Design Oriented Dynamics Modelling And Sensitivity Analysis Of Railway Vehicles

Product design is a circulate redesign process from the design-analysis-optimization and redesign. CAD and CAE play an important role in the design process of the products and they are relatively independent. Because of the different application fields of product, many different analysis works, such as dynamics analysis, FEA and so on, have to be done. The product design model needs to be transformed different analysis models according to the different analysis purposes. And due to the different analysis complexity, the analysis models are different even in the same analysis field. The design model, therefore, is unable to meet the follow-up demands of the analysis models well. Meanwhile, how to feedback the existing problems of the analysis result to the design model lacks the unified model language to describe this course of expression. It influences the automated design process. Based on analyses, features and describing standard of product integrations, a HPDA (Holistic Product Design and Analysis model) is proposed to define design and analysis at different levels, to enhance engineering design and analysis interoperability and to integrate the design methods and tools across multiple engineering domains. The main research work and study results are as follows in this dissertation:(1) HPDA is constructed with four levels (system, subsystem, machine and component), which is well supported by Top-Down design method. At each level, design and analysis models are integrated under a GMRA (Generalized Multi-Representation Rrchitecture) which supports design, analysis and optimization appropriately. The subsystem level is mainly researched. Design oriented SMM (Solution Method Model), SAM (Sensitivity Analysis Model) and optimization Technology are added in the GMRA. According to this model, the dynamics performance of the product can be designed and verified.(2) GMRA is defined based on describe method of STEP standard, and an object-oriented language EXPRESS and EXPRESS-G are used for modelling and analysis of complicated multibody system. The description of the features based semantics integration is proposed to describe the complicated multibody system. Regard complicated railway vehicle as the research object, decompose the vehicle model to the smallest analyzable element to obtain the smallest analyzable feature. These can be foundations to implement the circulate redesign process, which is from design model to analysis model and then from analysis model to solution method model and more to redesign model.(3) Railway vehicle systems consist of a large number of bodies that include carbodies, bogies, wheelsets, suspension elements, and other components. These bodies are interconnected by mechanical joints. Therefore, the multibody system dynamics and wheel-rail contact theory are combined to model and analyze the railway vehicle dynamics. The railway vehicle can be divided into carbody, bogie, suspension force element, constraints, track and so on. Cartesian coordinates with Euler parameters are used to describe the multibody system model. The railway vehicle system dynamics equations are built by the first kind Lagrange Equation. The constraint violation stabilization and augmented approaches are used to solve the differential-algebraic equations. In order to describe the contact feature of wheel and rail, nonlinear Hertz elasticity contact theory is adopted to compute the normal force of wheel and rail. The trace-line method is applied for contact geometry parameters. For the creep force of wheel and rail, the Kalker’s linear theory is used to solve initially and then the Shen’s Theory is used to revise them. The excitation of the vehicle is mainly produced by track irregularity. And the track irregularity can be expressed by power spectrum density of the track. The frequent characteristic of the power spectrum density must be transformed into time characteristics which is sutable for solving the track irregularity by Inverse Fourier Transform. In order to evaluate the railway vehicle dynamics capacity, the performance index has been researched.(4) Based on the multibody system theory and wheel-rail contact theory, the railway vehicle compute package named GVDS is developed by object oriented method, and the accuracy and the reliability of GVDS have been verified by commercial software, such as ADAMS, NUCARS, SIMPACK, etc. And the model of SMM in GMRA has been implemented.(5) Differential-algebraic equations of the multibody system, which include the design variable, are constructed based on The First Kind Lagrange Equation. The direct differentiation and adjoint variable methods are applied for the design sensitivity analysis of multibody system, and the sensitivity analysis of constraint, mass and generalized force are modeled. Some case studies have been done and the accuracy has been demonstrated. So, the sensitivity analysis model (SAM) in the GMRA is carried out.(6) Because the nonlinear Hertz elasticity theory is applied for the wheel-rail force calculation, the wheel-rail force can be described by spring-damper force and the sensitivity analysis of the spring damper force can be modeled. The sensitivity model of wheel-rail force can be achieved for performance optimization of the railway vehicle.According to the research, any complicated mechanical product can be regarded as multibody systems essentially. So, the smallest element feature model of multibody system has been built and the smallest sensitivity analysis feature and the specific wheel-rail smallest analysis feature are achieved. These smallest analyzable features are the smallest elements of analysis of mechanical product. And they are also the smallest elements for design model map into analysis model. So, any complicated mechanical product can be presented by composing the smallest analyzable element in theory.