非球面凹凸玻璃透镜模压成形过程的有限元分析

发布时间：2018-06-30 00:54

本文选题：模压成形 + 非球面　；参考：《湘潭大学》2017年硕士论文

【摘要】：光学元件在现代社会中起着重要的作用,用于娱乐、通信、制造和测量的光电装置被广泛使用,其中非球面玻璃透镜因为能够有效修正影像畸变、色差、慧差,改善成像质量、简化仪器结构而备受关注。相比于传统的去除加工方法,玻璃模压成形技术具有高效率、低成本、适合大批量生产等优点,模压成形获得的透镜无需后续抛光处理就可以直接使用。但是该技术在实际生产中存在两个难题:其一是成形透镜内部容易产生较大的残余应力,使成形透镜表面产生裂纹甚至破裂,影响其光学性能及使用寿命;其二是成形透镜的最终成形轮廓与原设计轮廓之间存在较大的成形误差。为了解决这些问题,本文使用Msc.Marc有限元分析软件建立了非球面凹凸玻璃透镜的数值模型,对成形透镜的残余应力及成形误差分别进行仿真预测,并通过模压成形实验来验证仿真预测结果的有效性,之后通过改变单一成形参数来研究其对残余应力和成形误差的影响规律。主要研究工作如下:1.基于广义Maxwell模型,分别建立加热、模压、退火和冷却四个阶段的数值模型,对整个成形过程中透镜的残余应力进行预测。预测结果表明透镜的残余应力主要集中于凹、凸面内侧,凹、凸面的最大残余应力都出现在拐点附近且凹面大于凸面,退火过程能够有效消除透镜内部的残余应力。通过进行模压成形实验,测量了非球面凹凸玻璃透镜的残余应力,测量结果与预测结果相吻合,验证了仿真预测的有效性。2.在仿真预测与实验相结合的基础上,研究了各成形参数对残余应力的影响规律,结果表明:在模压阶段,透镜的残余应力与模压温度成反比关系,与模压速率、摩擦系数成正比关系;退火阶段,透镜的残余应力与退火速率及保压力皆成正比关系;冷却阶段,冷却速率对残余应力并无明显影响。3.分析模压成形过程中造成成形误差的原因,成形误差主要出现在三个方面:1)模具成形腔表面的加工误差;2)模压阶段玻璃预形体复制热变形模具轮廓而产生的误差;3)退火阶段透镜结构松弛产生的误差。在此基础上,对透镜在成形过程中产生的成形误差进行预测,并对实验所获得的非球面凹凸玻璃透镜表面轮廓进行测量,测量结果与预测结果相吻合,表明了通过数值仿真来预测透镜成形误差的可行性。4.通过改变单一的成形参数来研究其对成形误差的影响规律。结果表明,成形误差随着模压速率的增大而增大,随着模压温度的增大而减小,但过高的模压温度会使成形误差变大,成形误差随着退火速率、保压力、摩擦系数的增大而减小,冷却速率对成形误差无明显影响。
[Abstract]:Optical elements play an important role in modern society, and optoelectronic devices used for entertainment, communication, manufacture and measurement are widely used. Among them, aspheric glass lenses can effectively correct image distortion, color aberration, and improve imaging quality. Simplification of the instrument structure has attracted much attention. Compared with the traditional removal process, the glass die forming technology has the advantages of high efficiency, low cost and suitable for mass production. The lens obtained by die forming can be used directly without subsequent polishing. However, there are two problems in the practical production of this technology: one is that the forming lens is prone to produce large residual stress, resulting in cracks or even rupture on the surface of the formed lens, which affects its optical properties and service life; The other is that there is a large forming error between the final profile of the forming lens and the original design profile. In order to solve these problems, the numerical model of aspheric concave convex glass lens is established by using the finite element analysis software Msc.Marc. The residual stress and the forming error of the forming lens are simulated and forecasted respectively. The effectiveness of simulation prediction is verified by die forming experiment, and the influence law of residual stress and forming error is studied by changing a single forming parameter. The main research work is as follows: 1. Based on the generalized Maxwell model, the numerical models of heating, moulding, annealing and cooling are established, and the residual stresses of the lens in the whole forming process are predicted. The prediction results show that the residual stresses of the lens are mainly concentrated in the concave, inner, concave and convex sides of the lens, and the maximum residual stresses of the concave and convex surfaces appear near the inflection point and the concave surface is larger than the convex surface. The annealing process can effectively eliminate the residual stress in the lens. The residual stress of aspherical concave convex glass lens is measured by die forming experiment. The results are in good agreement with the predicted results, and the validity of the simulation prediction is verified. 2. On the basis of simulation and experiment, the influence of various forming parameters on residual stress is studied. The results show that the residual stress of the lens is inversely proportional to the molding temperature and to the molding rate during the molding stage. The friction coefficient is proportional to the coefficient of friction, the residual stress of the lens is proportional to the annealing rate and the holding pressure in the annealing stage, and the cooling rate has no obvious effect on the residual stress at the cooling stage. The causes of forming errors in the process of die forming are analyzed. The forming error mainly appears in three aspects: 1) machining error of mold cavity surface 2) error caused by glass preform copying hot deformation die profile during molding stage and 3) error caused by lens structure relaxation in annealing stage. On this basis, the forming error of the lens in the forming process is predicted, and the surface profile of the aspherical concave convex glass lens obtained by the experiment is measured. The measured results are in good agreement with the predicted results. The feasibility of predicting lens forming error by numerical simulation. The influence of single forming parameters on forming error is studied. The results show that the forming error increases with the increase of the molding rate and decreases with the increase of the molding temperature. However, the forming error increases with the annealing rate and keeps the pressure when the molding temperature is too high. With the increase of friction coefficient, the cooling rate has no obvious effect on the forming error.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH74;TQ171.734

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