Dynamic Characteristic Analysis And Experimental Research On The In-situ Mechanics Of The Combined Loads Instrument

In the daily production and life, the service material is usually subjected to the combined action of many kinds of loads at the same time, which leads to the deformation damage and failure of the material and results in various accidents. Traditional mechanical properties of materials testing techniques are mostly single load test mode. And it is difficult to in-situ monitor the changes of the micro mechanical properties and the deformation and damage mechanism of the materials during the loading process. In order to study the materials’ micro mechanical properties by the combined loads, the principle and technology of the in-situ test is the starting point for the research on the requirement of the academic and engineering. Based on the prototype, the mechanical behavior and deformation damage mechanism of typical materials under various loads are tested and analyzed. Materials’ microstructure mechanical principle and technology of performance test and in-situ monitoring technology development status at home and abroad are reviewed on the basis of the analysis in the combined loadings’ conditions. The design, simulation analysis, instrument assembly, adjustment, calibration and other theories and techniques of the mechanical properties of the material under the condition of combined loadings are carried out. In this technology, the instrument is used to carry out test research and analysis on the micro mechanical properties of typical materials. The main contents of this paper are summarized as follows:ANSYS is used to carry out the static analysis and modal analysis of the structure and key elements. The simulation results show that the designed device meets the requirements. On the basis of the analysis of the test theory, the dynamic characteristic test of the instrument is developed. The test results are in agreement with the simulation results. In this paper, the samples are tested on the commercial test machine and the development of the instrument, respectively, which are made of the same batch of materials. Based on this, the experimental results are compared and analyzed. The frame flexibility of instrument is modified and calibrated base on the test results. After calibration, the relative error between the tensile test results and the commercial testing machine is 0.11%. The relative error of three point bending test results is 0.26%. The relative error of the torsion element is 0.58%.The crack initiation, crack propagation and the rapid crack failure are characterized by acoustic emission with 3V type defects, which are tested by self-made instrument. The type of crack can be determined by the method of parameter analysis of acoustic emission. The crack source is localized by the linear positioning method.The 20 steel and ductile iron are used to in-situ test by the combined tension-three-point bending loading, combined tension-torsion loading, combined torsion – tension loading, combined tension-torsion–three-point bending and combined torsion-tension-three-point bending loading, the results are as follows:It is found that the tensile strength of the material is increased by applying the combined torsion- tension loading. The changes of microstructure of the material under the combined torsion-tension loading can be seen from the in-situ microscope metallographic.When the specimens are loaded with pre tension stress and keeping the load, it is found that the material’s ability to resist twisting deformation is reduced. The changes of microstructure of the material under the combined tension-torsion loading can be seen from the in-situ microscope metallographic.When the tensile stress is applied to the specimen, the ability of the material to resist bending deformation is found to be improved. The changes of microstructure of the material under the combined tension-torsion loading can be seen from the in-situ microscope metallographic.The bending resistance of the material is improved by applying the combined tension-torsion-bending load to the specimen. The changes of microstructure of the material under the combined tension-torsion-bending loading can be seen from the in-situ microscope metallographic.The bending resistance of the material is increased by applying the combined tension-torsion-bending load to the specimen. The changes of microstructure of the material under the combined torsion-tension-bending loading can be seen from the in-situ microscope metallographic.For the pre-notch specimen in the single load, through in-situ observation, it can be seen clearly that the change of pre-notch tip morphology, crack initiation, crack propagation and crack instability fracture.