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Hot-formed steels, also called “Boron steels” or Ultra-High Strength Steels-UHSS, offer a great weight saving potential versus conventional cold-formed high strength steels used for crash relevant structural parts. Boron steels allow complex shaped parts due to the hot-forming process. In the hot forming process first the sheet metal with initial yield strength of around σy=400 MPa is blanked and then heated in an oven up to ∼950° Celsius. In the next step the “hot” sheet metal is stamped and at the same time rapidly cooled down and quench hardened in the stamping die. During this process the yield and ultimate tensile strength increase up to approximately σy>1100 MPa and UTS∼1500 MPa in the final stamped part. The enormous strength and the very good dimensional tolerances with nearly no springback result in the use of more and more hot-formed parts in the body, especially for crash relevant parts like structural reinforcements.

Structural adhesives are widely used across the automotive industry for several reasons like scale-up of structural performance and enabling multi-material and lightweight designs. Development engineers know in general about the effects of adding adhesive to a spot-welded structure, but they want to quantify the benefit of adding adhesives on weight reduction or structural performance. A very efficient way is to do that by applying analytical tools. But, in most of the relevant non-linear load cases the classical lightweight theory can only help to get a basic understanding of the mechanics. For more complex load cases like full car crash simulations, the Finite Element Method (FEM) with explicit time integration is being applied to the vehicle development process. In order to understand the benefit of adding adhesives to a body structure upfront, new FEM simulation tools need to be established, which must be predictive and efficient.

In this paper polymer structural foams are being investigated in body structure applications. There are two major polymer foam technologies for structural applications: the well-known epoxy based insert solutions and the PUR injection foams. Here we focus only on the PUR injection foams and its structural applications. It will be shown where such structural foams can be applied in the body structure in order to enable lightweight design or to scale the structural performance. Reliable CAE methods for crash simulation as well as several body structure application examples will be presented and evaluated.

Structural adhesives are widely used across the automotive industry for several reasons like scale-up of structural performance and enabling multi-material and lightweight designs. Nowadays for crash simulation with the explicit Finite Element Method (FEM), several simulation tools are in use for the thin layer of structural adhesives in crash loaded structures (e.g. solid element methods, beam type spring methods; several material models), but all of them show either deficits in accuracy or in computation time. Therefore a new simulation tool for the explicit FEM has been developed. This approach uses a user-defined contact definition for the modeling of the adhesive. It enables a user-friendly and time-efficient modeling of adhesives without using elements for the adhesives. The new method has been integrated into the commercial software tool RADIOSS and was implemented on the Ford supercomputer cluster.

Hydroformed components are replacing stamped parts in automotive frames and front end and roof structures to improve the crash performance of vehicles. Due to the increasing application of hydroformed components, a better understanding of the crash behavior of these parts is necessary to improve the correlation between full-vehicle crash tests and FEM analysis. Accurately predicting the performance of hydroformed components will reduce the amount of physical crash testing necessary to develop the new components and new vehicles as well as reduce cycle time. Virgin material properties are commonly used in FEM analysis of hydroformed components, which leads to erroneous prediction of the full-vehicle crash response. Changes in gauge and material properties during the hydroforming process are intuitive and can be reasonably predicted by using forming simulations. The effects of the forming process have been investigated in the FEA models that are created for crash analyses.

Hot-formed steels (here called “Boron steels”) offer a great weight saving potential versus conventional cold-formed steels used for crash relevant structural parts. Boron steels allow complex shaped parts due to the hot-forming process, which can be a direct or indirect process. In the direct hot forming process first the sheet metal with an initial yield strength of around σy=400 MPa is blanked and then heated in an oven up to some 950° Celsius. In the next step the “hot” sheet metal is stamped and at the same time rapidly cooled down (quench hardening process) in the stamping die. During this process the yield strength increases up to approximately σy > 1100 MPa in the final stamped part. Due to the enormous strength and the very good dimensional control (nearly no springback), more and more hot-formed parts are used in vehicle design. Especially in the body structure hot-formed steels are used for crash relevant parts.

The importance of new material applications for improved vehicle passive safety is increasing. Automotive companies are relying more and more on CAE methods to design and select materials for car body structures that fulfill the safety targets. This results in an increasing demand for improved quality of crash simulations. This quality heavily depends on the appropriate simulation strategies and methods used for these investigations. For Advanced High Strength Steels (AHSS), such as the multiphase grades DP600 (HXT600X) or DP800 (HXT800X), the material properties change significantly due to work-hardening during cold forming in the manufacturing process. For an efficient development process of parts made out of AHSS the forming history needs therefore to be considered within the crash simulation. In this paper, studies (CAE and test including validation) will be presented that demonstrate the effects of the sheet metal forming history on the results of the crash simulation.

The objective of this study is to evaluate the influence of the hydro-forming process and the effect of strain rate on crash performance and develop a modeling approach to improve the accuracy of crash prediction. Work hardening, thinning and strain rate effects are investigated in both component and full vehicle analyses to understand their sensitivities. Gages measured and material properties tested from post-formed tubes are compared with hydro-forming simulation results to confirm accuracy of the modeling methodology proposed in the paper. Front crash simulation using strain rate and forming effects are correlated with the test data for both component and full vehicle analyses and conclusion has been drawn from this comparison.

On the base of the Finite Element Method (FEM) a new constitutive model for extruded magnesium profiles, useful for crash relevant body components will be developed. This constitutive model will be implemented into commercial software as a user material law and can be used in the development of vehicle structures. First step is the material characterization of the magnesium extruded materials. On this base the constitutive model will be developed and validated. In the last step simulations will be performed with the new simulation tool and the results will be compared to test results.

On the base of the Finite Element Method (FEM) simulation models for structural foam in crash relevant body components will be developed. These models will be implemented into commercial software and can be used in the development of vehicle structures. The first step is the material characterization of the structural foam. On this base the simulation model will be developed and validated. In the last step simulations will be performed with the new simulation tool and the results will be compared to test results. The potential of structural foam in two crash relevant body areas, the bumper beam aluminum foam and a B-pillar polymer foam application will be shown.