Modal and Frequency Response Analysis of a Vehicle Frame using Finite Element Method (FEM)
As part of the Advanced CAE final assessment, I was assigned the task of creating a vehicle frame model and studying its modal and frequency response characteristics using the Finite Element Method (FEM). The objective was to analyse the frequency response, mode shapes, and resonant frequencies of the structure to ensure it would not experience failure or excessive vibration at the design stage.
This project combined three key aspects:
Modal & Frequency Response → representing the dynamic behaviour of the structure.
Vehicle Frame → the subject of analysis.
Finite Element Method (FEM) → the computational analysis technique used.
For this study, the Honda City Body-in-White (BIW) was selected as the model for structural dynamic analysis. The complex geometry of the original car frame was simplified by converting beam-like cross-sections into 1D beam elements with equivalent stiffness and mass properties to reduce model complexity while maintaining accuracy.
The BIW was modelled in Altair HyperMesh using multiple 1D beam elements, where stiffness was varied according to the load requirements of different sections. Both lateral and non-lateral members with two standard cross-sections were used to simulate realistic structural behaviour.
The completed model was exported to the MD Nastran solver for modal and frequency response analysis. Post-processing was carried out in HyperView and HyperGraph to visualise mode shapes and frequency response functions (FRF). Three types of excitation inputs such as single mode excitation, in-phase excitation, and out-of-phase excitation were applied to study the system’s response under different vibration modes.
The analysis provided valuable insights into the bending behaviour, torsional stiffness, and deflection patterns of the vehicle frame at various frequencies. Several iterations were performed by adjusting the beam cross-section dimensions to improve stiffness and minimise resonance. These results help designers identify critical locations and potential failure zones, allowing structural improvements to be made early in the design phase.
