| Popis: |
The pursuit to become a better and more efficient transportation mode and the need of renovation has led the railway industry to search for new technologies. An example to such reform is the ongoing efforts to implement new lightweight materials into the railway vehicles as primary load bearing structures, which can help to reduce energy consumption, maintenance costs, and to increase passenger and line capacity. Composite materials are promising candidates in this respect and this thesis addresses a railway specific risk namely flying object strike, which requires attention when composites are in use especially in high speed rail operation, consequently providing detailed analysis on impact behaviour of composite materials for rail specific applications. This thesis shows for the first time an approach to harmonise and unify different railway standards into a single method for small object strike against composite rail vehicles. The original and essential contribution of this study is a cost effective and practical method for the rail industry that removes the necessity of high velocity impact experiments. Quasi-static punch tests (QSPT) were carried out with glass fibre reinforced laminates and foam core sandwich materials incorporating such laminates. It has been shown that the failure modes experienced in a high velocity impact can be mimicked via QSPT method. A numerical model was developed and was validated with QSPT experiments. Following, the numerical model was used to perform high-velocity impact simulations in a velocity range that is relevant with rail service while considering the strain rate effects. Lastly, various standards for impact risks against railway vehicles were investigated from proposed methodology perspective, and discussed whether they can be harmonized into the presented assessment method. The results showed that the proposed methodology has considerable potential to be preferred over costly high velocity impact experiments. The analysis of the energy transfer characteristics, contact forces, impact velocity change of the projectile, and structural damage showed that the proposed method can be used alone instead of various existing standards, providing a significant reduction in sample size as well as avoiding the costly high-velocity impact experiments, hence resulting in substantial cost savings. |
