多层叠加蜂窝纸板压缩特性研究

通过RMT计算机辅助压力自动测试系统对多层叠加蜂窝纸板压缩特性进行了理论分析和不同速率下的静态压缩试验研究,得到了二层蜂窝纸板连续静、动态压缩F-δ、σ-ε特性曲线.试验结果表明:在2种速率压缩状态下,二层叠加蜂窝纸板的压缩特性基本一致,曲线明显呈周期性,每个周期都与其中一层的静态压缩特性一致;各层按照屈服强度(即弹性阶段应力峰值)由小到大的顺序依次屈服,经历弹塑性、塑性和压实变形各阶段;曲线中的周期脉动对其缓冲性能将产生不利影响,应加以注意.     

预压缩对蜂窝纸板能量吸收的影响

目的探究相同温湿度环境条件下,不同程度的预压缩对不同型号蜂窝纸板缓冲性能的影响。方法利用电子材料试验机对材料进行压缩,进而通过Matlab软件绘制出应力-应变曲线、静态缓冲系数曲线以及能量吸收曲线。结果预压缩限制在线弹性阶段,对蜂窝纸板各项性能无明显影响;当预压缩进入弹塑性阶段,蜂窝纸板的各项性能产生较为明显的下降;当预压缩进入塑性坍塌阶段,蜂窝纸板的各项性能显著下降,甚至丧失缓冲特性。结论随着预压缩程度的增加,蜂窝纸板静态压缩性能、静态缓冲性能及能量吸收性能都会降低。     

不同速率下蜂窝纸板静态压缩特性的试验研究

通过RMT计算机辅助压力自动测试系统对2种蜂窝纸板进行了不同速率下的静态压缩试验,得到了连续静态压缩F-δ、σ-ε特性曲线.试验结果表明:2种速率压缩状态下,蜂窝纸板的静态压缩特性基本一致,出现明显的弹性、弹塑性、塑性和压实变形4个阶段,因此在蜂窝纸板的某些设计与应用场合可采用小速率静态压缩特性代替大速率静态压缩特性,从而使问题简化.     

立式瓦楞复合纸板静态压缩试验与有限元分析

目的对立式瓦楞复合纸板的静态压缩过程进行试验研究和有限元分析,研究不同楞型立式瓦楞复合纸板的力学性能。方法制作A楞、AB楞、B楞等3种不同立式瓦楞复合纸板试样,进行静态压缩实验,得到其压缩应力-应变曲线;建立3种楞型的立式瓦楞复合纸板有限元模型,进行静力学分析,得到其压缩应力-应变曲线,并与实验结果进行对比分析。结果试验和有限元分析均显示立式瓦楞复合纸板的静态压缩过程与蜂窝纸板的静态压缩过程类似,包括弹性阶段、屈服阶段、平台阶段、密实化阶段,试验和有限元分析所得到的压缩应力-应变曲线相吻合。纸板的峰值应力和平台应力与楞型有关,且随着楞高的增大而减小。结论通过试验研究和有限元分析方法得到了不同楞型立式瓦楞复合纸板的静态压缩性能,对该新型材料的应用有重要参考价值。     

蜂窝纸板疲劳累积损伤模型实验研究

目的通过疲劳压缩实验,建立蜂窝纸板疲劳累积损伤模型。方法首先对蜂窝纸板进行一定的预压缩,然后进行不同次数疲劳压缩试验,最后将疲劳试样进行准静态压缩。结果随着压缩次数的增加,纸板的承载能力、平台应力均有所降低;蜂窝纸板的屈服应力尖峰消失;应力-应变曲线变为3个阶段,即线弹性阶段、平台阶段和密实化阶段;当压缩次数在30 000次左右时平台应力下降比较大,在30 000~50 000次时,下降比较小,之后微弱变化。结论蜂窝纸板疲劳压缩后平台应力会发生变化,呈现出先剧烈后微弱降低;选取剩余平台应力为损伤参量,结合损伤累积方法建立了蜂窝纸板疲劳累积损伤模型。     

不同规格蜂窝纸板缓冲性能的研究

通过静态压缩和动态压缩试验,研究蜂窝纸板的静态缓冲特性和动态缓冲特性与它的蜂窝芯柱、蜂窝孔径的关系.根据静态压缩试验所得的应力-应变曲线计算出蜂窝纸板的缓冲系数-应变曲线,根据动态压缩试验所得的最大加速度-时间曲线计算出缓冲系数-静应力曲线,为包装中蜂窝纸板的尺寸设计提供一定的参考.     

