Research On Leakage Mechanism And Prediction Method Of Non-metallic Gasket Based On Fractal Theory

With the development of equipment in various industries,the connection and sealing of equipment are facing more challenges.Gasket is a common material in gas sealing,and its leakage mechanism and prediction become increasingly important.Although gasket seal has a very simple working principle,it is not easy to control its air tightness and it is very difficult to accurately and effectively predict the leakage rate under specific conditions.The existing researches on gaskets focus more on metal gaskets,and the leakage research on non-metal gaskets often fails to distinguish the differences between interface leakage and penetration leakage.With the empirical parameters obtained under experimental conditions,the model is not conducive to the analysis of gasket leakage from the mechanism.Therefore,it is of great significance to study the leakage mechanism of non-metallic gaskets and establish a prediction model.In this paper,the leakage mechanism of non-metallic gasket is studied and the leakage prediction model is established.In order to effectively describe the micro-morphology of non-metallic gaskets,this paper choose perform scanning electron microscopy(SEM)on the slices of gasket materials.By comparing different automatic threshold segmentation methods,the maximum inter-class difference method(Otsu method)has better applicability to the binarization of non-metallic spacers with micro-nano-pore structure materials.Combined with the theory of fractal porous media transport,this paper uses the box counting method to determine the important fractal geometric parameters of the binarized image: porosity,fractal dimension and tortuosity.And the pore diameter of the porous material was measured through the scale-free interval and image segmentation method.In the study of penetration leakage,since the non-metallic material has a micro-nano pore structure,which means that the diameter of the flow path is very small,and the discussion of the flow slippage effect is inevitable.At the same time,considering that the gasket can maintain the original shape after the load is removed,this paper assumes that the non-metallic gasket material is elastically deformed during the compression process,that is,the Hook law is applied.A non-metallic gasket stress-sensitive model considering the slippage effect was established and the validity of the model was verified by comparison with the experimental results of existing flexible graphite gaskets.Since the pore size distribution is considered,the parameters of the model have a clear physical meaning,which is very valuable for effectively discussing the mechanism of the permeation leakage of non-metallic gaskets.In addition,the model can also be used for seepage studies of other dense porous media with complex structures under stress deformation.In the study of interface leakage,this paper firstly uses the W-M function to simulate the rough surface,and discusses the influence of the fractal dimension and scale factor of the rough surface on its shape.To establish the microporous channel,the contact between the two rough surfaces is equivalent to the contact between the rigid ideal smooth plane and the equivalent rough surface,and the stress displacement simulation under load is carried out by ABAQUS.An interface leakage prediction model under effective load conditions is established with the help of fractal porous medium transport theory.