钢化玻璃自爆机理与自爆准则及其影响因素

钢化玻璃应用广泛, 但其自爆问题是一个被称为玻璃癌症的难题, 其特征是突发性和灾难性, 因此如何减少和预防预测玻璃自爆是钢化玻璃工程应用领域的关键问题。本文重点探讨了钢化玻璃的自爆机理, 揭示了钢化玻璃为什么会自爆, 什么条件下可能自爆和各种影响玻璃自爆的内在与外在因素。研究发现由于杂质和缺陷引起的应力集中是导致自爆的关键因素, 证明钢化玻璃内部的残余应力和局部强度均是非线性分布, 局部强度在玻璃表面最高, 中间层最低, 自爆的根本原因是内部的应力集中超过了局部强度, 而传统认识的硫化镍或单质硅等各种杂质只是引起自爆的间接原因。提出的钢化玻璃自爆准则为玻璃破碎分析提供了有用的参考。     

江苏省建成全球唯一超薄物理钢化玻璃基材生产线

正近日,江苏省高透光率光伏玻璃工程技术研究中心全面实现了超薄物理钢化玻璃基材高新技术产品产业化目标,投资4亿多元,建成4条全球独一无二的超薄物理钢化玻璃基材生产线。玻璃厚度1mm的生产线,应用于OLED照明灯具与有机发光玻璃等领域,远远小于国际上的物理钢化玻璃厚度的极限在2.5mm。江苏省高透光率光伏玻璃工程技术研究中心2009年经省科技厅     

储能钠硫电池β″-Al2O3陶瓷管强度分析

针对储能钠硫电池中核心结构部件β″-Al2O3陶瓷管容易失效的问题,利用柱壳理论建立陶瓷管数学模型,采用ANSYS软件进行实体建模与数值模拟,并给出了陶瓷管壁厚、直径、长度与其机械强度的定量关系.结果表明:陶瓷管最大应力发生于根部,最大应力随壁厚的减小而增大,随直径的增大而增大,但与长度基本无关,陶瓷管关于壁厚和直径临界曲线基本呈线性关系,这为陶瓷管机械强度的优化设计提供量化依据.     

钢化真空玻璃支撑点的排布方式

钢化真空玻璃即为两片钢化玻璃间抽真空的结构件。为了保证在外界大气压力下真空层的存在,在两片玻璃之间要放置支撑物。针对钢化真空玻璃中支撑点的排布对玻璃力学特性的重要影响,本文通过建立钢化真空玻璃力学模型,数值分析了不同支撑点排布方式下钢化玻璃的力学性能。研究结果表明:随着支撑间距增大,单位面积支撑点数急剧减少,使钢化玻璃最大变形量和最大应力迅速增大。对于5mm厚的钢化玻璃,在满足力学性能和支撑点数最少的条件下,支撑点正方形排布时支撑点间距可采用8cm,单位面积支撑点数169个;支撑点正三角形排布时,支撑点间距可采用8cm,单位面积支撑点数188个;支撑点正六边形排布时支撑点间距可采用6cm,单位面积支撑点数290个。由此,建议优先采用支撑点间距8cm的正方形排布方式,其次采用支撑点间距为8cm的正三角形排布,此研究对制造钢化真空玻璃中支撑点的排布方式提供理论指导。     

玻璃粘结剂对陶瓷电容器镍电极性能的影响

研究了玻璃粘结剂组成和含量对陶瓷电容器镍电极附着力、方阻和可焊性的影响,并使用SEM和EDS分析了其中的影响机制.结果表明,ZnO和PbO能够提高玻璃对陶瓷基板的润湿性能,进而增强镍电极的附着强度;增大玻璃含量有助于增强镍电极的附着强度,但在晶界和镍晶粒内部析出的多余玻璃相会导致电极电性能和可焊性下降.镍导电浆料中玻璃与镍粉质量比为0.08是比较合适的.     

