微晶玻璃应力测量与退火实验研究

应力大小是玻璃光学性能的重要指标之一。介绍了玻璃应力的分类、计算方法、测量方法和先进测试设备。退火是消除应力的有效手段。采用最高575℃的温度曲线对微晶玻璃块(40mm×50 mm×30 mm)进行退火实验,退火前后采用高精度数字应力仪进行应力测量。退火前实验件的应力分布不均匀,应力最小值0.85 nm/cm,最大值25.06 nm/cm;退火后实验件的应力分布均匀,应力最小值为0.75 nm/cm,最大值2.39 nm/cm。实验结果表明此退火能够明显减小微晶玻璃应力值并大幅提高应力分布均匀性。     

玻璃的钢化和退火

讨论玻璃的钢化和退火工艺，涉及到许多玻璃的技术参数和温度点，在实际应用中如能将玻璃的实际温度点和应力的产生及分布机理相结合必将对指导生产起到积极作用。     

普通工业玻璃退火与应力的几个问题 Ⅳ浮法玻璃在退火过程中产生的结构应力及其近似计算

按 Adamsσ=1 3 ha2 公式计算出退火后浮法玻璃中的永久应力明显小于实测值的原因是在通常的冷却速度下退火后玻璃中不但存在温差应力而且还存在相当大的结构应力。结构应力产生的原因是从高于 Tg 温开始的冷却过程中在制品壁厚的内外层之间不仅存在温度差而且还存在显著的膨胀系数差。结构应力随温度下降而增大并同时也发生松弛 ,它与温度呈 S型曲线关系并在转变区下限温度时达到最大后就不再变化。在此基础上导出了结构应力随温度下降的增长系数Ψ(S) 。采用在 Tg 温度附近的玻璃的动力学平衡结构代替其热力学平衡结构的方法导出结构应力的计算式并验证了此式的可靠性。     

普通工业玻璃退火与应力的几个问题：Ⅴ退火后玻璃中永久应力的近似计算

退火玻璃中的永久应力是由温差应力和结构应力两者叠加而成。在冷制品的重热退火工艺中冷却开始时所形成的温度梯度产生的温差应力和热制品直接退火过程中退火上限温度处因冷却速度突变造成温度梯度变化伴随而产生的温差应力在冷至退火下限温度过程中都不会完全松驰。因而能使均温后初始温度梯度消失时所产生的反向温差应力减小或增大。结构应力在热制品直接退火工艺中能得到充分发展而在冷制品重热退火工艺中发展却受到限制，这也将     

化学强化后玻璃应力松驰与再加热温度的对应关系

高铝玻璃通过化学强化后,获得一定的表面应力(CS)和应力层深度(DOL),当它被再次加热(或退火)时,其表面的应力会产生松驰现象,松驰程度与加热温度及玻璃本身的黏温特性有着对应关系;当加热温度达到玻璃自身的转变点(T_g)温度时,应力松驰达到极限,即玻璃表面应力被全部松驰,CS、DOL值回到零。     

普通工业玻璃退火与应力的几个问题：Ⅳ浮法玻璃在退火过程中产生的结构应

按Ａｄａｍｓσ／１３ｈａ＾２公式计算出退火后浮法玻璃中的永久应力明显小于实测值的原因是在通常的冷却速度下退火后玻璃中不胆存在温差应力而且还存在相当大的结构应力而且还存在相当大批结构应力。结构应力产生的原因是从高于Ｔｇ温开始的冷却过程中在缺口壁厚的内外层之间不仅存在温度差而且还存在垢膨胀系数差。结构应胡温度下降而增大并同时也发生松弛，它与温度呈Ｓ型曲线关系并在转变区下限温度时达到最大后就不再变化。在     

冷端应力、厚度在线测量系统

传统应力与厚度测量采用人工测量的方式,无法固化控制制度。现有技术应力常用的补偿法可靠性差、测量精度低,厚度采用最终产品进行检测,玻璃厚度测量反馈信号滞后。基于此,开发了冷端应力与厚度在线测量系统。该系统用于连续自动测量平板玻璃生产线退火后玻璃的应力、厚度,为平板玻璃退火工艺人员提供准确、可靠的参数,同时又是检验玻璃退火质量的理想检测仪器,为实现快速调整玻璃应力、厚度提供数据源,提高玻璃成品率及玻璃质量。     

