Study On Deformation Mechanism Of Cutting Nickel-based High-temperature Alloy Based On Multi-scale Simulation

Inconel718 is widely used in aerospace engines and other fields because of its excellent properties,but the elemental composition of this alloy is complex,containing Ti C,Nb C and other interphase hard points make machining more difficult,and will also have a certain impact on the stress and temperature in cutting.The plastic deformation that occurs in cutting and the formation mechanism behind it have attracted the interest of scholars from various countries,and it is particularly important to study the deformation mechanism of Inconel 718,a nickel-based high-temperature alloy.To make the analysis process more efficient,a finite element simulation method is used to simulate high-speed cutting of Inconel718,in which the instantonal equations are the basis for the modeling as well as the subsequent analysis.The conventional Johnson-Cook instantonal structure does not consider the stress changes caused by hard points and does not take into account the dimensional effects caused by the material’s own endogenous dimensions,so in this paper,the original Johnson-Cook instantonal structure is modified by combining the strain gradient plastic deformation theory and the stress changes caused by hard points,and the modified instantonal structure is used as the basis for the Inconel718 cutting The modified eigenstructure was used as the basis for the improvement of the Inconel 718 cutting energy theory model.Fortran language is used to compile the subroutine for secondary development,so that the storage energy and overall dislocation density can be displayed in the finite element;and Python language is used to insert Ti C,Nb C and other interphase hard points into the model to establish a two-dimensional multi-scale finite element model.The change of different cutting parameters(cutting speed,cutting thickness,undeformed chip thickness)will lead to the change of cutting specific energy,and the cutting deformation mechanism will be analyzed in more detail by introducing the cutting specific energy and the dimensional effect caused by it.In this process,the material is more prone to shear instability,and the morphology of the removed material will change and gradually form serrated chips.In order to analyze the chip formation mechanism,classical chip separation parameters(chip split ratio and chip compression ratio)are introduced to analyze the changes of the parameters under different speeds and feeds to quantify the cutting process and conduct an in-depth analysis of the chip formation mechanism.The finite element model established by the secondary development of the subroutine can output the trends of stress,temperature and overall dislocation density,and analyze the storage energy of the shear zone by combining the trends of the three with the storage energy,based on the dynamic recrystallization and periodic fracture theory to analyze the formation mechanism of the adiabatic shear zone.Therefore,the evolution of microstructure such as dislocations and dynamic recrystallization induces the softening of the material,and the rate of change of storage energy will affect the nucleation rate of dynamic recrystallization and thus the rate of adiabatic shear zone formation.