Flaw-Insensitive Ion-Exchanged Glass: I, Theoretical Aspects

Stable crack growth can be produced on residually stressed surfaces, provided that the residual-stress profile is carefully chosen. Once identified, these conditions will lead to strengthening and an insensitivity of strength to the size of the initial surface flaw. Theoretical calculations are performed that involve choosing idealized forms of either the required toughness curve or the residual-stress profile. The results of this analysis allow the range of stable growth and the strengthening to be determined. Thus, in the material-design process, if the range of surface flaws in the stress-free surface are known, then the required stress profile or toughness curve for optimum performance can be selected.     

Subcritical Crack Growth in Soda-Lime Glass in Combined Mode I and Mode II Loading

Subcritical crack growth under mixed-mode loading was studied in soda-lime glass. Pure mode I, combined mode I and mode II, and pure mode II loadings were achieved in precracked disk specimens by loading in diametral compression at selected angles with respect to the symmetric radial crack. Crack growth was monitored by measuring the resistance changes in a microcircuit grid consisting of parallel, electrically conducting grid lines deposited on the surface of the disk specimens by photolithography. Subcritical crack growth rates in pure mode I, pure mode II, and combined mode I and mode II loading could be described by an exponential relationship between crack growth rate and an effective crack driving force derived from a mode I-mode II fracture toughness envelope. The effective crack driving force was based on an empirical representation of the non-coplanar strain energy release rate. Stress intensities for kinked cracks were assessed using the method of caustics and an initial decrease and a subsequent increase in the subcritical crack growth rates of kinked cracks were shown to correlate with the variations of the mode I and the mode II stress intensities.     

Measurement of Very Slow Crack Growth in Glass

The rate of very slow crack growth in glass is measured by inducing small, controllable changes in the direction of propagation of Hertzian cone cracks at known times. After completion of a growth sequence, the sample is sectioned to reveal the fracture surface. The stress intensity factor at each stage of crack growth is calculated by using finite-element modeling of the stresses near the crack tip. Data are presented for crack growth velocities as low as 10⁻¹⁴ m/s in soda–lime glass. These data provide strong evidence for the existence of a subcritical limit for crack growth in this material.     

离子交换增强玻璃研究进展

多年来,人们一直在研究提高玻璃强度的途径,利用离子交换增强技术对普通平板玻璃进行增强处理后得到了非常好的增强效果。本文总结了离子交换的工艺方法,并介绍了国内外对玻璃进行离子交换增强的研究进展与成果。     

含Cs+熔盐添加剂对离子交换玻璃力学性能的影响

本文采用熔盐法对普通钠钙硅玻璃进行化学钢化,研究了离子交换时间、温度和熔盐添加剂对化学钢化玻璃抗弯强度的影响,优化出一种含铯盐的熔盐配方,并探讨了Cs+的强化机制.结果表明:在410℃进行离子交换10h后,玻璃抗弯强度为原片的4.17倍,K+扩散深度约25μm.EDS、XPS分析结果表明,Cs+占据了Na+位置,与K+→Na+交换原理基本相同;少量Cs+的加入有助于提高玻璃的抗弯强度,但过量的Cs+会对K+向深处交换产生一定的阻碍.     

Subcritical Crack Growth in Soda–Lime Glass under Mixed-Mode Loading

Subcritical crack growth in glasses and ceramics has been studied extensively under Mode I loading. In this study, subcritical crack growth in soda–lime glass under mixed-mode loading has been determined, using the double cleavage drilled compression (DCDC) specimens with a hole offset from the center line. With this test configuration, cracks are nucleated at the pole of the hole and propagated parallel to the centerline of the specimen under mixed-mode loading. Under mixed-mode loading, subcritical-crack-growth rates are significantly less than those under Mode I loading at the same energy-release rates. Possible mechanisms for this increased resistance to subcritical crack growth under mixed-mode loading are discussed.     

Morphology of Vickers Indent Flaws in Soda–Lime–Silica Glass

The subsurface structure of Vickers indents in soda–lime–silica glass was investigated using confocal microscopy and conventional microscopy. It was determined that the lateral cracks that form beneath the indentation site propagate away from the surface. The median/radial (MR) crack system was found to be semielliptical in shape. The growth of the lateral and MR cracks was found to be codependent such that the depth of the lateral crack limited the depth of the MR crack, and the presence of the MR crack caused deflections in the direction and increased the extent of lateral crack growth.     

