Acoustic Emission in the Fracture of Glass Plates

The ring-down counting method was used to measure acoustic emission (AE) during the subcritical cracking of float-glass plates. It was found that AE emanated primarily from surface flaws and that a flaw =4 μm deep was capable of producing one AE count. The dependence of AE count rate on experimental parameters such as system gain and specimen size was determined and the use of AE simulators for calibrating AE systems was examined. The results were used to show how data on different ceramic materials might be compared.     

Mechanical Properties of Phosphate Glass Optical Fibers

In this work, step-index 40/125 μm diameter optical fibers produced from two slightly different lithium phosphate glasses were subjected to mechanical characterization. Tensile tests were carried out on fibers with gage length from 10 to 150 mm, allowing for the determination of the failure stress (ranging from ≈200 to 400 MPa) and the elastic modulus (60 GPa). Some tests were also performed with the fiber “immersed” in water; an important subcritical crack growth effect was pointed out, and a fatigue susceptibility parameter (n) equal to 11.4 was determined. The analysis of fracture mirror allows an estimated fracture toughness equal to 0.5 MPa m^0.5.     

Strength and Fatigue of Fluoride Glass Optical Fibers

Strength and fatigue characteristics of fluoride glass optical fibers, used as a new infrared transmission medium, were examined. A correlation parameter between mirror size and tensile strength of 0.826 MPa.m¹² was obtained, and a fatigue parameter of 16.2 was determined from a dynamic fatigue test at 20°C and 60% rh .     

Cladding Glass Development for Semiconductor Core Optical Fibers

Glass-clad optical fibers comprising a crystalline semiconductor core have garnered considerable recent attention for their potential utility as novel waveguides for applications in nonlinear optics, sensing, power delivery, and biomedicine. To date, cladding compositions have relied on commercially-available expedients and have not been tailored for the specific semiconductor core nor the application. In this work, more-optimum silicate and nonoxide glass compositions are developed for unary (Si, Ge), binary (InSb, GaAs), and ternary (GaAlSb) semiconductor cores based on two main design criteria: (1) matching the thermal expansion coefficient between semiconductor core and glass cladding and (2) matching the viscosity-temperature dependences such that the cladding glass draws into fiber at a temperature slightly above the melting point of the semiconductor. While this latter requirement is critical to the molten core fabrication method, which offers a practical approach to long fiber lengths at acceptable manufacturing speeds (>m/s), these compositions are more broadly applicable to other semiconductor fiber processing methods. Preliminary experimental results on silicon core optical fiber are provided and show a marked diminution in oxygen content relative to analogous fibers drawn using a pure silica cladding.     

中红外碲酸盐玻璃及光纤研究进展

近/中红外激光和超连续光源在红外光电对抗、生物医疗、遥测感知和激光探测及测距(LIDAR)等领域具有十分重要的应用价值。近年来,基于软玻璃光纤来产生和传输高亮度近/中红外(特别是2～5μm)激光方面的研究取得了显著进展。在中红外软玻璃基质中,具有相对较低声子能的碲酸盐玻璃对于设计近红外和中红外激光器和放大器、高功率中红外激光传输和传感应用无源光纤具有特别的吸引力。本文重点总结了低损耗碲酸盐玻璃的关键制备技术,并综述了碲酸盐玻璃及光纤在稀土掺杂中红外发光方面的研究进展,最后对碲酸盐玻璃及光纤应用存在的问题和发展趋势进行了总结和展望。     

碲卤系红外玻璃光纤的制备及性质

研究了碲卤系中远红外玻璃光纤的制备及性质,提出了制备碲卤系玻璃预制棒的一个改进的方法,用该方法制备出了高透光率的中远红外玻璃,拉制出了在１０．６μｍ附近光损耗约为１０ｄＢ／ｍｒ Ｔｅ３Ｓｅ４Ｉ３玻璃光纤,并测试了这种玻璃纤维的最小抗弯曲率半径。     

