Characterization And Measurement Of Plastic Parameters Of Surface Modified Layer Based On Indentation

Manufacturing industry is the blood of China's economy,the foundation of the nation,the weapon of rejuvenation and the cornerstone of a powerful country.Antifatigue manufacturing is a manufacturing technology that controls surface integrity,takes fatigue as criterion and improves fatigue strength.Compared with forming manufacturing,anti-fatigue manufacturing can make the key components have a longer life,higher reliability and lighter structure.The core of anti-fatigue manufacturing is to construct surface metamorphic layer and the traditional method is no longer suitable for the characterization and measurement of surface metamorphic layer with gradient mechanical properties.In this paper,the method of characterizing plastic parameters of surface metamorphic layer is proposed through the delamination indentation test and the integral indentation test,and the plastic parameters of the surface metamorphic layer formed by the heat-treated 18CrNiMo7-6 alloy steel are characterized and tested.The main work of this paper is as follows:(1)Firstly,the Vickers indenter contact finite element analysis of the gradient plastic parameters of the surface metamorphic layer is carried out.The loaddisplacement curve obtained by this model coincides with the load-displacement curve obtained by the Vickers indenter contact finite element model of homogeneous materials at the micron indentation depth scale.It is proposed that the homogeneous parameter model can be used to replace the gradient plastic parameter model of the surface metamorphic layer.Then,the numerical simulation database of loaddisplacement curve of homogeneous model under different plastic parameters is established.The method of layered characterization of plastic parameters of surface metamorphic layer is proposed.The surface metamorphic layer is layered to carry out micron indentation test on the laminated 18CrNiMo7-6 alloy steel samples.The plastic parameters of 18CrNiMo7-6 alloy steel surface metamorphic layer are finally obtained by inversion analysis of the load-displacement curves of each layer.(2)The Vickers indenter contact finite element model of the plastic parameters of the surface metamorphic layer is established and the influence of different plastic parameters on indentation response is studied by using ANSYS analysis software.According to the results of sensitivity analysis,this paper carries out the finite element simulation under different parameters and constructs the finite element simulation database under different gradient plastic parameters.According to the results of sensitivity analysis,the finite element simulation calculation under different parameters is carried out and the finite element simulation database under different gradient plastic parameters is established.An integral Vickers indentation test platform was built,and integral indentation test is carried out on alloy steel with surface metamorphic layer.Then the plastic parameters of the surface metamorphic layer are analyzed by inversion.Finally,the plastic parameters of surface metamorphic layer of 18CrNiMo7-6 alloy steel are characterized by the proposed integral indentation characterization method.(3)A characterization method of the surface metamorphic layer hardness is proposed.According to the relationship between hardness and depth,the variational hardness of the surface metamorphic layer is obtained by means of stepwise continuous indentation loading characterization.The gradient hardness of the surface metamorphic layer of 18CrNiMo7-6 alloy steel is characterized by this method.