The Design And Experimental Research On In-situ Mechanical Testing Instrument Combined Tension And Shear

To invent an in-situ mechanical testing instrument combined tension and shear is ofgreat importance for material mechanics performance combined tensile stress and shearstress in terms of science. At present, the material mechanical properties under the load oftension and shear are studies by mainly utilizing the Arcan fixtures to realize the combinedloads tensile and shear testing. However, the Arcan fixture in practical use can only producea limited number of tensile shear force ratio and the content of composite load which can bestudied; The utilization of improved Iosipescu shear test fixtures can not be easily combinedwith optical microscope. Therefore, this thesis put more emphasis on the testing instrumentcombined tension and shear are Ex-situ testing. Thus this thesis designs an in-situmechanical testing instrument combined tension and shear. The most important part of ourresearch in this thesis can be summarized as follows:(1) The design of the shape and size on the standard specimen and basic theoreticalanalysis of the combined tension and shearBased on the specimen type of material performance test in this design, The thesisdesigns the shape and relevant details aiming at standard metal specimen combined tensionand shear which is suitable for the instrument. It expounds the theory of the change of theproperties of material mechanical under the influence of combined tension and shear. Itproposes formulas for Elastic Modulus and Shear Modulus in pure tension, pure shear, orcombined tension and shear materials;(2) The design and analysis for the in-situ mechanical testing instrument combinedtension and shearThis thesis has made the study on the design, analysis, manufacture, assembly of themechanical structure and electric control part and software control of the in-situ mechanicaltesting instrument combined tension and shear. The dynamic and static characteristics of the key parts in the testing instrument has been analyzed by using the method of the finiteelement analysis software Abaqus;(3) Calibration for the precision sensor and correction coefficients for the impact ofinstrument stiffness on in-situ mechanical testing combined tension and shearCalibration devices for the force sensor and displacement sensor are designed andmanufactured respectively, and the job for calibration of precision force sensor anddisplacement sensor is completed by these two calibration devices; Tension correctioncoefficient and shear correction coefficient is proposed for the impact of instrument stiffnesson in-situ mechanical testing combined tension and shear; The revised tension testing curvewill be compared with tension testing curve of the commercial tension testing instrument bythe same material and same shape specimen.(4) Experimental research on in-situ mechanical testing instrument combined tensionand shearThe thesis has completed groups of experiments of the pure tension test and pure sheartest in order to obtain the material mechanical properties by utilizing4kinds of typicalmetal.The thesis conducted a series of more than pure tension test by AZ31B magnesiumalloy sample with different material rolling direction of0°,45°,90°. It can be found thatmaterial rolling direction will have an impact on material mechanical properties by puretensile test; The thesis also finds that shear head radius and shear head span have influenceon the material mechanical properties through pure shear test results; It is found that thetensile force has influence on the shear test,and shear force has influence on the tensile test.The thesis also observes and records the process of the changing of microstructure of theQ235specimen combined tension and shear with the Super depth of field microscope; Itcontrasts and analyzes the difference among various materials and various testing methodssuch as the pure tensile test, the pure shear test, and the test combined tensile and shear bycombing scanning electron microscope (SEM) and the depth of field microscope.