Mechanism of Mechanical Strength Increase of Soda–Lime Glass by Aging

Two models have been proposed to explain the mechanical strength increase of abraded or indented soda–lime glasses upon aging, namely, crack tip blunting and the release of residual tensile stress near the crack tip. To clarify the mechanism, the time dependence of the strengthening of an abraded soda–lime glass was investigated. Effects of aging media, such as moist air, distilled water, 1 N HCI and 1 N NaOH solutions, as well as the abrasion flaw depth, were determined. The strength increase rate in water of abraded soda–lime glass was compared with those of borosilicate and high-silica glasses. The effect of stressing during aging was also investigated. It was found that the rate of strength increase was faster with decreasing abrasion flaw depth and with decreasing chemical durability. For a given flaw depth, an acidic solution produced the fastest strengthening. The strengthening rate was found to accelerate because of the "coaxing'effect of stressing during aging. From these observations, it was concluded that the strengthening rates relate to the diffusion process and chemical reactions, especially the alkali–hydrogen (or hydronium) ion-exchange reaction, near the crack tip. The role of the residual tensile stress appears to be similar to that of the applied tensile stress, helping the diffusion process near the crack tip. The observed strength increase of soda–lime glass by aging was thus attributed to the effective blunting of the crack tip geometry by the glass–water reaction.     

Strength and Static Fatigue of Abraded Glass Under Controlled Ambient Conditions: II, Effect of Various Abrasions and the Universal Fatigue Curve

A controlled grit blast was found to be a reproducible method of producing standardized damage to a glass surface. The effects of grit size, blast pressure, and amount of grit on the strength of the resulting specimens are reported. Static fatigue curves (strength vs. load duration) were obtained for specimens immersed in room-temperature distilled water and in liquid nitrogen (77°K.) after the specimens had been subjected to various abrasion treatments. The low-temperature strength was independent of load duration, and for surface damage of simple geometry it was inversely proportional to the square root of the initial crack depth, consistent with the Griffith theory. Abrasions of different geometry produced differing static fatigue curves at room temperature, and in one case curves actually crossed. If, however, the strength values for each abrasion were divided by the low-temperature strength for that abrasion and plotted vs. a reduced time coordinate, all the data could be fitted to a single "universal fatigue curve." This analysis led to a clear distinction between "linear" and "point" flaws, the former being flaws (such as emery scratches) which have an extension in a direction perpendicular to the applied stress and the latter being of a more localized character. Linear flaws fatigue more rapidly than point flaws by a factor of fifty and for each type of damage the fatigue rate is inversely proportional to the exponential of the initial flaw depth. A detailed analysis of the data in terms of several static fatigue theories from the literature shows that none of them provides a complete and adequate explanation of these results.     

离子交换对硼硅酸盐平板玻璃表面组成及性能的影响

研究用低温离子交换法增强硼硅酸盐平板玻璃.以熔融KNO3作为离子交换源,分别加入少量KOH,KF和锑酸钾(K2H2Sb2O72H2O)添加剂,在玻璃转变温度以下对硼硅酸盐平板玻璃进行K -Na 离子交换处理.利用电子探针研究了离子交换前后玻璃的表面组成变化;测定了样品的显微硬度、抗折强度和透过率.研究了添加剂种类与玻璃抗折强度之间的关系.研究结果表明:经K -Na 离子交换处理后硼硅酸盐玻璃表面K 浓度增加,交换深度可达30μm.经K -Na 离子交换后硼硅酸盐平板玻璃的强度提高,其抗折强度约为交换前的3倍.     

