Design Analysis And Experimental Research Of Torsion Preload Three-point Bending Test Device In Situ

Traditional materials mechanical properties testing methods are often applied loads to the material sample such as stretching, bending, twisting or the like single loads, combined with the detection means measure basic mechanical parameters and mechanical behavior under load of these single material. With advances in technology, to ensure that the material in the process of service reliability, durability, academia and engineering of materials performance testing increase the requirements. The traditional single load test method has been unable to meet demand. Meanwhile, during the test, the researchers hope to see the mechanical behavior by scanning electron microscopy, optical microscopy, X-ray diffraction and other materials characterization instruments under dynamic load monitoring material and microstructure evolution of the situation, namely, in situ test. For this reason, it is more important to carry out research under complex micstructure mechanical loading in situ. This paper research the torsional pre-load three-point bending device analysis and test as the research topic.On the basis of the current situation in related fields to the mechanical properties test, this paper design the three point bending device under torsional preloadi in situ. On the basis of torsional preload applied on the material sample, achieve quasi-static bending load through a large reduction ratio of the reduction mechanism. This paper use ABAQUS software to achieve static analysis and modal analysis of the key mechanism and the whole device. The simulation results show that the design of the device in terms of stiffness and strength basically meet the requirements. This paper developed a in-situ three-point bending test device capable of multi-load which coupled by tensile, torsion, fatigue testing methods. Through the large reduction ratio reducer loading method, rational design can be achieved under the quasi-static bending device.Utilizing ABAQUS analyze the key mechanism and the whole machine of bending device in statics and modal to demonstrate the reasonableness of rigidity and strength of the device.For the development of the test apparatus, the paper respectively calirate the bending force sensors and torsion force sensor. And calirate the accuracy of the motor encoder by a laser displacement sensor. On this basis, the paper separately calculate and simulate analyze the frame compliance and the base deflection angle error. The bending device stability has been verified by brass and 7075 aluminum alloy repetitive test. The accuracy of the device has been verified by comparing to the industrialization results after error correction.This paper has researched the influence of the torsion preload bending mechanical response of the material by finite element simulation analysis. Aiming at 6061 aluminum alloy and 45 steel material respectively has carried out bending performance test and analysis under the condition of torsional elastic and plastic stage pre-load and studied From bending elastic stage, bending strengthening phase and the tested sample rebound ability three aspects to verify that the increase of torsion of pre-load enhance the bending strength and resilience of material samples. This paper also has analyzed macroscopic failure mode of the fracture analysis of cast iron and proved that the bending load fracture Angle will be along with the increase of torsional load in advance to the axis offset. At last, this paper has used CCD microscope observe the changes in the microstructure of Q235 material, analyzed bending and torsion failure mechanism and reveals that the lattice deformation of material samples earlier get into the failure forms under the torsion preload.