| In this thesis, new methods in solid mechanics are developed for analyzing vibrations in structural systems with particular emphasis on passenger cars in high-speed trains. Three interrelated problems are examined.;The first part of the thesis is on the propagation of vibration energy from the wheels to the car body. System identification is used to estimate the dynamic properties of the suspension using acceleration data from full speed test runs of a prototype train. Fatigue reliability is assessed using deterministic and stochastic methods, and static and dynamic fatigue test procedures are developed for an experimental test facility at the Korea Railroad Research Institute.;The highest stresses are found to be at the corners of the windows and doors of the aluminum car body panels. In the next part of the thesis, a semi-analytical method is developed for analyzing these stress concentrations. The basic idea is to combine a conformal mapping approach based on complex variable theory with finite element analysis. In this manner, a relatively coarse mesh can be used to predict highly localized stresses around openings in plates under bending loads. The approach is useful for complex structures where it would be difficult to include fine meshes around every panel opening.;Since advanced car body designs tend to have tubular frames, the last part of the thesis focuses on free vibrations of orthotropic cylindrical shells. Perturbation theory is used to derive closed-form analytical expressions for the frequency-wavelength dispersion relation and for the natural frequencies and mode shapes. These new analytical results provide insight into the characteristics of cylinder vibrations and are also useful for system identification. |