复合材料用缝合线的拉伸与摩擦性能研究

本文分析了几种高性能缝合线在缝合过程中的适用性与其强力损失及耐磨性的关系。采用对缝合线进行直拉与弯曲拉伸的方法分析纱线损伤;采用实验室自制的摩擦仪模拟缝合线与缝针摩擦,进行耐磨性测试。结果表明,缝合线弯拉时的强力约为直拉强力的两倍。摩擦作用是使纱线强力损失,影响其可缝合性的主要原因之一。张力越大,机速越高,同次数下缝合线受到的摩擦损伤越大,磨断次数越小。     

Effect of fine aggregate replacement with Class F fly ash on the abrasion resistance of concrete

This paper presents the abrasion resistance of concrete proportioned to have four levels of fine aggregate replacement (10%, 20%, 30%, and 40%) with Class F fly ash. A control mixture with ordinary Portland cement was designed to have 28 days compressive strength of 26 MPa. Specimens were subjected to abrasion testing in accordance with Indian Standard Specifications (IS: 1237). Tests were also performed for fresh concrete properties and compressive strength. Tests on compressive strength and abrasion were performed up to 365 days.Test results indicated that abrasion resistance and compressive strength of concrete mixtures increased with the increase in percentage of fine aggregate replacement with fly ash. Abrasion resistance of concrete was improved approximately by 40% over control mixture with 40% replacement of fine aggregate with fly ash, and concrete with fine aggregate replacement could be suitably used.     

多功能橡胶助剂ZNZB746在全钢载重子午线轮胎胎面胶中的应用

研究多功能橡胶助剂ZNZB746在全钢载重子午线轮胎胎面胶中的应用,并与增塑剂FS-200进行对比。结果表明,加入ZNZB746可以延长胶料的焦烧时间,赋予胶料更优的工艺性能,有效减少胎面半成品的气孔,提高致密性;可以提高胶料的定伸应力、拉伸强度和撕裂强度等物理性能和耐磨性能;ZNZB746能起到抗硫化返原剂的作用,使轮胎胶料老化后的耐磨性能明显改善。     

端羟基液体丁腈橡胶改性环氧树脂的结构与性能

用端羟基液体丁腈橡胶(HTLN)与2,4-甲苯二异氰酸酯进行反应得到HTLN预聚体,用其对环氧树脂进行化学改性,得到HTLN改性环氧树脂;考察了HTLN用量对改性环氧树脂微观形貌、拉伸强度和剪切强度的影响及改性环氧树脂的抗磨蚀性能。结果表明,随着HTLN预聚体用量的增加,改性环氧树脂的拉伸强度、剪切强度先升高后降低,在其质量分数为30%时,拉伸强度和剪切强度达到最高;在施加的负荷和HTLN用量一定的情况下,改性环氧树脂的磨蚀随滑动速率的增加而明显增加。     

碳纳米管对全钢胎胎面胶性能的影响

本文研究碳纳米管对全钢胎胎面胶加工工艺及性能的影响。结果表明,加入碳纳米管后,混炼胶的门尼粘度显著增大,耐磨性、撕裂强度、硬度大幅提高,拉伸强度稍有降低;密炼时在炭黑之后添加碳纳米管,开炼薄通10次时,硫化胶的DIN磨耗性能比不加碳纳米管的提高37.3%;在相同条件下添加碳纳米管GT-300橡胶的DIN磨耗、拉伸强度、撕裂强度等综合物理机械性能最佳。     

Abrasion erosion of concrete by water-borne sand

Hydraulic concrete structures frequently experience long-term abrasive erosion by water-borne sand, resulting in surface damage and eventually limiting their service life. In this study, the investigation of abrasion erosion tests on concrete with various water to cementitious material ratios (w/cm) was performed. The effects of the constituent materials on concrete structure abrasion erosion resistance were studied. The test results show that: (1) reduction in the w/cm ratio increases the tested concrete abrasion resistance; (2) the splitting tensile strength is a viable indicator for concrete abrasion resistance; (3) high permeability concrete exhibits weak abrasion resistance; and (4) concrete and low strength concrete made with coarser aggregate exhibit greater abrasion resistance.     

Research of the Thermal and Strength Properties for Materials Obtained with Sunflower Oil

The use of pulverized fly ash (PFA) obtained from thermal power plants and epoxidized sunflower oil (ESFO) as recycled material in the construction industry was investigated. Epoxidized sunflower oil, clay (C) and pulverized fly ash were mixed at various proportions and were fired at 160, 180 and 200°C. The thermal conductivity and strength (compressive strength, tensile strength and abrasion loss) of the samples were determinated. The lowest value of thermal conductivity, 0.25 W/mK, was measured for the sample with a 70% FA/30% C ratio and 50% ESFO processed at 200°C. This sample had the lowest compressivetensile strength (3.28 MPa–0.633 MPa) and the highest abrasion loss (4.39%). The highest compressivetensile strengths and the lowest value of abrasion loss observed, were 7.21 MPa–0.939 MPa and 1.15%, respectively.     

