| The thin layer regions below the metal working surface are different from the physical and mechanical properties of the matrix and have delamination characteristics.This paper proposes a contact modeling method that considers the layered structure of metal-working surfaces.In this paper,theoretical derivation,experimental verification and finite element numerical simulation are used to study the contact characteristics of metal working surface,and the relationship between the deformation amount of metallized surface layered structure and the actual contact area and contact load is established.The surface layered structure is equivalent to the finite element modeling method of virtual material with elastic modulus gradient.This article mainly studies the following aspects:Firstly,the surface structure characteristics and contact characteristics modeling scheme of metal working materials.Firstly,the white light copolymer interference microscope was used to measure the contour data of the 45 steel grinding surface,and then the influence of the sampling interval on the surface contour characteristics was analyzed.A rough surface contact model based on real contour data was established in ANSYS software,and then the influence of sampling interval on contact characteristics was analyzed.Secondly,As the existing joint surface contact study does not consider the layered properties of rough surfaces.So this paper proposes two contact modeling research schemes which all considering layered tissue on metal machined surfaces:(1)Research on contact modeling which is equivalent the layered tissue of the machined surface to the virtual material with elastic modulus gradient.(2)Research on layered rough surface contact modeling based on layered elastic system mechanics.The contact model was derived based on the proposed two contact modeling studies.Firstly,the elastic modulus of the processed surface layered structure is graded,and the relationship between the contact area,contact load and deformation amount of the single microprotrusion is derived according to the Hertz contact theory.According to the probability density function of the micro-convex,the relationship between the contact area,the contact load and the deformation amount on the entire bonding surface is integrated.Secondly,based on the layered elastic system mechanics,the stress,strain and displacement expressions of the lamellar structure at the surface of the machined surface are derived,and the algorithm is proposed according to the boundary conditions and the inter-layer bonding conditions.Then,a contact layer modeling method is proposed.According to the microscopic statistical characteristics of the surface profile,the calculation formula of the contact layer thickness is given.The layered structure of the metal working surface is equivalent to a homogeneous and anisotropic virtual material,and the material of the virtual material constitutive equation is determined.The expression of the argument.Finally,the application of the virtual material constitutive equation and the relationship between the elastic modulus and depth of the surface layered structure derived from the nanoindentation test unloading curve are used to establish a finite element simulation model based on the experimental device in ANSYS software.The low-order mode and natural frequency of the established model are calculated by the finite element method.A test device comprising a fixed joint was then established,and the low-order mode and natural frequency of the test device were obtained by hammering.Finally,the paper compares the finite element simulation results with the experimental results The result shows that the mode obtained by the test is basically the same as the mode obtained by finite element simulation,and the relative error of natural frequency is within ±10%.It proves the rationality of the contact model of the layered tissue of the machined surface and the virtual material model established in this paper. |
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