Research On O-ring Assembly Deformation Analysis And Bolt Tightening Process For Valves And Its Application

Load sensitive multi-way valve is the core control component of hydraulic system of engineering machinery,mining machinery,port machinery and other industries.The quality of O-ring seal and screw assembly directly affects the reliability of multi-way valves.Although there are corresponding sealing standards for domestic multi-way valve to follow at the design level,due to the lack of scientific tightening force design method for the multi-way valve assembly apart from tests,the consistency of assembly quality cannot be guaranteed.The multi-way valve seal failure will occur during the service life,especially when the internal pressure is high.Therefore,it has great significance to improve the tightening quality and seal reliability of the multi-way valve with the study of the O-ring sealing performance in the multi-way value assembly and optimization of the pre-tightening force of each nut bolt to make that the integral structure of multi-way valve achieve the expected sealing effect.Based on the assumption that the O-ring contact stress is uniform distributed,the decoupling strategy for the mechanical analysis of the O-ring assembly seal structure of the valves is studied.Considering the geometric structure of the seal model assembled from valve and O-ring,an assembly deformation analysis method for valves and O-ring based on rigid-flexible partition is proposed.The method disassembles the valve seal structure into two independent parts:Partially flexible(non-linear)sectorial segmentation O-ring-valve seal model and partially rigid(linear)valve-bolt assembly model.The O-ring-valve contact information is applied for the transfer of interaction between the two models.A method for establishing a 3D FE model of O-ring seal based on sector segmentation is proposed.Considering the maximum fluid pressure condition where no contact occurs between the sealing surfaces of adjacent valves on both sides of the O-ring and the concentric axis symmetry structure of the O-ring groove and the O-ring,the O-ring whole model is divided into several sectors to obtain a sector segmented 3D analysis model of the O-ring seal.The contact pressure of the O-ring full circle is solved by area weighting method.The O-ring contact information is obtained,providing the necessary conditions for the following establishment of the formula for the deformation of valve-bolt-O-ring.A method of constructing a valve-bolt assembly model for optimum preload distribution is proposed.The equivalent uniform pressure load is used to replace the contact pressure of the O-ring on the valves.The preloads of different bolts in the assembly model are adjusted to make the O-ring contact stress in the assembly model uniform distributed in the circumferential direction.A parameter planning method for bolt tightening of valves based on deformation coordination is proposed.Through analyzing the deformation of the valve seal structure in detail,the formula for deformation coordination of the valve-bolt-O-ring and two deformation coordination correction coefficients are proposed.It realizes the deformation coordination for the sector-segmented O-ring seal model and the valve-bolt assembly model.Combined with the fitting relationship of the contact pressure peak and the deformation rate of O-ring and the variation range of deformation rate,the minimum deformation rate that meets the sealing condition under the maximum internal fluid pressure is obtained.The contact information of the O-ring and the valve is obtained through a sector-segmented O-ring seal model,and substituted into the formula for deformation coordination of the valve-bolt-O-ring to obtain the average pre-stretching length of each bolt.According to the relative displacement value of the upper surface of the valve and the contact area of the bolt,the tightening force of each bolt and the average tightening length of each bolt,the bolt tightening parameters(turning angle values)under the target of uniform deformation of the contact area of the valve and the O-ring are achieved.Taking the tightening and assembly of a certain type of load-sensitive multi-way value as an example,the construction of the sealing assembly model of the valve and the O-ring and the deformation coordination method proposed in this paper is applied to the tightening assembly process planning of multi-way value.Through the adjusted of the preloads of each bolt,the difference between the maximum and minimum value of the Z-direction displacement of the contact nodes of the O-ring and the valve reduces from 0.1416 mm to 0.0435 mm,which improved the uniformity of the contact stress distribution of the O-ring.Finally,according to the tightening force of bolts,the value of the angle of rotation of each nut is calculated,and the optimum value of the tightening process parameters of multi-way value bolts is determined,which provides a scientific basis for the development of multi-way value bolt tightening process.