不同粒径TiB2/Cu复合材料热传导模拟与实验

采用ANSYS对不同粒径TiB₂/Cu复合材料热传导过程进行模拟。采用粉末冶金法制备了不同粒径TiB₂增强的Cu复合材料,采用LINSEIS LFA1600激光导热仪测试了室温至280℃下的TiB₂/Cu复合材料热传导性能变化,并与模拟结果进行对比。结果表明:热导率模拟结果与实验结果吻合较好。在50~200℃之间,复合材料热导率变化不大,在6%~9%范围内波动。200℃之后,模拟值与实验值均呈现出随温度升高而增大的趋势,且吻合度较高。这是由于温度低于200℃时,在模拟过程中未考虑材料界面处两相不同热膨胀系数的影响,导致模拟值与实验值有较大的差异。当温度高于200℃时,模拟值和实验值吻合程度趋于稳定。在200℃时,由于两相热膨胀系数的影响,复合材料内部界面处等效应力大于Cu基体屈服强度,使其发生塑性变形,从而引起热导率发生较大幅度变化。此外,热导率随着TiB₂粒径的增大呈现出先提高后降低的趋势,在10 μm时达到最大。这是由于当颗粒直径小于临界平均直径时,颗粒直径的增大会减少界面数量,从而降低界面热阻。当颗粒直径大于临界平均直径时,平均自由程l的急剧增加导致热导率降低。      

Z-pin的拔出强度试验研究

通过单根Z-pin从复合材料层合板中拔出的试验方法,测试了Z-pin的拔出强度,计算了Z-pin的临界埋入深度,并引入抗拉强度利用率概念来表征Z-pin的抗拉强度在拔出过程中的利用程度.结果表明,直径0.50mm和0.28mm的Z-pin临界埋入深度分别约为5.1mm和3.1mm.当Z-pin的埋入深度小于临界埋入深度...     

基体性能对复合材料热残余应力的影响

采用ANSYS有限元法建立三维模型,研究了基体热膨胀系数和弹性模量对复合材料界面径向、轴向和周向残余应力大小和分布的影响。结果表明,界面残余应力的改变量均与基体热膨胀系数的改变量成正比,且随着基体热膨胀系数的减小界面周向残余应力沿着纤维周向分布的不均匀性减弱;界面残余应力变化的总趋势是随着基体弹性模量的增大而增大,但是增加的幅度不断减小。     

缺陷/应力交互对碳钢L_(cr)波声弹性系数的影响

基于L_(cr)波声弹性理论,探讨缺陷及其尺寸对L_(cr)波评价应力的影响机理。结合"当量法"预制不同直径盲孔,采用互相关系数函数计算L_(cr)波时间差,通过线性拟合得到L_(cr)波声弹性系数,基于弹塑性变形和圆孔应力集中理论澄清盲孔直径对L_(cr)波声弹性系数的影响机理。结果表明:各直径盲孔L_(cr)波时间差随应力增大基本呈线性增加,但其非线性特征亦逐渐明显,线性阶段的最大应力值小于试样屈服强度;L_(cr)波声弹性系数随盲孔直径增大逐渐减小,并趋于平稳。分析认为,盲孔应力集中是导致上述结果的主要原因,试样各向异性组织及盲孔深度也是其重要因素。     

真空玻璃支撑压痕控制准则

为避免过大的支撑物支撑应力导致真空玻璃基片赫兹裂纹的产生,首先建立了力学模型,分析了支撑物接触部位玻璃的应力分布特征.应用Griffith断裂理论和均强度理论,分别得到了玻璃基片在不产生压痕下支撑物的最大临界支撑力计算公式.通过与试验结果进行比较,发现两种理论计算结果均与试验结果相吻合,,但断裂力学理论得到的支撑物临界支撑力比试验结果偏小,而均强度准则结果偏大.对真空玻璃结构设计,在已知的真空玻璃材料参数下,根据上述理论,计算出玻璃基片不产生压痕下支撑物的最大临界支撑力,从而确定支撑物最佳排列间距,使真空玻璃达到"热学与力学"最佳配制.     

