Modeling simulation and analysis of pressure field and velocity field for bonnet polishing of conical mirror
Conical mirror is an indispensable core optical element of laser instruments.Bonnet polishing has the advantages of high processing efficiency and good fitting,and is widely used in ultra-precision machining processes.Nevertheless,the current bonnet polishing process is limited to planar or low gradient surfaces.Due to large difference between principal curvatures and severe curvature distortion on the cone,the physical model of removal mechanism has not been established.Due to the geometrical specificity of the cone,it is difficult to obtain the pressure field distribution directly through the existing instruments.This paper uses the finite element method(FEM)to calculate the pressure field and the velocity field distribution under the local coordinate system at the contact position.The change laws of pressure field,velocity field and the removal rate at different positions of the conical mirror and different press amounts are analyzed.The experiments demonstrate that the proposed method yields about 12%less contour error between the deducted removal function and the practical one,compared with the conventional modelling method.That reveals the proposed model achieves more consistent result with the practical one.
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