The Design, Analysis And Experimental Research Of An In-Situ Torsion Testing Apparatus For Material Mechanical Properties

The development of materials science and technology accelerated the progress ofhuman society, the development and application of new materials to human broughtgreat convenience to human. But as the demand for materials increased continuously,people are troubled with the problems caused by material failure at the same time. It’sa great challenge for the whole science and engineering community to understand andcharacterize materials thoroughly. Traditional testing techniques could only get thefew mechanics parameters, which can’t meet testing demands now. The materialsIn-Situ testing technique not only have the functions of traditional testing techniques,but also could observe the micro deformation, damage and the evolution of microstructure of the materials under the loading dynamically. It has a profoundsignificance on researching macroscopic mechanical behaviors and the mechanism ofthe evolution of micro structure of materials.This paper has an overall summary and analysis about the present status ofdevelopment of torsional testing machine and In-Situ testing technique. On this basis,an In-Situ torsional testing apparatus which could compatible microscope devices isdesigned consequently, which provides a new method for researching microdeformation behaviors and the damage mechanism of materials.This paper propose the whole structure design of the testing apparatus, andanalyzed the strength, stiffness, service life of main mechanical components of theapparatus. The natural frequency of the parts and the whole apparatus was alsocalculated and analyzed. The results show that the apparatus could work properly. Inaddition, the electric control system of the testing apparatus was detailed illustrated.Based on the above work, the error of loading and angular displacement of theapparatus was detailed analyzed in the paper. The error of rotation angle wasmeasured by using the laser displacement sensor. Meanwhile the paper proposed the correction algorithm for the calculation of the equivalent length of test specimen andthe shear modulus of materials. The applicability of the correction algorithm wasverified by the torsion experiment of common materials.The mechanical behavior of2A12aluminum and H59brass under torsion cycleloading was researched, and the bauschinger effect was found. Compared with thenormal torsion testing, the torsional strength had no significant change.In addition,the difference of mechanical properties of Q235steel under different forming methodswas researched, the testing result reveals the yield strength of Q235cold-drawn steelwas much higher than Q235hot rolled steel, and the torsional strength had littledifference.At last, by means of combining the testing apparatus and Olympus BXFMmicroscope, the micro topography of H59brass and metallographic structure of Q235steel was observed under the torsion loading, the function of In-Situ testing wasverified.