DETERMINATION OF TIME-DEPENDENT CONSTITUTIVE MODEL PARAMETERS FOR MICROCRYSTALLINE CELLULOSE

ABSTRACT

Material parameters of a time-dependent elasto-viscoplaslic constitutive model, proposed by Adachi and Oka, have been determined for microcrystalline cellulose. Adachi and Oka model has eight material parameters, with five of them (i.e., consolidation index, swelling index, critical index, shear modulus, and Poisson's ratio) same as those in the more commonly used in time-independent modified Cam-clay model, and remaining three parameters account for time-dependency. To measure the time-dependent parameters, constant strain-rate conventional triaxial compression (CTC) test was designed and conducted using Penn Slate's flexible-boundary cubical triaxial tester (CTT) with microcrystalline cellulose as the test material. To deposit the powder, the sprinkle filling method was used in a layer by layer fashion with a small spoon. The three time-dependent Adachi and Oka parameters were determined from these tests. Adachi and Oka model was verified by comparing the predicted values from the model with measured values from the CTT at 0.05 level of significance. Results showed that: 1) there were no significant differences (p > 0.05) between measured and predicted HTC responses at all loading rates; 2) failure values were predicted accurately (p > 0.05); and 3) there were significant differences (p < 0.05) between measured and predicted CTC responses at all loading rates.     

M厂HFCG辊压机水泥挤压联合粉磨系统的运行剖析

M厂HFCG160-140辊压机+SF600-140组合式分级机+Φ4.2m×14m球磨机的开流水泥挤压联合粉磨系统的运行指标明显高于其他厂。通过易磨性试验并与其他厂家原材料的易磨性进行对比发现,M厂的原料易磨性是高产低耗的原因之一;其次是系统中组合式分级机的应用和组合稳流称重仓的内部改造所致。另外,还对M厂添加矿渣微粉的入库水泥与未加矿渣微粉的出磨水泥的使用性能进行了研究,结果是:二种水泥的减水剂相容性适中,差距较小,且其他品质性能相差也较小,但总体是入库水泥性能更优一点。     

新型干法水泥熟料易磨性概论

基于国外的研究论点,对新型干法水泥熟料及配料进行试验实测对比。结果表明：熟料热工形成过程影响易磨性的主要因素是C2S含量,其他矿相、液相含量以及密度/升重的影响不明显;快冷熟料优于慢冷;水泥粉磨过程的影响取决于熟料及其配料原料的易磨性,挤压终粉磨、联合粉磨等工艺可以忽略所有影响易磨性的因素,易磨性试验可节能30%~60%以上。     

煤质变化对钢球磨煤机贮仓式热风送粉制粉系统的影响

以华北某电厂的燃煤锅炉及制粉系统为研究对象,基于锅炉和制粉系统的热力计算及现场实际测量数据,定量分析了煤质变化与粗粉分离器后煤粉细度、煤粉水分、磨煤机最佳通风量、磨煤出力、出力储备系数、单位磨煤电耗、露点温度和三次风率的关系,并在此基础上确定了合适的煤种,提出了相应的改造措施.分析表明：对制粉系统运行安全性、磨煤出力和经济性影响最大的煤质因素是可磨性指数和原煤水分.计算结果与实际运行测量基本吻合,采用的计算与分析方法对普遍存在的同类问题具有参考价值.表9参6     

影响煤的可磨指数测定的因素探讨

可磨指数是煤加工利用过程中一个重要指标,就煤的可磨指数测定中存在的问题及影响因素进行了探讨,提出做好这项工作的几点建议和体会,希望能对有关从事此项工作的同志有所借鉴和帮助。     

Effect of carbonization temperature on the grindability of carbonaceous material produced from different coals

Carbonization experiments were conducted on four kinds of sub‐bituminous coal particles at a temperature range of 450–1200 °C. The effect of treating temperature on the grindability of produced carbonaceous materials was investigated, and its mechanism was analyzed through various means. Results show that the grindability of all coals, whether caking or slightly‐caking, exhibit the same variation trend with an increase in carbonization temperature. Moreover, the entire process can be divided into four stages. (1) After the most intense devolatilization stage, the grindability of carbonaceous material exhibited different degrees of increase compared with that of raw coal because of the development of a pore structure. (2) The first significant decrease in the grindability occurred from the plastic stage to the complete resolidification of the coal matrix. (3) After the aromatic polycondensation stage accompanied by a large amount of H₂ release, the coal molecular structure became compact, such that the grindability of semi‐coke considerably decreased again. (4) At high temperatures, the coal matrix underwent graphitization, which changed semi‐coke to coke. The molecular structure of coal became ordered, and the grindability decreased again. The analysis shows that a change in the internal chemical structure of carbonaceous material has a much more pronounced effect on grindability than a change in its pore structure, except in the first stage. The constant compaction and regularization of the coal molecular structure continued happening throughout the entire process and play a decisive role in the change in grindability.     

高压料床挤压对钢渣易磨性改善的应用研究

在分析了大量钢渣原料的化学成分、矿物组成和粉磨邦德功指数基础上，依据辊压机高压料床挤压粉碎原理，本文采用辊压机对钢渣进行预挤压试验，并参照相对易磨性试验方法，对比了挤压前后钢渣粉磨特性的变化，试验结果表明辊压机高压料床的挤压粉碎作用大大改善了钢渣的易磨性，有效的降低了钢渣的粉磨电耗。     

Relationships between Bond's grindability (Gbg) and breakage parameters of grinding kinetic on limestone

The grindability of a material is the only factor used to determine the required size of a grinding machine. Although, Bond's grindabilty test is widely used to the estimate power required of an industrial grinding mill. Recently, kinetic model has been mostly used to the design of grinding circuits.In this study, the relationship between the Bond's grindability (G_bg) and breakage parameters (S_i, a_T, γ and β) were examined. The validity of the obtained relationship parameters of S_i, a_T, γ and β has been confirmed with correlation coefficients of 0.96, 0.92, 0.90 and 0.78, respectively, through a regression analysis of samples of limestone.     

Grindability of high-temperature alloy with ceramic alumina wheels

The grindability of high-temperature alloy by using ceramic alumina wheels is studied on the basis of extensive analysis of the grinding force, grinding temperature, surface roughness and topography of ground surfaces, residual stress, hardness distribution of surface layer, and morphology of the surface layer from a metallographic point of view. The grinding burn mechanism of high-temperature alloy is unveiled and the feasible grinding parameters to avoid burning are analyzed. Some conclusions are obtained as follows. Increasing the grinding depth or the wheel velocity makes grinding temperature and residual tensile stress of the surface rise, which deteriorates the surface topography. Appropriate liner velocity of the wheel is 18–22 m/s and the depth of grinding should not exceed 0.02 mm in grinding GH2132 alloy with ceramic alumina wheels to assure the surface quality. When a _p increases enough to cause grinding burn, the strengthening effect of particles γ′ in γ base decrease and the micro-hardness of the surface is obviously lower than that of the base material, which deteriorates the mechanical properties and heat resistance of GH2132 alloy. Results provide a theoretical and experimental basis for technical optimization in the grinding of high-temperature alloy with high efficiency and high quality.     

聚氨酯改性不饱和聚酯木器底漆的研究

为了提高不饱和聚酯木器底漆的低温打磨性,采用聚氨酯对不饱和聚酯进行改性,形成互穿聚合物网络(IPN)结构,通过IPN协同效应,结合聚氨酯涂料和不饱和聚酯涂料的优点,获得干燥速度快,易打磨,性能优异的漆膜,聚氨酯用量为30%～50%时效果最佳。