Optimization design of rail clip in Vossloh fastening system by uniform design and grey relation analysis

Abstract

This study presents the innovative optimization design procedure to increase the strength and fatigue safety of a fastening system under the static and fatigue loading. Applying the uniform design of experiment, a group of simulation experiment is generated. Utilizing ANSYS/Workbench software, the finite element models are constructed and used to evaluate the von Mises stress of rail clip for EN 13146-1 and EN 13146-2 testing simulations. Furthermore, the fatigue safety factor of rail clip for EN 13146-4 testing simulation is also presented. By the Kriging interpolation method, the surrogate models are rebuilt by the input and output data from the uniform design. Applying grey relational analysis, entropy weighting method, genetic algorithm and Hooke–Jeeves algorithm, the improvement design version is presented by solving the multi-objective optimization problem. Compared with the original design, the maximum von Mises stress of rail clip has been decreased to 25.189 MPa, the fatigue safety factor is upgraded to 3.829. As a result, the strength and fatigue safety of the rail clip in the fastening system is increased.

Development of a new and modification of existing elastic clips for rails fastening

“…In both research groups, the magnitude of the fastening force, clip's geometry and material properties, and operation loads are the most critical parameters affecting the static and dynamic properties of the entire fastening system [12]. Therefore, changing these parameters can improve the fastening system's efficiency [77]. Consequently, the shape and dimensions of the existing clips as well as their material properties must be optimized [66,68].…”

“…Solving the common problems of fastening systems and understanding that a good grasp of the complex mechanical behaviour of the fastening system (which could only be determined by long-term and financially expensive tests) can provide the possibility to improve its efficiency have intensified research using FE models and CAE tools in the last two decades [10-16, 18, 19, 23, 47, 74, 79, 80]. Moreover, efficiency improvement is often achieved using parametric analysis by changing the geometry of the clip to extend its durability as well as the durability of the fastening system [77,80,81].…”

“…Such an approach saves time and money. Thus, in recent research studies on clips and fastening systems, simulations of the test procedures according to the standards are increasingly performed [48,66,77,83]. An example of developing a detailed numerical model for the Safelok I fastening system is shown in Figure 11, and the procedure is described in detail in the research studies [23,63,84,85].…”

“…The first phase represents the simulation of the fastening force, that is, the introduction of a static stress state in the clip and fastening system. Depending on the simulated test, the second phase is the numerical simulation of the test load [10,48,66,77,78,83].…”

“…After the calibration and validation of the clip's and/or fastening system's numerical model, parametric analyses can be performed. The most frequently considered parameters are the dimensions, shape [ [16,74,77,80] and material properties of the clip [68], the magnitude of the axle load and its position on the rail running surface [23,47], and the distance of concrete sleepers, that is, the distance of the rail supports [23], the change in the stiffness of the rail pad [48,49].…”