马来酸单酯稀土包覆硅灰石改性PA6的研究

采用马来酸单酯稀土(RETM)对硅灰石表面进行包覆后用于尼龙6(PA6)的改性,研究了RETM对改性PA6的拉伸强度、缺口冲击强度、耐磨损性能、吸水性及成型收缩率等的影响。结果表明,与硅烷偶联剂包覆处理的硅灰石相比,采用RETM包覆处理的硅灰石改性PA6时硅灰石的分散均匀性较好,改性PA6的拉伸强度、缺口冲击强度、耐磨损性能都得到了提高,吸水率及成型收缩率显著降低。     

Strengthen adhesion between zirconia and resin cement using different surface modifications

The aim of this research was to assess the influence of different surface modifications on the bond strength between resin cement and zirconia ceramics. Eighty-four zirconium samples were prepared. Four different surface treatments were applied; nano-alumina coating, 2 minutes gas-phase fluorination, 50 μm alumina airborne-particle abrasion, and 50 μm airborne-particle abrasion + 2 minutes gas-phase fluorination. Then specimens were bonded to resin cement. Half of the samples were then incubated in 37°C distilled water for 24 hours. The remaining samples were subjected to thermocycling for 5000 cycles. Shear-bond strength testing was applied at a cross head speed of 5 mm/s. Two-way ANOVA was used in comparison between groups. There is a significant difference between the groups with 5000 cycles and the groups with 24 hours of water cycling. The highest shear-bond strength values were observed in the groups with airborne-particle abrasion + 2 minutes fluorination (27.57 MPa) and nano-alumina coating (26.45 MPa) which were not subjected to thermal cycling. Nano-alumina coating of the zirconia surface and the 2 minutes gas-phase fluorination method following airborne-particle abrasion process increased bond strength between resin cement and zirconia.     

The Effect of Abrasion Surface Treatment on the Bonding Behavior of Various Carbon Fiber-Reinforced Composites

Abstract

In this paper we show that current abrasion surface preparation practices do not perform equally on all composite surfaces. The effect of abrasion on the adhesive bond strength of various carbon fiber (CF) composites was investigated. Cyanate ester composites were fabricated using a low, a high and an ultra high modulus carbon fiber (T300, M55J, K13C2U). XPS and contact angle measurements showed that the surface energy of all three composites increased due to the removal of contaminants as well as increased in surface roughness. However, the lap shear strength degraded sharply for a number of cases, irrespective of roughness, depending on the fiber used. Composites utilizing lower modulus carbon fibers increased in adhesive bond strength following abrasion in comparison to composites with higher modulus fibers. As the modulus of the fiber and the abrasive grit size increased, the degree of degradation caused by abrasion was shown to increase significantly. Scanning electron microscopy (SEM) and profilometry measurements showed the development of an abrasion-affected zone that was especially prevalent for higher stiffness composites. The failures for the higher modulus specimens were caused by subsurface damage located a few fiber diameters below the abraded surface. However, an alternate technique using atmospheric plasma surface treatment exhibited efficient removal of contaminants while showing no degradation of bond quality when treating these ultra high modulus composites.     

Determining the dependence of colour values on yarn structure

The colour values of knitted cotton fabrics made from single and plied ring and compact yarns were investigated before and after dyeing. The fabric samples were knitted under the same constructional properties and then dyed with direct and reactive dyes. It was found that fabrics with ring yarns had high lightness and low chroma and colour strength values compared with fabrics with compact yarns. Also colour strength and colour difference values of dyed fabrics were assessed after increasing abrasion cycles (2500, 5000, 7500 and 10 000). The main changes in colour strength values were observed at 2500 abrasion cycles. The effect of abrasion on colour difference values of fabrics having ring yarns was more obvious than fabrics having compact yarns.     

