Abstract
The fatigue strength validation by tests of the railway bogie frames requires existence of an expensive laboratory and a long time for testing, of about 6 to 10 months. Considering these aspects, the european norms admit that fatigue tests can be replaced by finite elementes analysis, with condition that analytical model to be correctly realized and validated by tests. Experimental modal analysis provides a powerful tool for validation of the FEA model through experimental data. The article presents an application for analytical assessment of the fatigue strength for a three-axle locomotive bogie frame, before sending it to the laboratory fatigue tests. Using Ansys, it was carried out the structural analysis of the bogie frame, rezulting the modal model characterized by the modal parameters: eigenfrequencies and eigenshapes. The analytical model was validated through an EMA application carried out on the bogie frame and correlation analysis of the EMA and FEA models. The analytical model and data files containing the simulated vertical, transverse and twist loads, applied to the bogie frame according to EN13749/2011, constitutes the input data for nCode program, that evaluates the bogie frame lifetime using appropriate stress curves and a recognized hypothesis of damage accumulation.
Highlights
Background of EMA and Finite Element Analysis (FEA) analysisExperimental Modal Analysis (EMA) is the procedure of building the mathematical model of a structure based on the experimental data obtained by measurements made on the structure brought into a controlled vibrational state
The system is excited under well-defined conditions and, determining the evolution laws of excitation and vibratory response, is identified the modal model characterized by a minimum number of modal parameters, describing its vibration eigenmodes: eigenfrequencies, damping factors and eigenshapes
The most general EMA mathematical model which describes the dynamics of a system with N degrees of freedom (DOF) is formulated as a system of differential equations adapted to the calculation method, which can be in time domain or in frequency domain
Summary
Experimental Modal Analysis (EMA) is the procedure of building the mathematical model of a structure based on the experimental data obtained by measurements made on the structure brought into a controlled vibrational state. The most general EMA mathematical model which describes the dynamics of a system with N degrees of freedom (DOF) is formulated as a system of differential equations adapted to the calculation method, which can be in time domain or in frequency domain.
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