The strength of two-phase ceramic/glass materials

The strengths of various glasses, with a range of expansion coefficients, containing 10 vol % thoria spheres, of diameter 50 to 700m, have been measured. Stresses occur around the spheres, due to differences in the expansion coefficients of the glass and the spheres, on cooling from the fabrication temperature. Stress magnification occurs near the spheres, due to differences in elastic properties, in the presence of an applied stress. When the expansion coefficient of the sphere is greater than that of the glass, circumferential cracks form around the spheres but only when the sphere diameter is greater than a critical value. An approximate value for the critical diameter may be obtained by an energy balance criterion. Cracks may form around spheres smaller than the critical diameter under application of applied stress at stresses below the macroscopic fracture stress. In these cases the strength is governed by a Griffith relationship with the crack size equal to the sphere diameter. When the expansion coefficients of the spheres and glass are similar, the strength of the glass is reduced only when large spheres (300m diameter) are present. When the expansion coefficient of the spheres is less than that of the glass, linking radial cracks form between the spheres and the material has very low strength.     

Tensile strength of fibre-reinforced metal matrix composites with non-uniform fibre spacing

The influence of non-uniform fibre spacing on the strength of unidirectional fibre-reinforced metal matrix composites was studied by means of a Monte-Carlo computer simulation experiment. The influence of yield stress of the matrix and scatter of the fibre strength on the strength of composites were also studied for both uniform and non-uniform fibre spacings. It was demonstrated that (1) the strength of composites with non-uniform fibre spacing is lower than that with uniform spacing due to the high stress concentration arising from the breakage of fibres, and (2) the reduction in strength of composites due to the non-uniformity increases with increasing scatter of fibre strength. For both cases of uniform and non-uniform spacings, the following tendencies were observed : (a) the strength of composites increases but then decreases with increasing yield stress of matrix, (b) it is very sensitive to yield stress of the matrix when the scatter of fibre strength is large but not when it is small, and (c) it decreases but then increases with increasing scatter of fibre strength when the yield stress of the matrix is high, while it decreases monotonically with increasing scatter of fibre strength when the yield stress is low.     

Spontaneous failure of a passable laminated glass floor element

It is well-known that thermally toughened safety glass is subjected to a certain risk of spontaneous failure due to nickel sulphide particles included in the material. However, the present contribution focuses on a very uncommon case in which two out of three glass layers of a thermally toughened laminated slab of a passable floor element failed spontaneously.After initial on-site observations, witness interviews and reconstruction of the exact circumstances of the failure, no direct external cause such as hard or soft body impact, and local heating could be found. Consequently, the laminated glass slab was further investigated in the laboratory. During the laboratory analysis, several techniques have been used, such as crack pattern analysis, optical microscopy, and FEG scanning electron microscopy.As a result of the failure analysis, a nickel sulphide particle could be clearly detected. Based on striking similarities, a.o. in the crack pattern, breakage of the underlying glass layer of the laminate could be attributed to nickel sulphide as well.A method to assess the probability of failure of a double NiS failure is proposed. In spite of the design philosophy followed by the designer, in which the probability of this failure mode was not considered to be significant, this failure and risk analysis demonstrated clearly its importance for building practice.     