普通薄玻璃化学钢化

以普通钠钙硅浮法玻璃为原片,用低温型离子交换法进行试验,通过对试验样品的表面应力、应力层深度、显微硬度及抗折强度等数据的测试,研究普通浮法玻璃离子交换的工艺制度。     

Crack Propagation in Polymer Adhesive/Glass Sandwich Specimens

Moisture-assisted crack growth in polymer adhesive/glass interfaces was measured as a function of the applied energy release rate, G, using a four-point flexure test coupled with an inverted microscope. The specimens consisted of two glass plates bonded together with an epoxy or an epoxy-acrylate adhesive. It was found that cracks formed and grew on both interfaces if the glass surfaces were both smooth; however, roughening the surface of one of the glass plates increased the fracture resistance of the interface sufficiently so that crack growth occurred only on the remaining “smooth” interface (top or bottom). Finite element analysis was used to determine the G and ψ (phase angle) appropriate for the different crack geometries. It was found experimentally that crack growth rates for all crack geometries depended on the applied G via a power law relationship and that for a given applied G, crack growth rates were sensitive to the crack geometry. The results indicate that the primary driving force for moisture-assisted crack growth at a polymer/glass interface is the applied G at the crack tip and that the effect of the phase angle for the different crack geometries (13° to 54°) is negligible.     

Crack Propagation in Polymer Adhesive/Glass Sandwich Specimens

Moisture-assisted crack growth in polymer adhesive/glass interfaces was measured as a function of the applied energy release rate, G, using a four-point flexure test coupled with an inverted microscope. The specimens consisted of two glass plates bonded together with an epoxy or an epoxy-acrylate adhesive. It was found that cracks formed and grew on both interfaces if the glass surfaces were both smooth; however, roughening the surface of one of the glass plates increased the fracture resistance of the interface sufficiently so that crack growth occurred only on the remaining “smooth” interface (top or bottom). Finite element analysis was used to determine the G and ψ (phase angle) appropriate for the different crack geometries. It was found experimentally that crack growth rates for all crack geometries depended on the applied G via a power law relationship and that for a given applied G, crack growth rates were sensitive to the crack geometry. The results indicate that the primary driving force for moisture-assisted crack growth at a polymer/glass interface is the applied G at the crack tip and that the effect of the phase angle for the different crack geometries (13° to 54°) is negligible.     

Static and Cyclic Fatigue of Alumina at High Temperatures: II, Failure Analysis

Failure mechanisms of an alumina, tested at 1200°C under static and various cyclic loading conditions, were examined. Slow crack growth of a single crack is the dominant mechanism for the failure in specimens under cyclic loading with a short duration of maximum stress at all applied stress levels, as well as at high applied loads for static loading and cyclic loading with a longer hold time at maximum stress. At low stress levels, failure of static loading and cyclic loading with a longer hold time at maximum stress might occur by formation and/or growth of multiple macrocracks. More importantly, for all the given loading conditions. The viscous glassy phase behind the crack tip could have a bridging effect on the crack surfaces. A simplified model for calculating effective stress intensity factor at the crack tip under static and various cyclic loading demonstrated a trend consistent with the stress–life data.     

离子交换对磷酸盐玻璃表面裂纹扩展的影响

采用LiNO3和NaNO3混合熔盐在250℃对N31型磷酸盐玻璃表面进行离子交换处理,研究了小离子交换大离子对玻璃表面和亚表面裂纹的扩张作用.利用偏光显微镜、扫描电子显微镜、能谱仪对离子交换前后玻璃表面形貌和成分进行了测试,根据有限源扩散动力学和离子交换表面应力分布理论,分析了离子交换时间和H2O对裂纹扩张的影响.结果...     

