Effect of Agglomerate Strength on Sintered Density for Yttria Powders Containing Agglomerates of Monosize Spheres

The effect of agglomerate strength on sintered density, was determined for several yttria powders made by intentionally agglomerating 0.1-μm, monodisperse yttrium hydroxycarbonate precursor spheres and calcining separate portions of the precursor at different temperatures to vary the strength of the intraagglomerate bonds. In this way, the effects of differences in particle morphology and other characteristics among the powders were minimized and the effect of agglomerate strength could be seen more clearly. The sintered density of the yttria powders decreased with increasing agglomerate strength, and even a small fraction of unbroken fragments of agglomerates in the pressed powder caused a substantial decrease in the sintered density.     

高固含量推进剂模压工艺

探索了一条高固含量推进剂较安全的成型工艺路线,重点介绍了一种高固含量球形药工艺.采用内溶法制得纯硝化棉黏合剂体系及硝化棉与ETPE(含能热塑性弹性体)混合黏合剂体系的高固含量(RDX(黑索今)质量分数为55％～60％)球形药,其球形药密度接近理论计算值,颗粒饱满,粒度均匀致密.采用模压成型工艺将其压制成推进剂药柱,药柱经无损检测,均匀致密,内部无气孔.同时药柱进行了各项性能实验.研究结果表明:该工艺方法简单可行,安全可靠.     

A Direct Comparison of the Fragmentation Test and the Microbond Pull-out Test for Determining the Interfacial Shear Strength

Experiments were conducted to compare the fragmentation test with the microbond pull-out test for determining the interfacial shear strength between carbon AS4 fibers and a thermoset matrix consisting of a Di-Glycidyl Ether of Bisphenol A (DGEBA) resin cured with a diamine (meta-phenylenediamine, m-PDA) curing agent. The results indicate that, for the microbond test, diffusion of the rather volatile m-PDA curing agent at early stages of cure leads to low values of interfacial shear strengths when compared with results obtained for the same system with the fragmentation test.

With the microbond test, a distinct relationship between the glass transition temperature of the droplets and their size is noticed. Smaller (< 150 μm) droplets have very low Tg's and are incompletely cured. While changing to a modified curing cycle and/or using a m-PDA-rich curing environment alleviates the diffusion problem, the interfacial shear strength values are still not in good agreement with the fragmentation test results. Microbond data from another system consisting of DGEBA resin cured with a different, less volatile dimaine curing agent indicates that diffusion of the curing agent becomes less severe as the volatility of the curing agent decreases and the corresponding microbond interfacial shear strengths agree better with fragmentation test results.     

Surface Properties of Ceramic Laminates Fabricated by Die Pressing

The simple die-pressing technique has been used to fabricate thick-layer zirconia/alumina ceramic laminates in the forms of film/substrate and multilayer systems. A "vibration sieve" method is used to achieve uniform layer thickness. In order to suppress surface crack initiation and propagation, the laminates are designed to retain residual compressive stresses in the surface layers. As a result, the surface fracture/fatigue resistance has been significantly improved, and the microhardness of the surface layer has also been increased to a certain degree.     

Hot Isostatic Pressing and High-Temperature Strength of Silicon Nitride-Silica Ceramics

Dense Si₃N₄ ceramics containing 2.5 and 20 wt% SiO₂ were hot isostatically pressed by a glass-encapsulation method. Their fracture strengths showed no degradation up to 1400°C, despite the presence of a large amount of SiO₂ glass. Moreover, in the case of Si₃N₄-20 wt% SiO₂, plastic deformation of as much as 2.5% was observed during bending tests at the strain rate ε = 1.5 × 10⁻⁴/s. The α- to β-phase-transformation rate decreased with increasing SiO₂ content.     

A Test Method for Torsion Strength of Refractory Materials at Elevated Temperatures

New apparatus for the determination of torsion strength of refractory materials at elevated temperatures has been developed in this work. With the employment of heating wire and induction heating unit,this device can carry out torsion strength test at high temperatures at the heating rate ranging from 10 ℃/min to 200 ℃/min.Torsion strength of high alumina brick,magnesia brick and Si3 N4 bonded SiC brick has been tested at different heating rates of 10 ℃/min,100 ℃/min and 200℃/min,separately. Results indicate that,for high alumina brick,the tested torsion strength at the heating rate of 10 ℃/min is very close to that at 100 ℃/min,but very different from that at 200 ℃/min. The tested torsion strength of magnesia brick at different heating rates differs greatly,while that of Si3 N4 bonded SiC brick is similar. This suggests that the structure of refractory materials with poor thermal shock resistance might be damaged when the heating rate of 200 ℃/min was applied,but the heating rate of 100 ℃/min is possible for a lot of refractory products. At fast heating rates,it takes only1 h to finish a test at elevated temperatures,thus saving a lot of time and energy.     

