Damage Diagnosis of Railway Vehicle Car Body Based on Strain Modes

In the rail vehicle structure design, the key of the strength design and fatigue life estimation is to analyse the stress state of the structure under the dynamic load. As the stress cannot be measured directly, the displacement response model of the body structure is established by the displacement mode analysis method, and the strain response of the car body is obtained by the relationship between displacement and strain, thus the stress state is obtained. Since displacement to strain is a differential process, the variation of displacement will be magnified and the error will be generated. Strain mode theory and its property are derived from displacement mode theory. The results show that it is more sensitive for strain mode than displacement mode through the simulation analysis of the car body equivalent vertical model calculation. Strain mode difference curve can determine the structural damage location. The vehicle FE model verifies this result. The strain and stress versus time history of car body can be obtained by the mode superposition method, which provides basis for fatigue life prediction and load spectrum research.