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Technical Paper

Wear of D2 Tool Steel Dies during Trimming DP980-type Advanced High Strength Steel (AHSS) for Automotive Parts

Automobile body panels made from advanced high strength steel (AHSS) provide high strength-to-mass ratio and thus AHSS are important for automotive light-weighting strategy. However, in order to increase their use, the significant wear damage that AHSS sheets cause to the trim dies should be reduced. The wear of dies has undesirable consequences including deterioration of trimmed parts' edges. In this research, die wear measurement techniques that consisted of white-light optical interferometry methods supported by large depth-of-field optical microscopy were developed. 1.4 mm-thick DP980-type AHSS sheets were trimmed using dies made from AISI D2 steel. A clearance of 10% of the thickness of the sheets was maintained between the upper and lower dies. The wear of the upper and lower dies was evaluated and material abrasion and chipping were identified as the main damage features at the trim edges.
Technical Paper

DP590 GI Mechanical Property Variability and Structural Response CAE Studies

Advanced High Strength Steels (AHSS) such as DP590 HDGI are helping automakers meet increasingly higher structural performance requirements while maintaining or reducing weight of the vehicle body structure [7]. One of the issues facing design engineers implementing new materials such as AHSS is the lack of understanding the expected material variability within a steel supplier and also from one steel supplier to another; and how the variability affects product attribute performances. In this paper, we present an analysis of the aggregated mechanical property variability data obtained from several steel suppliers for a popular AHSS grade and also present studies related to the effect of material variability on structural responses.
Technical Paper

Forming Effects to Product Attribute Coupled CAE Process and Benefits Investigation

Typical automotive body structures are assemblies of stamped steel parts. The stamping process work hardens and thins the parts. The work hardening effects are more pronounced for advanced high strength steels such as DP600. It is now widely accepted in the industry that forming effects must be incorporated into the product attribute models to improve simulation accuracy. This paper investigates some of the challenges in incorporating the forming effects into product attribute models during the automotive product development process and presents solutions. It also investigates how the significance of the coupled forming to attribute CAE method varies based on the initial design thickness of a part. The paper concludes by reviewing component and vehicle level results achieved by the incorporation of the coupled process.
Technical Paper

Weldability Prediction of AHSS Stackups Using Artificial Neural Network Models

Typical automotive body structures use resistance spot welding for most joining purposes. New materials, such as Advanced High Strength Steels (AHSS) are increasingly used in the construction of automotive body structures to meet increasingly higher structural performance requirements while maintaining or reducing weight of the vehicle. One of the challenges for implementation of new AHSS materials is weldability assessment. Weld engineers and vehicle program teams spend significant efforts and resources in testing weldability of new sheet metal stack-ups. In this paper, we present a methodology to determine the weldability of sheet metal stack-ups using an Artificial Neural Network-based tool that learns from historical data. The paper concludes by reviewing weldability results predicted by using this tool and comparing with actual test results.
Technical Paper

IMPACT Phase II - Study to Remove 25% of the Weight from a Pick-up Truck

This paper describes a joint project between Ford, the American Iron & Steel Institute, the University of Louisville, and the U. S. Army to reduce the weight of a full size pick-up truck by 25%, while keeping incremental costs to a minimum. Several alternate technologies were evaluated for each system, subsystem, and component of the vehicle and based on analysis of all combinations of these technologies, the solution which yielded the best overall cost and weight balance, while meeting all of the functional requirements, was selected. The major focus of the project was to develop new steel architectures and materials, since this would assure the maintenance of the lowest possible cost, though the study was not restricted to steel alone. The project was successful in meeting all of its targets, and a vehicle was built to demonstrate the feasibility of the various concepts.
Technical Paper

Advanced High Strength Steels for Chassis Structures

Even though the use of AHSS such as DP590 for body structure applications is becoming relatively common among automobile manufacturers, application of AHSS for chassis structures is relatively new. Chassis structures such as frames and sub-frames typically use hot rolled steel grades in the yield strength range of 220 MPa to 250 MPa. For body-on-frame vehicles, the primary load carrying and energy absorbing structure is the frame. Therefore, hot rolled AHSS such as HR DP590 would be key enablers for weight reduction and strength enhancement of these structures. This paper presents a case for developing AHSS grades for chassis structures, some of the challenges for implementing them, and related work done at Ford Motor Company.
Journal Article

Analysis of Tool Wear for Trimming of DP980 Sheet Metal Blanks

In recent years, implementation of dual phase (DP) Advanced High Strength Steels (AHSS) and Ultra High Strength Steels (UHSS) is increasing in automotive components due to their superior structural performance and vehicle weight reduction capabilities. However, these materials are often sensitive to trimmed edge cracking if stretching along sheared edge occurs in such processes as stretch flanging. Tool wear is another major issue in the trimming of UHSS because of higher contact pressures at the interface between cutting tools and sheet metal blank caused by UHSS’s higher flow stresses and the presence of a hard martensitic in the microstructure. The objective of the present paper is to discuss the methodology of analyzing die wear for trimming operations of UHSS components and illustrate it with some examples of tool wear analysis for trimming 1.5mm thick DP980 steel.