浮法玻璃退火过程中玻璃带内的温度场和应力松弛

本文建立了浮法玻璃退火过程中玻璃带内温度场的数值计算与制图方法，并得出了玻璃带厚度方向温度分布随时间的变化关系。本文还做了玻璃应力松弛试验，结果表明，采用RD2-3型改进应力松弛试验机是可靠的。     

液晶玻璃基板应力分析与对策

光电产业对液晶基板玻璃的要求向超薄化、高清晰、全面屏发展,对液晶玻璃基板的品质需求也日益提高。由于玻璃基板行业竞争日益强烈,对生产企业来说,提升玻璃基板品质尤为关键。为降低TFT-LCD液晶玻璃生产过程中因退火温度不均、厚薄差异大、形状不稳、环境压差波动及切割晃动造成成型品质应力的波动,从溢流下拉法生产原理、应力分类、应力影响因素及对策方法展开深入研究,并通过实践加以论证,为TFT-LCD液晶玻璃生产中应力分析与对策提供正确思路,同时提升高效对策,促进行业健康稳定发展。     

玻璃内应力分析及其在线检测仪

本文详细阐述了玻璃应力形成的原因,后果及其所特有的双折射现象,利用双折现象就可以对玻璃内应力进行检测与分析。“３５００玻璃在线应力仪”作为检测与分析玻璃表层应力的有效仪器,被广泛使用在浮法玻璃生产线上。通过对玻璃表层应力的检测与分析,来调整玻璃的冷却速度及退火窑的工艺参数,从而大大提高玻璃质量和产量。     

热应力松弛公式在玻璃退火上下限测定中的应用

热应力松弛公式在玻璃退火上下限测定中的应用葛荣田（成都红光实业股份有限公司）ＵｓｉｎｇＴｈｅｒｍａｌＳｔｒｅｓｓＲｅｌｉｅｖｉｎｇＥｑｕａｔｉｏｎｆｏｒＤｅｔｅｒｍｉｎａｔｉｏｎｏｆＵｐｐｅｒａｎｄＬｏｗｅｒＬｉｍｉｔｏｆＧｌａｓｓＡｎｎｅａｌｉｎｇ...     

Microstructure‐property relation in alumina ceramics during post‐annealing process after laser shock processing

Laser shock processing (LSP) is a new surface engineering approach to introduce significant compressive residual stress into ceramics to improve their mechanical properties. However, LSP of ceramics may induce microcracks, which limit the further improvement of mechanical properties of ceramics. In this research, the effect of a post‐LSP annealing process on α‐Al₂O₃ ceramics was investigated. The annealing treatment can cause thermal relaxation of compressive residual stress generated by LSP while still maintain the positive attribute of LSP. The compressive residual stress was stabilized after annealing after 10 hours at 1100‐1300°C. The healing of microcracks in α‐Al₂O₃ ceramics was observed during the post‐LSP annealing process, which is caused by diffusion bonding mechanisms and accompanied by dislocation and void formation. The combination of the stabilized compressive residual stress and microcrack healing can improve the cracking resistance of α‐Al₂O₃ ceramics to mechanical impact on the surface by 69%.     

Analysis of Shear Stress Growth Experiments for Linear Constitutive Equations

Shear stress growth curves for viscoelastic fluids at low shear rates are analyzed using two linear rheological constitutive equations, an integral constitutive equation and a mixed type constitutive equation. It is shown that some published solutions do not satisfy all of the pertinent boundary conditions. For the low shear rate region, available experimental shear stress curves show a monotonic increase with decreasing slope in the shear stress. Shear stress curves calculated using a mixed type constitutive equation are found to exhibit this type of behavior while curves calculated using an integral constitutive equation do not. For the mixed type constitutive equation, the calculated developing velocity distribution is used to examine its effect on the developing shear stress distribution. For low values of E (the elasticity number), there is a moderate effect, but, for sufficiently large values of E, the developing velocity distribution has a negligible effect. It is also shown that results consistent with experimental data obtained at low shear rates can be attained using a single relaxation time. Additionally, incompressible Newtonian fluids are considered, and it is found that there can be single maxima in some shear stress curves with no maxima occurring in the velocity curves. Multiple maxima were not obtained in the Newtonian shear stress results unlike some published results.     

