaccuracy issues. Conical punch leads to the uniform diametrical enlargement according to the measurement. To uncover the mechanism of the hole dimensional change and various cutting modes, a series of finite element simulations were established for numerical investigation. The tooling effects on cutting edge quality and associated tool protection was also investigated.

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.

Background:
I-CAR, the Inter-Industry Conference on Auto Collision Repair, is a not-for-profit education, knowledge, and solutions organization whose vision is that “Every person in the collision repair industry has the information, knowledge, and skills to perform complete, safe, and quality repairs for the ultimate benefit of the consumer. ” In June of 2014, I-CAR launched its Repairability Technical Support (RTS) initiative. This initiative is designed to support the collision repair inter-industry and to address gaps in collision repair information, tools, and processes.

Approach:
The I-CAR RTS initiative is comprised of four key elements: the RTS website; Repairability Summits; OEM & Industry Linking Pin Mechanism; and OEM and tool and equipment Technical Advisory Councils (TAC). The RTS website offers repair professionals tens of thousands of pages of collision repair information, including our Ask I-CAR feature.

Findings:
Recently, the collision repair industry witnessed a monumental example of why following OEM repair procedures is required for complete, safe, and quality repairs. Failure to follow OEM repair procedures resulted in a multi-million-dollar settlement for a couple that was badly injured in an improperly repaired vehicle. OEM repair information, and its importance, is the most frequently discussed issue facing repairers today. Information on material types, repairability guidelines, and attachment methods have rocketed to the forefront of every collision repair conference and publication across the country.

Conclusion:
Last year, I-CAR discussed the need for improved material identification, repairability guidelines, and standardization of repair information. This year’s presentation will expand on that conversation and offer insight into how the steel market can support the development of best-in-class repairability guidelines and procedures to support the I-CAR Vision of complete, safe, quality repairs for the ultimate benefit of the consumer. During this session, I-CAR will compare and contrast several examples of the types of information that is currently available to the collision repair inter-industry.

Florian Kiefer from TRUMPF and Brandon Reinhold from Comau discuss lasers in automotive – precision and flexibility for advanced manufacturing.