【作者】 李岩；

【导师】 林彬；

【作者基本信息】 天津大学 ， 机械工程， 2017， 博士

【摘要】 光学技术的迅猛发展需要以高质量的光学元件作为基础,大口径非球面光学元件以其诸多优点被广泛应用于现代光学设备中,在实际加工过程中,通常需要组合使用多种加工技术完成光学元件的制造。光学加工体系经过数百年的发展,已经包含了非常丰富的加工手段,基本能够满足现阶段光学加工的需要,然而,光学加工技术一直处于不断的发展之中,人们对于新抛光方法的探索和尝试也从未停止。本文以国家工程对大口径光学元件的加工需求为基础,以补充和完善现有光学加工体系为目的,对新抛光方法进行尝试,基于中心供液流体动压原理提出了接触式中心供液盘式流体动压抛光(Contact Center-inlet Disc Hydrodynamic Polishing,简称CCDHDP)和浮式中心供液盘式流体动压抛光(Floating Centerinlet Disc Hydrodynamic Polishing,简称FCDHDP),并以理论分析和实验验证为基础对两种抛光方法进行了研究。首先,研究了CCDHDP的去除函数。根据去除函数研究的需求,设计并搭建了具有中心供液功能的工艺研究实验台,同时,研制了CCDHDP工具。基于单磨粒去除模型对抛光过程进行解释,发现工具转速通过影响磨粒运动速度提高材料去除效率,工具载荷通过影响有效接触面积和半嵌入磨粒的切深提高材料去除效率,而对处于完全嵌入状态的磨粒,工具载荷的改变不会对其切深产生影响。通过实验证明了中心供液方式能够提高磨粒供给的充分性和均匀性、延长抛光垫的使用寿命、提高去除函数的稳定性。随后,研究了CCDHDP的面形修整能力。将去除函数视作一定带宽内不同波长正弦分量的组合,通过模拟加工发现,去除函数对波长小于其带宽的面形误差难以去除;对波长处于其带宽之中的面形误差能够实现部分去除;对波长大于其带宽的面形误差能够实现完全去除。进行了CCDHDP面形修整实验,证明了去除函数越小,所包含的带宽截止频率越低,其面形控制能力越强,同时还验证了相对于四周供液方式,中心供液方式能够提高面形控制能力。因此,CCDHDP更适合于在粗抛阶段对中低频面形误差进行修整。之后,研究了FCDHDP液膜流场。设计了抛光工具,并通过可行性实验验证了液膜的存在性和该抛光方法的可行性。基于计算流体力学(Computational Fluid Dynamics,简称CFD)建立了液膜流场数学模型,并通过液膜厚度测量实验验证了该模型的准确性。随后基于数学模型分析了液膜流场的压强场和速度场分布,验证了动压槽对流体动压效应的增强作用。以载荷-膜厚曲线为对象进行研究,发现对于无槽工具,工具转速不会对载荷-膜厚曲线产生影响,而供液压强的增加会使载荷-膜厚曲线整体上移,对于有槽工具,除供液压强的提高会使载荷-膜厚上移外,动压效应也会使载荷-膜厚曲线因工具转速的增加而上移。最后,基于理论与实验研究了FCDHDP的加工性能。建立了基于CFD的粗糙度预测模型,得出工件表面最大粗糙度正比于磨粒最大切深。基于实验研究了磨粒尺寸、工具载荷、工具转速、供液压强对抛光效果的影响,发现对于有槽和无槽两种抛光工具,使用的磨粒尺寸、工具载荷、供液压强越小,工件表面粗糙度越小。同时,工具转速不会对无槽工具获得的表面粗糙度产生影响,但会因为增强了流动动压效应对有槽工具表面粗糙度产生影响,表面粗糙度会随工具转速的增加而减小。FCDHDP能够在基本保持原有面形轮廓的基础上改善工件表面粗糙度,因此该方法适合于对高频面形误差进行修整。更多还原

【Abstract】 The rapid development of optical technology is based on high quality optics.Due to their advantages,large aspherical optical elements are widely used in modern optical devices.In actual machining process,a variety of polishing methods are needed to finish manufacturing of optical components.After hundreds of years of development,modern optical processing system which contains a wealth of poilishing methods can meet the requirement of current optical processing.However,optical processing technology has been in constant development.At the same time,the exploration and attempt of new polishing methods have never been stopped.In this paper,in order to meet the machining requirements of large aperture optical components,new polishing methods are tried to perfect existing optical processing system.Based on center-inlet hydrodynamic theory,Contact Center-inlet Disc Hydrodynamic Polishing(CCDHDP)and Floating Center-inlet Disc Hydrodynamic Polishing(FCDHDP)are proposed.Then,studies on these two polishing methods are carried out by theoretical analysis and experimental verification.Firstly,removal function of CCDHDP is studied.According to the requirement of removal function study,a process experimental equipment with slurry supplied from the tool’s center hole is designed.Then,the material removal process is studied based on single particle removal model.It is found that tool rotary speed increases material removal efficiency by affecting particle movement velocity,and tool load improves material removal efficiency by affecting effective contact area and cutting depth of halfembedded abrasive particles.However,change of tool load won’t affect cutting depth of abrasive particles in full-embedded state.Experimental results show that center-inlet method can improve sufficiency and uniformity of abrasives supply,prolong life of polishing pad,and improve stability of removal function.Secondly,surface shaping ability of CCDHDP is studied.Removal function can be considered as a combination of different wavelengths in a certain bandwidth.Through simulative processing,it is found that removal function can not remove the surface error whose wavelength is less than its wavelength bandwidth,can partly remove the surface error whose wavelength is in its wavelength bandwidth,can fully remove the surface error whose wavelength is larger than its wavelength bandwidth.CCDHDP surface shaping experiments are completed to prove that the smaller the removal function is,the better its surface shaping ability is.At the same time,it is verified that surface shaping ability can be improved when slurry is supplied from the center hole.Therefore,CCDHDP is more suitable for the correction of medium and low frequency errors in rough polishing stage.Thirdly,slurry film of FCDHDP is studied.A polishing tool is designed,and feasibility of this polishing method is verified by experiments.A CFD model of slurry film is established,and the accuracy of this model is verified by slurry film thickness experiments.Pressure field and velocity field distribution of slurry film are analyzed based on this CFD model.For tool without grooves,tool rotary speed does not affect load-thickness curve.However,increase of input pressure will make load-thickness curve move up.For tool with grooves,increase of input pressure will lead to increase of load-thickness curve,and increase of tool rotary speed will also lead to increase of load-thickness curve.Finally,studies on FCDHDP are carried out by theoretical analysis and experimental verification.Based on CFD,A roughness prediction model is established,and maximum roughness of workpiece surface is proportional to maximum cutting depth of abrasives.Based on experiments,effects of abrasive particle size,tool load,tool rotary speed and input pressure on the polishing effect are investigated.It is found that for both kinds of polishing tools with or without grooves,the smaller the particle size,the tool load and the input pressure is,the smaller the surface roughness.At the same time,tool rotary speed does not affect surface roughness obtained by tool without grooves.However,due to hydrodynamic effect,surface roughness obtained by tool with grooves will become smaller with increase of tool rotary speed.FCDHDP can improve the surface roughness on the basis of maintaining the original profile.Therefore,this method is suitable for the correction of high frequency.更多还原