Session: 01-06-01: New Advances in Acoustics and Vibration: AI and Machine Learning, New Methods and Materials

Paper Number: 143333

143333 - Vibration Modeling of Vehicle Structure Incorporating the Dynamic Characteristics of Helical Springs Under Road Excitation 

The aim of this research is to investigate the boundary conditions for vehicle body analysis by applying the wave equation and dynamic stiffness formulation of helical springs, aiming to identify dynamic vulnerabilities in automotive frames. With the advent of electric vehicles, the structural composition of vehicle body in white (BIW), particularly the base where the battery pack is located, has undergone significant changes. To analyze the deformation in automotive structures, the Spectral Element Method (SEM) or Finite Element Method (FEM) is employed to predict vibration responses in the frequency domain. SEM enhances efficiency and accuracy by transforming the governing motion's partial differential equations from the time domain into the frequency domain via Discrete Fourier Transform (DFT).  This study underscores how the dynamic stiffness of structural responses is intricately linked to changes in the positioning of structural supports and the characteristics of boundary conditions. The direct coupling of the suspension assembly to the vehicle's BIW provides the pivotal role of helical springs in transmitting operational vibrations. At low frequencies, helical springs act as simple massless force elements, but critical dynamic responses occur around 40 Hz, necessitating a detailed understanding of the springs' dynamic characteristics. The propagation of resonance responses within this frequency domain is highlighted as a potential threat to the automotive body's durability, thus necessitating a detailed analysis of the dynamic properties of helical springs. This analysis is conducted through a dynamic stiffness formulation, aimed at establishing well-defined boundary conditions for analytical techniques such as SEM and FEM. The formulation of dynamic stiffness is obtained through the analysis of the partial differential equation governing motion, which explain the relationship between the wavenumber and the frequency characteristic of the wave form. To corroborate the reliability of spring analysis, hammer impact experiments were established with different types of helical springs. Employing a jig that implements a vehicle's suspension assembly, these experiments simulated the actual weight of a vehicle on the springs, setting precise boundary conditions. The experimentation with four distinct springs, each differing in coil number, center diameter, static stiffness and wire diameter, revealed that the Frequency Response Function (FRF) relationships derived from these impact tests align closely with those from the helical spring analysis. This congruence not only validates the experimental approach but also confirms the integrity of the data used for SEM and FEM analyses. This thesis develops a vibration input model based on the dynamic properties of helical springs for automotive structure analysis methods such as SEM or FEM, pinpointing system vulnerabilities to the dynamic properties and wave motion of the suspension system's helical springs.

Presenting Author: Seongwook Jeon Hanyang University

Presenting Author Biography: - Hanyang University, Seoul, Korea
Bachelor of Mechanical Engineering, Feb 2021

-Hanyang University, Seoul, Korea
Ph.D Coarse in Mechanical Engineering

Authors:

Seongwook Jeon Hanyang University
Yeonjin Jang Hanyang University
Chan Lee Hyundai Motor Company
Junhong Park Hanyang University