Material Models of Metals for Crash Simulation

Description

Besides an appropriate spatial discretisation of the structure and a profound knowledge of the required load cases, appropriate material modelling is a key ingredient for predictive crash simulations. The load carrying structure of a car today still mainly consists of metallic materials. The materials to be described are diverse. The seminar deals with the following materials:

• Mild and high strength steels,
• cold formable AHSS and UHSS steels,
• hot formable and quenchable boron steels,
• wrought Al and Mg alloys,
• cast Al and Mg alloys,
• metalic material produced by additive manufacturing.

The objective of this 1-day course is to give the participants an overview of material models of metals used in crash simulation. Within the first chapter the deformation behavior and the failure mechanisms of each material class are explained based on the material structure. In the second chapter phenomenological models for crash simulation of metals are introduced. This includes elasticity, viscoplasticity and failure due to localized necking, ductile normal fracture and ductile shear fracture. In case of crashworthiness simulation the influence of strain rate on the aforementioned properties is of high interest. In the third chapter the tests needed for the characterization of materials are described and the parameter identification for the material models is discussed. The manufacturing process can have a significant impact on the material properties (pre-straining of sheets, paint bake heat treatment, local heating in joining processes etc.). Within the fourth chapter simulation examples are discussed which show the sensitivity of simulation results regarding the identified material parameters. In the final chapter the influence of the discretization on the predictive quality of a crashworthiness model is discussed. This includes both the element size and the type of element (shell vs. solid).

Content

• Overview of metallic materials used in cars
• Influence of material structure on mechanical behavior
• Phenomenological material models for metals
• Overview of experimental methods for material characterization
• Identification of material parameters from experiments
• Discussion of the sensitivity material parameters