Finite Element Modelling Of Constrained Surface Roughness Evolution And Its Application To Waveguide Forming

As a key component in the propagation of electromagnetic signals,the inner surface of the waveguide is required to have a very high surface quality.The internal surface morphology of the finished waveguide mainly changes in the cold drawing and forming process,during which the internal surface of the waveguide undergoes both free and restricted deformation.In this dissertation,based on the cold drawing process of Al6061 rectangular waveguide and the evolution of Al6061 surface roughness in the free deformation state established by our group in the previous research,an analysis model of the evolution of Al6061 surface roughness in the restricted deformation state was established and used to analyze the evolution of surface roughness of the waveguide inner surface in the forming process.The boundary conditions of the microscopic representative volume element(RVE)finite model were obtained by data extraction and processing of the analysis results of the macroscopic finite element model,so as to realize the cross-scale coupling calculation.Based on the free surface roughness evolution model,the restricted surface roughness evolution model was established by coupling the wear model and the flow-solid coupling model,which provides a certain basis for optimizing the inner surface morphology of aluminum alloy waveguide.The main research contents of this paper are as follows.(1)For 6061 aluminum alloy material,the calibration of the material Archard wear coefficient was completed by pin-disk friction wear experiments;the macro-micro coupling method was used to realize the iteration for the evolution of the aluminum surface micromorphology in the process of aluminum-steel friction.(2)A fluid-structural interaction model was established to simulate the influence of the closed lubricant pockets between the contact pairs on the surface morphology of the material.The model was then extended to establish a finite element model of an RVE model with initial roughness under mixed lubrication conditions with the formation of closed lubrication pockets under pressure,and the influence of the liquid between contact pairs on the evolution of surface morphology under pressure is discussed.(3)Based on the actual process of cold drawing and forming of aluminum alloy waveguide,the effect of free surface deformation of the forming process on the surface morphology of the critical region was investigated using the macro-micro coupling method.On this basis,a fluid-structural interaction model and a wear model were introduced to establish an analytical model for the evolution of the restricted surface morphology of the forming process.The model was used to simulate the surface morphology evolution in the critical area of the inner wall of the waveguide,and the experimental results in the critical area of the inner wall of the waveguide were collected using a roughness meter.The consistency between simulation and experiment was found by comparison,and the validity of the finite element simulation was confirmed.