Springback is an important issue for the application of advanced high-strength steels (AHSS) in the automobile industry. Various studies have shown that it is an effective way to predict springback by using path-dependent material models. The accuracy of these material models greatly depends on the experimental test methods as well as material parameters calibrated from these tests. The present cyclic sheet metal test methods, like uniaxial tension–compression test (TCT) and cyclic shear test (CST), are nonstandard and various. The material parameters calibrated from these tests vary greatly from one to another, which makes the usage of material parameters for the accurate prediction of springback more sophisticated even when the advanced material model is available in commercial software. The focus of this work is to compare the springback prediction accuracy by using the material parameters calibrated from tension–compression test or cyclic shear test, and to further clarify the usage of those material parameters in application. These two types of nonstandard cyclic tests are successfully carried out on a same test platform with different specimen geometries. One-element models with corresponding tension–compression or cyclic shear boundary conditions are built, respectively, to calibrate the parameters of the modified Yoshida–Uemori (YU) model for these two different tests. U-bending process is performed for springback prediction comparison. The results show, for dual phase steel (DP780), the work hardening stagnation is not evident by tension–compression tests at all the prestrain levels or by cyclic shear test at small prestrain γ = 0.20 but is significantly apparent by cyclic shear tests at large prestrain γ = 0.38, 0.52, 0.68, which seems to be a prestrain-dependent phenomenon. The material parameters calibrated from different types of cyclic sheet metal tests can vary greatly, but it gives slight differences of springback prediction for U-bending by utilizing either tension–compression test or cyclic shear test.

The necking behavior of sheet metals under stretch-bending process is a challenge for the forming limit prediction. State-of-the-art forming limit curves (FLCs) allow the prediction under the in-plane stretching but fall short in the case under out-of-plane loading condition. To account for the bending and straightening deformation when sheet metal enters a die cavity or slide along a radius, anisotropic hardening model is essential to reflect the nonproportional loading effect on stress evolution. This paper aims to revisit the M-K analysis under the stretch-bending condition and extend it to accommodate both distortionless and distortional anisotropic hardening behavior. Furthermore, hardening models are calibrated based on the same material response. Then the detailed comparison is proposed for providing better insight into the numerical prediction and necking behavior. Finally, the evolution of the yield surface and stress transition states is examined. It is found that the forming limit prediction under stretch-bending condition through the M-K analysis strongly depends on the employed anisotropic hardening model.

The relevance of protocol conformance testing techniques to hardware testing is discussed. It is shown that the ioconf (input-output conformance) approach used in protocol testing can be applied to generate tests for a synchronous hardware design using its formal specification. The generated tests are automatically applied to a circuit by a VHDL testbench, thus giving confidence that the hardware design meets its high-level formal specification. Case studies illustrate how the ideas can be applied to standard hardware verification benchmarks such as the Single Pulser and Black-Jack Dealer.