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This paper focus on the design approach of mapping the equivalent bead to the physical bead geometry. In principle, the physical character and geometry of equivalent bead is represented as restraining force (N/mm) and a line (bead center line). During draw development, the iterations are performed to conclude the combination of restraining force that obtains the desired strain state of a given panel. The objective of physical bead design to determine a bead geometry that has the capacity to generate the same force as specified in 2D plane strain condition. The software package ABAQUS/CAE/Isight with python script is utilized as primary tool in this study. In the approach, the bead geometry is sketched and parameterized in ABAQUS/CAE and optimized with Isight to finalize the bead geometry.

The risk of skid lines for Class A panels has to be assessed before releasing the die development for hard tooling. Criteria are needed to predict skid lines in the formability evaluation stage to avoid expensive changes to tooling and process for resolving skid line issue in production. In this study, criteria using three different measured parameters were developed and validated. A draw-stretch-draw (DSD) test procedure was developed to generate skid lines on lab samples for the physical evaluation. This was done using tooling with various die entry radii and different draw beads. The skid line severity of lab samples was rated by specialists in the inspection of automotive outer panel surface quality. The skid line rating was correlated with geometric measurements of the lab samples after the DSD test. The sensitivity of the appearance of skid lines to tooling and process parameter variations was identified.

Rollover crash is one of the important fatal crash modes in highway accidents. To protect occupant safety, the National Highway Traffic Safety Administration (NHTSA) has proposed a higher roof strength requirement in the upcoming new federal regulation. Meanwhile fuel efficiency and environmental friendliness demands that the safety cage design should have the minimum weight while providing the sufficient roof crush strength. These requirements pose a challenge to automotive design engineers. In this paper, Advanced High Strength Steels (AHSS) are introduced as an enabler to support this challenging task. The advantages of different types of AHSS for vehicle crashworthiness are presented. The criteria to select materials to improve the roof crush performance are discussed in detail.

Increasingly stringent requirements for auto safety, fuel consumption and environmental friendliness require lightweight and efficient vehicle designs. Advanced High Strength Steel (AHSS) tubes, including hydroformed tubular parts, are one of the key enablers used today. However, conventional tube joint designs, in general, are difficult to utilize with spot welding processes, a preferred and commonly used assembly process in North America's automotive industry. This is particularly true for light gauge tubes. In this paper, a new tube joint design is proposed and this new proposed joint is applicable for spot welding, adhesive bonding, and other joining methods. From a performance perspective, this joint design utilizes the advantages of the box joint, which distribute load more uniformly through the whole joint structure, and thus it provides better stiffness and stability to the vehicle structure.

Springback is one of the major concerns as more advanced high strength steels are used in the automotive industry. Unlike FEA forming simulation, FEA springback simulation is not widely used in the production due to its poor accuracy. One of the reasons for this is that some complex material behaviors are not fully considered in the FEA simulations. In this study, a number of experiments were conducted to study the unloading behavior of steels with different pre-strain levels. Unloading modulus and related damage parameters at 1%, 2% and 5% pre-strain are calculated for 14 different steel grades from the experimental data to consider the inelastic effects during unloading. The unloading modulus was found to be 10% to 20% lower than the Young's modulus. FEA springback simulations were conducted for a benchmark test with two steel grades. Simulated springback results are compared with the experimental data.