Iso-Geometric Analysis for Crash Simulation: Study of Anisotropy and Fracture Behaviour in Extruded Aluminium Structures

Abstract

Achieving reliable crash and impact simulations is essential for improving vehicle safety, reducing development time, and minimizing costs associated with physical testing. Although the finite element (FE) method remains the established standard for crashworthiness analysis in the automotive industry, its dependence on mesh generation, geometric approximation, and reduced continuity can limit predictive accuracy and efficiency in complex structural applications. Isogeometric Analysis (IGA) has emerged as a promising alternative by directly incorporating computer-aided design (CAD) geometry into numerical simulation through spline-based basis functions. This framework enables exact geometry representation and higher-order continuity, offering improved capability for capturing nonlinear deformation, stress evolution, and damage initiation under crash-relevant loading conditions. This study investigates the applicability of IGA to automotive crash simulations, with particular emphasis on the anisotropic behaviour of extruded aluminium components and stress triaxiality-dependent ductile fracture. Numerical investigations are carried out across multiple scales, ranging from material characterisation via tensile testing to component- and assembly-level crash simulations. The study includes a systematic evaluation of strain formulations, refinement strategies, and solid discretisation approaches, motivated by the need to improve correlation between numerical simulations and physical testing at Volvo Cars. The results demonstrate that IGA improves geometric fidelity and produces smoother and more stable solution fields, leading to enhanced prediction of stress distribution, deformation patterns, and damage evolution compared to conventional FE formulations. However, challenges remain, including numerical locking phenomena, sensitivity to discretisation parameters, convergence issues in highly nonlinear regimes, and limitations in preprocessing workflows and implementation complexity. Overall, IGA shows strong potential for high-fidelity crash simulation, although further developments are required to improve robustness and enable efficient largescale industrial applications.