Fracture mechanics analysis of thermally tempered glass plate: fracture induced by an embedded crack

This paper presents a fracture mechanics analysis of a thermally tempered glass plate. The fracture is induced by an embedded penny-shaped crack. The analysis shows that the existence of a penny-shaped crack will reduce the strength of tempered glass. The impact and fatigue resistance of the glass is related to the position and size of the penny-shaped crack. When the tempering intensity reached to a certain level, thermally tempered glass with a penny-shaped crack could experience spontaneous fracture. The damage of a central crack on glass is more severe than a surface crack. With surface compression, thermal tempering will increase the critical applied stress of the glass if the surface penny-shaped crack size is in the range of 0 < a/d < 0.27, where a is the crack size, d is the half thickness of the glass plate. For a small surface crack with the size of a/d 0.09, the tempering can hinder its extension. However, if there is a central penny-shaped crack, the critical applied stress of the tempered glass will decrease with the intensity of tempering.*Author for correspondence. (E-mail: lejun@mail.sic.ac.cn)     

The Effects of Particle Structure and Stress Application on Breakage Behavior in Fine Grinding

ABSTRACT

The magnitude of applied stress relative to particle fracture strength determines breakage mechanisms and fragmentation behavior. As the size being ground decreases, the relative strength increases, while power input to the mill must be divided among ever increasing numbers of particles. The resulting changes in breakage mechanism and fragment characteristics are discussed in the context of measurements on a variety of materials in different grinding environments.     

DEM simulation of the shear behaviour of breakable granular materials with various angularities

Particle shape is an important factor that affects particle breakage and the mechanical behaviour of granular materials. This report explored the effect of angularity on the mechanical behaviour of breakable granular materials under triaxial tests. Various angular particles are generated using the quasi-spherical polyhedron method. The angularity α is defined as the mean exterior angle of touching faces in a particle model. A breakable particle is constructed as an aggregate composed of coplanar and glued Voronoi polyhedra. After being prepared under the densest conditions, all assemblies were subjected to triaxial compression until a critical state was reached. The macroscopic characteristics, including the shear strength and dilatancy response, were investigated. Then, particle breakage characteristics, including the extent of particle breakage, breakage pattern and correlation between the particle breakage and energy input, were evaluated. Furthermore, the microscopic characteristics, including the contact force and fabric anisotropy, were examined to probe the microscopic origins of the shear strength. As α increases, the peak shear strength increases first and then remains constant, while the critical shear strength generally increases. Assemblies with larger angularity tend to cause more serious particle breakage. The relative breakage is linearly correlated with α under shear loading. Compared with unbreakable particles, the peak shear strength and the critical volumetric strain decline, and the degree of decline linearly increases with increasing α.     

中空玻璃微珠增强酚醛泡沫的压缩性能及热稳定性

为了改善酚醛泡沫（PF）的力学性能,通过模压成型制备了中空玻璃微珠（HGB）增强的PF复合材料,采用力学性能测试、热重分析和燃烧试验研究了HGB用量对复合材料压缩性能和热性能的影响,并对其增强机制进行了分析。结果表明：当HGB质量分数为树脂的10%时,增强PF的压缩比强度和压缩比模量达到最大值;经过硅烷偶联剂表面处理的HGB增强PF的压缩比强度和压缩比模量提高幅度较大。热重分析和垂直燃烧试验表明：HGB的加入降低了PF的热降解速率,使其热稳定性有所提高,阻燃性能略有下降。SEM、FTIR和EDS分析表明：HGB增强PF的破坏方式为泡孔受挤压破碎,并最终导致HGB脱粘或刚性破碎。HGB增强PF的泡孔密度增加、泡孔直径变小,HGB表面与树脂基体间界面粘结状况良好,在树脂基体中均匀分散。     

Simulation of cooling and solidification of three-dimensional bulk borosilicate glass: effect of structural relaxations

The modeling of the viscoelastic stress evolution and specific volume relaxation of a bulky glass cast is presented in this article and is applied to the experimental cooling process of an inactive nuclear waste vitrification process. The concerned borosilicate glass is solidified and cooled down to ambient temperature in a stainless steel canister, and the thermomechanical response of the package is simulated. There exists a deviant compression of the liquid core due to the large glass package compared to standard tempered glass plates. The stress load development of the glass cast is finally studied for different thermal load scenarios, where the cooling process parameters or the final cooldown rates were changed, and we found a great influence of the studied cooldown rates on the maximum stress build-up at ambient temperature.