Consideration of Manufacturing Effects to Improve Crash Simulation Accuracy

The confidence level of crash simulations is mainly determined by a well-defined finite element representation of the vehicle structure, correct modelling of the kinematics, and the material properties being applied. In the past, materials were described by quasistatic – or, if available – dynamic stress-strain characteristics. Besides this, each sheet metal part was assumed to have a uniform gage and material characteristics. However, it is a well-known effect that the physical properties of steel can alter significantly during the manufacturing process. This comprises an increase of material stiffness due to plastic deformation as well as gage changes. The amount of these changes is of very local nature and cannot be covered by simply scaling material properties and gages. In the past, crash software tools didn’t support the introduction of these local effects, so that they couldn’t be taken into account. In the meanwhile LS-DYNA has the capability to import information provided by stamping tools such as PAMSTAMP or AutoForm. Thereby a very important part of the material properties can be introduced into the crash simulation models, leading to a significantly increased correlation to test results. The impact of this effect on crash performance was analysed for a recent vehicle project and will be discussed in detail.