Noise and Vibration Control in Automotive Bodies

2Vibration Control of Overall Body Structure

2.1 Introduction

Body stiffness is not only one of the most important indicators in vehicle body design, but also an important indicator to determine the vehicle’s driving quality and performance. This chapter introduces overall body stiffness and modal analysis, whereas Chapter 3 focuses on local body stiffness and modes.

2.1.1 Overall Body Stiffness

Structure stiffness refers to the structure’s capability to resist deformation under the action of an external force: i.e. its capability of elastic deformation to restore its original shape. A vehicle body is a structure, so it has certain stiffness.

2.1.1.1 Classification of Vehicle Body Stiffness

A vehicle body undergoes two major forms of deformation: bending deformation and torsional deformation. Accordingly, the body stiffness can be categorized by these deformations: i.e. the body stiffness is divided into bending stiffness and torsional stiffness. Bending stiffness refers to the ratio of an external applied force to its corresponding displacement deformation, which represents the structure’s capability to resist bending deformation, and its unit is N mm⁻¹. Torsional stiffness is the ratio of an external applied torque to its corresponding angle deformation, which refers to the structure’s ability to resist torsional deformation, and its unit is KN‐m rad⁻¹.

The body is divided into the body‐in‐white (BIW), trimmed body or body‐in‐prime (BIP), and full vehicle body. Accordingly, ...