Transformation-induced plasticity (TRIP) assisted steels possess improved strain hardening behavior and resistance to necking that are favorable for automotive body applications. However, the TRIP effect causes complex springback behavior of these steels that can hardly be predicted by existing constitutive models for other steels. In this work, the functions in the original Yoshida-Uemori model describing isotropic and kinematic hardening were modified by adding new parameters that can represent the TRIP effect. Cyclic tension/compression experiments were performed on a selected TRIP-steel grade, and the results were used to calibrate the modified model. The modified model was coded via user subroutine into a commercial FE solver. The springback predictions were compared with actual try-out stamping experimental results for highlighting the improvement of predictions with the modified model.

A cyclic tension-compression testing program was conducted on flat specimens of TPN-W (R) 780 (Three Phase Nano) and DP980 (Dual Phase) Advanced High Strength Steels (AHSS). This experimental method was enabled utilizing an anti-buckling clamping device performed in a test machine, and the surface strains along the thickness edge are measured with a three-dimensional Digital Image Correlation (DIC) system. The in-plane pre-strain and reversed strain values, at specified strain rates, are investigated to observe the potential plastic flow and the nonlinear strain hardening behavior of the materials. The validity of the test results is established with the monotonic tension tests, to substantiate the true stress-strain curves corrected for the frictional and biaxial stresses induced by the clamping device. A process method for analyzing the correction using a macro script is shown to simplify the output of the true stress-strain results for material model calibration. An in progress study to validate the forming and spring-back predictive capabilities of a calibrated TPN-W (R) 780 complex material model to an actual stamping of an automotive component will demonstrate the usefulness of the experimental cyclic test method. Suggestions to improve the testing, strain analysis and calibration of the model parameters are proposed for augmented use of this test method.

The ThyssenKrupp InCar Project is a comprehensive R&D development that gives automotive manufacturers modular solution kits for body, chassis and powertrain applications. The solution kits developed within this project offer weight reduction, cost savings or improved functionality. This paper will focus on the two front door solutions developed within the InCar project. The first door solution, called the Lightweight Door, achieved a 13% weight reduction. This door features a 4-piece tailored blank inner panel and a sandwich material outer panel. The second door solution, called the Advanced Door, is a completely new and innovative door architecture that uses a 2-piece tailored blank mid panel and ultra thin Dual Phase 500 outer panel to achieve an 11% weight reduction. Prototypes were manufactured and tested for both door solutions. This paper will provide a detailed description of everything related to the development of these door solutions, including manufacturing and assembly processes, performance, materials, and cost estimation.