Study On The Degradation Of Mechanical Properties Of Rubber Bearings After The Coupling Effect Of High Temperature And Load Deformation

Rubber bearing is one of the most widely used building vibration isolation technologies due to its simple structure,obvious effect and stable performance,but its vulnerability and temperature sensitivity in service are also becoming increasingly apparent.Firstly,as a key and sensitive part of the seismic isolation structure damage,the rubber bearing is prone to structural damage deformation and external structural damage under seismic and other vibration effects.Secondly,due to the poor heat resistance of rubber materials,by the ambient temperature and fire high temperature,resulting in the deterioration of the mechanical properties of the rubber bearing.In particular,in service the two are prone to coupling,resulting in further degradation of the bearing performance ’one plus one is greater than two’,leading to safety hazards such as reduced isolation effect and loss of bearing capacity.Therefore,this paper will mainly focus on rubber bearings and its rubber materials used in engineering,considering the temperature range from room temperature to 150℃ under the fireproof structure of the bearings,and combining with the common residual deformation and load effects in service,carry out multi-level test analysis through ’material-laminated bodybearing’,while scanning electronic microscope and finite element simulation analysis will be carried out.To study the degradation law and damage mechanism of the mechanical properties of rubber bearings under the joint influence of high temperature and load deformation,and provide theoretical and technical support for the performance evaluation and optimal design of rubber bearings in service.The specific research content and results were as follows:(1)Thermogravimetric tests were carried out on the vulcanized rubber materials used for rubber bearings,and the results showed that the pyrolysis temperature of the rubber was around 150℃.Therefore,a test temperature range of 20℃ to 140℃ was established,mainly focusing on the mechanical properties changes of the rubber under the coupling effect of high temperature and load deformation under fireproof structures.The tensile properties of the dumbbell rubber specimens were tested after the coupling of high temperature and load deformation,and the fitting equation of the tensile properties with temperature was established.The degradation law and microscopic influence mechanism of the tensile properties of rubber materials under the coupling of high temperature and load were analyzed by combining the scanning electronic microscope of the rubber.The results showed that the tensile properties of rubber showed little change within the range of 20℃ to 100℃,while the porosity and pore size of rubber increase and the crosslinking density decreases after 100℃ to 140℃,and the degradation of mechanical properties is obvious,especially after the load coupling effect.This indicates that the impact of load coupling effect cannot be ignored in the study of rubber high temperature resistance.(2)Shear performance tests were conducted on rubber steel plate laminated specimens subjected to the coupling effect of high temperature and load deformation,and a fitting equation for the variation of shear properties with temperature was established.Combined with scanning electronic microscope of the rubber cross-section,the degradation law and microscopic influence mechanism of the shear properties of laminated rubber under the coupling of high temperature and load were analyzed.The results showed that the shear performance of rubber decreases slightly from 20℃ to 100℃,while the shear performance of rubber decreases significantly from 100℃ to 140℃.The inherent pore defects in the internal structure of rubber expand,the surface structure becomes sparse and produces diagonal cracks,and the crosslinking density decreases,in which the degradation of the shear modulus of rubber was exacerbated by the load coupling effect.Therefore,compared to ultimate performance,more attention should be paid to the degradation process of the working performance of laminated rubber during service.(3)Conduct vertical and horizontal shear performance tests on rubber isolation bearings after the coupling effect of high temperature and load deformation,mainly including vertical stiffness,horizontal equivalent stiffness,equivalent damping ratio and single loop hysteresis area.Compare the initial performance under room temperature testing,and analyze the degradation law of mechanical properties of rubber bearings under the combined influence of high temperature and load deformation.The results show that there is no significant change in the performance of rubber bearings between 20℃ and 100℃.Under the coupling effect of 140℃ and load deformation,the vertical stiffness and horizontal equivalent stiffness of rubber bearings significantly decrease,and the bearing capacity and horizontal shear deformation capacity of bearings deteriorate,which will affect the normal use of bearings.Comprehensive’material-laminated body-bearing’ test research results,it is recommended in the project to 100℃ as a temperature threshold for the new product rubber bearings fireproof structure design.For old rubber bearings that are in service,fire-resistant structures can be appropriately installed or more reasonable limit devices can be set up to reduce the adverse effects of high temperature and load deformation coupling on bearings engineering performance.(4)The finite element numerical simulation of the mechanical properties of rubber isolation bearings was carried out.According to the simple shear property test results of laminated rubber specimens,the Neo-Hookean rubber constitutive material constants were determined,and the ABAQUS finite element model of rubber bearings was established.The vertical stiffness and horizontal equivalent stiffness of the test rubber bearings were simulated and analyzed,and compared with the test values and theoretical values.The results showed that the finite element model of the rubber bearings established by the Neo-Hookean constitutive model is more reasonable for simulating their mechanical properties.The numerical simulation of the rubber material constants obtained based on the G25 of laminated rubber is more accurate,and can provide a reasonable reference for the finite element simulation analysis of the mechanical properties of rubber bearings under the coupling effect of high temperature and load.In summary,the performance degradation of the rubber bearing in the range of room temperature to 150℃ is worthy of attention.Tests and analyses have been conducted on the uneven degradation characteristics of performance,the coupling effect of high temperature and load,and damage differences between the ’material-laminated body-bearing’ within this temperature range.Relevant conclusions have been obtained regarding the high temperature resistance performance,mechanical properties evaluation,and degradation law of rubber bearings during service.