Predicted Static Fatigue Behavior of Specially Coated Optical Glass Fibers

Long-term static fatigue behavior of optical glass fibers is controlled by their strength, fatigue resistance, and zerostress aging behavior. The effectiveness of four special coatings in preventing the long-term static fatigue deterioration of optical glass fibers was evaluated by determining the dynamic fatigue behavior and the effects of zero-stress aging on strength of the four specially coated optical glass fibers in water from 25° to 85°C. The results clearly show that the strength, fatigue resistance, and aging behavior varied significantly between these specially coated fibers. By analysis of these experimental results in terms of fracture mechanics principles, the predicted static fatigue behaviors of the four fibers were compared. Ideally the optimum fiber is one that exhibits a high strength, low strength variability, high fatigue resistance, and high aging resistance. Each of these specially coated fibers had a deficiency in at least one of these properties.     

远红外Ge-Te-Se硫系玻璃与光纤(英文)

采用传统的熔融–淬冷法制备了系列GexTe65Se(35–x)(x=20,22,23,24;摩尔分数,x%)Te基硫系玻璃。利用X射线衍射、差示扫描量热分析、分光光度计、红外光谱仪等设备研究了玻璃的性能。这些玻璃具有良好的热稳定性和红外透过性能。组分为Ge23Te65Se12,Ge24Te65Se11的玻璃的差示扫描量热曲线中没有出现析晶峰,表明玻璃具有良好的抗析晶性能。组分为Ge24Te65Se11的玻璃的转变温度Tg最高,达到了188℃。这些玻璃样品的红外透过范围都很宽,从近红外的1.8μm到远红外的18μm。通过在玻璃的制备工艺中引入蒸馏提纯工艺可以有效减弱杂质吸收峰对玻璃红外透过性能的影响。最后,选用Ge23Te65Se12玻璃作为包层,Ge24Te65Se11玻璃作为纤芯,采用棒管法完成了具有纤芯包层结构的Ge-Te-Se红外光纤的拉制。     

Strength and Fatigue Properties of Optical Glass Fibers Containing Microindentation Flaws

The inert strength and dynamic fatigue properties of fused-silica optical fibers are studied using subthreshold indentation flaws, i.e., flaws without radial cracks. These subthreshold properties differ from those obtained in comparative tests on silica rods containing postthreshold indentation flaws in three major respects: (1) the inert strengths are significantly higher than predicted by extrapolation of the postthreshold data; (2) the slopes of the dynamic fatigue plots are likewise greater, indicating a greater susceptibility of the subthreshold flaws to chemical kinetic effects; and (3) the scatter in strengths is wider. These trends reflect the change in mechanical response reported for optical fibers with "natural" flaw populations in going from ordinary to ultra-high-strength regions. Direct observations of the indentation sites up to the point of failure indicate that the property differences can be interpreted in terms of a transition from propagation-controlled to initiation-controlled fracture instabilities at reduced contact loads. The subthreshold instability condition is modeled qualitatively as a two-step, deformation-fracture process, with strong emphasis on the importance of residual stress fields in parametric evaluations. The relevance of the results to the practical issue of fiber reliability, most notably in connection with the potential dangers of using macroscopic crack velocity data to predict long-lifetime characteristics, is addressed.     

Compaction Effects in Glass Fibers

Glass fibers as commercially produced have physical and mechanical properties which differ from those of the massive form of the same glass. When these fibers are subjected to subsequent heat-treatments, the values of the measured properties tend to return to those of the massive glass. This phenomenon is called compaction because in the process density increases. The effect of compaction on the physical properties of fibers is discussed and the mechanism of this phenomenon is described briefly.     

Yttrium-Silicon-Aluminum Oxynitride Glass Fibers

Fibers were made from Y-Si-Al-O-N glasses previously shown to have excellent mechanical properties and outstanding water corrosion resistance. Fibers of glasses containing, respectively, 3.2 and 6.6 wt% N were pulled free-hand in air and from glass rods in N₂ Continuous fibers (up to several kilometers long) of the former glass were melt-drawn in N₂ while being wound in air outside of the glass-melting furnace. The fibers, some as small as 10 μm in diameter, retained the desirable properties of the bulk glass.     