Effects of Postsintering Hot Isostatic Pressing on the Strength of an Aluminosilicate Ceramic

Postsintering treatments of annealing and hot isostatic pressing were applied to an aluminosilicate ceramic body. The strength parameters and the structure were monitored, and their changes were related to the reduction of surface residual compressive stresses. It is concluded that property improvements to ceramic bodies through postsintering hot isostatic pressing treatments are material-specific, depending on the availability of appropriate processes and mechanisms for improvement or change.     

弹性体材料介电强度测试探讨

从不同弹性体的测试中总结可能出现的问题,参考GB及IEC标准,介绍了弹性体测试需要注意的问题,探讨了标准修订的可能性。     

Thin-Disk Test for Adhesion-Bond Strength in Solvent Environments

A number of the popular tests for adhesive strength are difficult to apply to the study of adhesion under solvent environments. Complex applications, in which two different substrate materials need to be bonded and for which the substrates are thin sections, can be particularly difficult to study. The thin-disk test described here uses a thin annular disk of adhesive to bond two dissimilar materials while exposing the bond line to a circulating solvent. The new test was evaluated for a typical inkjet print-head application using surrogates for inkjet water-based inks. The joint is an epoxy adhesive joining a silicon wafer to a thermoplastic part (Rynite®), in which the silicon substrate, the thermoplastic, or the various adhesive interfaces might fail.

A conventional lap-shear test was compared with the thin-disk test for samples exposed to four different solvent systems plus water at two different temperatures. Lap-shear test failures occurred mostly in the thermoplastic part, with the exception of two samples exposed to the most aggressive solvents at high temperature. By contrast, thin-disk test failures occurred either in the silicon substrate or in the thermoplastic–adhesive interface. The thin-disk failure strengths at the thermoplastic–adhesive interface correlated with the equilibrium solvent swelling that could occur in the adhesive under the test conditions. This method could be adapted to other mixed-substrate bonding systems and would be particularly appropriate for thin section solids and thin adhesive layers.     

水泥抗压强度检测结果偏低的原因

一些检验机构以及相关的水泥企业在实际进行水泥抗压强度比对以及验证的过程中发现,水泥抗压强度实际检测结果经常会出现偏低的问题。主要对整个水泥强度检测过程进行了详细分析,进一步指出了在实际进行水泥强度检测的过程中一些容易被忽视的问题进行了指正,并对水泥抗压强度检测结果出现偏低现象的各种因素进行了分析。     

影响塑料冲击试验结果的因素

阐述了试样尺寸,温度、湿度、缺口以及缺口加工方式等因素对塑料冲击强度测试结果的影响。     

氨合成催化剂机械强度标准测定

本文简要地介绍了美国ASTM标准中的“催化剂和催化剂载体耐磨性”标准化测试方法。采用此方法测定了A110-1型氨合成催化剂的机械强度性能,并对测试结果作了讨论和评价。     

A Test Method for Accelerated Humidity Conditioning and Estimation of Adhesive Bond Durability

The ability to determine the durability of adhesive bonds remains an elusive task, especially when the service environment involves exposure to diluents such as water. Moisture continues to be of major concern for many adhesive bond systems for a number of reasons including:

1) many adhesives are hydrophilic, picking up significant amounts of moisture over time;

2) most adhesives and some adherends allow moisture permeation, eventually reaching the adhesive/adherend interface;

3) the high surface energies of metallic and certain other substrates result in moisture migrating to the adherend surfaces and displacing the adhesive from the substrates, and possibly oxidizing the adherend, etc., and

4) absorbed moisture induces swelling stresses which can reduce the bond strength.

