Study On Static & Dynamic Numerical Simulation Of Bolted Flange Joints Of Gear Compressor

Bolted flange joints are widely used in industrial structures such as aerospace engineering, petrochemical industry, mechanical engineering. Compressors usually works in the dynamic environment, the mechanics characteristic of the bolted flange joints is typical nonlinear status problem, which mostly couples with nonlinear geometry and material, it makes the nonlinear degree more complicated. As most of contact problems are hardly resolved by classic mathematic and mechanical methods, the numerical simulation technology which is based on finite element method is widely used within the development of the modern computer aided engineering technology based on finite element method. The multiple nonlinearities have important influence on the static and dynamic mechanical properties, therefore the nonlinear characteristics of the bolted flange joints were thoroughly studied and which were applied in static and dynamic modeling and numerical simulation in this dissertation. The model analysis of the global structure and the check of static strength and connection status were put into action by ANSYS Workbench.Main works of this dissertation are:1. The basic theory of contact problem was introduced in detail, Pure Penalty and Augmented Lagrangian contact algorithm were mainly analyzed, and the FKN(contact stiffness factor) which enormously influences the convergence was thoroughly studied.2. The reasonable finite element modeling method which is namely 3-D solid element modeling was applied by the comparison of different finite element modeling methods. The pretension elements method could accurately and effectively simulate the bolt pretension by the comparison of different numerical simulation methods of bolt pretension.3. The static analysis for the bolted flange joints of the gear compressor was put into action, some main factors influencing computational convergence were mainly analyzed, such as:the construction of contact pairs, FKN and the choices of contact type and contact algorithm. The influence of FKN on computation convergence was mainly discussed, the rational FKN was acquired by trial computation, and the check of static strength and connection status was put into action.4. The modal analysis for the entity structure was put into action, the contact nonlinearities were applied to the modal analysis for the entity structure, and 3-D solid element method was applied to the finite element modeling of the connection structure. The computation results of two different modeling methods which are namely the modeling method including nonlinearities and linearity were compared, and the influence of pretension on frequency and vibration of the whole structure was analyzed.