Dynamic Property Research Of Highway Vehicle-Barrier Crash

Traffic barriers are important for the vehicle safety. With increasing of highway building in the country, vehicle-barrier crash research is developing. Vehicle-barrier crash is a nonlinear large deformation dynamic procedure, so it is a very difficult problem. In this dissertation, The author studied the problem from the theory and test The main tasks of present dissertation include:1 Two large scope tests, including 27 full-scale vehicle crash tests, were completed. By the tests, two type barriers with different posts (circular and z type section) were researched, their favor and defect were compared, the impact energy bearing ratio and the applied limits were given. The test results supplied a solid foundation for investigating vehicle crash procedure and building barriers design theory.2. An approach angle that set to the barriers design and tests of half and full scope highway was researched, it supplied a basis for formulating barriers design and test standard. The author taken parts in research and manufacture of the first set of vehicle crash tests devise in the country. The device is important for creating the vehicle crash technology and test standard suiting to domestic conditions.3. Basis to full scale vehicle crash tests, a simple vehicle crash simulation methods—flexible beams method is developed. The method simulates the vehicle crash procedure by assumption the mass (vehicle ) rolling on the beam-post system ( beams were flexible, posts were stiff-plastic or elastic-plastic), and gives the vehicle trajectory and the barriers displacement. The flexible beams mode supplies a simple method for the barriers design and test, and has the reference and practical value in a certain extent.4. By analysis of the variation of energy in vehicle crosswise movement and overturn during the course of vehicle crash, a model for rolling and overturn of vehicles (the vehicle overturn model) was established. The critical value of the displacement for the vehicle rolling and overturn in the course of the vehicle crash can be obtained by use of the model. The model is suitable to various types of wave-beam barriers and is of universal sense.5. Combined with the flexible beam method and the overturn model, the cases of vehicle crash in different angles and velocities are analyzed, the relation curve of the crash angle versus critical crash velocity and then the critical curve of the crash energy barrier bearing are obtained. The analytical and numerical results are valuable to the complement of the experimental data and the predication of the crash course.6. The problems of vehicle-barrier impact are studied using three-dimensional finite element method for impact and contact problems. Based on the Fortran program DYNA3D. a special program for analyzing three-dimensional impact and contact of barriers and a corresponding post processor are modified and completed. According to the characteristic of the vehicle-barrier crash, the analysis of the whole course of the dynamic impact are accomplished and the results are compared with the simplified model and the experimental data. It is shown that the finite element method can simulate the crash course and can make up the insufficiency of information obtained in experiments and simplified computations and the oversimplicity of the model...