Research On Modeling And Mechanism Of Static Sealing Based On Percolation Theory

Static seal which plays an important role in sealing devices is used in aviation, aerospace and vehicle extensively. The leakage of oil, water and gas due to the failure of static seal has puzzled enterprises such as heavy vehicle enterprises for a long time. The static seal technology has been one of pivotal factors to keep products working unfailingly. Aimed at handling the problem of static sealing failure, the metal static sealing mechanism and its theories, methods are studied in this paper. The main research work is as follows:(1) Based on the analysis of previous work on static seal, the existed problems in current research work are indicated. The framework and content of this study are given.(2) The pattern, reason and outcome are analyzed by taking heavy vehicle as an example. On the basis of the analysis, the basic model of static seal is presented, and the connection between static seal and percolation theory is established.(3) To study the contact behavior of metal surface in different scale, the method based on deterministic model to analyze the rough surface multi-scale contact behavior is presented. In this method, the surface data is measured using the profilometer, then the wavelet filter is adopted to decompose the measured rough surface; lastly the deterministic model is built based on finite element method. The method is used to analyze the variation of dimensionless contact area with dimensionless contact load. The results show that the curves rise linearly with same slope in the small pseudo-period, while the curves in large pseudo-period rise in exponential trends and the rises grow steeper as the pseudo-period increase. The effect of material properties and loading/unloading on contact behavior in different scale is also analyzed. At last, the presented model and the results are validated by solving the Gaussian surface.(4) Aimed st solving large-scale contact problem raised from deterministic model, the performance of preconditioned Krylov subspace methods at solving finite element formulated contact problem based on FEAP and PETSc is studied. Numerical experiments were carried out in respect of time consumption, parallelism, memory usage and stability. The results show block Jacobi and Jacobi preconditioned conjugate gradient and conjugate residual methods have better potential for large-scale problem in the given and similar case.(5) A lattice based static sealing predicting model is presented by discretizing and approximating the sealing interface in order to reveal the sealing mechanism. First, the method of building lattice leakage model is given, the phase transition in sealing interface is researched by carrying out large numbers of numerical experiments based on this model, and meanwhile the mathematical model is obtained by curve fitting the cumulated distributed function. The results show probability of leaking takes on the steep transition around system-related threshold, and the phase transition of the sealing interface is influenced by the size of model and orientation of surface texture.(6) By directly solving Navier-Stokes equations in hundreds of configurations of leak channels formed in percolation network, the transport properties of the sealing interface are studied. Numerical results show that the variation of the mean leak rate in the subcritical phase presents different characteristics compared with that in the supercritical phase. It is also observed that the mean leak rate in supercritical phase and that at critical point are distinctly different when the system scale changes. The mean leak rate at critical point changes exponentially, and has sharper declining trend than that in supercritical phase(7) The integrated sealing test platform and the bolt force measurement equipment are designed and developed. Combined with practical case, the static seal experiment is designed to validate the presented results and study the sealing performance...