Study On Load Spectrum Of Straddle-type Monorail Vehicle Carbody

As the core component of train load,the fatigue strength of straddle-type monorail vehicle body directly affects the safety of train operation.Load spectrum has an important influence on the fatigue life prediction and reliability design of vehicle body.How to compile accurate load spectrum consistent with the actual load characteristics is of great practical significance and application value for the study of fatigue life of service vehicle body.In this thesis,the straddle-type monorail vehicle body was taken as the research object,and the dynamic load of the vehicle body was obtained through dynamic simulation and line measurement.Two kinds of extrapolation methods,parametric and non-parametric,were adopted to carry out research on the preparation of the vehicle body strength load spectrum,and the compatibility between the calculated results of the fatigue strength of the vehicle body and the actual fatigue failure parts of the vehicle body was compared and analyzed.It is proved that the non-parametric extrapolation method based on kernel density estimation has higher accuracy.The main research contents are as follows:(1)The dynamic load at the operating point of the load outside the vehicle was obtained based on the dynamic simulation.The load transfer characteristics between the straddle-type monorail body and the running part were analyzed,the topological configuration of the monorail was analyzed,the spatial coupling dynamics model of the monorail was established,and the load time history at the operating points of the coupler,empty spring and center pin seat of the monorail body was obtained through dynamic simulation.(2)The dynamic load of vehicle body measurement point was obtained based on the real vehicle line tracking test.The finite element model of monorail vehicle body was established,and three measuring points with large response of floor plane stress were determined by the results of stress analysis of the vehicle body.The load transfer coefficients of the three measuring points were calculated based on the finite element model of the vehicle body,and the load time history obtained from the test was converted into dynamic loads by combining the load transfer coefficients.(3)The life cycle load spectrum of vehicle body was obtained based on two kinds of extrapolation methods: parametric and non-parametric.The rain-flow counting method was used to convert the vehicle body dynamic load obtained from dynamic simulation and line measurement into rain-flow matrix.The load average amplitude characteristics of rain-flow matrix were analyzed based on mathematical statistics theory.The parameter extrapolation joint distribution model was constructed with mean value obeying normal distribution and amplitude obeying Weibull distribution,and the parameter rain-flow extrapolation based on joint distribution was carried out.Reasonable kernel function and fixed bandwidth were determined,adaptive bandwidth factor was introduced,and nonparametric extrapolation probability density function was obtained based on adaptive bandwidth kernel density estimation,and non-parametric rain-flow extrapolation based on kernel density estimation was carried out.(4)The application of two kinds of extrapolated load spectra on the fatigue strength of the monorail body of Chongqing Line 3 is carried out.Based on the fatigue analysis software FEMFAT,the fatigue damage calculation of the monorail body of Chongqing Line 3 was carried out by using the parametric and non-parametric extrapolated load spectra.The fatigue damage values of the straddle-type monorail body under the two extrapolated load spectra were analyzed,and the fatigue damage locations of the monorail body were compared with the actual monorail body.It is proved that the non-parametric extrapolation based on kernel density estimation is more suitable as the extrapolation method to compile the intensity load spectrum of straddle-type monorail vehicle.Through the research,this thesis proposes a set of methods suitable for the compilation of the body strength load spectrum of the span monorail vehicle,which provides a reference for the subsequent research on the load spectrum of bogies and other components,and provides technical support for the formulation of the industry standard for the structural fatigue strength of monorail vehicles,which has important engineering application value.