Research On The Test Experiment For Measuring Shear Modulus Of Materials In Deep-sea Environment

Shear modulus testing of deep-sea materials is an indispensable part of the evaluation of high-performance materials in the marine field.It is widely used in marine engineering equipment,harbour and coastal defense construction.Shear modulus,one of the mechanical properties of materials,which represents the ability of material to resist shear strain.The shear modulus of deep-sea materials determines the application range of materials to a certain extent.Therefore,the measurement of shear modulus of deep-sea materials is of great significance.In this paper,a shear modulus test bench for deep-sea materials was developed.The main research contents of this subject were as follows:A closed-loop control strategy to simulate the temperature and pressure in deepsea environment was proposed,through the study of environmental simulation mechanism.According to the design code of pressure vessel,the strength of simulated pressure tank was calculated and checked.The stress and strain distribution characteristics of pressure tank were studied by finite element analysis with ABAQUS software.Ideal point algorithm was used to arrange pressure cabin bolts.Three working conditions of preloading force are studied by ABAQUS,which to study the effect of pre-tightening force on structural stiffness of pressure tank.The results show that the temperature and pressure of deep-sea environment can be simulated effectively by using high and low temperature test box and constant pressure control system.According to the stress analysis of the pressure tank,the maximum stress of the ballast tank is 48.1 MPa and the maximum deformation is 2.625 micron.By analyzing the three working conditions of preloading force,it is concluded that applying appropriate preloading force can improve the structural stiffness of ballast tank,reduce deformation,too large preloading force can reduce structural stiffness of pressure tank,too small is not conducive to ballast tank sealing.The advantages and disadvantages of dynamic and static testing were analyzed,and the three-dimensional digital design of the shear modulus dynamic testing device was completed.The stress distribution characteristics and deformation size of the shear modulus testing device structure in deep sea environment were studied,and the parameters of the testing device bracket were optimized.The five natural frequencies of the bracket were extracted by modal analysis,and the influence of the natural frequencies of the bracket on the testing device was studied.The results show that the stress and deformation of the test device structure are small under high pressure.The maximum stress of the support is 8.41 MPa,and the maximum deformation is 2.41 um,the maximum Mises stress of the Clamping sleeve is 15.27 MPa and the maximum deformation is 7.18 um.The lower order frequency of the bracket is higher from the modal analysis,which has little influence on the testing device.A test-bed for testing shear modulus of materials in deep-sea environment was built.The linear calibration of sensors was carried out by least square method,and the shear modulus of materials was tested.The results show that the storage modulus of material A and B increases with the increase of driving frequency and the loss factor decreases with the decrease of driving frequency under the condition of constant temperature.The experimental data curves conform to the theory of polymer viscoelasticity,which verifies the reliability of the experimental platform.