Analysis And Research On Tensile Mechanical Properties Of Carbon Steel Based On 3D-DIC Method

Nowadays,a large number of metal workpiece is used in medical,mechanical,aviation and other fields.However,due to the action of external forces,the deformation of these workpieces will occur to a certain extent,and the common measurement method can no longer meet the demand.Therefore,a convenient,on-site measurement and strong adaptability method is needed to obtain the deformation information of the material.The mainstream measurement methods include optical measurement methods,and digital image correlation method is an optical measurement method that can obtain the parameter variation of the speckle image of the object surface through the relevant calculation of the acquired speckle image.Its non-contact measurement and the advantages of strong adaptability to environment,and on the basis of the traditional digital image correlation method,3 d digital image correlation rule double set of camera is adopted to measure,and connecting with the computer vision technology,can be relatively accurate measurement of 3 d information on the surface of the object,and to process information of objects on the surface of the three-dimensional reconstruction of its morphology characteristics,implementation of surface displacement and strain measurement.In this paper,carbon steel such as Q235 and no.20 steel is taken as the material.Through the change of its loading rate,the change of its displacement and strain is studied,and the necking phenomenon in the process of stretching is also studied(1)For a single bar tensile displacement the slower growth rate,the closer the clamping endpoint for bar stock shrinkage,bar in each phase of the bar stock shrinkage rate is different,its shrinkage rate is relatively slow,in yield phase in necking stage shrinkage rate faster,at the same time bar during the process of maximum tensile strain values for necking split position.(2)With the increase of the tensile speed,the tensile strength and yield strength of low carbon steel will increase,and the yield strength is sensitive to the tensile speed,but the elongation after fracture will decrease.Bar stock shrinkage rate will be increased with the increase of stretch rate increases,and began to necking phenomenon occurs bar radius value also increased with the increase of speed,but the final breakup of smaller radius change,and also on necking place strain values increased with the increase of speed decreased,but its rate of change will gradually increase.(3)The higher the carbon content,the higher the strength of the bar,and the lower the elongation after fracture.In the case of the same speed of stretching,the high carbon steel shrinkage rate is faster,and its radius value when the necking phenomenon is larger,after the final tensile high carbon steel section shrinkage rate is smaller than low carbon steel,and with the increase of carbon content,its strain value at the necking will gradually decrease,but the growth rate will gradually increase.(4)Relatively low carbon steel and high carbon steel,it is more sensitive to the change of drawing speed,the change of both strength and break elongation,even the bar stock shrinkage radius change values and strain values of necking place after increasing the same tensile speed of stretching,mild steel is the change of the value is bigger,it compared with high carbon steel is more sensitive to the change of drawing speed.