Structure Analysis And Optimization Of Concrete Temperature-stress Testing Machine

Concrete temperature-stress testing machine is a variety of temperature-stress experimental equipment.Its main function is providing 0-100% of the different constraints in the test to measure the cracking temperature of the specimen,Cracking stress,room temperature stress,the first zero stress temperature and other experimental parameters based on different environments and conditions,so as to evaluate the performance of different formulations of concrete to guide the selection of concrete formulations.The evaluation of the crack resistance of concrete and as the basis for design,construction and selection of raw materials has become a hot spot in the field of concrete research in today's world,and the lack of high-precision advanced test equipment greatly limits the level of research and engineering technology progress.Aiming at the key problems existing in the temperature-stress testing machine,its structure was analyzed and optimized in this thesis.The main contents are as follows:Firstly,the thesis summarized the research on concrete temperature-stress machine in the domestic and overseas,analyzed the key problems of the existing temperature stress testing machine;The main function,working principle and overall design scheme of concrete temperature-stress machine were introduced.The three-dimensional structure model of temperature-stress testing machine was established.ANSYS software was used to analyze the active fixture and concrete specimen of the testing machine,obtaining the maximum stress and maximum deformation,checking its strength and stiffness;In order to improve the dynamic performance of the testing machine frame,the modal analysis of its structure was carried out,and the improvement scheme of the frame structure was put forward based on the modal analysis results.Secondly,the kinematic simulation of the transmission system of the testing machine was carried out by ADMAS software.The displacement,velocity and acceleration curve of the movable fixture of the testing machine were obtained.The dynamic model of the transmission system was established by using the mechanical system dynamics theory,and its transfer function was deduced.The performance of the system was analyzed by using the mechanical engineering control theory,and the Simulink components in MATLAB were used to simulate and analyze the system,as a result,the key factors influencing the system performance were found out.Thirdly,the structure of movable fixture of the testing machine was designed by using the mechanical optimization design theory.The topology optimization of the fixture structure was carried out by using the variable density method.And the size of the fixture structure was designed by using the response surface method and the multi-objective genetic algorithm based on the results of topology optimization,obtaining the optimum design scheme of the fixture structure.Then,the shape optimization design of the chuck part of the testing machine was carried out by using the method of the shape optimization design and the finite element analysis.The straight line-single arc,single arc,elliptical arc,double curvature arc curve,and spline curve were proposed as the optimal design scheme of specimen transition curve,and respectively optimized by using the ANSYS optimization module,obtaining the best shape of the curve;The optimal design results of each line were compared,and the optimum design scheme of transition curve of concrete specimen was obtained.Lastly,the temperature-stress experiment was respectively carried out by using the modified and original concrete temperature-stress testing machine as the experiment equipment with selecting a kind of concrete material,comparing the results of temperature-stress test of the concrete specimen,and the working performance of the modified concrete temperature-stress testing machine was analyzed based on the experimental results.The research on the structural analysis and optimization of concrete temperature-stress testing machine is focused on the enhancement of the work performance of the concrete temperature.The research results will promote the improvement of concrete temperature-stress testing equipment,and the development of evaluation technology of crack resistance of concrete,having strong theoretical and practical significance.