Electrically Conducting Glass Fibers

Fiber formation and electrical conductivity were investigated in molybdenum phosphate glasses containing Ag₂O; PdO was substituted for Ag₂O and other constituents in the base glass. Temperature coefficients of electrical resistivity and linear expansion and other properties were determined for the bulk glasses. X-ray diffraction confirmed that some compositions were amorphous; these glasses could be drawn by conventional methods into continuous filaments. Migration and reduction of Ag⁺ at the glass fiber surfaces, induced by a secondary heat treatment, formed a metallic, electrically conducting, solder-able surface film. Filament resistance of 0.07 Ω/ft/2000 fibers was achieved; resistance increased nearly linearly with temperature from −200° to 200°C. Imperfections in the metallic film, acting as flaw sites, contributed to a reduction of ∼50% in tensile strength compared to that of pristine fibers.     

聚合物光纤

本文介绍了聚合物光纤的特性及其分类,论述了9种聚合物光纤的性能及其应用,综述了当今聚合物光纤的发展和现状。     

Fracture of Glass in Vacuum

The fracture of 6 glasses was studied in vacuum, <10⁻⁴ torr (10⁻² N/m²), as a function of temperature from 25° to 775°C. Subcritical crack growth was observed in 4 of the glasses. Activation energies for crack motion ranged from 60 to 176 kcal/mol. The glasses which did not exhibit slow crack growth were "anomalous" glasses with abnormal thermal and elastic properties. Critical stress intensity factors for these 2 glasses increased ∼10% as the temperature increased to ∼600°C. It is felt that subcritical crack growth is not the result of alkali-ion diffusion or viscous flow but rather of a thermally activated growth process which depends on the crack-tip structure in the glass. A narrow cohesive region at the crack tip favors subcritical crack growth, whereas a wide region favors abrupt fracture.     

玻璃纤维在防水材料中的应用

介绍了建筑防水材料的种类和国内外市场情况,从生产工艺和施工应用的角度分析了玻纤在防水材料中的应用分布,解读了玻纤胎基的质量要求,并对玻纤在防水材料中的应用前景及发展方向进行了展望。     

玻璃纤维在临床医学领域的应用

介绍了玻璃纤维在临床领域中的应用,如骨科外固定器材、牙科器材、过滤器、内窥镜、传感器、医用导丝、急救止血绷带、大型医用仪器的外壳、骨移植物等,并指出应进一步研究玻璃纤维在医学领域的应用,选择有价值产品,加大投入,形成产业规模,促进经济发展。     

Light-Focusing Glass Fibers and Rods

Glass fibers and rods with radially parabolic refractive-index distributions were produced by exchanging potassium ions from a salt bath or a lower-index cladding glass for thallium ions in the glass composition. A fiber 1 m long and 0.25 mm in diameter could be bent around a curve of radius 10 cm without deforming the Gaussian mode pattern; the depolarization of a laser beam was < −20 dB. The resolution of a rod 3.14 mm long and 1.0 mm in diameter with a focal length of 1.64 mm was of the order of 450 lines/mm. Attenuation (caused primarily by absorption induced by trace impurities) was 100 to 250 dB/km at 6328 Å; since further improvement with respect to loss is expected, these fiber guides are promising materials for use in long-distance optical communications.     

Fracture of Tempered Glass

The fracture of thermally tempered glass is discussed in terms Of both the stored elastic strain energy in the glass due to tempering and the elastic energy release rate Of crack extension, 9. The latter is used to obtain an analytical correlation between the maximum tensile stress and the average particle size at time of fracture. The theoretical predictions are supported by experimental data obtained for various glass thicknesses and temper levels.     

不同玻璃纤维耐碱性能的对比

为了比较不同玻璃纤维的耐碱性能,分别将耐碱玻璃纤维、中碱玻璃纤维、无碱玻璃纤维置于不同的碱性环境中(砂浆、NaOH溶液、混合碱液)进行加速老化试验,对比不同玻璃纤维在不同碱性介质中的耐碱性能差异。研究发现,在长期(96h)加速老化试验后耐碱玻璃纤维的强度保留率高于中碱玻璃纤维和无碱玻璃纤维。