蜂窝-瓦楞复合纸板的面外承载及静态缓冲性能研究

通过静态压缩试验,测定了蜂窝纸板、蜂窝-瓦楞复合纸板的静态缓冲特性曲线,讨论了蜂窝-瓦楞双面复合纸板的静态压缩变形过程,并分析了复合层数和瓦楞楞型对蜂窝-瓦楞复合纸板的面外承载性能和静态缓冲性能的影响。结果表明,蜂窝-瓦楞复合纸板的面外承载能力明显低于未经复合的蜂窝纸板;蜂窝-瓦楞复合纸板在低应力阶段的缓冲性能明显优于蜂窝纸板,但在高应力阶段与蜂窝纸板的缓冲性能基本一致。     

含线性阻尼的正切型包装系统跌落冲击响应分析的NHB法

目的 研究温湿度对蜂窝纸板力学性能的影响规律,提高蜂窝纸制品包装在高温高湿环境下的承载性能和使用寿命。方法 制作不同温湿度参数下处理的蜂窝纸板试样,进行静态压缩试验,得到其应力-应变曲线;建立一定温湿度环境下的蜂窝纸板有限元模型,进行有限元仿真分析,得到其位移云图和应力-应变曲线,并与试验结果进行对比分析。结果 蜂窝纸板静态压缩试验结果和有限元仿真结果相似,包括弹性、屈服和平台等阶段,试验和有限元分析所得的应力-应变曲线吻合。蜂窝纸板的等效弹性模量和屈服应力与温湿度有关,且随着相对湿度的增大而减少,随着温度的升高而增加。结论 通过试验研究和有限元分析,发现湿度对蜂窝纸板力学性能影响显著,研究结果对蜂窝纸制品包装的承载应用有重要参考价值。     

准静态压缩下的蜂窝纸板承载性能实验研究

对蜂窝纸芯和纸板准静态压缩实验,测定分析面纸、孔径比、厚度对蜂窝承载性能的影响.结果表明:蜂窝纸板压缩呈非线性特征,其压缩变形过程经历黏弹性、黏弹塑性、塑性坍塌3个阶段;面纸、厚度、孔径比不同程度影响蜂窝纸板的承载性能.随厚度、孔径比增大,承载力降低,面纸对承载力的影响减小;原纸定量增大,抗弯性能增强,纸板纵向弯曲强度大于横向弯曲强度.     

相对湿度对蜂窝纸板静态压缩特性影响的试验研究

通过静态压缩试验,研究了相对湿度的变化对蜂窝纸板静态压缩性能的影响,并分析了相应的变化规律.结果表明随着相对湿度的增加,在线性阶段,蜂窝纸板的极限应力不断减小,但相应应变的变化并不显著;在屈服阶段,平均应力降低.这些研究的结果可能有助于缓冲包装的设计和材料的选择.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Effect of Permeable Crystalline Material on Steel Reinforcement Corrosion of Concrete

Permeable crystalline materialcan permeate into pores and cracks of concrete and catalyze the reaction between Ca(OH) 2and unhydrated cement to generate a great quantity needle non-soluble crystals, which can stop up the pores and cracks of concrete, and increase the impermeability of concrete. This paper reported the results of a study conducted to evaluate steel reinforcement corrosion of concrete specimens uncoated and coated with permeable crystalline material as well as mixed with the permeable crystalline material. The properties evaluated for corrosion test were water impermeability, water absorption, compressive strength and potential. The results of water impermeability, water absorption, compressive strength clearly showed that the permeable crystalline material could prohibit water, any soluble salts and moisture from penetrating the concrete to cause corrosion, leaking, and other problems, and it did increase the compressive strength, which was favorable for protection of corrosion of reinforcing steel. Moreover, it was concluded from the potential-time curve that the steel reinforcement of uncoated specimen was in the state of activation whereas that of other specimens coated and mixed with the permeable crystalline material was in the state of inactivation. Above all, it was indicated that the permeable crystalline materialis very effective to protect the steel reinforcement of concrete from corrosion.     

The Research and Application About "Dry Peeling Off" Technology for Airplane Surface Paint Layer

In this paper, the principle of spurting take off lacquer were introduced; and with orthogonal method the unsaturate polyester was prepared ;it was easy to peel airplane paint layer off with this material and equipment.     

Quality Study of Honeycomb Core Shaping Without Wax Stabilization

Sandwich panels utilizing honeycomb cores result in lightweight, high-strength units that are very rigid. Indeed, they give honeycomb panels the best strength-to-weight ratio of any construction type available. Conventionally, the wax is poured into the cell of the core to strengthen the structure and prevent the core from being crushed during milling. Much time and labor is required to wax, mill, and clean the cores. In this study, the process of pouring wax into the core was skipped. In other words, the cutter directly milled the core. Experiments showed that the compressive strength of the core produced without wax stabilization was only 3% lower than that of cores produced using the traditional method. In addition, the drum peel strengths of cores produced without wax stabilization were 38.4% higher than cores produced using the traditional method, in which residual wax seriously polluted the adhesive. It was also found that eliminating the wax process can reduce costs.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

In-process thermal treatment of polylactic acid in fused deposition modelling

Polylactic acid (PLA) is one of the most widely used open source fused filament fabrication materials due to its ease of extrusion, biodegradability, and mechanical strength. The mechanical strength of PLA largely depends on the proper growth of its semi-crystalline structure, which can be severely impaired by a low rate of crystallization, particularly in open source printers. This can be further aggravated by the non-uniform thermal distribution of heat that causes improper curing among the extruded beads of the printing material. As a result, PLA printed on open source printers does not achieve the best mechanical properties. This research, for the first time, proposes an additive-free solution implemented through a detailed set of experimentation to improve the curing rate through in-process temperature variations to cure the joints among the beads. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy is used to confirm the improvements in the bead joints. This work is conducted in two phases of experiments. In the first phase, a full factorial ANOVA is used to investigate various process parameters and the important variables are used in the second phase to print test specimens in four different sets.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.