Recognition of this susceptibility to moisture has led to extensive studies aimed at evaluating the effects of moisture, developing an understanding of the responsible mechanisms, and predicting the performance of adhesive bonds subjected to humid environments. While some studies have focused on the effect of humidity on neat adhesive samples, most studies have recognized the significance of the adhesive/adherend interactions, and have evaluated strength of actual bonded joints. Unfortunately, the time required for typical bonded geometries to reach moisture equilibrium can be quite long. Single lap joints (SLJ) and double cantilever beam (DCB) specimens with a width of 25mm may take several years to equilibrate, depending on the temperature and adhesive. Such lengthy conditioning times hamper the development of improved adhesives, and may delay the acceptance of these adhesives because of the time required to certify them. Methods to accelerate the conditioning of test specimens would be of significant benefit to adhesive formulators and users.     

仪表阀门壳体强度试验和阀泄漏量试验的计算

在炼油及化工装置施工过程中,根据SH/T3521石油化工仪表工程施工技术规范和SH/T3543石油化工建设工程项目施工过程技术文件规定,需要对仪表阀门进行壳体强度试验及泄漏量试验。虽然在石油化工仪表施工规范中都有对此部分的描述,但是所讲述的内容并不是非常的详细,所以实际工作中,大家对此部分并没有一个很清晰的认知,对壳体试压及泄漏量试验、公称压力、工作压力、设计压力容易产生不理解的地方,甚至出现好多错误。文章将对此部分内容进行详细的描述及扩充,让大家对此部分有一个清晰的认识。     

Strength of Explosives. Trauzl Test

A simple formula for calculating the absolute strength of an explosives as determined by the Trauzl test (expansion in a lead block) is proposed that contains only one parameter — the relative strength of the explosive calculated from the heat of explosion and the volume of explosion gases.     

Controlled Nucleation in Aerosol Reactors for Suppression of Agglomerate Formation: A Numerical Study

The formation of agglomerated particles can be a detriment to the production of highly sinterable materials. It has been seen experimentally that agglomerates are almost exclusively constructed from 10–30-nm primary particles. This paper develops criteria for the avoidance of these small primary particles through control of the nucleation rate. The relationship between particle size and number density can be used to obtain regions of stable and unstable particle growth. It is seen that the critical source rate for the prevention of runaway nucleation can be scaled without knowledge of the monomer number density.     

简支梁冲击强度能力验证用材料选择的研究

简要介绍了实验室能力验证用材料选择的依据和基本方法,研究了简支梁冲击强度能力验证选用的苯乙烯-丙烯腈共聚物(SAN)材料及制备的样品在不同型腔位置、不同贮存环境和状态调节时间、试样的摆放位置偏离等因素影响下对冲击试验结果的影响,探讨了不同能量摆锤对于SAN样品冲击试验的影响。结果表明,在严格执行有关材料试样制备与性能测定标准和简支梁冲击强度测定方法标准下,上述差异对试验结果影响很小,不会对实验室能力构成影响,确定了所选材料适用于简支梁冲击能力验证试验。     

分层输送带全厚度拉伸强度稳定性的控制

分析分层输送带全厚度拉伸强度稳定性的影响因素,主要包括结构设计(骨架材料类型、浸胶帆布层数)、帆布的使用情况、生产工艺、生产设备和特殊生产环境,排查了引起分层输送带全厚度拉伸强度不合格的原因。通过对分层输送带全厚度拉伸强度质量控制的研究,大幅度减少了分层输送带拉伸强度不合格的产品数量。     

纤维增强塑料弯曲强度测量不确定度评定

基于GB/T 1449–2005和JJF l059–1999标准,对影响纤维增强塑料弯曲强度的各个因素进行分析,通过对各不确定度分量的计算,给出了扩展不确定度以及分析结果,在置信概率为95%的条件下,当弯曲强度为368.96 MPa时,扩展不确定度为9.82 MPa(k=2)。     

轮胎强度试验不确定度评定

对轮胎强度试验的不确定度进行评定。轮胎强度试验的不确定度来源为作用力和行程位移。作用力测量不确定度包括试验机作用力示值分辨力引入的标准不确定度、作用力校准引入的标准不确定度和作用力测量重复性引入的标准不确定度。行程位移测量不确定度包括试验机行程位移示值分辨力引入的标准不确定度、行程位移校准引入的标准不确定度和行程位移测量重复性引入的标准不确定度。