浅谈Low-E玻璃的生产及其节能环保特性

从介绍热辐射、建筑能耗、玻璃光污染的基本知识出发,较为详细地介绍了Low-E玻璃的定义、基本术语、生产技术、产品特点及其节能环保特性,对于有兴趣了解、学习、掌握Low-E玻璃知识的有关人员和有志于攻克Low-E玻璃生产及应用难题的科技工作者具有参考意义。     

热处理对离子交换高碱铝硅酸盐玻璃性能的影响

将离子交换高碱铝硅酸盐玻璃在340~460℃热处理1 h,研究热处理对离子交换玻璃性能的影响。测试了热处理后玻璃的表面应力、应力层深度、强度和硬度。结果表明:随着热处理温度的升高,玻璃的表面应力及强度明显下降,应力层深度有所增加,而硬度略微下降。     

Water Entry into Silica Glass During Slow Crack Growth

Hydrogen concentration depth profiles on surfaces of SiO₂ glass fractured slowly in water and rapidly in oil were determined by nuclear reaction analysis. It was found that water enters SiO₂ glass during slow crack growth in water.     

Subcritical Crack Growth in Soda-Lime Glass under Combined Modes I and III Loading

Fracture and subcritical crack-growth characteristics under combined Modes I and III loading were studied using the modified compact tension (CT) specimens of soda-lime glass. The combined mode load was applied to the specimen in the direction β with respect to the initial crack. By superposition of Mode III, the advancing crack begins to rotate at an angle Ψ to the initial crack plane, which nearly maximizes the Mode I stress intensity factor K _I(Ψ), and the crack continues to propagate in the same direction. In this case, unlike combined Modes I and II, the crack breaks into multiple partial fronts, and ligamentary bridging forms fracture lances when these segmented cracks are held together. The crack velocity d a /d t was plotted versus the maximum Mode I stress intensity factor K _I(Ψ) for combined Modes I and III loading. The d a /d t values are initially high, and the crack growth tends to be discontinuous compared with the result for pure Mode I. The subcritical crack growth seems to occur when the K _I value for the initial crack reaches a certain value. The d a /d t - K _I(Ψ) curves for combined Modes I and III lie roughly on the same curve as that for pure Mode I as the crack growth increases.     

Low-Temperature Crack Closure in Fluoride Glass

Radial cracks generated in heavy-metal fluoride glass (HMFG) by Vickers indentation were found to decrease in length as a function of time when exposed to humid environments in the temperature range of 22° to 80°C. Inspection by optical and electron microscopy indicated that the cracks appear to be closing, leaving little or no evidence of the original crack aperture. The effect was observed to increase with time, temperature, and humidity levels for all conditions studied. Possible explanations for this behavior include viscous relaxation of glass in the region of the crack tip, or the generation and transport of a fluoride gel phase to the crack aperture.     

物理气相沉积对离子交换玻璃中钾离子浓度的影响(英文)

采用真空烘烤热蒸发沉积和离子束辅助沉积两种方法在离子交换玻璃上分别镀制ZnS薄膜,用扫描电镜和电子探针线扫描分析了物理气相沉积对离子交换玻璃中K＋浓度的影响,并测量了经不同方法镀膜玻璃的抗弯强度。结果表明：镀膜的离子交换玻璃中K＋的分布峰值减小并从玻璃表面向玻璃内部移动;与真空烘烤热蒸发沉积相比,离子束辅助沉积ZnS薄膜的离子交换玻璃中K＋的分布峰值增大且继续向玻璃内部移动,K＋浓度分布也随之移动,并导致离子交换玻璃力学性能下降。     

蒸汽发生器在TCO玻璃生产中的应用

主要分析了蒸汽发生器在TCO镀膜玻璃生产工艺中的作用,并介绍了蒸汽发生器的结构、分类以及应用范围,阐明了通过调节蒸汽发生器产生的水蒸气量大小对TCO玻璃产品主要功能参数如雾度、方阻、透过率的影响。     

含玻璃粉超高性能混凝土力学性能及微观结构研究

玻璃粉(GP)是一种环保型的固废材料。为了有效节约资源和解决环境污染问题,本文利用GP制备了一种绿色超高性能混凝土(UHPC),研究了GP作为一种矿物掺合料对UHPC力学性能和微观结构的影响。研究结果表明:GP的掺入改善了UHPC的流动性,并且降低了UHPC早期力学性能,但对后期力学性能产生显著的增强作用。当GP掺量为20%(质量分数)时,UHPC试样28 d的抗压强度趋近于基准组,而90 d的抗压强度较基准组提高了13.2%。且UHPC试样(90 d)表现出最低的总孔隙率,与基准组试样相比降低了14.6%。同时高密度水化硅酸钙凝胶的含量增加了20%,从而使UHPC形成更加致密的微观结构。GP具有良好的微集料填充效应和火山灰效应。