A twist-beam is the core part of a typical semi-independent rear suspension of a passenger vehicle. The first principal strain at each point of a twist-beam is used to predict the potential damage location. A new damage identification index is addressed, which applies the first principal strain difference to identify the cracked twist-beam's damage location. The finite element model of a twist-beam is established for numerical modal analysis and validated by experimental modal analysis. A set of the first principal strain at each point of a twist-beam is generated from the proposed FE model's numerical strain modal analysis. The maximum first principal strain of the derived set is used as the reference indicator for damage prediction. The accuracy of the proposed damage prediction indicator is verified by numerical and experimental modal analysis and compared with the strain mode shape in a single direction of a twist-beam. Finally, a twist-beam with two predefined cracks is used to evaluate the new damage identification method. Compared with the displacement mode difference, a significant order of magnitude mutation of the first principal strain difference appears at the damage location after cracks introduced to the twist-beam. The absolute value of the first principal strain difference at each point of the structure between the intact and damaged state can be utilized as a quantitative index for damage identification. The application of the first principal strain of a twist-beam is of great theoretical and practical value to improve the damage identification methods based on strain modal analysis.
 

Twist-beam; first principal strain; strain modal analysis; damage prediction; damage identification