Study On Three-Dimensional Fractal Numerical Reconstruction And Interfacial Phenomena Of Sealing Interfaces

Various sealing structures are widely used in petroleum,chemical and nuclear industries,and their tightness is directly related to the safety and reliability of operation of systems and equipments.Due to microcosmic roughness characteristics that are difficult to eliminate on machined surfaces,the contact between any two surfaces is incomplete,non-contact areas are usually reduced by increasing contact stresses on contact seal structures.These non-contact areas form tiny pores,and connected pores form a meandering leak path,thus interface leakage occurs.At present,researches on leakage between sealing interfaces mostly adopt a simplified model and cannot accurately reflect characteristics of sealing interfaces.Firstly,research background of rough surface contact problems is introduced,and research progresses in the related fields such as fractal numerical simulation of rough surface,crack leakage rate during leak before break(LBB),interface leakage and contact thermal resistance at home and abroad are introduced in detail.On this basis,the content of this paper is put forward.Secondly,contours of a fractal rough surface are simulated based on two-dimensional W-M function,and then extends it to three-dimensional W-M function,and hence isotropic fractal numerical models of rough surfaces are modeled.Three-dimensional fractal surfaces with different topographical features can be obtained by adjusting fractal dimension and characteristic scale factor,and their micropore structures of sealing interfaces are analyzed.Thirdly,fractal geometry is introduced into LBB process to obtain effective fractal height of roughening elements on crack micro-channels wall,and energy conservation equation of thermodynamics is combined to work up the relationship between leakage rates and geometry of fractures and gas state in the vessel by using when gas medium in the pressure vessel leaks through crack microchannel.Based on verification of correctness of leakage model,factors of effective fractal height and leakage rate are analyzed.Finally,in order to study effect of rough surface topography on sealing performances of contact interface,relationship between deformation characteristics of rough surface and geometry parameters of interface micropore structures is obtained by A-Roth model based on three-dimensional fractal numerical rough surface,which takes the influence of the stagnation zone into account,and fractal transport theory of porous media is combined to gain a numerical model for calculating leakage rates of sealing interfaces.