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Contact problems of rubber seals for high pressure vessels_Rubber seals_Rubber seal manufacturers

by:ORK      2022-11-23
The contact problem of the rubber seal of the high-pressure container Because the initial contact between the conical surface of the rubber seal and the conical surface of the top cover and the cylinder is line contact, it cannot bear a large axial force, so a certain amount of force will be generated under the action of the clamping force. The taper is deformed, causing the top cover to contact the upper plane of the rubber seal, and the cylinder to contact the lower plane of the rubber seal. If ANSYS only considers the upper and lower conical surfaces when creating the contact pair, and ignores the upper and lower planes and applies the load directly, due to the extremely poor axial bearing capacity of the line contact, the model is extremely unstable and cannot be calculated correctly. In order to improve the convergence of the calculation and get the ideal result, the usual processing method is to make the target face the contact surface for initial penetration before loading, that is, to flatten the gap in Figure 2 and also create a contact pair on the upper and lower planes, and use the rubber seals on the upper and lower planes. Add auxiliary constraints, so that there is enough bearing capacity, and the calculation can achieve ideal results. The loading calculation conditions are defined as axisymmetric, and the initial calculation conditions are as follows: (1) The self-weight of the top cover is not considered; (2) The lower part of the cylinder Add axial restraint to the intercepted part; (3) pressure p1 is applied to the inner wall of the cylinder; (4) pressure ps is applied to the clamp. The selection of the clamp loading pressure ps is based on the fact that the sealing device is a self-locking type, and the clamping force of the clamp changes with the air pressure of the cylinder. When only the air pressure inside the cylinder is known, the clamping force of the clamp and the rubber seal cannot be determined at the same time. The pressure on the upper and lower cone surfaces of the piece. Under the premise of being as close as possible to the actual working situation, and considering the computability of ANSYS, the following schemes are proposed: (1) A total of 4 contact pairs are created on the upper and lower cone surfaces, upper and lower planes, top cover and cylinder of the rubber seal. (2) Ensure that the rubber seal is sealed by the conical surface no matter under high pressure or low pressure, and the upper and lower planes have no contact pressure or are extremely small. That is, under various working conditions, use ANSYS to calculate the pressure on the clamp when 0.55 mm is flattened, which is slightly larger than the air pressure in the cylinder. The distribution trend of the contact pressure on the conical surface of the rubber seal: no matter what the gas pressure state is, it is the pressure under the node 1, that is, the point below the initial line contact point. Figure 4 Contact pressure Figure 5 Comprehensive stress curve Figure 6 Radial deformation The force of the curve is the largest; each node participating in the contact increases with the increase of the pressure inside the cylinder. The 2 and 3 nodes on the upper conical surface also participate in the contact at ultra-high pressure, and the contact of the conical surface changes from line contact to small torus contact. 2) The comprehensive stress can be seen from Fig. 5, the stress of the upper conical surface of the rubber seal increases with the increase of the internal pressure of the cylinder, and there is stress concentration at node 1, the upper conical surface and the rounded corners of the upper plane; under the same working conditions : At low pressure, the stress on the cone surface of the rubber seal increases sequentially from top to bottom; at high pressure, it first increases, then decreases, and then increases continuously. Therefore, the material requirements are relatively high. 3) Radial deformation As shown in Figure 6, when the rubber seal is at low pressure, the deformation of the cone surface is negative. This is because the clamping force of the clamp is large and the air pressure in the cylinder is small, which is not enough to make the rubber seal along the diameter. expand outward. At high pressure, the deformation of the nodes on the upper conical surface of the rubber seal is negative, and the nodes on the lower part are positive, which indicates that the inner ring surface of the rubber seal is concave and the contact area becomes larger. When the ultra-high pressure rubber seal is subjected to strong extrusion, the material of the rubber seals seal is prone to large plastic deformation and loses elasticity, which causes the sealing performance to drop sharply, resulting in a low reuse rate of the rubber seal. Therefore, the maximum comprehensive stress calculated by ANSYS should be referred to when selecting materials. , determined after a combination of many factors. The processing of rubber seals must maintain the overall consistency of the cone surface to avoid local large uneven deformation of the contact surface. The working pressure of the ultra-high pressure sealed container fluctuates greatly, and the instantaneous temperature rises, which can easily lead to aggravation of the plastic rheology of the rubber seal, resulting in large deformation and even local cracks. At the same time, due to the periodic cyclic change of the air pressure load, the upper and lower contact surfaces of the rubber seal are prone to wear and even fatigue. More information on rubber seals
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