| With the rapid progress of nuclear power,chemical industry,aerospace and other industries,once the bolt-flange-gasket sealing structure,reactor coolant pipe fuel rods,pressure vessel and other key components fail,it will inevitably cause leakage,explosion and other accidents.This brings about higher demanding and greater challenges to the reliability of the sealing system.The gasket is a sealing member widely used in machinery,equipment,and pipelines.Most systems that use fluid as a medium require gaskets to participate in the sealing process to keep the inside isolated from outside.The compression resilience performance of the gasket is an important indicator for evaluating its sealing performance.In this thesis,the graphite seal gasket widely used in nuclear power sealing system is taken as the research object,and the compression resilience performance experimental of the gasket is carried out,the relevant factors and mechanisms affecting the compression resilience performance of gasket is revealed,providing substantial data support for the normal operation of nuclear power sealing systems.In this study,according to experimental requirements,the MTS 809 experimental machine was upgraded by equipping with a high-temperature experimental electric furnace,GW-1200 B temperature control box,external pressure head,and other equipment.Through reasonable experiments design,the compression resilience experiment of standard nuclear-grade graphite gaskets was realized.The compression resilience performance of nuclear-grade graphite gaskets is studied.By comparing the compression resilience curve,compression rate,and resilience rate,the influence law of loading method,gasket diameter and working temperature on the compression resilience performance of nuclear-grade graphite sealing gasket is preliminarily verified.Subsequently,based on Matlab software,regression analysis was used to characterize the compression resilience performance of the gasket.Finally,the Ansys software was used to establish a finite element model of bolt-flange-gasket structure to study the stress and deformation of the seal structure.The main contents of this paper are as follows:1.By using the experimental method,the compression resilience curve of the nuclear-grade graphite sealing gasket was obtained,and then the compression ratio and the rebound ratio of the gasket were calculated.The results showed that:(1)Nuclear-grade graphite gaskets exhibited great resilience performance,and the compression resilience curve showed significant nonlinearity.(2)Due to the existence of threshold stress,when metal-to-metal contact occurred in the sealing system,the compression resilience curve rose sharply,and the sensitivity of the gasket to the working stress was greatly reduced,thereby ensuring the stability of the gasket during service.(3)When the pressure of the gasket was higher than the load value corresponding to the threshold stress,the resilience of the gasket mainly depended on the metal restraint ring.2.The compression resilience curves of the gasket under different loading methods,different diameters,different operating temperatures,and other factors were given,and the compression rate and resilience rate of the gasket were compared in turn.The results showed that:(1)The stepped loading method significantly increased the maximum compression of the gasket,while the resilience rate of the gasket decreased significantly.(2)The larger the diameter of the gasket,the greater the compression rate and resilience rate,but the lower the threshold stress.(3)Under high-temperature working conditions,the graphite,which is packing material of the gasket sealing ring softened,so that the compression rate and the resilience rate of the gasket increased with the increasing of temperature,and still showed great compression resilience performance.3.The Matlab software was used to perform numerical analysis on the compression resilience experimental data of the gasket.Comparing the different fitting equations,a method that can better characterize the compression resilience performance of the gasket was given,and based on this method,the compression resilience curve characteristic equations of nuclear-grade graphite gaskets affected by temperature and size were provided.Comparing with the experimental data,the compression resilience characteristic equation with temperature and gasket size as parameters can better describe the compression resilience curve and performance of the gasket.4.The Ansys software was used to establish a 3-D finite element model of the bolt-flange-gasket seal structure for practical engineering applications.The stress and deformation of the components of the sealing structure under the pretension load were analyzed.And the correctness of the compression resilience characteristic equation was further verified. |
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