Fluid-Solid Coupling Simulation Study On Mechanical Properties Of Waterproof Air Cushion Of Underwater Shaking Table

The underwater shaking table is an important test equipment to simulate the underwater seismic response of the structure.The mechanical properties of the waterproof sealing structure are of great significance to the safe,reliable and efficient operation of the underwater shaking table.In this paper,the mechanical properties of waterproof air cushion under the motion state of underwater shaking table are studied to ensure the safe operation of shaking table.The main research contents are as follows :Firstly,the tensile strength,elastic modulus and other material performance parameters of PA6 nylon skeleton and polymer sulfide elastomer with PA6 nylon and PA1010 nylon skeleton materials were measured by tensile test.Then,PA1010 material was made into connection specimens to carry out tensile test to study the connection performance and sliding deformation under reciprocating tensile.Secondly,the scale verification test of underwater shaking table waterproof air cushion is carried out,which proves that the air cushion is safe and reliable.The coupled Euler-Lagrangian method(CEL method)in ABAQUS was used for the numerical simulation of fluid-structure coupling.The Euler domain model of water body,the element model of waterproof air cushion membrane,and the solid model of platform and ground were established to realize the fluid(water)-flexible solid(waterproof air cushion)coupling simulation.The inflating effect is simulated by applying uniform pressure load inside the air cushion.Based on the test results and compared with the simulation results,the maximum error between the test results and the simulation results of the shaking table motion reaction is 12.82%,and the simulation method is feasible.Based on the verified CEL simulation,the performance of waterproof air cushion with PA6 material at the initial pressure of 50 k Pa was analyzed,and the motion conditions of the shaking table were considered as the maximum horizontal stroke and the maximum vertical stroke.The analysis results show that the maximum stress of the air cushion appears at the corner of the air cushion during the horizontal movement of the shaking table,and the maximum stress is 81.74 MPa,which does not exceed the material strength and the air cushion is safe.When the fold is formed,the stress mutation will occur in the fold part,the stress along the fold direction will suddenly decrease,and the stress near the fold will suddenly increase.The maximum stress value of the air cushion in the vertical movement is less than that in the horizontal movement,and the most unfavorable situation occurs in the process of horizontal movement.Finally,the maximum stress of the air cushion is analyzed when the initial pressure is 32-60 k Pa and the shaking table moves horizontally.The analysis results show that during the movement of the air cushion,the maximum circumferential stress of the air cushion ranges from 56.30 MPa to 103.9MPa,and the safety factor ranges from 6.12 to 3.32.The maximum stress variation range in the bus direction is35.55MPa-48.71 MPa,and the minimum safety factor is 3.46.The air cushion is safe and effective.It is suggested that the initial pressure value is slightly higher than the water pressure.