Research On The Influence Of Hardened Steel40CrNiMo Residual Stress By Turning Parameters

TBM is widely used in tunneling engineering, but the domestic key technologyof TBM machine is not yet mature, the key parts are imported, the related technologyof TBM machine research is particularly important and urgent.The steel40CrNiMo is a kind of typical medium carbon high alloy steel, widelyused in automobile manufacture and ultrasonic technology because of its goodcomprehensive mechanical properties, its tensile strength is upon980Mpa, belongs tothe high strength alloy steel and sensitive to stress concentration. The TBM machinemostly domestic used are imported from abroad, the material performance of theknife ring is very close to the performance of domestic40CrNiMo steel, can choose40CrNiMo steel as the material of the knife ring,, but in the using process fatiguefailure happens, affect the construction progress seriously and cause a huge economicloss. As the residual stress of the Surface Integrity of components has enormousinfluence on the fatigue performance, so in this thesis use the TBM machine knifering similar material (Steel40CrNiMo) as the research object, research on theinfluence of hardened steel40CrNiMo residual stress of surface integrity after cuttingthrough experiment and simulation, mainly studies the following aspects:(1) Carrying out the stress analysis on the TBM machine hob, determine thestress state of the TBM machine hob in the process of rock fragmentation is contacttensile stress, choose the process that can generate surface pressure stress for theTBM machine knife ring as the final machining process;(2) Establishing the steel40CrNiMo workpiece hard turning processing modelin the process system simulation software DEFORM-3D,and using Johnson-Cookmodel as the stress of the work piece material flow model, choosing the based on theCoulomb model friction law as knife-chip model of the friction and wear. Andanalysis the simulation results from DEFORM-3D post, obtained the distribution stateof the residual stress under different cutting condition, and the law of residual stressinfluenced by the cutting speed, turning back, and feeding;(3) Carrying out the hard turning processing experiment of steel40CrNiMo in different cutting conditions, using the hole-drilling method to measure the surfaceresidual stress after cutting, comparing the experimental results with the simulationresults，verified the correctness of the simulation results. Sum up the laws of hardenedsteel40CrNiMo residual stress influenced by turning parameters comprehensively.