Design And Experimental Research Of An In-Situ Tensile Device For Characterizing Micro-Mechanics Of Materials

Materials science is the foundation of modern science and technology, and alsothe driving force of all the advances in technology industry. The material productiontechnology of a country determines the integrity of the national industrial system, andhas some influences on the national voice in regional affairs. Considering thesignificant role of the materials science and technology, many countries put a lot ofenergies on the research of new materials and new processes. The service life ofmaterial is determined by the overload condition and microstructure, so the studies ofthe material mechanism, such as microstructure, deformation, damage and failure arevery important. The microstructure observation and mechanical properties can beachieved by in-situ tensile test. Comparative analysis of the material microstructurechanges in the test and the mechanical properties curve contributes to in-depth studyof the material. On the basis of a comprehensive analysis of material microstructuremechanical properties testing technology development status, this paper develops thematerial microstructure mechanical properties in-situ tensile tester.This paper gives a comprehensive analysis of development status of in-situtensile test and microscopic imaging technology both at home and abroad; On thebasis of that, the overall design of the material microstructure mechanical propertiesof in-situ tensile tester based on metallurgical microscope is put forward; After that,analyzing the work principle of the tester, of which the worker module includes driveunit, power transmission and conversion unit, guide mechanism, signal detection unitand test execution body, the working principle of each unit is analyzed, also finiteelement simulation and structure optimization design are conducted; Miniature highprecision extensometer and force sensors applied in this tester are developed, andfinite element simulation through imitating the actual working condition is conducted.The signal amplifying circuit and the low-pass filtering circuit are designed foramplification and filtering of displacement sensor and the force sensor signal, thecircuits are simulated by Multisim10simulation software. During the simulation, thethree-stage analog signal amplifier circuits have no obvious distortion; In this paper,the performance parameters of USB2817data acquisition card are introduced, and between the two connections, the single-mode connection is selected; Talking aboutthe principles of servo motor drive and encoder; Analog signal acquisition program isdeveloped based on LabVIEW software. After testing, the results show that the signalacquisition program can satisfy the use requirement; Serial communication is used forservo motor drive signal transmission, and servo motor control program is developedto control the servo motor.Proposing static and dynamic calibration methods for the force sensor calibration,the force sensor is conducted dynamic and static calibration, and the result shows thatthe force sensor has a good static characteristic and detection error of impact load;The work principle of the linear potentiometer displacement sensor is introduced, andthe displacement sensor is calibrated by high-precision small scale image pixelsmethod， with which selecting the best performance of the full scale as thedisplacement sensor using interval which is selected by full scale calibration method;The variable section nonstandard test piece is designed, the elastic deformationequivalent gauge length is proposed, and the plastic deformation equivalent gaugelength of steel of Q235-A (F) is calculated; T2copper and AZ31B magnesium alloyare tested by in-situ tensile tester developed in this paper, and different stages of testspecimen deformation microstructure images are analyzed. Then it is concluded thatthe T2copper is the ductile fracture and AZ31B magnesium alloy is thequasi-cleavage fracture. According to mechanical properties of the test result，thematerial micro-mechanical properties in situ tensile tester in this paper are in high testaccuracy, stability and repeatability.