Abrasion resistance of thermoplastic polyurethane materials blended with ethylene–propylene–diene monomer rubber

The effect of ethylene–propylene–diene monomer rubber (EPDM) as an additive on the abrasion resistance of a thermoplastic polyurethane (TPU) resin was investigated. The mechanical properties and microstructure of the resultant TPU/EPDM composites were evaluated, and the surface morphology of the composites after abrasion testing was examined. The results showed that the addition of EPDM greatly improved both the mechanical properties and abrasion resistance of the TPU resin. A TPU/EPDM composite with 8 wt % EPDM demonstrated the highest tensile strength, the largest elongation at break, and the best overall performance. The abrasion of this composite was 27 mg, whereas that of the pure resin was 73 mg. With the further addition of EPDM, the abrasion resistance of the resultant composites decreased, whereas the viscosity increased. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Strengthening by Ion Exchange

This paper is a brief review of the physical and chemical methods of strengthening glass, in particular that due to the large for small ion exchange resulting from treatment in molten salt at temperatures below the annealing range for the glass. Abrasion of treated glass is shown to reduce markedly the strength of experimental alkali-lime-silica glasses as well as commercial glasses of this and other types. Treated alkali-alumina-silica and alkali-zirconia-silica glasses, however, are less affected by abrasion. Strength after abrasion increases with alumina or zirconia content, reaching 117,000 psi for cane of a 35% alumina glass. The explanation for the aluminum or zirconium effect may involve an unusual ionic environment caused by their presence in the lattice.     

不同硫化体系对天然橡胶的动静态性能的影响研究

分别制备了以炭黑和白炭黑为补强填料的不同硫化体系天然橡胶(NR)复合材料,研究硫化体系对NR胶料静态和动态性能的影响。结果表明:普通硫化体系硫化胶具有较高的交联密度、较好的物理性能和优异的耐磨性能;对于白炭黑补强体系,普通硫化体系硫化胶具有最低的滚动阻力;而对于炭黑补强体系,平衡硫化体系硫化胶具有最低的滚动阻力;胶料拉伸强度的增大有利于耐磨性的提高。     

Effects of laser irradiation on polyester textile properties

Modifications in textile properties of polyester because of laser irradiation were studied. Properties included fabric weight, fiber diameter, tensile strength and elongation, yarn abrasion, bending, surface luster, wetting, air permeability as well as crystallinity. Some properties were affected significantly while others were found unchanged. Besides, some properties were positively affected and some were adversely changed. Generally speaking, laser irradiation could not affect the bulk property of polymer because of its low penetration depth, and hence, the effect of the laser irradiation on the bulk and structural properties was limited. However, the performance and comfort properties of the laser irradiated polyester could be largely affected by laser irradiation as these properties could have been changed considerably if the surface was modified. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of zirconia additives on β-tricalcium-phosphate cement for high strength and high injectability

Injectable calcium phosphate cements (CPCs) exhibit many advantages as bone substitution materials. However, the strength of injectable CPCs after setting are often insufficient. In our previous studies, mechano-chemically modification of β-tricalcium phosphate cement powder through a planetary ball-milling process exhibited simultaneous improvement in the strength and injectability of CPC. Two plausible effects of this process are: changes in the CPC powder properties and zirconia abrasion powder contamination from the milling pot and balls. The objective of the present study is to separately evaluate these two effects on the strength and injectability of CPCs.The calculated injectability of the cement paste with and without the addition of zirconia powder were higher than 65% at 6 h after mixing. These values were much higher than that of the CPC paste without mechano-chemically modification, and similar to that of CPC with zirconia abrasion powder contamination. By contrast, the compression strength of the set CPC with zirconia powder additives were higher than that without the addition, and similar to that of CPC with zirconia abrasion powder contamination. These results suggest that the changes in the CPC powder properties due to mechano-chemically modification mainly affected the injectability of the CPC paste, and the zirconia abrasion powder contamination of the CPC powder affected the strength of the set CPC.