Effects of External Stress on Defect Annihilation and Bubble Swelling During Annealing of Neutron-Irradiated Silicon Carbide

Silicon carbide ceramics fabricated by three different methods were neutron-irradiated in the Japan Materials Testing Reactor and were subsequently annealed free from stresses or under compressive external stresses. The macroscopic length monotonically decreased with annealing above the irradiation temperature, when annealing was performed below ∼1300°C. This decrease was not affected by the external stresses. However, annealing above ∼1300°C led to an increase in length in B-containing SiC. The expansion was caused by the formation and growth of He bubbles at grain boundaries. The growth occurred by flow of vacancies into bubbles. The compressive stress retarded the expansion along the loading direction. This retardation was compensated by a length incrase along the lateral direction. The effect of external stresses was discussed by considering differently oriented He bubbles. One bubble was stress favored and the other stress unfavored. The stress determined the diffusional flow of vacancy-He atom complexes between the favored and unfavored bubbles which were caused by anisotropic expansion under a directional stress.     

浮法玻璃的应力与退火

玻璃的退火是浮法平板玻璃生产过程的一个重要环节。文章阐述了玻璃热应力产生和消除方法,指出在线应力检测是控制退火质量的较好途径。     

Formation of thermally induced craze and prevention by using infrared radiation annealing method

It is important to study the residual stress distribution and craze formation of transparent overmolded polymeric parts, because the overmolding can cause stress concentration near the interface region and the craze can be generated by the concentrated stress. Thermally induced crazing of an electric appliances product overmolded by using a transparent polymer is discussed in this study. Craze criterion was determined to be 20 MPa at the temperature higher than 60°C by using mechanical characteristic analysis of the polymeric material. Crazes were observed in the product annealed at over 60°C due to thermal residual stresses generated by the temperature difference between the surface and inside of the part upon surface heating. However, they were not observed in the product annealed by infrared radiation (IR) at over 60°C due to simultaneous heating throughout the thickness of the product. The numerical residual stress results were in good agreement with the experimental results, indicating that overmolding process, thermoviscoelastic stress development of the polymeric part, and IR annealing process were considered properly in the three-dimensional numerical analysis. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

热力历史对PMMA残余应力和光学性能的影响

利用光弹测量对注射成型过程不同热力历史的聚甲基丙烯酸甲酯(PMMA)样件进行了残余应力的定量表征,并测试分析了样件的透光率和雾度。研究表明,成型过程中的工艺选择对样件的残余应力影响显著,提高熔体温度和模具温度、增大保压压力和注射速度、缩短保压时间和冷却时间都可以有效降低残余应力;退火温度升高可明显削弱成型过程热力历史的差异,降低残余应力并使之趋于一致,偏差最小为0.71 MPa。热力历史对光学性能的影响与残余应力相关性较大,总体上残余应力降低,透光率升高而雾度降低,可分别达到93.1%和1.1%。     

Healing of Glass in Humid Environments

Chill checks of controlled depth were produced in soda-lime-silica glass, and an optimum humidity of 30 kPa (300 mbar) water vapor pressure was found to heal these checks in an annealing cycle. Critical factors were found to be a fluxing effect, having a direct dependence on moisture, followed by a drying operation at the annealing temperature. A four-step model is proposed for crack healing: (1) exposure of the crack surface to moisture at temperatures below T_g, (2) formation of a gel layer, (3) closure of the crack resulting from the relief of stress (a minimum of 10 to 20 MPa applied compressive stress was determined to be necessary for complete closure), and (4) drying in the presence of a controlled atmosphere.