Fatigue Verification And Structural Optimization Of Hourglass Spring Based On Stiffness Matching

With the development of rail transit industry, people have increasing requirements for the amenity and speed of railway vehicles. It is harder to use rubber materials in the design and development of railway vehicles’ parts, mainly because of their stiffness and fatigue. Many studies are about the application of structural optimization method on metal materials while only a few are about the application of that method on rubber materials. Taking hourglass spring as the research object, this thesis optimizes the geometric parameters of hourglass spring to meet stiffness matching requirements and improve fatigue performance. Based on the sensitivity analysis of the influence of structural parameters on hourglass spring’s vertical stiffness, this thesis establishes design methods and procedures for stiffness matching of hourglass spring through the software ISIGHT. The thesis discusses the matching optimization of hourglass spring’s stiffness and the improvement of its fatigue life. The main work can be generalized as follows:1. The application of rubber materials on railway vehicles is introduced and the importance of optimization of rubber’s parameters for the design and development of railway vehicles’ parts is explained. Research progress of structural optimization theory is summarized and the content of the thesis is briefly described.2. Hyperelastic constitutive model is briefly introduced. A series of standard samples of rubber materials are used for mechanical properties tests, such as uniaxial test, biaxial test and planar test. Some commonly-used rubber hyperelastic constitutive models are analyzed. The result shows that the reduced polynomial(N=5) can well describe the hyperelastic properties of rubber materials.3. Finite element model of hourglass spring is built by the software Abaqus. Based on the sensitivity analysis of the influence of structural parameters on hourglass spring’s vertical stiffness under the effect of vertical load, the thesis studies how the stiffness is affected by the structural parameters of simplified hourglass spring model. To obtain stiffness matching under different load, the thesis proposes a mathematical model that takes various design variables into consideration. This model is also used to optimize the structural parameters of hourglass spring.4. To verify optimized structure’s effectiveness, the fatigue life of the optimized structure is compared with that of the original structure on uniaxial load by taking maximum principal strain as the damage parameter. The result shows that the fatigue life of the optimized structure is improved, compared with that of the original structure.